Next Article in Journal
The IL-8/IL-8R Axis: A Double Agent in Tumor Immune Resistance
Previous Article in Journal
Aeromonas hydrophila OmpW PLGA Nanoparticle Oral Vaccine Shows a Dose-Dependent Protective Immunity in Rohu (Labeo rohita)
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:

Mitochondrion: A Promising Target for Nanoparticle-Based Vaccine Delivery Systems

NanoTherapeutics Research Laboratory, Department of Chemistry, University of Georgia, Athens, GA 30602, USA
School of Medicine, Department of Pulmonary and Critical Care, University of Virginia, Charlottesville, WV 22908, USA
Author to whom correspondence should be addressed.
Vaccines 2016, 4(2), 18;
Received: 8 February 2016 / Revised: 31 March 2016 / Accepted: 8 April 2016 / Published: 1 June 2016


Vaccination is one of the most popular technologies in disease prevention and eradication. It is promising to improve immunization efficiency by using vectors and/or adjuvant delivery systems. Nanoparticle (NP)-based delivery systems have attracted increasing interest due to enhancement of antigen uptake via prevention of vaccine degradation in the biological environment and the intrinsic immune-stimulatory properties of the materials. Mitochondria play paramount roles in cell life and death and are promising targets for vaccine delivery systems to effectively induce immune responses. In this review, we focus on NPs-based delivery systems with surfaces that can be manipulated by using mitochondria targeting moieties for intervention in health and disease.

1. Introduction

Vaccines are designed immunogenic antigens used to intentionally trigger the memory component of the immune system by stimulating humoral immunity via the production of antibodies for long term protection against various diseases [1] (Figure 1). Attenuated or inactivated vaccine can elicit immunoprotection but duration of effect is limited and concerted to cellular immune responses [2]. Vectors and/or adjuvant delivery systems are widely used to augment immunogenicity of antigens, to protect vaccines from degradation in physiological environment, to improve efficacy of vaccines, and to target specific sites preventing unwanted accumulation [3].
For effective therapeutic use, vectors should be stable, biodegradable, biocompatible, easy to prepare, low cost, immunologically inert, and/or serve synergistically as an adjuvant. Nanoparticle (NP)-based payload cargos and adjuvants for vaccines are growing technologies due to their intrinsic immune-stimulatory properties, ability to co-entrap antigen adjuvants such as toll-like receptor (TLR) and enhancement of the antigen uptake by cells, e.g., by professional antigen presenting cell (APC) manipulation [4,5,6].
Mitochondria play essential roles for life and death processes of cells. This complex organelle participate in energy generation, intermediary metabolism, exchange of information, calcium signaling, and regulation of apoptosis [7,8,9]. Mitochondria-associated dysfunctions provide a predictable prospectus of defects in tissues for many ailments, spanning from subtle alterations causing symptomatic illness, to major functional defects leading to death [10,11]. Mitochondria play an important role in the immune system, which involves signaling platforms, effector responses [12], and modulating the antigen-specific T cell activation via reactive oxygen species (ROS) signaling [13,14]. Mitochondrial antigens, such as M2 autoantigens [15], oxo-acid dehydrogenase complexes [16] and 2-oxoglutarate dehydrogenase complex [17], are known to induce disease-related autoimmune responses such as primary biliary cirrhosis (PBC) [15,16,17,18,19]. The targets located in the different compartments of mitochondria for possible vaccine development are listed in Table 1. There are reports of mitochondria-targeted NP systems with the ability to produce tumor associated antigens (TAAs) that have the potential to act as preventive/therapeutic vaccines [20]. A mitochondria targeted vaccine was recently reported to stimulate the immune response by mitochondrial DNA (mtDNA) mutations upon immunization in a renal cancer murine model [21]. Such findings support previous studies performed by West et al. illustrating that mtDNA stress primes immune response [22], which may be critical to encourage effective immune stimulation, modulation, and memory-like protection in the context of vaccines. Therefore, mitochondria are promising targets for vaccine delivery systems to effectively induce immunity against diseases and to establish and/or boost therapeutic effects.
Although mitochondria can serve as important modulators for vaccines by serving as unique targets, the field of mitochondria targeted vaccines by using NP delivery system is still in infancy. This might be due to limited availability of NP systems for vaccine design. In this review, we highlight recent advances of antigen delivery carriers that can be manipulated to achieve mitochondria targeting and their potential interventions as preventive/therapeutic vaccines, by categorizing them into compositional classes of: (a) polymeric; (b) liposomal; and (c) other types of antigen carrier systems. Along with discussion of mitochondria targeting moieties, examples of mitochondria targeted NP vaccines are provided as well as future directions for this field.

2. NP-based Vaccine Delivery Systems

NP-based therapeutics are emerging as a noteworthy field in clinical research. Currently, there are several FDA approved cancer nanomedicines, such as Abraxane, Doxil, Oncaspar, etc. NPs provide an important tool for clinical application and, thus, should and can be evolved for systems that aim for various functions, such as in the case of vaccines. Adjuvant or antigen-targeting delivery systems are critical for efficient immune modulation by protecting antigens from extracellular enzymes and pH changes, and translocation of antigens to the target sites [32]. Here, we have categorized these NP-based vaccine delivery systems as polymeric, liposome, and others types of NP based carriers.

2.1. Polymeric NPs as Antigen Carriers

Antigens loaded into nanometer-sized polymeric particles were recently shown to produce good adjuvant effect [33,34,35,36]. Polymeric NPs are used as adjuvants or antigen delivery cargos that can potentially be used in mitochondria-targeted vaccines. Polymeric NP are desirable platforms due to relative ease in tailoring (i) biodegradation properties and (ii) physical properties, such as size, surface charge, and hydrophobicity, for optimum cargo delivery/circulation and mitochondrial access. A list of polymeric NP based antigen delivery systems is summarized in Table 2.
Biodegradable NPs constructed from poly(lactic-co-glycolic acid) (PLGA) polymer are widely used as antigen carriers/adjuvants due to its biocompatible and biodegradable characteristics, with a safety profile approved by the US Food and Drug Administration (FDA) and European Medicine Agency (EMA) [37], good and controlled long-term release which results in strong immune response. Furthermore, PLGA NPs can carry a variety of antigens including gp120 and gp140 of the human immunodeficiency virus [38,39,40]. Not only were PLGA adjuvant NP systems reported to elicit a strong T cell immune response using 100-fold lower doses (0.05 µg) of CpG oligodeoxynucleotide antigen, NP systems also showed significantly higher cytokine secretion (up to 10-fold), as well as a comparative antibody response to normal saline delivery [41].Thus, PLGA systems may be further developed for tailored vaccines towards increasing Th1 cell and innate immune response (e.g., viral hepatitis clearance).
There are considerable challenges that must be overcome in order to develop strong PLGA-based NP systems for vaccines. For one, PLGA-based NPs have poor payload loading and display accelerated burst release of vaccines to unwanted tissue or cells. Thus, several modifications have been done to overcome these issues. For examples, a pH sensitive PLGA NPs system was developed for rapid release of ovalbumin (OVA) antigen in acidic environments to improve immune response [42]. NPs were prepared by combination methods of emulsion-diffusion-extraction and emulsification and were ~890 nm in diameter with zeta potentials of ~ −12 mV. The antigen release profile was pH-dependent with over 85% release in acidic environments (pH 5.0 or 6.5) and low release (10%) at physiological pH for 24 h. In vitro studies showed that PLGA-OVA NPs significantly enhanced CD86 and CD40 co-stimulatory factors, which induced higher level of cytokines IL-1β, IL-6, IL-12p70 and TNF-α than their control groups. In vivo studies of PLGA-OVA NPs demonstrated enhanced activation of B cells, CD8+ T cells, IgG titers, and Th1 polarization than their non-pH responsive control.
Delivery of dual or triple antigens in PLGA-NPs is also a possible strategy to enhance immune response efficiency. Co-delivery of TLR 4 ligand and TAA using PLGA-based NPs were reported to stimulate strong anti-tumor immune response [43]. This dual antigen loaded PLGA-based NP was prepared by double emulsion/solvent evaporation technique and vaccination of these NPs in healthy mice activated CD8+ T cell immune responses with greater Th1 cytokines including IFN-γ, TNF-α, and IL-2, -6, -12 production in both lymph nodes and spleen compared to 7-acyl lipid A NPs and empty-NP immunization. Polyethylene glycol (PEG) is a flexible, biocompatible, inert, amphiphilic, and non-toxic polymer that is FDA-approved for use in human. PEG is water soluble and, in NPs, prevents interactions between NPs and the cell surface environment. However, PEG-NP’s hydrophilic properties may lead to poor recognition and cellular uptake. NPs from other polymers such as poly(d,l-lactide) (PLA), poly (anhydride), poly(methyl methacrylate) (PMMA), poly(glycolic acid) (PGA), poly(ε-caprolactone) (PCL), chitosan, poly-L-lysine, poly(γ-glutamic acid) (PGA), can also serve as carriers for vaccine delivery.
Conjugation of two or more types of polymers by creating block copolymers, such as PLGA-b-PEG and PLA-b-PEG, are of particular interests as NPs carriers in vaccine development. Copolymers can be varied for ratios that to allow for the combined advantages of individual polymers and maximizes delivery and uptake efficiency. Factors including chain length of polymers, particle size, targeting moiety, and surface properties of NPs play significant roles in cellular uptake and immune efficacy of antigen. For example, Cruz et al. demonstrated significant effects of chain length of PEG and targeting moiety of antibody on the vaccine delivery and immune responses [44]. Chemically modified PLGA NPs were prepared by emulsification/solvent diffusion with various chain lengths of PEG via coupling to activated carboxyl groups. The NPs surface was coated with an antibody (hD1 or ZN-D1) identifying receptor for dendritic cells (DCs). The size of modified PLGA NPs increased with PEG chain length. The PLGA modified NPs with shorter chain length of PEG (MW: 2000–3000) and hD1 antibody showed higher uptake efficiency than longer PEG chain (MW: 6000–20000) modified larger NPs either with or without hD1 antibody. PLGA modified NPs coated with hD1 or AZN-D1 were more efficient for cellular uptake and targeting than those coated with H200, neck motif receptor. These results indicated that chain length of PEG and antibody types influence the ligand-receptor targeting by tailoring the size and surface properties of NPs. Plasmid DNA was loaded into PLGA-polyethyleneimine (PEI) NPs with positive surface charge of 40–70 mV and size of 230–280 nm by precipitation-evaporation-filtration method [45]. In vitro studies showed that PLGA-PEI-DNA NPs could stimulate human DCs to secrete IL-12 and TNF-α. In vivo study demonstrated enhanced T cell proliferation by immunization with PLGA-PEI-DNA NPs.
Biopolymers, like chitosan, can also be used to prepare comparably cost-effective NPs as stable carriers for antigens to trigger immune response for diseases, such as Hepatitis B, Tetanus, and Leishamaniasis [46,47,48]. For example, chitosan NPs prepared by ionic gelation were developed to successfully deliver TLR3 agonist poly (I:C) (pIC) and a T-Helper peptide (PADRE) to produce antibody against disease [49]. In vivo studies in mice indicated that both immunostimulant pIC and T helper peptide were critical to reach valuable immune responses upon immunization with chitosan NPs. The present condition of antigen in the NPs was an important factor for immune responses, whereas the adsorption of peptide on the surface of NPs showed higher antibody response than the entrapping counterpart.

2.2. Liposomal Systems as Antigen Carrier/Adjuvant

Liposomes are effective antigen carriers due to biodegradable, nontoxic, non-immunogenic, and antigen loading properties. These systems are reported to deliver a wide range of antigens, such as E7 peptide and HSP70, which can potentially vaccinate against many disease, such as cancer and human papilloma virus [14,60]. Table 3 summarizes the liposome-based NPs in vaccine delivery systems. Lipids, such as dioleoyl phosphatidyl ethanolamine (DOPE), dioleoyl phosphatidylcholine (DOPC) cholesterol, dioleoyldimethylammonium chloride (DODAC), dioleoyldimethylaminopropane (DOTAP), dipalmitoylphospatidylcholine (DPPC), dipalmitoylphospatidylglycerol (DPPG), can be used to prepare liposome-based NP delivery systems for vaccines. The endosomolytic lipid DOPE can enhance the efficacy of vaccine delivery by endosomal escape through membrane disruption and fusion processes [61]. For instance, Cui et al. [62] reported DOPE as lipid source for preparation of liposome-based adjuvant NPs as plasmid DNA (pDNA) vaccine carriers. The pDNA-lipid adjuvant NPs had a 250-fold enhanced activity than pDNA alone for in vivo immunization in BALB/c mice model.
Liposomal NPs are potentially able to cross epithelial barriers and protect encapsulated antigens from enzymatic attack in physiological environment [63]. Oral route delivery of vaccine is one of the most challenging and difficult tasks in vaccine development. Towards the development of oral or nasal vaccines, liposomal NPs can undergo reverse denaturation, surviving GI tract and other enzyme-rich environments. However, liposomal NPs are unstable and rapidly cleared by the mononuclear phagocyte system (MPS). The combination of liposome and polymer is a possible strategy for construction of antigen nanovesicles to resolve deficiencies in uptake efficacy and immune response enhancement. Many types of combination nanocarriers, such as liposome-chitosan NPs [64], were reported for drug-delivery and such systems may be further evolved for antigen delivery as well. Polymerized liposomes, which can be prepared under mild conditions comparable to conventional liposomes, exhibit greater encapsulation efficiency, better activity of antigen, and more controllable antigen release profile than conventional liposomes. The solid and stable structure of polymerized liposomes with easy preparation method make these NPs a promising antigen delivery vesicle [65]. Polymerized liposomes showed their potential as oral vaccine delivery system [66], however, further studies are required for clinical application.
Solid Lipid NPs (SLNPs) with a diameter of 50–1000 nm can be prepared by replacing the liquid lipid by various types of solid lipids, such as fatty acids, triglycerides, and their combinations [67]. The uptake efficiency and immunogenicity of antigen loaded SLNPs can be affected by size, lipid source, preparation method, and surface properties. For example, Bhargava et al. reported SLNPs as tumor antigen carriers, which demonstrated immune signal induction with no toxicity [68]. With tumor lysate as antigen, SLNPs were synthesized by solvent injection method with tristearin as a lipid source. SLNPs size was controlled by varying preparation parameters. The monomannosyl–dioleyl glycerol modified SLNPs showed the highest uptake efficiency and immune response among other lipid modified controls, which may be attributed to efficient antigen capture by mannose receptors of DCs.
The efficacious delivery and safety profile of liposome-based NP systems make them as promising vehicles for vaccine delivery. The immune-stimulant sipuleucel-T received FDA approval for asymptomatic or minimally symptomatic prostate cancer in 2010 and is used to prime metastatic prostate cancer patient’s T-cells to target the patient’s own cancer cells. Liposomes formulated prostate-specific antigen (PSA) is reported to generate immune response when injected into patients (65–80 years old) with prostate cancer. Out of 10, 8 patients showed PSA-reactive T-cell frequencies using in vitro sensitization method. The vaccination trial indicated that the patients survived within 22–33 months with one still alive during the testing timeline, whereas eight patients were stable and the rest of them deteriorated to progressive disease [69]. Another pilot study demonstrated the safety profile of MUC1 BLP25 liposomal vaccine. L-BLP25 was prepared by encapsulating BLP25 lipopeptide to form liposomal adjuvant with monophosphoryl lipid A and 3 lipids (cholesterol, dimyristoyl phosphatidylglycerol and dipalmitoyl phosphatidylcholine). Twenty patients (≥18-year-old) were continuously vaccinated with BLP25 liposome vaccine after single dose of cyclophosphamide for up to 1 year. No autoimmunity was observed, indicating that L-BLP25 vaccine is safe for therapeutic use [70]. A recent internationally randomized and double-blind phase III clinical trial composed of 1513 patients with non-small-cell unresectable stage III lung cancer, tested L-BLP25 as an immunotherapeutic [71]. The overall survival was 25.6 months for patients vaccinated with L-BLP25 compared to 22.3 months for patients treated with placebo. These results indicate the potential clinical benefit of L-BLP25 for cancer immunotherapy and warrant further studies [71].

2.3. Others Types of NP-based Systems as Antigen Carrier/Adjuvant

There are reports on other NP carriers for the delivery of vaccines other than polymeric or liposome-based NPs. For instance, inorganic NPs are suitable antigen delivery systems due to wide availability, rich functionality, and good biocompatibility. Many inorganic materials, such as aluminum salt, silver, gold, carbon materials, silicon oxide, and iron oxide were studied for use as antigen delivery carriers. Table 4 summarizes these NP carriers for antigen delivery. For example, Villa et al. [72] reported single-wall carbon nanotubes (SWNTs) as human tumor antigens carriers to improve immune responses. SWNT-peptide delivery systems were constructed using weakly immunogenic cancer-associated peptide WT1-Pep427 consisting of 19 amino acids. The SWNT-peptide delivery systems showed enhanced in vivo immune responses in mice model. More importantly, SWNTs alone did not show any toxicity or immunogenicity in vitro or in vivo, and no immunogenic responses were reported for this SWNT construct.
Layered double hydroxides NPs (LDH-NPs) are considered as potential vaccine nanocarriers due to good biocompatibility, low toxicity, great antigen protective and controllable release properties. LDH-NPs are hydrotalcite-like anionic clays with a common formula as [M2+1−xM3+x(OH)2]x+(An−)x/n·yH2O, where M is a metal cation (e.g., Mg2+, Al3+) located at octahedral sites and A is a inorganic anion (e.g., Cl, CO32−) situated at interlayers [73]. LDH-NPs provides efficient uptake of antigens due to their high endosomal buffering capacity and controllable released profiles [74]. Yan et al. demonstrated that OVA loaded LDH-NPs (~100 nm in diameter) prepared by a combination of precipitation and hydrothermal methods exhibited less inflammation but comparable adjuvanticity to induce Th1/Th2 immune response [75]. Modification of OVA-LDH-NPs by CpG receptor ligand significantly enhanced immune response. In vivo studies showed that LDH-CpG-OVA NP injections had six-fold of IgG2a/IgG1 ratio and less inflammatory activity than mice treated with Alum-CpG-OVA. Hybrid of different types of NPs to combine the advantages of individual NPs is an effective strategy to enhance vaccine immune response. This hybrid strategy is widely used in drug delivery, and can also be applied to vaccine developments. For example Wang et al. reported SiO2@LDH NPs as adjuvant for DNA vaccination to improve immune response for hepatitis B [76]. Core-shell SiO2@LDH (~210 nm in diameter) NPs showed adjuvant activity for maturation of DC in vitro and enhanced immune responses with greater generation of IFN-γ, IL-6, MHCII, and CD86 in vivo. However, toxicity of LDH NPs needs to be addressed for clinical applications.

3. Mitochondria Targeting Moiety

As mentioned previously, mitochondria have unique immunostimulatory capabilities that can enhance vaccine activity. Mitochondria targeting can be achieved by selectively conjugating the polymer or modifying the particle surface with a mitochondria targeting moiety. The unique properties of the mitochondrion, such as the existence of a mitochondrial membrane potential (Δψm) across a mitochondrion’s double membrane, and the mitochondrial protein import machinery indicates that lipophilic cations and specific mitochondrial targeting sequences (MTS) can be used to achieve effective mitochondria targeting.
(i) Lipophilic cation: One approach to confer mitochondria targeting properties to a vaccine is through conjugation to a delocalized lipophilic cation, such as triphenylphosphonium (TPP) cation [28,56,117], rhodamine 123 [118], or methyltriphenylphosphonium (TPMP) cation [119]. Lipophilic cations access the mitochondrion through a driving force caused by the Δψm gradient [120]. Cancer cells display a hyperpolarized Δψm across membranes in their mitochondrial population, which facilitate the accumulation of lipophilic cations. Thus, lipophilic cation conjugated NPs can be used as carriers to target the antigens to mitochondria. A summary of mitochondria targeting moieties is shown in Table 5.
TPP is a commonly used cation for mitochondria targeting due to its characteristic facile conjugation and efficient rapid uptake into mitochondrion. Nevertheless, the toxicity of TPP-based small organic molecules limits its use in therapeutic applications. Conjugation of TPP cations into a stable polymer, lipid or other nanomaterials can solve this problem. TPP derived polymers used as mitochondria targeting moiety for polymer surface manipulation as delivery systems exhibited less toxicity in recent studies. We recently reported a biocompatible polymeric NP for mitochondria targeting, where biodegradable PLGA-b-PEG was functionalized with a terminal TPP cation, forming PLGA-PEG-TPP [56,131]. This polymer has the advantages of being non-toxic, easy to prepare, and stable. Furthermore, it demonstrated success in efficient mitochondria associated delivery of different small molecules which included Pt(IV) compounds [132,133,134], ZnPc [21,27], aspirin [135]. Tagging to other nanomaterials with TPP cation is widely used and achieved by our group. For instance, gold nanoparticle (AuNP) to 3-bromopyruvate, high density lipoproteins [136,137], and all display no differences between controls and TPP conjugated NPs in toxicity and immunogenicity evaluations. Hence, these TPP-modified NP systems are promising for antigen delivery to mitochondria as well.
(ii) Mitochondria targeting sequence (MTS): Mitochondrial proteins are encoded by nuclear gene and further synthesized by cytoplasmic free ribosomes [138]. The translocation and intracellular sorting of these proteins to mitochondrial compartments depend on MTS [139]. Thus, MTS can be used as the targeting moiety. MTS commonly have a length of 20-40 amino acids and are located at the amino terminal of the precursor proteins. MTS form amphiphilic α-helical conformations with cationic amino acids on one side and hydrophobic amino acid on the opposing surface [140,141,142]. Table 6 summarizes MTS as mitochondria targeting ligands and their targets in the protein import machinery pathway.

4. Examples of Targeted NP-Based Vaccine

To demonstrate how mitochondria targeting NP-based vaccines can be developed, here we will provide possible modifications for immune modulation and vaccine development.
T lymphocytes with CD4 and CD8 surface proteins are referred to as CD4+ and CD8+ T cells, respectively. CD8+ T cells are cytotoxic when activated within the immune system, whereas CD4+ T cells are helpers in activating CD8+ T cells or humoral immune responses [161]. The activation of CD8+ T cells requires the presence of APCs. DCs, the most effective APCs, present antigens to B and T lymphocytes for initiating antigen-specific immune responses or immunological tolerance through antigen and costimulatory molecules [162,163]. T-cell antigen receptors recognize antigens by binding APC surface major histocompatibility complex (MHC) molecules, whereas CD8+ T cells are activated by DCs [164,165]. Thus, DCs are attractive for therapeutics that rely on immune mediation, such as vaccines, and can be used to target infection, cancer, and tumor immunity [165,166,167].
DCs play an important in role in shaping adaptive immune responses. When activated, immature DCs express increased levels of co-stimulatory molecules, consequently leading to potent adaptive immune response [168]. Activation of DCs occurs in response to inflammatory chemokines, such as MCP1, MI-3α. DCs are recruited to the inflammation site, where they mature into functional DCs to regulate antigen capturing, processing, and expression of co-stimulatory molecules for activating T cells [165,169,170]. Because DCs are the primary APCs and their activation and maturation is crucial in shaping an effective T-cell response against invading pathogens or cancer cells, approaches aimed to increase uptake, activation and efficiency in antigen presentation should improve vaccine efficacy. In this way, NP-based antigen delivery systems can be used to drive immature DCs towards maturation for immune response activation against a delivered antigen.
Chong et al. [38] reported PLGA NPs for co-delivery of hepatitis B core antigen (HBcAg) and monophospholipid A (MPLA), a ligand for TLR, as therapeutic vaccines. A PLGA NP system was used to deliver antigen and Th1 promoting adjuvant to DCs to enhance immune response. The study demonstrated a synergistic effect, in regards to the PLGA NP co-delivery system, with anti-HBcAg IgG detection in sera and robust T cell proliferation response in mice via a booster dose. IFN-γ produced by T cells from the spleen and lymph nodes were 4- and 6-fold enhanced in mice immunized with HBcAg + MPLA-NPs than HBcAg NPs, respectively. Furthermore, no IL-4, a cytokine associated with cytotoxic immune response dampening, was found. Pulsing synthetic tumor peptides to DCs was demonstrated to elicit protective and therapeutic antitumor immunity [171]. A mitochondria targeting NP vaccine can be achieved by modifying this PLGA-NP carrier with a mitochondria targeting ligand, such as TPP.
A mechanism in which a vaccine can confer immune protection against disease using APCs is through triggering the selective or abundant expression or release of internal antigen in dysfunctional cells. Apoptotic cells, tumor lysates, and TAAs are all types of internal antigens that can be recognized by APCs. Rahma et al. [172] reported that pre-immature DCs pulsed with HPV16 E6 or E7 peptide derived from early genes E6 and E7 in high-risk HPV types 16 and 18 were well tolerated and able to induce specific immune responses in patients for therapeutic cervical cancer. Other vaccines are being developed against TAAs for vaccination of patients with various cancers. Rong et al. [173] developed a DC-based vaccine using MUC1-peptide, a TAA associated with late stage pancreatic cancer. In preliminary studies, IFN-γ and granzyme B, markers for cytotoxic immune response, were significantly enhanced in some patients. Phuphanich et al. [174] demonstrated the feasibility, safety, and bioactivity of TAA peptide for autologous vaccines by pulsing a class 1 peptide TAA expressed in patient’s glioma onto DCs. The TAA peptide pulsed DC vaccine administered intradermally into patients was nontoxic and led to elimination of CD133+ recurrent tumors cells. It is possible to target mitochondria of dysfunctional cells using NP-based system to trigger increased expression of internal antigens, especially TAAs, by inducing apoptosis (and generating apoptotic cells) for APC recognition and vaccines.
Antigen simulating activity by adjuvant has potential for synergistic effects resulting in stronger immune responses compared to antigen or delivery system alone. Tamayo et al. [175] reported a poly(anhydride) NP system for Th1 adjuvant immunoprophylaxis and immunotherapy. Studies demonstrated that poly(anhydride) NPs can act as agonists of various TLRs (e.g., TLR2, -4, and -5), to induce Th1-cytokine production (IFN-γ, IL-12) and trigger the expression of CD54 and CD86 co-stimulatory molecules after incubation with DCs. The in vivo studies suggested that NPs help elicit CD8+ T cell response. The co-administration of empty NPs with OVA showed induction of cytotoxic T cells specific for target cells. Furthermore, IFN-γ was detected in splenocytes from mice immunized with NPs and OVA. Aluminum-based adjuvants are licensed in vaccine with long record of safety without side effects of immune complex disorders [176]. α-Al2O3 NPs is reported to be a promising adjuvant in therapeutic cancer vaccines [177]. In vitro and in vivo studies demonstrated that the required antigen necessary to activate T cells was reduced by using α-Al2O3 NP adjuvant system. Notably, tumor growth was inhibited for more than 40 days and high levels of OVA-specific T cells were detected in mice immunized by α-Al2O3-OVA NPs.
Photodynamic therapy (PDT) is a rapidly developing tactic for therapeutic vaccines. It has the advantage of accurately locating photosensitizer (PS) to the desired sites by light irradiation [178]. PS molecule can be excited to produce reactive oxygen species (ROS) [179,180]. The increase in ROS results in tumor cell apoptosis and stimulates the host’s immune response. A combination of PDT with mitochondria targeted NP is a possible strategy to stimulate the immune system. Our group [21] reported mitochondria targeted NPs containing ZnPc and combined with PDT to ex vivo stimulate DCs to secrete the cytokines, especially IFN-γ and DC mediated activation of CD8+ T cells by procuring antigens from MCF-7 breast cancer cells (Figure 2). The mitochondria-targeted polymer PLGA-b-PEG-TPP was employed as ZnPc delivery cargo with TPP cation as mitochondria targeting moiety. The targeted ZnPc NPs showed enhanced apoptotic properties compared to non-targeted NPs by triggering mitochondria-mediated apoptosis. The TAAs from apoptotic cancer cells were then released and internalized by DCs, which further led to the CD8+ T cell activation. Cytokines IL-18 and IFN-γ were secreted by bone marrow derived DCs stimulated by apoptotic cancer cells produced by mitochondria targeted ZnPc NP treatment in the presence of light.
These results indicated that mitochondria-targeted-NP delivery systems containing mitochondria-acting photosensitizers are suitable for activating tumor cells which can further activate DCs for subsequent immune response. Our group also reported the combination of ZnPc and CpG-ODN in PLGA-b-PEG polymer carrier, which resulted in significant phototoxicity of 4T1 metastatic mouse breast carcinoma cells [28]. The PLGA-b-PEG-NP system was modified with CpG-ODN-coated gold NPs on the surface. The CpG-ODN–Au–ZnPc–Poly-NPs were highly toxic to 4T1 cells under irradiation [28]. These results suggest that patients with light accessible cancers may be treated by administration of a PDT active mitochondrial targeting vaccine NP systems that capitalize on optimizing immune function for cancer cell death and prevention, overall preventing the need for harsh chemotherapeutics and decreasing the rate of recurrence via lingering immune surveillance by memory cells.
Besides DCs, microfold cells (M cells), specific epithelial cells of mucosa-related lymphoid tissues that transport antigens from the lumen to immune cells, and macrophages can also initiate immune response and/or tolerance. Thus, it is possible to target mitochondria of macrophages and/or M cells with mitochondria-targeted NPs for therapeutic vaccine [181]. Fievez et al. [182] reported NPs with non-peptide ligands for targeting M cells for oral vaccination. The targeted OVA NPs showed enhanced cellular immune response with high levels of IFN-γ production and consistently low levels of IL-4 in splenocytes. In vivo studies in mice indicated higher IgG immune response than non-targeted formulations. Chen et al. [183] reported liposomal NPs as antigen delivery systems for macrophages. By decorating liposomes with 3’-BPCNeuAc ligands and glycan ligand, delivery of the antigens to endosomes and lysosomes, respectively, were achieved. Results demonstrated that liposomal NPs were efficient in delivering OVA to bone marrow derived macrophages and significantly enhanced T cell proliferation. By modifying the liposome with mitochondria targeting moiety, it will be possible to target the antigen NPs into mitochondria for efficient antigen delivery and immune response. Zhou et al. [184] reported that graphene nanosheets of diameter 172.7±75.6 nm and of thickness 2–3 nm induced the secretion of Th1/Th2 cytokines (IL-1α, IL-6, IL-10, TNF-α) and chemokines (GM-CSF MCP-1, MIP-1α, MIP-1β, RANTES) in murine macrophages. These settings of NPs can be potentially designed to target mitochondria by conjugating or surface modified with mitochondria targeting moiety.
Most human tumors are MHC class II negative, which CD4+ T cells cannot recognize. NPs have potential to elicit the immunomodulatory cytokines which favor the proliferation and differentiation of cell-mediated immunity. Sena et al. [13] reported that increased mitochondrial ROS was able to produce nuclear factor of activated T cells and subsequent IL-2 cytokine expression. Specifically, the study demonstrated that mitochondrial complex III ROS is required for CD4+ T cell activation in mice model. The Uqcrfs1−/− T cells, lacking mitochondrial complex III ROS and mitochondrial production of ATP, and controls WT CD4+ T cells were isolated from Cd4-cre mice, which had the same cell viability after 24 h of cell culture. The Uqcrfs1−/− CD4+ T cells failed to induce IL-2 and were less activated (reduced CD69 and CD25 markers) in response to anti-CD3 and anti-CD28 stimulation. Hence, mitochondria targeting to immune cells (e.g., T cell, natural killer cells) by NP-systems can be a promising method to enhance cytokine generation efficiency via mitochondria pathways.
Some efforts were made towards using NPs to potentiate cytokine generation for immune response. For example, Hanley et al. [185] reported ZnO NPs as modulators of pro-inflammatory cytokines, IFN-γ, TNF-α, and IL-12 in primary human immune cells. ZnO NPs with size range of 4–20 nm were prepared by forced hydrolysis of zinc acetate. The 8-nm ZnO NPs were used to evaluate the generation of cytokines of immune cells in isolated peripheral blood mononuclear cells (PBMC). A pretreatment with low level of IFN-γ before treatment by ZnO NPs resulted in a significant amount of IL-12 expression, indicative of a synergistic relationship between ZnO NPs and IFN-γ. The ZnO NP treated PBMC showed significant enhancement of IL-12, IFN-γ, and TNF-α cytokine levels, which were dose dependent for ZnO NP. The cytokines (IFN-γ, TNF-α, and IL-12) produced by ZnO NPs aided in antigen processing and immune cell differentiation for enhanced destruction of cancerous cells, virally infected cells, and/or intracellular pathogens. ZnO NPs are also reported to enhance inflammatory cytokines levels in murine macrophages [186]. Liu et al. [187] reported that poly-hydroxylated metallofullerenol [Gd@C82(OH)22]n modulates levels of Th1 (IL-2, IFN-γ, and TNF-α) and Th2 (IL-4, IL-5, and IL-6) cytokines in T cells and macrophages. The ratio of CD4+ to CD8+ T cells was significantly increased by [Gd@C82(OH)22]n treatment. Polyvinylpyrrolidone (PVP)-PEG-Ag nanorods were reported for HIV vaccine [188]. Au NPs were modified with glycopolymer to be used as synthetic cancer vaccines [189] and showed strong antibody production. Further modification of these sets of NPs by mitochondria targeting moiety can potentially modulate immune response.

5. Conclusions and Future Outlook

Mitochondria play critical roles in cell life and death, and their dysfunction is indicative of mitochondria-associated diseases. An ever-increasing number of investigations are focused on mitochondria targeting for efficient disease therapeutics, indicating the potential for such strategy in preventive/therapeutic vaccine. Possible roles for targeting mitochondria in vaccine development can be: (1) as targets of APCs (e.g., DCs) for external antigen delivery systems; (2) as targeting sites of immune cells activation (e.g., T and B cell); (3) as targets in dysfunctional cells (e.g., tumor cells) for apoptosis and production of TAAs available for APC uptake and subsequent activation of immune cells. NP-based vaccine systems are promising for: (1) carriers for delivery of external antigens; (2) inducers of apoptosis for release of internal antigens; and/or (3) inducers of cytokine production via due to their intrinsic properties. There are relatively fewer studies concerning mitochondria-targeted NP vaccine delivery systems. Mitochondrial targeting NP systems can provide for both cell-mediated (Th1; CD8+ T cell) and humoral (Th2; B cell) immune response via activation of various pathways, such as complex III, ROS, and are promising tools for vaccines with effective immune responses. To achieve the mitochondria targeting purpose, the well-developed antigen nanocarriers, consisting of polymer-based and liposome-based antigen delivery systems, should be modified with a mitochondria targeting moiety, such as TPP or MTS, in order to direct antigen systems to the mitochondria. NP based vaccine delivery system has been shown to be a promising method for enhancing vaccine efficacies and can potentially be translated in to a worldwide immunization scope in the near future.


We thank the Department of Defense Prostate Cancer Idea award (W81XWH-12-1-0406); American Heart Association National Scientist Award (14SDG18690009); National Heart, Lung, and Blood Institute of National Institutes of Health (NIH) under award number R56HL121392; National Institute of Neurological Disorders and Stroke of NIH under award number R01NS093314 and Georgia Research Alliance for supporting various projects related to nanoparticle-based technologies in our lab.

Author Contributions

R.W., A.C.U., L.F., S.T. and S.D. wrote the paper. N.S. participated in the construction of Table 2.

Conflicts of Interest

S.D. discloses financial interest in Partikula LLC. All other authors declare no conflict of interest.


  1. Liu, M.A. Immunologic basis of vaccine vectors. Immunity 2010, 33, 504–515. [Google Scholar] [CrossRef] [PubMed]
  2. Geels, M.; Ye, K. Developments in high-yield system expressed vaccines and immunotherapy. Recent Pat. Biotechnol. 2010, 4, 189–197. [Google Scholar] [CrossRef] [PubMed]
  3. Irvine, D.J.; Hanson, M.C.; Rakhra, K.; Tokatlian, T. Synthetic nanoparticles for vaccines and immunotherapy. Chem. Rev. 2015, 115, 11109–11146. [Google Scholar] [CrossRef] [PubMed]
  4. Rice-Ficht, A.C.; Arenas-Gamboa, A.M.; Kahl-McDonagh, M.M.; Ficht, T.A. Polymeric particles in vaccine delivery. Curr. Opin. Microbiol. 2010, 13, 106–112. [Google Scholar] [CrossRef] [PubMed]
  5. Bachmann, M.F.; Jennings, G.T. Vaccine delivery: A matter of size, geometry, kinetics and molecular patterns. Nat. Rev. Immunol. 2010, 10, 787–796. [Google Scholar] [CrossRef] [PubMed]
  6. Zhao, L.; Seth, A.; Wibowo, N.; Zhao, C.X.; Mitter, N.; Yu, C.; Middelberg, A.P. Nanoparticle vaccines. Vaccine 2014, 32, 327–337. [Google Scholar] [CrossRef] [PubMed]
  7. Wen, R.; Banik, B.; Pathak, R.K.; Kumar, A.; Kolishetti, N.; Dhar, S. Nanotechnology inspired tools for mitochondrial dysfunction related diseases. Adv. Drug Deliv. Rev. 2016, 99, 52–69. [Google Scholar] [CrossRef] [PubMed]
  8. Chan, D.C. Mitochondria: Dynamic organelles in disease, aging, and development. Cell 2006, 125, 1241–1252. [Google Scholar] [CrossRef] [PubMed]
  9. Pathak, R.K.; Kolishetti, N.; Dhar, S. Targeted nanoparticles in mitochondrial medicine. Wiley Interdiscip. Rev. Nanomed. Nanobiotechnol. 2015, 7, 315–329. [Google Scholar] [CrossRef] [PubMed]
  10. Duchen, M.R. Mitochondria in health and disease: Perspectives on a new mitochondrial biology. Mol. Aspects Med. 2004, 25, 365–451. [Google Scholar] [CrossRef] [PubMed]
  11. Marrache, S.; Kumar Pathak, R.; Darley, K.L.; Choi, J.H.; Zaver, D.; Kolishetti, N.; Dhar, S. Nanocarriers for tracking and treating diseases. Curr. Med. Chem. 2013, 20, 3500–3514. [Google Scholar] [CrossRef] [PubMed]
  12. West, A.P.; Shadel, G.S.; Ghosh, S. Mitochondria in innate immune responses. Nat. Rev. Immunol. 2011, 11, 389–402. [Google Scholar] [CrossRef] [PubMed]
  13. Sena, L.A.; Li, S.; Jairaman, A.; Prakriya, M.; Ezponda, T.; Hildeman, D.A.; Wang, C.R.; Schumacker, P.T.; Licht, J.D.; Perlman, H.; et al. Mitochondria are required for antigen-specific T cell activation through reactive oxygen species signaling. Immunity 2013, 38, 225–236. [Google Scholar] [CrossRef] [PubMed]
  14. Yan, W.; Chen, W.; Huang, L. Reactive oxygen species play a central role in the activity of cationic liposome based cancer vaccine. J. Control. Release 2008, 130, 22–28. [Google Scholar] [CrossRef] [PubMed]
  15. Yeaman, S.; Danner, D.; Mutimer, D.; Fussey, S.; James, O.; Bassendine, M. Primary biliary cirrhosis: Identification of two major M2 mitochondrial autoantigens. Lancet 1988, 331, 1067–1070. [Google Scholar] [CrossRef]
  16. Fussey, S.P.; Lindsay, J.G.; Fuller, C.; Perham, R.N.; Dale, S.; James, O.F.; Bassendine, M.F.; Yeaman, S.J. Autoantibodies in primary biliary cirrhosis: Analysis of reactivity against eukaryotic and prokaryotic 2-oxo acid dehydrogenase complexes. Hepatology 1991, 13, 467–474. [Google Scholar] [CrossRef] [PubMed]
  17. Moteki, S.; Leung, P.; Dickson, E.R.; Van Thiel, D.H.; Galperin, C.; Buch, T.; Alarcon-Segovia, D.; Kershenobich, D.; Kawano, K.; Coppel, R.L. Epitope mapping and reactivity of autoantibodies to the E2 component of 2-oxoglutarate dehydrogenase complex in primary biliary cirrhosis using recombinant 2*oxoglutarate dehydrogenase complex. Hepatology 1996, 23, 436–444. [Google Scholar] [CrossRef] [PubMed]
  18. Chen, L.; Duvvuri, B.; Grigull, J.; Jamnik, R.; Wither, J.E.; Wu, G.E. Experimental evidence that mutated-self peptides derived from mitochondrial DNA somatic mutations have the potential to trigger autoimmunity. Hum. Immunol. 2014, 75, 873–879. [Google Scholar] [CrossRef] [PubMed]
  19. Gershwin, M.E.; Mackay, I.; Sturgess, A.; Coppel, R. Identification and specificity of a cDNA encoding the 70 kd mitochondrial antigen recognized in primary biliary cirrhosis. J. Immunol. 1987, 138, 3525–3531. [Google Scholar] [PubMed]
  20. Marrache, S.; Tundup, S.; Harn, D.A.; Dhar, S. Ex vivo programming of dendritic cells by mitochondria-targeted nanoparticles to produce interferon-gamma for cancer immunotherapy. ACS Nano 2013, 7, 7392–7402. [Google Scholar] [CrossRef] [PubMed]
  21. Pierini, S.; Fang, C.; Rafail, S.; Facciponte, J.G.; Huang, J.; De Sanctis, F.; Morgan, M.A.; Uribe-Herranz, M.; Tanyi, J.L.; Facciabene, A. A tumor mitochondria vaccine protects against experimental renal cell carcinoma. J. Immunol. 2015, 195, 4020–4027. [Google Scholar] [CrossRef] [PubMed]
  22. West, A.P.; Khoury-Hanold, W.; Staron, M.; Tal, M.C.; Pineda, C.M.; Lang, S.M.; Bestwick, M.; Duguay, B.A.; Raimundo, N.; MacDuff, D.A.; et al. Mitochondrial DNA stress primes the antiviral innate immune response. Nature 2015, 520, 553–557. [Google Scholar] [CrossRef] [PubMed]
  23. Smith, R.; Huston, M.M.; Jenkins, R.N.; Huston, D.P.; Rich, R.R. Mitochondria control expression of a murine cell surface antigen. Nature 1983, 306, 599–601. [Google Scholar] [CrossRef] [PubMed]
  24. Loveland, B.; Wang, C.R.; Yonekawa, H.; Hermel, E.; Lindahl, K.F. Maternally transmitted histocompatibility antigen of mice: A hydrophobic peptide of a mitochondrially encoded protein. Cell 1990, 60, 971–980. [Google Scholar] [CrossRef]
  25. Kita, H.; Matsumura, S.; He, X.S.; Ansari, A.A.; Lian, Z.X.; Van de Water, J.; Coppel, R.L.; Kaplan, M.M.; Gershwin, M.E. Quantitative and functional analysis of PDC-E2-specific autoreactive cytotoxic T lymphocytes in primary biliary cirrhosis. J. Clin. Invest. 2002, 109, 1231–1240. [Google Scholar] [CrossRef] [PubMed]
  26. Berard, M.; Mondière, P.; Casamayor-Pallejà, M.; Hennino, A.; Bella, C.; Defrance, T. Mitochondria connects the antigen receptor to effector caspases during B cell receptor-induced apoptosis in normal human B cells. J. Immunol. 1999, 163, 4655–4662. [Google Scholar] [PubMed]
  27. Marrache, S.; Tundup, S.; Harn, D.A.; Dhar, S. Ex Vivo Generation of functional immune cells by mitochondria-targeted photosensitization of cancer cells. Methods Mol. Biol. 2015, 2, 113–122. [Google Scholar]
  28. Marrache, S.; Choi, J.H.; Tundup, S.; Zaver, D.; Harn, D.A.; Dhar, S. Immune stimulating photoactive hybrid nanoparticles for metastatic breast cancer. Integr. Biol. 2013, 5, 215–223. [Google Scholar] [CrossRef] [PubMed]
  29. Panneerselvam, P.; Singh, L.; Selvarajan, V.; Chng, W.J.; Ng, S.; Tan, N.; Ho, B.; Chen, J.; Ding, J.L. T-cell death following immune activation is mediated by mitochondria-localized SARM. Cell Death Differ. 2013, 20, 478–489. [Google Scholar] [CrossRef] [PubMed]
  30. Van de Water, J.; Ansari, A.; Surh, C.; Coppel, R.; Roche, T.; Bonkovsky, H.; Kaplan, M.; Gershwin, M. Evidence for the targeting by 2-oxo-dehydrogenase enzymes in the T cell response of primary biliary cirrhosis. J. Immunol. 1991, 146, 89–94. [Google Scholar] [PubMed]
  31. Murphy, M.P.; Siegel, R.M. Mitochondrial ROS fire up T cell activation. Immunity 2013, 38, 201–202. [Google Scholar] [CrossRef] [PubMed]
  32. Storni, T.; Kündig, T.M.; Senti, G.; Johansen, P. Immunity in response to particulate antigen-delivery systems. Adv. Drug Deliv. Rev. 2005, 57, 333–355. [Google Scholar] [CrossRef] [PubMed]
  33. Jewell, C.M.; López, S.C.; Irvine, D.J. In situ engineering of the lymph node microenvironment via intranodal injection of adjuvant-releasing polymer particles. Proc. Natl. Acad. Sci. USA 2011, 108, 15745–15750. [Google Scholar] [CrossRef] [PubMed]
  34. Demento, S.L.; Cui, W.; Criscione, J.M.; Stern, E.; Tulipan, J.; Kaech, S.M.; Fahmy, T.M. Role of sustained antigen release from nanoparticle vaccines in shaping the T cell memory phenotype. Biomaterials 2012, 33, 4957–4964. [Google Scholar] [CrossRef] [PubMed]
  35. Rahimian, S.; Kleinovink, J.W.; Fransen, M.F.; Mezzanotte, L.; Gold, H.; Wisse, P.; Overkleeft, H.; Amidi, M.; Jiskoot, W.; Löwik, C.W. Near-infrared labeled, ovalbumin loaded polymeric nanoparticles based on a hydrophilic polyester as model vaccine: In vivo tracking and evaluation of antigen-specific CD8+ T cell immune response. Biomaterials 2015, 37, 469–477. [Google Scholar] [CrossRef] [PubMed]
  36. Rahimian, S.; Fransen, M.F.; Kleinovink, J.W.; Christensen, J.R.; Amidi, M.; Hennink, W.E.; Ossendorp, F. Polymeric nanoparticles for co-delivery of synthetic long peptide antigen and poly IC as therapeutic cancer vaccine formulation. J. Control. Release 2015, 203, 16–22. [Google Scholar] [CrossRef] [PubMed]
  37. Cruz, L.J.; Tacken, P.J.; Fokkink, R.; Joosten, B.; Stuart, M.C.; Albericio, F.; Torensma, R.; Figdor, C.G. Targeted PLGA nano-but not microparticles specifically deliver antigen to human dendritic cells via DC-SIGN in vitro. J. Control. Release 2010, 144, 118–126. [Google Scholar] [CrossRef] [PubMed]
  38. Chong, C.S.; Cao, M.; Wong, W.W.; Fischer, K.P.; Addison, W.R.; Kwon, G.S.; Tyrrell, D.L.; Samuel, J. Enhancement of T helper type 1 immune responses against hepatitis B virus core antigen by PLGA nanoparticle vaccine delivery. J. Control. Release 2005, 102, 85–99. [Google Scholar] [CrossRef] [PubMed]
  39. Wendorf, J.; Chesko, J.; Kazzaz, J.; Ugozzoli, M.; Vajdy, M.; O’Hagan, D.; Singh, M. A comparison of anionic nanoparticles and microparticles as vaccine delivery systems. Hum. Vaccin. 2008, 4, 44–49. [Google Scholar] [CrossRef] [PubMed]
  40. Solbrig, C.; Saucier-Sawyer, J.; Cody, V.; Saltzman, W.; Hanlon, D. Polymer nanoparticles for immunotherapy from encapsulated tumor-associated antigens and whole tumor cells. Mol. Pharm. 2007, 4, 47–57. [Google Scholar] [CrossRef] [PubMed]
  41. Diwan, M.; Elamanchili, P.; Cao, M.; Samuel, J. Dose sparing of CpG oligodeoxynucleotide vaccine adjuvants by nanoparticle delivery. Curr. Drug Deliv. 2004, 1, 405–412. [Google Scholar] [CrossRef] [PubMed]
  42. Danhier, F.; Ansorena, E.; Silva, J.M.; Coco, R.; Le Breton, A.; Préat, V. PLGA-based nanoparticles: An overview of biomedical applications. J. Control. Release 2012, 161, 505–522. [Google Scholar] [CrossRef] [PubMed]
  43. Hamdy, S.; Molavi, O.; Ma, Z.; Haddadi, A.; Alshamsan, A.; Gobti, Z.; Elhasi, S.; Samuel, J.; Lavasanifar, A. Co-delivery of cancer-associated antigen and Toll-like receptor 4 ligand in PLGA nanoparticles induces potent CD8+ T cell-mediated anti-tumor immunity. Vaccine 2008, 26, 5046–5057. [Google Scholar] [CrossRef] [PubMed]
  44. Cruz, L.J.; Tacken, P.J.; Fokkink, R.; Figdor, C.G. The influence of PEG chain length and targeting moiety on antibody-mediated delivery of nanoparticle vaccines to human dendritic cells. Biomaterials 2011, 32, 6791–6803. [Google Scholar] [CrossRef] [PubMed]
  45. Bivas-Benita, M.; Lin, M.Y.; Bal, S.M.; van Meijgaarden, K.E.; Franken, K.L.; Friggen, A.H.; Junginger, H.E.; Borchard, G.; Klein, M.R.; Ottenhoff, T.H. Pulmonary delivery of DNA encoding Mycobacterium tuberculosis latency antigen Rv1733c associated to PLGA–PEI nanoparticles enhances T cell responses in a DNA prime/protein boost vaccination regimen in mice. Vaccine 2009, 27, 4010–4017. [Google Scholar] [CrossRef] [PubMed]
  46. Prego, C.; Paolicelli, P.; Díaz, B.; Vicente, S.; Sánchez, A.; González-Fernández, Á.; Alonso, M.J. Chitosan-based nanoparticles for improving immunization against hepatitis B infection. Vaccine 2010, 28, 2607–2614. [Google Scholar] [CrossRef] [PubMed]
  47. Barzegar-Jalali, M. Nanovaccine for leishmaniasis: Preparation of chitosan nanoparticles containing Leishmania superoxide dismutase and evaluation of its immunogenicity in BALB/c mice. Int. J. Nanomedicine 2011, 6, 835–842. [Google Scholar]
  48. Vila, A.; Sánchez, A.; Janes, K.; Behrens, I.; Kissel, T.; Jato, J.L.; Alonso, M.J. Low molecular weight chitosan nanoparticles as new carriers for nasal vaccine delivery in mice. Eur. J. Pharm. Biopharm. 2004, 57, 123–131. [Google Scholar] [CrossRef] [PubMed]
  49. Correia-Pinto, J.F.; Csaba, N.; Schiller, J.T.; Alonso, M.J. Chitosan-poly (I: C)-PADRE based nanoparticles as delivery vehicles for synthetic peptide vaccines. Vaccines 2015, 3, 730–750. [Google Scholar] [CrossRef] [PubMed]
  50. Sarti, F.; Perera, G.; Hintzen, F.; Kotti, K.; Karageorgiou, V.; Kammona, O.; Kiparissides, C.; Bernkop-Schnürch, A. In vivo evidence of oral vaccination with PLGA nanoparticles containing the immunostimulant monophosphoryl lipid A. Biomaterials 2011, 32, 4052–4057. [Google Scholar] [CrossRef] [PubMed]
  51. Ataman-Önal, Y.; Munier, S.; Ganée, A.; Terrat, C.; Durand, P.Y.; Battail, N.; Martinon, F.; Le Grand, R.; Charles, M.H.; Delair, T. Surfactant-free anionic PLA nanoparticles coated with HIV-1 p24 protein induced enhanced cellular and humoral immune responses in various animal models. J. Control. Release 2006, 112, 175–185. [Google Scholar] [CrossRef] [PubMed]
  52. Okamoto, S.; Yoshii, H.; Akagi, T.; Akashi, M.; Ishikawa, T.; Okuno, Y.; Takahashi, M.; Yamanishi, K.; Mori, Y. Influenza hemagglutinin vaccine with poly (γ-glutamic acid) nanoparticles enhances the protection against influenza virus infection through both humoral and cell-mediated immunity. Vaccine 2007, 25, 8270–8278. [Google Scholar] [CrossRef] [PubMed]
  53. Singh, J.; Pandit, S.; Bramwell, V.W.; Alpar, H.O. Diphtheria toxoid loaded poly-(ε-caprolactone) nanoparticles as mucosal vaccine delivery systems. Methods 2006, 38, 96–105. [Google Scholar] [CrossRef] [PubMed]
  54. Hirosue, S.; Kourtis, I.C.; van der Vlies, A.J.; Hubbell, J.A.; Swartz, M.A. Antigen delivery to dendritic cells by poly (propylene sulfide) nanoparticles with disulfide conjugated peptides: Cross-presentation and T cell activation. Vaccine 2010, 28, 7897–7906. [Google Scholar] [CrossRef] [PubMed]
  55. Thomas, C.; Rawat, A.; Hope-Weeks, L.; Ahsan, F. Aerosolized PLA and PLGA nanoparticles enhance humoral, mucosal and cytokine responses to hepatitis B vaccine. Mol. Pharm. 2011, 8, 405–415. [Google Scholar] [CrossRef] [PubMed]
  56. Marrache, S.; Dhar, S. Engineering of blended nanoparticle platform for delivery of mitochondria-acting therapeutics. Proc. Natl. Acad. Sci. USA 2012, 109, 16288–16293. [Google Scholar] [CrossRef] [PubMed]
  57. Jain, A.K.; Goyal, A.K.; Mishra, N.; Vaidya, B.; Mangal, S.; Vyas, S.P. PEG-PLA-PEG block copolymeric nanoparticles for oral immunization against hepatitis B. Int. J. Pharm. 2010, 387, 253–262. [Google Scholar] [CrossRef] [PubMed]
  58. Gou, M.; Dai, M.; Li, X.; Yang, L.; Huang, M.; Wang, Y.; Kan, B.; Lu, Y.; Wei, Y.; Qian, Z. Preparation of mannan modified anionic PCL–PEG–PCL nanoparticles at one-step for bFGF antigen delivery to improve humoral immunity. Colloids Surf. B: Biointerfaces 2008, 64, 135–139. [Google Scholar] [CrossRef] [PubMed]
  59. Slütter, B.; Bal, S.; Keijzer, C.; Mallants, R.; Hagenaars, N.; Que, I.; Kaijzel, E.; van Eden, W.; Augustijns, P.; Löwik, C. Nasal vaccination with N-trimethyl chitosan and PLGA based nanoparticles: Nanoparticle characteristics determine quality and strength of the antibody response in mice against the encapsulated antigen. Vaccine 2010, 28, 6282–6291. [Google Scholar] [CrossRef] [PubMed]
  60. Ito, A.; Shinkai, M.; Honda, H.; Kobayashi, T. Medical application of functionalized magnetic nanoparticles. J. Biosci. Bioeng. 2005, 100, 1–11. [Google Scholar] [CrossRef] [PubMed]
  61. Ellens, H.; Bentz, J.; Szoka, F.C. Fusion of phosphatidylethanolamine-containing liposomes and mechanism of L. alpha.-HII phase transition. Biochemistry 1986, 25, 4141–4147. [Google Scholar] [CrossRef] [PubMed]
  62. Cui, Z.; Mumper, R.J. The effect of co-administration of adjuvants with a nanoparticle-based genetic vaccine delivery system on the resulting immune responses. Eur. J. Pharm. Biopharm. 2003, 55, 11–18. [Google Scholar] [CrossRef]
  63. Krishnamachari, Y.; Geary, S.M.; Lemke, C.D.; Salem, A.K. Nanoparticle delivery systems in cancer vaccines. Pharm. Res. 2011, 28, 215–236. [Google Scholar] [CrossRef] [PubMed]
  64. Diebold, Y.; Jarrín, M.; Sáez, V.; Carvalho, E.L.; Orea, M.; Calonge, M.; Seijo, B.; Alonso, M.J. Ocular drug delivery by liposome–chitosan nanoparticle complexes (LCS-NP). Biomaterials 2007, 28, 1553–1564. [Google Scholar] [CrossRef] [PubMed]
  65. Jeong, J.M.; Chung, Y.C.; Hwang, J.H. Enhanced adjuvantic property of polymerized liposome as compared to a phospholipid liposome. J. Biotechnol. 2002, 94, 255–263. [Google Scholar] [CrossRef]
  66. Chen, H.; Torchilin, V.; Langer, R. Polymerized liposomes as potential oral vaccine carriers: Stability and bioavailability. J. Control. Release 1996, 42, 263–272. [Google Scholar] [CrossRef]
  67. Malam, Y.; Loizidou, M.; Seifalian, A.M. Liposomes and nanoparticles: Nanosized vehicles for drug delivery in cancer. Trends Pharmacol. Sci. 2009, 30, 592–599. [Google Scholar] [CrossRef] [PubMed]
  68. Bhargava, A.; Mishra, D.; Khan, S.; Varshney, S.K.; Banerjee, S.; Mishra, P.K. Assessment of tumor antigen-loaded solid lipid nanoparticles as an efficient delivery system for dendritic cell engineering. Nanomedicine 2013, 8, 1067–1084. [Google Scholar] [CrossRef] [PubMed]
  69. Meidenbauer, N.; Harris, D.; Spitler, L.; Whiteside, T. Generation of PSA-reactive effector cells after vaccination with a PSA-based vaccine in patients with prostate cancer. Prostate 2000, 43, 88–100. [Google Scholar] [CrossRef]
  70. North, S.A.; Graham, K.; Bodnar, D.; Venner, P. A pilot study of the liposomal MUC1 vaccine BLP25 in prostate specific antigen failures after radical prostatectomy. J. Urol. 2006, 176, 91–95. [Google Scholar] [CrossRef]
  71. Butts, C.; Socinski, M.A.; Mitchell, P.L.; Thatcher, N.; Havel, L.; Krzakowski, M.; Nawrocki, S.; Ciuleanu, T.E.; Bosquée, L.; Trigo, J.M.; et al. Tecemotide (L-BLP25) versus placebo after chemoradiotherapy for stage III non-small-cell lung cancer (START): A randomised, double-blind, phase 3 trial. Lancet Oncol. 2014, 15, 59–68. [Google Scholar] [CrossRef]
  72. Villa, C.H.; Dao, T.; Ahearn, I.; Fehrenbacher, N.; Casey, E.; Rey, D.A.; Korontsvit, T.; Zakhaleva, V.; Batt, C.A.; Philips, M.R. Single-walled carbon nanotubes deliver peptide antigen into dendritic cells and enhance IgG responses to tumor-associated antigens. ACS Nano 2011, 5, 5300–5311. [Google Scholar] [CrossRef] [PubMed]
  73. Kuang, Y.; Zhao, L.; Zhang, S.; Zhang, F.; Dong, M.; Xu, S. Morphologies, preparations and applications of layered double hydroxide micro-/nanostructures. Materials 2010, 3, 5220–5235. [Google Scholar] [CrossRef]
  74. Xu, Z.P.; Niebert, M.; Porazik, K.; Walker, T.L.; Cooper, H.M.; Middelberg, A.P.; Gray, P.P.; Bartlett, P.F.; Lu, G.Q. Subcellular compartment targeting of layered double hydroxide nanoparticles. J. Control. Release 2008, 130, 86–94. [Google Scholar] [CrossRef] [PubMed]
  75. Yan, S.; Rolfe, B.E.; Zhang, B.; Mohammed, Y.H.; Gu, W.; Xu, Z.P. Polarized immune responses modulated by layered double hydroxides nanoparticle conjugated with CpG. Biomaterials 2014, 35, 9508–9516. [Google Scholar] [CrossRef] [PubMed]
  76. Wang, J.; Zhu, R.; Gao, B.; Wu, B.; Li, K.; Sun, X.; Liu, H.; Wang, S. The enhanced immune response of hepatitis B virus DNA vaccine using SiO2@LDH nanoparticles as an adjuvant. Biomaterials 2014, 35, 466–478. [Google Scholar] [CrossRef] [PubMed]
  77. Wang, D.; Christopher, M.E.; Nagata, L.P.; Zabielski, M.A.; Li, H.; Wong, J.P.; Samuel, J. Intranasal immunization with liposome-encapsulated plasmid DNA encoding influenza virus hemagglutinin elicits mucosal, cellular and humoral immune responses. J. Clin. Virol. 2004, 31, 99–106. [Google Scholar] [CrossRef] [PubMed]
  78. Ito, A.; Matsuoka, F.; Honda, H.; Kobayashi, T. Antitumor effects of combined therapy of recombinant heat shock protein 70 and hyperthermia using magnetic nanoparticles in an experimental subcutaneous murine melanoma. Cancer Immunol. Immunother. 2004, 53, 26–32. [Google Scholar] [CrossRef] [PubMed]
  79. Alvarez, M.; Echechipia, S.; Garcia, B.; Tabar, A.; Martin, S.; Rico, P.; Olaguibel, J. Liposome-entrapped D. pteronyssinus vaccination in mild asthma patients: Effect of 1-year double-blind, placebo-controlled trial on inflammation, bronchial hyper-responsiveness and immediate and late bronchial responses to the allergen. Clin. Exp. Allergy 2002, 32, 1574–1582. [Google Scholar] [CrossRef] [PubMed]
  80. Rosada, R.S.; de la Torre, L.G.; Frantz, F.G.; Trombone, A.P.; Zárate-Bladés, C.R.; Fonseca, D.M.; Souza, P.R.; Brandão, I.T.; Masson, A.P.; Soares, É.G.; et al. Protection against tuberculosis by a single intranasal administration of DNA-hsp65 vaccine complexed with cationic liposomes. BMC Immunol. 2008, 9, 1–13. [Google Scholar] [CrossRef] [PubMed]
  81. Just, M.; Berger, R.; Drechsler, H.; Brantschen, S.; Glück, R. A single vaccination with an inactivated hepatitis A liposome vaccine induces protective antibodies after only two weeks. Vaccine 1992, 10, 737–739. [Google Scholar] [CrossRef]
  82. Zheng, L.; Huang, X.L.; Fan, Z.; Borowski, L.; Wilson, C.C.; Rinaldo, C.R. Delivery of liposome-encapsulated HIV type 1 proteins to human dendritic cells for stimulation of HIV type 1-specific memory cytotoxic T lymphocyte responses. AIDS Res. Hum. Retroviruses 1999, 15, 1011–1020. [Google Scholar] [CrossRef] [PubMed]
  83. Wilson, K.D.; de Jong, S.D.; Tam, Y.K. Lipid-based delivery of CpG oligonucleotides enhances immunotherapeutic efficacy. Adv. Drug Deliv. Rev. 2009, 61, 233–242. [Google Scholar] [CrossRef] [PubMed]
  84. Almeida, A.J.; Souto, E. Solid lipid nanoparticles as a drug delivery system for peptides and proteins. Adv. Drug Deliv. Rev. 2007, 59, 478–490. [Google Scholar] [CrossRef] [PubMed]
  85. Cui, Z.; Huang, L. Liposome-polycation-DNA (LPD) particle as a carrier and adjuvant for protein-based vaccines: Therapeutic effect against cervical cancer. Cancer Immunol. Immunother. 2005, 54, 1180–1190. [Google Scholar] [CrossRef] [PubMed]
  86. Kumar, A.; Kolar, S.S.; Zao, M.; McDermott, A.M.; Cai, C. Localization of antimicrobial peptides on polymerized liposomes leading to their enhanced efficacy against Pseudomonas aeruginosa. Mol. BioSyst. 2011, 7, 711–713. [Google Scholar] [CrossRef] [PubMed]
  87. Kossovsky, N.; Gelman, A.; Hnatyszyn, H.J.; Rajguru, S.; Garrell, R.L.; Torbati, S.; Freitas, S.S.; Chow, G.M. Surface-modified diamond nanoparticles as antigen delivery vehicles. Bioconjugate Chem. 1995, 6, 507–511. [Google Scholar] [CrossRef]
  88. Mendonça, E.; Diniz, M.; Silva, L.; Peres, I.; Castro, L.; Correia, J.B.; Picado, A. Effects of diamond nanoparticle exposure on the internal structure and reproduction of Daphnia magna. J. Hazard Mater. 2011, 186, 265–271. [Google Scholar] [CrossRef] [PubMed]
  89. Safari, D.; Marradi, M.; Chiodo, F.; Th Dekker, H.A.; Shan, Y.; Adamo, R.; Oscarson, S.; Rijkers, G.T.; Lahmann, M.; Kamerling, J.P. Gold nanoparticles as carriers for a synthetic Streptococcus pneumoniae type 14 conjugate vaccine. Nanomedicine 2012, 7, 651–662. [Google Scholar] [CrossRef] [PubMed]
  90. Lee, I.H.; Kwon, H.K.; An, S.; Kim, D.; Kim, S.; Yu, M.K.; Lee, J.H.; Lee, T.S.; Im, S.H.; Jon, S. Imageable Antigen-Presenting Gold Nanoparticle Vaccines for Effective Cancer Immunotherapy In Vivo. Angew. Chem. 2012, 124, 8930–8935. [Google Scholar] [CrossRef]
  91. Rogers, J.V.; Parkinson, C.V.; Choi, Y.W.; Speshock, J.L.; Hussain, S.M. A preliminary assessment of silver nanoparticle inhibition of monkeypox virus plaque formation. Nanoscale Res. Lett. 2008, 3, 129–133. [Google Scholar] [CrossRef]
  92. Lara, H.H.; Ayala-Nuñez, N.V.; Ixtepan-Turrent, L.; Rodriguez-Padilla, C. Mode of antiviral action of silver nanoparticles against HIV-1. J. Nanobiotechnol. 2010, 8, 1–8. [Google Scholar] [CrossRef] [PubMed]
  93. Frey, A.; Neutra, M.R.; Robey, F.A. Peptomer aluminum oxide nanoparticle conjugates as systemic and mucosal vaccine candidates: Synthesis and characterization of a conjugate derived from the C4 domain of HIV-1MN gp120. Bioconjugate Chem. 1997, 8, 424–433. [Google Scholar] [CrossRef] [PubMed]
  94. Uto, T.; Akagi, T.; Toyama, M.; Nishi, Y.; Shima, F.; Akashi, M.; Baba, M. Comparative activity of biodegradable nanoparticles with aluminum adjuvants: Antigen uptake by dendritic cells and induction of immune response in mice. Immunol. Lett. 2011, 140, 36–43. [Google Scholar] [CrossRef] [PubMed]
  95. Moon, J.J.; Suh, H.; Bershteyn, A.; Stephan, M.T.; Liu, H.; Huang, B.; Sohail, M.; Luo, S.; Um, S.H.; Khant, H. Interbilayer-crosslinked multilamellar vesicles as synthetic vaccines for potent humoral and cellular immune responses. Nat. Mater. 2011, 10, 243–251. [Google Scholar] [CrossRef] [PubMed]
  96. Plummer, E.M.; Manchester, M. Viral nanoparticles and virus-like particles: Platforms for contemporary vaccine design. Wiley Interdiscip. Rev. Nanomed. Nanobiotechnol. 2011, 3, 174–196. [Google Scholar] [CrossRef] [PubMed]
  97. Savard, C.; Laliberté-Gagné, M.È.; Babin, C.; Bolduc, M.; Guérin, A.; Drouin, K.; Forget, M.A.; Majeau, N.; Lapointe, R.; Leclerc, D. Improvement of the PapMV nanoparticle adjuvant property through an increased of its avidity for the antigen [influenza NP]. Vaccine 2012, 30, 2535–2542. [Google Scholar] [CrossRef] [PubMed]
  98. Okuno, J.; Maehashi, K.; Kerman, K.; Takamura, Y.; Matsumoto, K.; Tamiya, E. Label-free immunosensor for prostate-specific antigen based on single-walled carbon nanotube array-modified microelectrodes. Biosens. Bioelectron. 2007, 22, 2377–2381. [Google Scholar] [CrossRef] [PubMed]
  99. Wang, T.; Jiang, H.; Zhao, Q.; Wang, S.; Zou, M.; Cheng, G. Enhanced mucosal and systemic immune responses obtained by porous silica nanoparticles used as an oral vaccine adjuvant: Effect of silica architecture on immunological properties. Int. J. Pharm. 2012, 436, 351–358. [Google Scholar] [CrossRef] [PubMed]
  100. Goto, N.; Kato, H.; Maeyama, J.I.; Eto, K.; Yoshihara, S. Studies on the toxicities of aluminium hydroxide and calcium phosphate as immunological adjuvants for vaccines. Vaccine 1993, 11, 914–918. [Google Scholar] [CrossRef]
  101. Aggerbeck, H.; Fenger, C.; Heron, I. Booster vaccination against diphtheria and tetanus in man. Comparison of calcium phosphate and aluminium hydroxide as adjuvants—II. Vaccine 1995, 13, 1366–1374. [Google Scholar] [CrossRef]
  102. He, Q.; Mitchell, A.; Morcol, T.; Bell, S.J. Calcium phosphate nanoparticles induce mucosal immunity and protection against herpes simplex virus type 2. Clin. Diagn. Lab. Immunol. 2002, 9, 1021–1024. [Google Scholar] [CrossRef] [PubMed]
  103. Jones, L.S.; Peek, L.J.; Power, J.; Markham, A.; Yazzie, B.; Middaugh, C.R. Effects of adsorption to aluminum salt adjuvants on the structure and stability of model protein antigens. J. Biol. Chem. 2005, 280, 13406–13414. [Google Scholar] [CrossRef] [PubMed]
  104. Wang, S.; Liu, X.; Fisher, K.; Smith, J.G.; Chen, F.; Tobery, T.W.; Ulmer, J.B.; Evans, R.K.; Caulfield, M.J. Enhanced type I immune response to a hepatitis B DNA vaccine by formulation with calcium- or aluminum phosphate. Vaccine 2000, 18, 1227–1235. [Google Scholar] [CrossRef]
  105. Ludwig, C.; Wagner, R. Virus-like particles—universal molecular toolboxes. Curr. Opin. Biotechnol. 2007, 18, 537–545. [Google Scholar] [CrossRef] [PubMed]
  106. Crawford, S.E.; Labbe, M.; Cohen, J.; Burroughs, M.H.; Zhou, Y.J.; Estes, M.K. Characterization of virus-like particles produced by the expression of rotavirus capsid proteins in insect cells. J. Virol. 1994, 68, 5945–5952. [Google Scholar] [PubMed]
  107. Storni, T.; Ruedl, C.; Schwarz, K.; Schwendener, R.A.; Renner, W.A.; Bachmann, M.F. Nonmethylated CG motifs packaged into virus-like particles induce protective cytotoxic T cell responses in the absence of systemic side effects. J. Immunol. 2004, 172, 1777–1785. [Google Scholar] [CrossRef] [PubMed]
  108. Gahéry-Ségard, H.; Pialoux, G.; Charmeteau, B.; Sermet, S.; Poncelet, H.; Raux, M.; Tartar, A.; Lévy, J.P.; Gras-Masse, H.; Guillet, J.G. Multiepitopic B-and T-cell responses induced in humans by a human immunodeficiency virus type 1 lipopeptide vaccine. J. Virol. 2000, 74, 1694–1703. [Google Scholar] [CrossRef] [PubMed]
  109. Klinguer, C.; David, D.; Kouach, M.; Wieruszeski, J.M.; Tartar, A.; Marzin, D.; Levy, J.P.; Gras-Masse, H. Characterization of a multi-lipopeptides mixture used as an HIV-1 vaccine candidate. Vaccine 1999, 18, 259–267. [Google Scholar] [CrossRef]
  110. BenMohamed, L.; Wechsler, S.L.; Nesburn, A.B. Lipopeptide vaccines—yesterday, today, and tomorrow. Lancet Infect. Dis. 2002, 2, 425–431. [Google Scholar] [CrossRef]
  111. Minigo, G.; Scholzen, A.; Tang, C.K.; Hanley, J.C.; Kalkanidis, M.; Pietersz, G.A.; Apostolopoulos, V.; Plebanski, M. Poly-l-lysine-coated nanoparticles: A potent delivery system to enhance DNA vaccine efficacy. Vaccine 2007, 25, 1316–1327. [Google Scholar] [CrossRef] [PubMed]
  112. Locher, C.P.; Putnam, D.; Langer, R.; Witt, S.A.; Ashlock, B.M.; Levy, J.A. Enhancement of a human immunodeficiency virus env DNA vaccine using a novel polycationic nanoparticle formulation. Immunol. Lett. 2003, 90, 67–70. [Google Scholar] [CrossRef] [PubMed]
  113. Jiang, L.; Qian, F.; He, X.; Wang, F.; Ren, D.; He, Y.; Li, K.; Sun, S.; Yin, C. Novel chitosan derivative nanoparticles enhance the immunogenicity of a DNA vaccine encoding hepatitis B virus core antigen in mice. J. Gene Med. 2007, 9, 253–264. [Google Scholar] [CrossRef] [PubMed]
  114. Gómez, S.; Gamazo, C.; San Roman, B.; Ferrer, M.; Sanz, M.L.; Espuelas, S.; Irache, J.M. Allergen immunotherapy with nanoparticles containing lipopolysaccharide from Brucella ovis. Eur. J. Pharm. Biopharm. 2008, 70, 711–717. [Google Scholar] [CrossRef] [PubMed]
  115. Persing, D.H.; Coler, R.N.; Lacy, M.J.; Johnson, D.A.; Baldridge, J.R.; Hershberg, R.M.; Reed, S.G. Taking toll: Lipid A mimetics as adjuvants and immunomodulators. Trends Microbiol. 2002, 10, 32–37. [Google Scholar] [CrossRef]
  116. Li, A.; Qin, L.; Wang, W.; Zhu, R.; Yu, Y.; Liu, H.; Wang, S. The use of layered double hydroxides as DNA vaccine delivery vector for enhancement of anti-melanoma immune response. Biomaterials 2011, 32, 469–477. [Google Scholar] [CrossRef] [PubMed]
  117. Pathak, R.K.; Marrache, S.; Harn, D.A.; Dhar, S. Mito-DCA: A mitochondria targeted molecular scaffold for efficacious delivery of metabolic modulator dichloroacetate. ACS Chem. Biol. 2014, 9, 1178–1187. [Google Scholar] [CrossRef] [PubMed]
  118. Biswas, S.; Dodwadkar, N.S.; Sawant, R.R.; Koshkaryev, A.; Torchilin, V.P. Surface modification of liposomes with rhodamine-123-conjugated polymer results in enhanced mitochondrial targeting. J. Drug Target. 2011, 19, 552–561. [Google Scholar] [CrossRef] [PubMed]
  119. Midgley, M.; Thompson, C. The role of mitochondria in the uptake of methyltriphenylphosphonium ion by Saccharomyces cerevisiae. FEMS Microbiol. Lett. 1985, 26, 311–315. [Google Scholar] [CrossRef]
  120. Murphy, M.P. Targeting lipophilic cations to mitochondria. Biochim. Biophys. Acta 2008, 1777, 1028–1031. [Google Scholar] [CrossRef] [PubMed]
  121. Zhou, F.; Xing, D.; Wu, B.; Wu, S.; Ou, Z.; Chen, W.R. New insights of transmembranal mechanism and subcellular localization of noncovalently modified single-walled carbon nanotubes. Nano Lett. 2010, 10, 1677–1681. [Google Scholar] [CrossRef] [PubMed]
  122. Chen, L.B. Mitochondrial membrane potential in living cells. Annu. Rev. Cell Biol. 1988, 4, 155–181. [Google Scholar] [CrossRef] [PubMed]
  123. Appleby, R.D.; Porteous, W.K.; Hughes, G.; James, A.M.; Shannon, D.; Wei, Y.H.; Murphy, M.P. Quantitation and origin of the mitochondrial membrane potential in human cells lacking mitochondrial DNA. Eur. J. Biochem. 1999, 262, 108–116. [Google Scholar] [CrossRef] [PubMed]
  124. Schneider Berlin, K.R.; Ammini, C.V.; Rowe, T.C. Dequalinium induces a selective depletion of mitochondrial DNA from HeLa human cervical carcinoma cells. Exp. Cell Res. 1998, 245, 137–145. [Google Scholar] [CrossRef] [PubMed]
  125. Weissig, V.; Lizano, C.; Torchilin, V.P. Micellar delivery system for dequalinium-A lipophilic cationic drug with anticarcinoma activity. J. Liposome Res. 1998, 8, 391–400. [Google Scholar] [CrossRef]
  126. Wang, X.X.; Li, Y.B.; Yao, H.J.; Ju, R.J.; Zhang, Y.; Li, R.J.; Yu, Y.; Zhang, L.; Lu, W.L. The use of mitochondrial targeting resveratrol liposomes modified with a dequalinium polyethylene glycol-distearoylphosphatidyl ethanolamine conjugate to induce apoptosis in resistant lung cancer cells. Biomaterials 2011, 32, 5673–5687. [Google Scholar] [CrossRef] [PubMed]
  127. Deocaris, C.C.; Widodo, N.; Shrestha, B.G.; Kaur, K.; Ohtaka, M.; Yamasaki, K.; Kaul, S.C.; Wadhwa, R. Mortalin sensitizes human cancer cells to MKT-077-induced senescence. Cancer Lett. 2007, 252, 259–269. [Google Scholar] [CrossRef] [PubMed]
  128. Fantin, V.R.; Leder, P. F16, a mitochondriotoxic compound, triggers apoptosis or necrosis depending on the genetic background of the target carcinoma cell. Cancer Res. 2004, 64, 329–336. [Google Scholar] [CrossRef] [PubMed]
  129. Xiang, C.; Li, D.W.; Qi, Z.D.; Jiang, F.L.; Ge, Y.S.; Liu, Y. Synthesis of F16 conjugated with 5-fluorouracil and biophysical investigation of its interaction with bovine serum albumin by a spectroscopic and molecular modeling approach. Luminescence 2013, 28, 865–872. [Google Scholar] [CrossRef] [PubMed]
  130. Hickey, J.L.; Ruhayel, R.A.; Barnard, P.J.; Baker, M.V.; Berners-Price, S.J.; Filipovska, A. Mitochondria-targeted chemotherapeutics: The rational design of gold (I) N-heterocyclic carbene complexes that are selectively toxic to cancer cells and target protein selenols in preference to thiols. J. Am. Chem. Soc. 2008, 130, 12570–12571. [Google Scholar] [CrossRef] [PubMed]
  131. Marrache, S.; Pathak, R.K.; Dhar, S. Formulation and optimization of mitochondria-targeted polymeric nanoparticles. Methods Mol. Biol. 2015, 2, 103–112. [Google Scholar]
  132. Marrache, S.; Pathak, R.K.; Dhar, S. Detouring of cisplatin to access mitochondrial genome for overcoming resistance. Proc. Natl. Acad. Sci. USA 2014, 111, 10444–10449. [Google Scholar] [CrossRef] [PubMed]
  133. Feldhaeusser, B.; Platt, S.R.; Marrache, S.; Kolishetti, N.; Pathak, R.K.; Montgomery, D.J.; Reno, L.R.; Howerth, E.; Dhar, S. Evaluation of nanoparticle delivered cisplatin in beagles. Nanoscale 2015, 7, 13822–13830. [Google Scholar] [CrossRef] [PubMed]
  134. Pathak, R.K.; Dhar, S. A Nanoparticle Cocktail: Temporal Release of Predefined Drug Combinations. J. Am. Chem. Soc. 2015, 137, 8324–8327. [Google Scholar] [CrossRef] [PubMed]
  135. Kalathil, A.A.; Kumar, A.; Banik, B.; Ruiter, T.A.; Pathak, R.K.; Dhar, S. New formulation of old aspirin for better delivery. Chem. Commun. 2016, 52, 140–143. [Google Scholar] [CrossRef] [PubMed]
  136. Marrache, S.; Dhar, S. The energy blocker inside the power house: Mitochondria targeted delivery of 3-bromopyruvate. Chem. Sci. 2015, 6, 1832–1845. [Google Scholar] [CrossRef] [PubMed]
  137. Marrache, S.; Dhar, S. Biodegradable synthetic high-density lipoprotein nanoparticles for atherosclerosis. Proc. Natl. Acad. Sci. USA 2013, 110, 9445–9450. [Google Scholar] [CrossRef] [PubMed]
  138. Omura, T. Mitochondria-targeting sequence, a multi-role sorting sequence recognized at all steps of protein import into mitochondria. J. Biochem. 1998, 123, 1010–1016. [Google Scholar] [CrossRef] [PubMed]
  139. Neupert, W. Protein import into mitochondria. Annu. Rev. Biochem. 1997, 66, 863–917. [Google Scholar] [CrossRef] [PubMed]
  140. Kalafut, D.; Anderson, T.N.; Chmielewski, J. Mitochondrial targeting of a cationic amphiphilic polyproline helix. Bioorg. Med. Chem. Lett. 2012, 22, 561–563. [Google Scholar] [CrossRef] [PubMed]
  141. von Heijne, G. Mitochondrial targeting sequences may form amphiphilic helices. EMBO J. 1986, 5, 1335–1342. [Google Scholar] [PubMed]
  142. Yousif, L.F.; Stewart, K.M.; Kelley, S.O. Targeting Mitochondria with Organelle-Specific Compounds: Strategies and Applications. ChemBioChem 2009, 10, 1939–1950. [Google Scholar] [CrossRef] [PubMed]
  143. Metón, I.; Egea, M.; Fernández, F.; Eraso, M.A.; Baanante, I.V. The N-terminal sequence directs import of mitochondrial alanine aminotransferase into mitochondria. FEBS Lett. 2004, 566, 251–254. [Google Scholar] [CrossRef] [PubMed]
  144. Shokolenko, I.N.; Alexeyev, M.F.; LeDoux, S.P.; Wilson, G.L. TAT-mediated protein transduction and targeted delivery of fusion proteins into mitochondria of breast cancer cells. DNA Repair 2005, 4, 511–518. [Google Scholar] [CrossRef] [PubMed]
  145. Takaya, K.; Higuchi, Y.; Kitamoto, K.; Arioka, M. A cytosolic phospholipase A2-like protein in the filamentous fungus Aspergillus oryzae localizes to the intramembrane space of the mitochondria. FEMS Microbiol. Lett. 2009, 301, 201–209. [Google Scholar] [CrossRef] [PubMed]
  146. Marchenko, N.D.; Zaika, A.; Moll, U.M. Death signal-induced localization of p53 protein to mitochondria a potential role in apoptotic signaling. J. Biol. Chem. 2000, 275, 16202–16212. [Google Scholar] [CrossRef] [PubMed]
  147. Zhao, K.; Zhao, G.M.; Wu, D.; Soong, Y.; Birk, A.V.; Schiller, P.W.; Szeto, H.H. Cell-permeable peptide antioxidants targeted to inner mitochondrial membrane inhibit mitochondrial swelling, oxidative cell death, and reperfusion injury. J. Biol. Chem. 2004, 279, 34682–34690. [Google Scholar] [CrossRef] [PubMed]
  148. Thomas, D.A.; Stauffer, C.; Zhao, K.; Yang, H.; Sharma, V.K.; Szeto, H.H.; Suthanthiran, M. Mitochondrial targeting with antioxidant peptide SS-31 prevents mitochondrial depolarization, reduces islet cell apoptosis, increases islet cell yield, and improves posttransplantation function. J. Am. Soc. Nephrol. 2007, 18, 213–222. [Google Scholar] [CrossRef] [PubMed]
  149. Xun, Z.; Rivera-Sánchez, S.; Ayala-Peña, S.; Lim, J.; Budworth, H.; Skoda, E.M.; Robbins, P.D.; Niedernhofer, L.J.; Wipf, P.; McMurray, C.T. Targeting of XJB-5-131 to mitochondria suppresses oxidative DNA damage and motor decline in a mouse model of huntington’s disease. Cell Rep. 2012, 2, 1137–1142. [Google Scholar] [CrossRef] [PubMed]
  150. Wipf, P.; Xiao, J.; Jiang, J.; Belikova, N.A.; Tyurin, V.A.; Fink, M.P.; Kagan, V.E. Mitochondrial targeting of selective electron scavengers: Synthesis and biological analysis of hemigramicidin-TEMPO conjugates. J. Am. Chem. Soc. 2005, 127, 12460–12461. [Google Scholar] [CrossRef] [PubMed]
  151. Jiang, J.; Belikova, N.A.; Hoye, A.T.; Zhao, Q.; Epperly, M.W.; Greenberger, J.S.; Wipf, P.; Kagan, V.E. A mitochondria-targeted nitroxide/hemigramicidin S conjugate protects mouse embryonic cells against gamma irradiation. Int. J. Radiat. Oncol. Biol. Phys. 2008, 70, 816–825. [Google Scholar] [CrossRef] [PubMed]
  152. Robin, M.A.; Anandatheerthavarada, H.K.; Fang, J.K.; Cudic, M.; Otvos, L.; Avadhani, N.G. Mitochondrial targeted cytochrome P450 2E1 (P450 MT5) contains an intact N terminus and requires mitochondrial specific electron transfer proteins for activity. J. Biol. Chem. 2001, 276, 24680–24689. [Google Scholar] [CrossRef] [PubMed]
  153. Nargund, A.M.; Pellegrino, M.W.; Fiorese, C.J.; Baker, B.M.; Haynes, C.M. Mitochondrial import efficiency of ATFS-1 regulates mitochondrial UPR activation. Science 2012, 337, 587–590. [Google Scholar] [CrossRef] [PubMed]
  154. Jiang, L.; Li, L.; He, X.; Yi, Q.; He, B.; Cao, J.; Pan, W.; Gu, Z. Overcoming drug-resistant lung cancer by paclitaxel loaded dual-functional liposomes with mitochondria targeting and pH-response. Biomaterials 2015, 52, 126–139. [Google Scholar] [CrossRef] [PubMed]
  155. Nakase, I.; Okumura, S.; Katayama, S.; Hirose, H.; Pujals, S.; Yamaguchi, H.; Arakawa, S.; Shimizu, S.; Futaki, S. Transformation of an antimicrobial peptide into a plasma membrane-permeable, mitochondria-targeted peptide via the substitution of lysine with arginine. Chem. Commun. 2012, 48, 11097–11099. [Google Scholar] [CrossRef] [PubMed]
  156. Lee, C.; Zeng, J.; Drew, B.G.; Sallam, T.; Martin-Montalvo, A.; Wan, J.; Kim, S.J.; Mehta, H.; Hevener, A.L.; de Cabo, R.; et al. The mitochondrial-derived peptide MOTS-c promotes metabolic homeostasis and reduces obesity and insulin resistance. Cell Metab. 2015, 21, 443–454. [Google Scholar] [CrossRef] [PubMed]
  157. Flierl, A.; Jackson, C.; Cottrell, B.; Murdock, D.; Seibel, P.; Wallace, D.C. Targeted delivery of DNA to the mitochondrial compartment via import sequence-conjugated peptide nucleic acid. Mol. Ther. 2003, 7, 550–557. [Google Scholar] [CrossRef]
  158. Horton, K.L.; Stewart, K.M.; Fonseca, S.B.; Guo, Q.; Kelley, S.O. Mitochondria-penetrating peptides. Chem. Biol. 2008, 15, 375–382. [Google Scholar] [CrossRef] [PubMed]
  159. Kawamura, E.; Yamada, Y.; Yasuzaki, Y.; Hyodo, M.; Harashima, H. Intracellular observation of nanocarriers modified with a mitochondrial targeting signal peptide. J. Biosci. Bioeng. 2013, 116, 634–637. [Google Scholar] [CrossRef] [PubMed]
  160. Yamada, Y.; Harashima, H. Enhancement in selective mitochondrial association by direct modification of a mitochondrial targeting signal peptide on a liposomal based nanocarrier. Mitochondrion 2013, 13, 526–532. [Google Scholar] [CrossRef] [PubMed]
  161. Shedlock, D.J.; Shen, H. Requirement for CD4 T cell help in generating functional CD8 T cell memory. Science 2003, 300, 337–339. [Google Scholar] [CrossRef] [PubMed]
  162. Brossart, P.; Wirths, S.; Brugger, W.; Kanz, L. Dendritic cells in cancer vaccines. Exp. Hematol. 2001, 29, 1247–1255. [Google Scholar] [CrossRef]
  163. Banchereau, J.; Steinman, R.M. Dendritic cells and the control of immunity. Nature 1998, 392, 245–252. [Google Scholar] [CrossRef] [PubMed]
  164. Valitutti, S.; Müller, S.; Cella, M.; Padovan, E.; Lanzavecchia, A. Serial triggering of many T-cell receptors by a few peptide MHC complexes. Nature 1995, 375, 148–151. [Google Scholar] [CrossRef] [PubMed]
  165. Zhang, X.; Gordon, J.R.; Xiang, J. Advances in dendritic cell-based vaccine of cancer. Cancer Biother. Radiopharm. 2002, 17, 601–619. [Google Scholar] [CrossRef] [PubMed]
  166. Steinman, R.M.; Banchereau, J. Taking dendritic cells into medicine. Nature 2007, 449, 419–426. [Google Scholar] [CrossRef] [PubMed]
  167. Butterfield, L.H. Dendritic cells in cancer immunotherapy clinical trials: Are we making progress? Front. Immunol. 2013. [Google Scholar] [CrossRef] [PubMed]
  168. Gregoire, M.; Ligeza-Poisson, C.; Juge-Morineau, N.; Spisek, R. Anti-cancer therapy using dendritic cells and apoptotic tumour cells: Pre-clinical data in human mesothelioma and acute myeloid leukaemia. Vaccine 2003, 21, 791–794. [Google Scholar] [CrossRef]
  169. Figdor, C.G.; de Vries, I.J.; Lesterhuis, W.J.; Melief, C.J. Dendritic cell immunotherapy: Mapping the way. Nat. Med. 2004, 10, 475–480. [Google Scholar] [CrossRef] [PubMed]
  170. Lanzavecchia, A.; Sallusto, F. Regulation of T cell immunity by dendritic cells. Cell 2001, 106, 263–266. [Google Scholar] [CrossRef]
  171. Mayordomo, J.; Zorina, T.; Storkus, W.; Zitvogel, L.; Celluzzi, C.; Falo, L.; Melief, C.; Ildstad, S.; Kast, W.M.; Deleo, A. Bone marrow-derived dendritic cells pulsed with synthetic tumour peptides elicit protective and therapeutic antitumour immunity. Nat. Med. 1995, 1, 1297–1302. [Google Scholar] [CrossRef] [PubMed]
  172. Rahma, O.E.; Herrin, V.E.; Ibrahim, R.A.; Toubaji, A.; Bernstein, S.; Dakheel, O.; Steinberg, S.M.; Abu, E.R.; Mkrtichyan, M.; Berzofsky, J.A. Pre-immature dendritic cells (PIDC) pulsed with HPV16 E6 or E7 peptide are capable of eliciting specific immune response in patients with advanced cervical cancer. J. Transl. Med. 2014, 12, 1–10. [Google Scholar] [CrossRef] [PubMed]
  173. Rong, Y.; Qin, X.; Jin, D.; Lou, W.; Wu, L.; Wang, D.; Wu, W.; Ni, X.; Mao, Z.; Kuang, T. A phase I pilot trial of MUC1-peptide-pulsed dendritic cells in the treatment of advanced pancreatic cancer. Clin. Exp. Med. 2012, 12, 173–180. [Google Scholar] [CrossRef] [PubMed]
  174. Phuphanich, S.; Wheeler, C.J.; Rudnick, J.D.; Mazer, M.; Wang, H.; Nuno, M.A.; Richardson, J.E.; Fan, X.; Ji, J.; Chu, R.M. Phase I trial of a multi-epitope-pulsed dendritic cell vaccine for patients with newly diagnosed glioblastoma. Cancer Immunol. Immunother. 2013, 62, 125–135. [Google Scholar] [CrossRef] [PubMed]
  175. Tamayo, I.; Irache, J.M.; Mansilla, C.; Ochoa-Repáraz, J.; Lasarte, J.J.; Gamazo, C. Poly (anhydride) nanoparticles act as active Th1 adjuvants through Toll-like receptor exploitation. Clin. Vaccine Immunol. 2010, 17, 1356–1362. [Google Scholar] [CrossRef] [PubMed]
  176. Clements, C.; Griffiths, E. The global impact of vaccines containing aluminium adjuvants. Vaccine 2002, 20, 24–33. [Google Scholar] [CrossRef]
  177. Li, H.; Li, Y.; Jiao, J.; Hu, H.M. Alpha-alumina nanoparticles induce efficient autophagy-dependent cross-presentation and potent antitumour response. Nat. Nanotechnol. 2011, 6, 645–650. [Google Scholar] [CrossRef] [PubMed]
  178. Hamblin, M.R.; Hasan, T. Photodynamic therapy: A new antimicrobial approach to infectious disease? Photochem. Photobiol. Sci. 2004, 3, 436–450. [Google Scholar] [CrossRef] [PubMed]
  179. Juarranz, Á.; Jaén, P.; Sanz-Rodríguez, F.; Cuevas, J.; González, S. Photodynamic therapy of cancer. Basic principles and applications. Clin. Transl. Onco. 2008, 10, 148–154. [Google Scholar] [CrossRef]
  180. Triesscheijn, M.; Baas, P.; Schellens, J.H.; Stewart, F.A. Photodynamic therapy in oncology. Oncologist 2006, 11, 1034–1044. [Google Scholar] [CrossRef] [PubMed]
  181. Pozzi, L.A.; Maciaszek, J.W.; Rock, K.L. Both dendritic cells and macrophages can stimulate naive CD8 T cells in vivo to proliferate, develop effector function, and differentiate into memory cells. J. Immunol. 2005, 175, 2071–2081. [Google Scholar] [CrossRef] [PubMed]
  182. Fievez, V.; Plapied, L.; des Rieux, A.; Pourcelle, V.; Freichels, H.; Wascotte, V.; Vanderhaeghen, M.L.; Jerôme, C.; Vanderplasschen, A.; Marchand-Brynaert, J. Targeting nanoparticles to M cells with non-peptidic ligands for oral vaccination. Eur. J. Pharm. Biopharm. 2009, 73, 16–24. [Google Scholar] [CrossRef] [PubMed]
  183. Chen, W.C.; Kawasaki, N.; Nycholat, C.M.; Han, S.; Pilotte, J.; Crocker, P.R.; Paulson, J.C. Antigen delivery to macrophages using liposomal nanoparticles targeting sialoadhesin/CD169. PLoS ONE 2012, 7, e39039. [Google Scholar] [CrossRef] [PubMed]
  184. Zhou, H.; Zhao, K.; Li, W.; Yang, N.; Liu, Y.; Chen, C.; Wei, T. The interactions between pristine graphene and macrophages and the production of cytokines/chemokines via TLR-and NF-κB-related signaling pathways. Biomaterials 2012, 33, 6933–6942. [Google Scholar] [CrossRef] [PubMed]
  185. Hanley, C.; Thurber, A.; Hanna, C.; Punnoose, A.; Zhang, J.; Wingett, D. The Influences of Cell Type and ZnO Nanoparticle Size on Immune Cell Cytotoxicity and Cytokine Induction. Nanoscale Res. Lett. 2009, 4, 1409–1420. [Google Scholar] [CrossRef] [PubMed]
  186. Roy, R.; Tripathi, A.; Das, M.; Dwivedi, P.D. Cytotoxicity and uptake of zinc oxide nanoparticles leading to enhanced inflammatory cytokines levels in murine macrophages: Comparison with bulk zinc oxide. J. Biomed. Nanotechnol. 2011, 7, 110–111. [Google Scholar] [CrossRef] [PubMed]
  187. Liu, Y.; Jiao, F.; Qiu, Y.; Li, W.; Lao, F.; Zhou, G.; Sun, B.; Xing, G.; Dong, J.; Zhao, Y.; et al. The effect of Gd@C82(OH)22 nanoparticles on the release of Th1/Th2 cytokines and induction of TNF-α mediated cellular immunity. Biomaterials 2009, 30, 3934–3945. [Google Scholar] [CrossRef] [PubMed]
  188. Liu, Y.; Balachandran, Y.L.; Li, D.; Shao, Y.; Jiang, X. Polyvinylpyrrolidone-poly (ethylene glycol) modified silver nanorods can be a safe, noncarrier adjuvant for HIV vaccine. ACS Nano 2016, 10, 3589–3596. [Google Scholar] [CrossRef] [PubMed]
  189. Parry, A.L.; Clemson, N.A.; Ellis, J.; Bernhard, S.S.; Davis, B.G.; Cameron, N.R. Multicopy multivalent’ glycopolymer-stabilized gold nanoparticles as potential synthetic cancer vaccines. J. Am. Chem. Soc. 2013, 135, 9362–9365. [Google Scholar] [CrossRef] [PubMed][Green Version]
Figure 1. Overview of possible vaccines that can be generated using NPs.
Figure 1. Overview of possible vaccines that can be generated using NPs.
Vaccines 04 00018 g001
Figure 2. The schematic diagram of action of mitochondria targeted ZnPc NPs. Redrawn from Reference [21].
Figure 2. The schematic diagram of action of mitochondria targeted ZnPc NPs. Redrawn from Reference [21].
Vaccines 04 00018 g002
Table 1. Summary of possible mitochondrial targets for vaccine development.
Table 1. Summary of possible mitochondrial targets for vaccine development.
Cell typePossible targetsImmune responsePossible ApplicationRef.
Dendritic cell (DC)Mitochondrial DNA (mtDNA)Induces CD8+, IFN-γ, T cell response specific for tumor-associated mitochondrial antigensCancer[19]
Cytolytic T lymphocytesmtDNAControls the expression of maternally transmitted antigensHearing impairment[23,24]
Pyruvate dehydrogenase complexesIncreases CD8+ T cells for immune-pathogenesis of PBC.Primary biliary cirrhosis[25]
B cellsMitochondrial permeability transition pore (MPTP)Connects the B cell antigen receptor to the effector caspases of apoptotic cell deathacute cerebral ischemia[26]
Breast cancer cell (MCF-7) and DCsMitochondrial matrix (MM)Generates the apoptotic cancer cells providing tumor antigens for immune responseCancer[21,27]
4T1 cellMMIncreases pro-inflammatory IL-2, IL-6, IL-12, TNF-α cytokinesCancer[28]
T cellsBcl-xL/Bcl-2 proteins in outer mitochondrial membrane (OMM)SARM causes T cell death by inhibiting Bcl-xL and down regulating signal-regulated kinase phosphorylation for immune homeostasisInfluenza[29]
2-oxo-dehydrogenase enzymes in inner mitochondria membrane (IMM)Up regulates the expression of MHC class II, produces IL-2 cytokine in response to PDH-E2/BCKD-E2Primary biliary cirrhosis[30]
Electron transport chain (ETC)Generates ROS for the nuclear factor of activated T cells (NFAT) and IL-2 inductionCancer[31]
Cytolytic T lymphocytesPyruvate dehydrogenase complexesIncreases CD8+ T cells for immune-pathogenesis of PBCPrimary biliary cirrhosis[25]
Table 2. Polymeric NP based antigen delivery systems.
Table 2. Polymeric NP based antigen delivery systems.
Polymer SystemPreparation/Diameter (nm)Activity/OutcomeDelivery routeCommentsRef.
PLGADouble emulsion method/320 nmOVA and MPLA dual loading PLGA NPs show enhanced mucosal immune response with higher IgA titers production than individually loaded NPs.OralFDA approved delivery system, (OVA +MPLA) PLGA NPs were stable up to one month.[50]
PLADialysis method/300–600 nmHIV-1 p24 PLA NPs show the best CTL results, antibody production, cytokine secretion (IL-2, 4, 6, 10, INF-γ) within the controls.Subcutaneous injectionPLA NPs were stable for months[51]
PGADialysis method/200 nmThe hemagglutinin (HA) loaded PGA-NPs show enhanced CTL activity and greater production of IFN-γ, IL-4, and IL-6 in vitro. NPs vaccination shows better defense to influenza virus infection in vivo than controls.Subcutaneous injectionLow cost, safe, relatively abundance, water-soluble, biodegradable[52]
PMMAReflux-filtration methodsHIV-1 Tat Protein loaded PMMA NPs show efficient cellular uptake, well-patterned antigen release properties, and enhanced immune responses with greater proliferation index and cytokine level (INF-γ, IL-2) compared to Tat alone.IntramuscularCore-shell NPs were prepared. Tat was protected from oxidation. No severe damage was observed for Tat PMMA NPs.[53]
PPSEmulsion-incubation/size was not specifiedOVA loaded PPS NPs with longer peptide showed greater cellular uptake, enhanced IFN-γ secretion, and T cell activation both in vitro and in vivo.Tail vein injectionSurfactant pluronic F127 was used to stabilize NPs, PPS NPs internalized into cell via miscellaneous pathways.[54]
PLA-PLGADouble Emulsion-solvent evaporation method/450–800 nmHBsAg co-polymeric NPs show increased immune responses with enhanced sIgA levels and greater production of cytokines (IL-2, IFN-γ) in vivo.Intramuscular injection via pulmonary routeTo deliver hepatitis B vaccine; Certain toxicity to pulmonary epithelium still exists. Limited for oral vaccine delivery [55]
PLGA-PEG-TPPNano-precipitation methodZnPc loaded co-polymeric NPs showed greatly enhanced T cell activation with combination of photodynamic therapy.Ex vivoCopolymer is of non-immunogenic and nontoxic, and designed for mitochondria targeting delivery.[21,56]
PEG-PLA-PEGDouble emulsion & solvent evaporation/215 nmThe co-polymeric NPs showed elevated immune response in vivo. Cytokine levels (IFN-γ and IL-2) were greatly enhanced.OralThe NPs was stable in gastric and intestinal fluids. 90% of hepatitis B antigen was encapsulated.[57]
PCL–PEG–PCLEmulsion-solvent evaporation method/137 nmThe co-polymeric NPs delivery of bFGF antigen induces better antibody production for immune response in vivo than antigen alone.Subcutaneous injectionA few studies have been made on this co-polymeric system.[58]
ChitosanIonotropic gelation technique/160–200 nmrHBsAg loaded chitosan NPs induced pretty delay immune response but much greater production of IgG than conventional alum vaccines in vivo.Intramuscular or intranasalNPs could be damaged by centrifugation-resuspension cycles. NPs could release antigen in a well-controlled pattern.[46]
Chitoson-PLGAEmulsification-solvent extraction/448 nmChitoson/PLGA NPs show gradual release of OVA up to 100% in 15 days, effective cellular uptake by crossing nasal epithelium, efficient T cell proliferation and stimulation in vivo.NasalNPs charge, size, and antige release properties are critical factors for vaccination.[59]
PLA: poly(d,l-lactide); PCL: poly(ε-caprolactone); PGA: poly(γ-glutamic acid); PLGA: poly(lactic-co-glycolic acid); PEG: Polyethylene glycol; PCL: poly(ɛ-caprolactone); PPS: Poly(propylene sulfide); PMMA: poly(methylmethacrylate).
Table 3. A summary of liposome-based antigen delivery systems.
Table 3. A summary of liposome-based antigen delivery systems.
Liposome TypeExampleAdvantageDisadvantage
Liposomal NPE7 Peptide vaccinates against HPV [14]No hypersensitivity reactionsVulnerable to deoxyribonulease
Plasmid DNA vaccinates against influenza [77]
HSP70 targets tumors [78]
D. pteronyssinus vaccination againsts asthma [79]Do not create antibodies against the phospholipid componentsDo not target antigen-presenting cells well
DNA-hsp65 vaccinates against tuberculosis [80]Can release antigens over long period of timeShort systemic half life
Hepatitis A virus vaccinates against Hepatitis A [81]Potential to cross epithelial barriersDifficulty keeping certain molecules encapsulated
HIV type 1 vaccinates against AIDS [82]Low toxicity
Solid Lipid NPCystosine-guanine containing oligodeoxynucleotides (CpG ODN) antigen treats allergies and inflammatory disease [83]Stimulate a more effective immune response due to a good pharmacokinetic profilePoor stability and biodistribution
Capable of reversible denaturationLow loading capacity
Protein antigen vaccinates against hepatitis B and malaria [84]Quick production timeColloidal structures are present
Liposome-polycation-DNA (LPD)HPV 16 E7 protein used to vaccinate against cervical cancer and HPV [85]Safe toxicity profileMost effective targeting is with proteins
The plasmid DNA and cationic liposomes are immunostimulatory
Polymerized LiposomesCationic antimicrobial peptides (AMPs) vaccinates against Pseudomonas aeruginosa [86]Stable in the GI tractInconsistent targeting
Table 4. Summary of other NPs-based antigen delivery systems.
Table 4. Summary of other NPs-based antigen delivery systems.
Surface-Modified Diamond NPsMussel Adhesive Protein (MAP) antigenStrong and specific antibody responseStudies show that the NPs may adhere to the GI tract and block gut cells[87,88]
NPs have efficient surface exposure
Gold NPT-helper ovalbumin323–339 peptide (OVA323–339), CpG1668 oligodeoxynucleotideAble to deliver fully synthetic carbohydrate-antigens, larger accumulation in a local lymph nodeThey are highly polarizable and are prone to aggregation[89,90]
Silver NPCD4 and gp120 for HIV and monkey poxExhibit antiviral tendenciesTests show that these NPs aggregate in the presence of cations[91,92]
Has electrostatic double layer repulsion which stabilizes dispersion
Aluminum Oxide NPHIV gp120 C4 antigen for HIVLess inhibited by pinocytosis and phagocytosis once in the bodyTend to aggregate when the pH changes[93,94]
Surface charge is not particularly stable
Interbilayer-crosslinked multilamellar vesiclesVMP001- protein based malaria antigen for malariaElicit a powerful T-cell responseRapid release when exposed to endolysosomal lipases[95]
Papaya Mosaic Virus Capsid Protein NP (PapMV)Nucleoprotein Antigen for influenzaVery stable NPOnly been used when working with influenza[96,97]
Single Walled Carbon NanotubesProstate-Specific Antigen for prostate cancerHigh affinity for graphite structuresPoor survival times[98]
High selectivity
Active immune response
Silica NPBovine Serum Albumin for HIV, influenza, and HepatitisChemically stable, good biocompatibility, low toxicityIneffective for quick release[99]
Calcium Phosphate AdjuvantMucosal delivery of herpes simplex virus type 2 antigen against the herpes virusVery low toxicityTendency towards adverse reactions[100,101,102]
Epstein-Barr virus proteins against Epstein-Barr virus
Diphtheria Toxoid against DiphtheriaNo detectable immunoglobulin E responseRelatively small binding capacity
Tetanus Toxoid against tetanus
Aluminum Phosphate AdjuvantHepatitis B surface antigen against Hepatitis BEnhance antibody responses in DNA vaccinesThermal stability of the protein is reduced once absorbed[103,104]
Proteins absorb well if oppositely charged
Virus-like ParticlesHPV-16/18 against human papilloma virusCan be produced for mucosal deliveryIncapable of co-expression[105,106,107]
Cheap production
Hepatitis B core antigen against Hepatitis BVLP size is favorable for being taken up by dendritic cellsNot readily taken up by cells other than DCs
LipopeptidesHepatitis B vaccine, Human immunodeficiency virus vaccineHighly immunogenicRequire organic solvents or detergents[108,109,110]
Do not need ad adjuvantPoor stability over time
Bacterial DNAOvalbumin antigen against tumor growthActivate natural killer cellsLow immunogenicity[111,112,113]
Gp140 against human immunodeficiency virusCost efficientDNA is subject to degradation
Hepatitis B core antigen against Hepatitis BNon toxic
LipopolysaccharideBrucella against brucellosisBiodegradableHigh toxicity[114,115]
Allergy vaccinesGood bindingHigh inflammatory response
Layered double hydroxideOvalbumin against tumor, DNA against melanomaLow toxic, biocompatible, controllable antigen releaseToxic activity of LDHs still exists in in vitro and in vivo models[75,116]
Table 5. Summary of the lipophilic cations as mitochondria targeting moiety.
Table 5. Summary of the lipophilic cations as mitochondria targeting moiety.
Targeting moietyExamplesOutcomeRef.
Phospholipid (PL)-PEG-NH2Single walled carbon nanotube functionalization (SWNT-PL-PEG)To reduce nonspecific binding effect of SWNT surface. To improve the solubility of SWNTs in aqueous solutions. To accumulate in the mitochondria of normal and cancer cells[121]
TPP+PLGA-PEG-TPP as carrier for ZnPcTo induce cytotoxicity in cancer cells under light irradiation, which is used to activate DCs [21]
Rhodamine 123Liposomes-rhodamine-123-conjugated polymerLeast toxic among the liphophilic dye[118,122]
Facilitate the cellular association and internalization, direct the trafficking of NPs to mitochondria, and substantial cell killing was observed as the drug cargo
Methyltriphenyl phosphoniumNADid not protect against cell death.[119,123]
Δψm was selectively depolarized
Dequalinium (DQA)DQA-PEG(5000)-DSPETo cause cell death by inhibiting the mtDNA synthesis[124,125,126]
MKT-007NAA mitochondria localized cationic dye, causes selective death of cancer cells[127]
F16F16 conjugated with 5-fluorouracilF16 was used as a vehicle, selectively inhibits tumor cell proliferation and dissipates Δψm[128,129]
N-Heterocyclic Carbene (NHC)Gold(I)-NHC ComplexAu(I)-NHC complexes toxic to breast cancer cell (MDA-MB-231, MDA-MB-468), but not to normal cells[130]
Table 6. Summary of peptides with a mitochondria targeting sequence.
Table 6. Summary of peptides with a mitochondria targeting sequence.
Mitochondrial alanine aminotransferase (mALT)MSATRMQLLSPRNVRLLSRGRSELFAGGSGGGPRVRSLISPPLSSSSPGRALSSVSATRRGLPKEKMTENGVSSRAKVLTIDTThrough interaction with translocases of the outer and inner mitochondrial membranesExhibits higher affinity for L-alanine[143]
Amino acids 1–83 contains MTS
MTS-ExoIII-TAT-fusion proteinMLSRAVCGTSRQLAPALGYLGSRQMitochondrial matrixMore efficient in mtDNA damage and less repair to cancer cell[144]
AoPlaAMLSCTSPLLRGACHNMGAAKALRLRWTVPPAVLIALGSGALYTTSGQTLYYKNSVQQTDMitochondrial intermembrane spaceIt is a cytosolic phospholipase A2 (cPLA2) like protein[145]
p53 ProteinMLFNLRILLNNAAFRNGHNFMVRNFRCGQPLQLocalizes within the membrane compartmentMitochondrial accumulation of p53 is rapid, and precedes the apoptotic cascade.[146]
SS peptide2’,6’-dimethyltyrosine-D-Arg-Phe-Lys-NH2Inner mitochondrial membranePrevents mitochondrial depolarization[147,148]
XJB-5-1314-hydroxy-2,2,6,6-tetramethyl piperidine-1-oxyl conjugated to nitroxide-Leu-D-Phe-Pro-Val-OrnMitochondrial membraneROS/RNS scavenger[149]
Gramicidin SBoc-Leu-DPhe-Val-Orn(Cbz)-OMeMitochondrial membraneElectron scavenger[150]
Nitroxide/Hemigramicidin S ConjugateHemigramicidin S-4-amino-2,2,6,6-tetramethyl-piperidine-N-oxyl (hemi-GS-TEMPO) 5-125Accumulates at the interface of mitochondrial membraneActs as electron scavenger and provides the radioprotection of gamma[151]
COX1291–306MFTVGLDVDTRTYFTmtDNAStimulates the CD8+ IFN-γ+ T cell response specific for tumor-associated mitochondrial Ags[19]
Cytochrome P450 2E1 (P450 MT5)MAVLGITVALLGWMVILLFIMitochondrial out and inner membraneReacts with cytochrome P450 in mitochondria [152]
Activating transcription factor associated with stress-1 (ATFS-1)AAVAYREAARAEInner mitochondrial membraneATFS-1 is degraded in mitochondria, which helps to maintain the mitochondrial homeostasis[153]
KLA peptideD(KLAKLAK)2Mitochondrial membraneKLA lysine units interact with the membranes for mitochondria uptake via hydrogen bonding and electrostatic attraction[154]
RLA peptideD[RLARLAR]2Mitochondrial outer membraneThe substitution of D-lysines in KLA with D-arginines improves the plasma membrane permeability and increases mitochondrial accumulation of RLA (as early as 6 min)[155]
Mitochondrial open reading frame of the 12S rRNA-c (MOTS-c)MRWQEMGYIFYPRKLRmtDNA16-amino-acid peptide, which promotes metabolic homeostasis and prevents the obesity and insulin resistance [156]
Y- or M-conjugateNH2-MLSLRQSIRFFKPAT-o-o-N-TTCCTCGCTCACT-c (Y conjugate)MatrixAccesses into the matrix through outer and inner mitochondria protein import channels [157]
Mitochondria-penetrating peptides (MPPs)FX-r-FX-K-FX-r-FX-K, F-r-F-K-F-r-F-K, F-r-FX-K-F-r-FX-K, F-r-Y-K-F-r-Y-K, FX-r-FX-K,F-r-F-K, F-r-FX-K, F-r-F2-K, F-r-Nap-K, F-r-Hex-K, F-r-YMe-K, F-r-FF-K, F-r-Y-K, Y-r-Y-KMatrixSystematic series of MPPs were studied, delivery of nonpolar species into mitochondria has been demonstrated to be successful[158]
MTS-Cys peptideNH2-MVSGSSGLAAARLLSRTFLLQQNGIRHGSYCMitochondrial outer membraneMTS peptide can be enhanced slightly outer stearyl-R8 modification[159,160]

Share and Cite

MDPI and ACS Style

Wen, R.; Umeano, A.C.; Francis, L.; Sharma, N.; Tundup, S.; Dhar, S. Mitochondrion: A Promising Target for Nanoparticle-Based Vaccine Delivery Systems. Vaccines 2016, 4, 18.

AMA Style

Wen R, Umeano AC, Francis L, Sharma N, Tundup S, Dhar S. Mitochondrion: A Promising Target for Nanoparticle-Based Vaccine Delivery Systems. Vaccines. 2016; 4(2):18.

Chicago/Turabian Style

Wen, Ru, Afoma C. Umeano, Lily Francis, Nivita Sharma, Smanla Tundup, and Shanta Dhar. 2016. "Mitochondrion: A Promising Target for Nanoparticle-Based Vaccine Delivery Systems" Vaccines 4, no. 2: 18.

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop