Search Results (133)

Adjuvants are chemical substances used in vaccines to enhance immunogenicity. Among them, aluminum-based nanoparticles are some of the oldest and most widely employed adjuvants in vaccine formulations. A key function of aluminum adjuvants is thought to involve acting as an antigen depot, enabling slow antigen release and providing sufficient time for effective immune activation. Therefore, understanding antigen–adjuvant interactions is essential, as these interactions influence antigen stability, release kinetics, and overall vaccine performance. In this study, we investigated how the physicochemical properties of aluminum hydroxide nanoparticles modulate antigen–protein interactions and affect protein stability. Nanoparticles synthesized under acidic (pH » 5.0) to near-neutral (pH » 7.1) conditions exhibited lower crystallinity, reduced hydroxyl density, and higher interfacial hydration, whereas those prepared under basic conditions (pH » 9.0) displayed increased crystallinity, enriched surface hydroxyl groups, and markedly reduced hydration. Antigen proteins bound to low-crystallinity aluminum hydroxide nanoparticles showed improved thermal stability, while those associated with highly crystalline nanoparticles exhibited reduced thermal stability. Complementary ITC study further suggests that these stability differences are accompanied by changes in their interaction behavior. These findings indicate that the structural and interfacial properties of aluminum hydroxide nanoparticles strongly influence their interactions with antigen proteins and the resulting physical stability. Together, our results demonstrate that the balance among crystallinity, hydroxyl organization, and interfacial hydration governs the thermal behavior of antigen proteins adsorbed onto aluminum hydroxide. This work provides a rational design principle for engineering aluminum-based adjuvants that optimize antigen–protein stability in vaccine formulations. Full article

Background: A quadrivalent HPV vaccine (BPV) has been developed to prevent diseases caused by HPV types 6, 11, 16, and 18 for the first time in Iran. The BPV is composed of the papillomavirus major capsid protein L1, which serves as the primary target in the design of the prophylactic HPV vaccines. To enhance immunogenicity, BPV was formulated with an amorphous aluminum hydroxy phosphate sulfate adjuvant. Methods: The immunogenicity and safety of BPV were assessed through analyses of both humoral and cell-mediated immunity, single and repeated doses, and reproductive effects using animal models. Results: Acute toxicity assessments showed no abnormalities in ophthalmic examinations, biochemical profiles, hematological parameters, and gross pathology findings. Additionally, no mortality or abnormal clinical signs were observed during a 90-day repeated-dose toxicity study. While some inflammatory reactions were noted at the injection sites and in the liver tissues of BPV-treated groups, these reactions were resolved by day 90 after the initial BPV administration. Furthermore, no signs of toxicity were detected in F1 offspring, and no adverse effects were identified in maternal reproductive performance, fertility, or hematological or biochemical parameters throughout the study duration. The BPV candidate successfully induced T-cell proliferation and increased the proportions of CD₃⁺ CD₄⁺ and CD₃⁺ CD₈⁺ T cells. It also stimulated the secretion of both interferon gamma (IFN-γ) and interleukin-4 (IL-4) cytokines in splenocytes isolated from animal models after the third dose. Moreover, anti-HPV L1 IgG antibody production was confirmed on day 14 after administration of each of the three BPV vaccine doses. Conclusions: The findings suggest that BPV is a vaccine candidate that stimulates both cellular and humoral immunity and demonstrate its safety profile in animal models. Full article

Varicella-zoster virus (VZV) is a human neurotropic herpesvirus. The primary infection with VZV causes chickenpox and establishes latency in sensory and dorsal root ganglia. Viral reactivation leads to herpes zoster (HZ), which is accompanied by complications such as postherpetic neuralgia (PHN), causing a significant disease burden. At present, vaccination is the most effective preventive measure. We developed a recombinant zoster vaccine, gE/BFA01, which comprises truncated VZV glycoprotein E and the liposome-based adjuvant BFA01 (containing MPL and QS-21). In this study, we evaluated the recombinant zoster vaccine’s immunogenicity in a live attenuated VZV-primed C57BL/6N mouse model and explored the mechanism of action of the BFA01 adjuvant. The results indicate that the gE/BFA01 vaccine induces superior antibody responses and stronger cellular immune responses compared with gE with aluminum hydroxide. Furthermore, gE/BFA01 showed comparable immunogenicity to the licensed vaccine Shingrix. Mechanistic investigations revealed that the BFA01 adjuvant can enhance the recruitment of innate immune cells at the injection site, increase the expression of DCs surface maturation markers, and activate multiple inflammatory signaling pathways in lymph nodes. Collectively, these findings indicate that gE/BFA01 can induce potent humoral and cellular responses, supporting its further development as a high-efficiency vaccine candidate. Full article

This study evaluated the formulation and stability of a quadrivalent glycoconjugate Shigella vaccine candidate based on four predominant strains (S. flexneri; 2a, 3a, and 6, and S. sonnei) covering ~64% of global Shigella infections. Each glycoconjugate antigen consists of a strain-specific O-polysaccharide (O-PS) covalently linked to the carrier protein IpaB, a component of the Shigella type III secretion system. First, selective competitive ELISAs were developed to measure antigenicity of the four O-PS-IpaB conjugates formulated with different adjuvants (i.e., Alhydrogel^®, AH; Adju-phos^®, AP; and CpG-1018^®, CpG). Next, the monovalent S. sonnei O-PS-IpaB conjugate was studied to elucidate interactions with aluminum salt adjuvants (AH, AP) under different solution conditions. Third, the stability profiles of AH- or AP-adjuvanted S. sonnei O-PS-IpaB conjugate in various formulations (±CpG) were determined at different temperatures. Interestingly, incubation at 25 °C for 2 weeks resulted in increased antigenicity values when the antigen was bound to AP or AH, suggesting increased epitope exposure upon adjuvant binding. When bound to AP adjuvant at pH 5.8, the best glycoconjugate antigen stability was observed at elevated temperatures. The CpG adjuvant under these conditions, however, displayed incompatibility (i.e., material loss), presumably from precipitation due to lack of interaction with AP and presence of the detergent LDAO from the bulk antigen buffer. In contrast, the glycoconjugate antigen and CpG adjuvant were both bound to the AH adjuvant and stable at 2–8 °C, pH 7.0. This AH-CpG formulation of the O-PS-IpaB conjugate antigens was identified as a promising candidate for future animal immunogenicity testing. Full article

The ongoing global monkeypox outbreak since 2022 has highlighted the urgent need for vaccine development. Current vaccination strategies rely on cross-protective immunity provided by orthopoxvirus-based live-attenuated vaccines. However, these vaccines not only exhibit suboptimal efficacy against monkeypox virus (MPXV) but also raise safety concerns, particularly given the significant global overlap between MPXV infections and HIV. Owing to their superior safety profile and accessibility, recombinant subunit vaccines represent a highly promising platform for monkeypox vaccine development. In this study, we developed a subunit vaccine comprising A29L, B6R, and M1R antigens formulated with a proprietary nanoemulsion adjuvant and evaluated its immunogenicity and protective efficacy. In mice immunized with a prime-boost regimen of the three individual antigens combined with the nanoemulsion adjuvant, comparable serum IgG levels against each antigen were elicited. Both A29 and M1 formulations induced serum antibodies with potent neutralizing activity against MPXV and Vaccinia virus Western Reserve strain (VACV-WR). Notably, M1 antiserum exhibited stronger neutralization than A29 antiserum, whereas B6R immune serum showed no significant neutralizing activity. Splenocytes from B6R-immunized mice mounted a robust IFN-γ response, which was markedly lower in those immunized with A29 or M1. All three monovalent vaccines conferred complete survival following an intranasal lethal MPXV challenge, with M1 providing the strongest protection. In a lethal VACV-WR challenge model, only M1 immunization conferred significant protection. Histopathological analysis of lung tissues on day 5 post-infection revealed more pronounced inflammatory features in B6R-immunized mice compared to the nanoemulsion adjuvant control group. Furthermore, the nanoemulsion-adjuvanted bivalent A29L + B6R formulation induced significantly higher IgG and neutralizing antibody titers and demonstrated superior protective efficacy compared to the aluminum hydroxide-adjuvanted formulation. This comparative preclinical evaluation provides important evidence to support the development of a safe and effective subunit vaccine against monkeypox. Full article

Background/Objective: Alzheimer’s disease (AD) is a neurodegenerative condition characterized by oxidative stress, neuroinflammation, amyloidogenesis, and tau-related pathology. This study investigated the macronutrient and phytochemical composition of strawberry (S), lemon (L), and lemon juice-assisted strawberry (S/L) extracts and evaluated their neuroprotective efficacy relative to selenium (Se) in an aluminum chloride (AlCl₃)-induced rat model of AD. Methods: Macronutrients and phenolics were quantified in S, L, and S/L, and the extracts were profiled using high-performance liquid chromatography and electrospray ionization tandem mass-spectrometry. Male Sprague–Dawley rats received AlCl₃ with or without S, L, S/L, or Se, and their cognitive performance was assessed using the Morris water maze, Y-maze, and conditioned avoidance tests. Markers of oxidative status, inflammation, cholinergic function, apoptotic signaling, and Wnt3/β-catenin pathway activity were quantified in the brain tissue, and cortico-hippocampal morphology was examined. Results: The S/L extract showed the highest carbohydrate, protein, and lipid content. The total phenolic content was highest in S/L (60.46 mg gallic acid equivalents/g), followed by L (55.08) and S (44.75), with S/L also being the richest in gallic, ellagic, and chlorogenic acids. S/L attenuated AlCl₃-induced cognitive deficits, restored antioxidant status, suppressed neuroinflammation, improved cholinergic indices, modulated apoptotic signaling, and downregulated amyloidogenic and NLRP3 inflammasome markers, consistent with histological evidence of neuronal preservation. Conclusions: Lemon juice-assisted extraction enhanced the macronutrient and phenolic richness and multitarget neuroprotection of strawberries. S/L co-extracts represent promising functional food–derived adjuvants for AD management and support integrative compositional–mechanistic profiling to optimize natural product–based interventions. Full article

Influenza is a highly contagious disease and is transmitted by the upper respiratory tract. Vaccination is an effective strategy to prevent and control seasonal influenza. The current predominant split-inactivated influenza vaccine presents a high safety profile but has weak immunogenicity. The addition of adjuvants is one method to optimize the immunogenicity of the seasonal influenza vaccine. In this study, we compared the effect of aluminum (Alum), MF59-like adjuvant AddaVax, and ISA71 VG adjuvants for the seasonal split influenza vaccine in a mouse model based on the induction of influenza-virus-specific antibody levels, body weight changes, and survival rates after lethal challenge. Two very low and sub-optimal HA doses, 0.003 µg and 0.01 µg, representing the calculated amount of HA from the A/California/07/2009 (H1N1) strain only per mouse dose, were selected and used in this study. The 0.003 µg antigen (Ag) plus AddaVax showed the best adjuvant effect among these three adjuvants. The 0.01 µg Ag plus ISA 71 VG induced the highest total IgG, IgG1, and IgG2a. Both the 0.003 µg and 0.01 µg Ag plus AddaVax protected all the immunized mice from the lethal challenge, and Alum exhibited the protective potency intermediate between that of the AddaVax and ISA 71VG. The 0.01 µg Ag plus one of these three adjuvants could enhance the efficacy of the split influenza vaccine against lethal challenge. Therefore, AddaVax is the first candidate for the further development of the adjuvanted split seasonal influenza vaccine among these three adjuvants. These initial findings offer valuable guidance for selecting promising adjuvanted influenza vaccine formulations. Full article

Substance use disorders (SUDs) remain a major global health challenge with limited treatment options and high relapse rates. Vaccines that induce drug-sequestering antibodies have shown promise, but their efficacy is hindered by the poor immunogenicity of small-molecule haptens. Adjuvants, substances that enhance immune responses, are critical for overcoming this limitation and improving vaccine efficacy. This review synthesizes over two decades of preclinical and clinical research to guide rational adjuvant design for SUD vaccines. Five major adjuvant classes are examined: aluminum-salt adjuvants, emulsion adjuvants, toll-like receptor (TLR) agonists, protein immunopotentiators, and cytokine modulators. Their physicochemical properties, innate immune activation profiles, and applications in nicotine, stimulant, and opioid vaccines are discussed. Comparative analyses reveal pronounced drug-specific and carrier-specific variability. Case studies illustrate the superior performance of a complementary TLR-agonist pair in a nicotine nanovaccine versus its limited effect in oxycodone vaccines. They also reveal the differential efficacy of an oil-in-water emulsion adjuvant across antigen types. Four principles emerge: (i) no adjuvant is universally optimal; (ii) drug pharmacology influences immune signaling; (iii) adjuvant-carrier compatibility is important; (iv) complementary adjuvant pairings often outperform single agents. These insights support a precision-vaccinology paradigm that tailors adjuvant strategies to each drug class and the delivery vehicle, advancing the development of next-generation SUD vaccines. Full article

Background/Objectives: The global spread of Mycoplasma pneumoniae (MP) poses a significant threat to public health; however, no licensed vaccine for human use is currently available. The development of a safe and effective vaccine is a critical priority. This study systematically evaluated the protective efficacy and safety of an inactivated MP vaccine using different adjuvants and immunization routes. Methods: Mice were immunized with inactivated vaccines via either intramuscular (IM) injection with aluminum hydroxide (alum) or a combination of CpG+QS21 (CQ) or via intranasal (IN) administration of Flagellin from Salmonella Typhimurium (FLA-ST), a potent Toll-like receptor 5 (TLR5) agonist, as a mucosal adjuvant. Vaccine-induced immunogenicity, protective efficacy against MP challenge, and associated lung pathology were assessed. Results: Both IM-vaccinated groups (alum and CQ) exhibited robust systemic immune responses. However, upon subsequent MP challenge, these groups exhibited significant inflammatory pathology in the lung tissues. Notably, the CQ-adjuvanted group displayed severe pulmonary inflammatory infiltration. In stark contrast, compared with the IM-vaccinated group, the IN-immunized group with the FLA-ST mucosal adjuvant achieved significant clearance of MP from the lungs and showed markedly milder histopathological lung damage. Conclusions: Our findings suggest that IM immunization with CQ-adjuvanted inactivated vaccines may represent a suboptimal strategy for MP, given the risk of exacerbating lung immunopathology. Conversely, a mucosal immunization approach using the FLA-ST adjuvant demonstrates considerable promise, offering an effective balance between bacterial clearance and an improved safety profile, highlighting its potential for future MP vaccine development. Full article

Glycosylation plays a pivotal role in regulating the functions and immunogenicity of antigens. Targeting the receptor-binding domain (RBD) of the spike protein (S protein) of SARS-CoV-2, we examined the impact of different glycoforms on RBD antigen immunogenicity and the underlying mechanisms. IgG-specific antibody titers and pseudovirus neutralization were compared in mice immunized with RBD antigens bearing different glycoforms, which were prepared using glycoengineering-capable Pichia pastoris and mammalian cell expression systems with distinct glycosylation pathways. The glycosylation impacted the surface charges of the RBD antigen, and influenced its adsorption onto alum. This may further lead to variations in the antigen’s immunogenicity. The high-mannose variant of the RBD antigen (H-MAN/RBD) expressed in wild-type Pichia pastoris induced significantly higher IgG-specific antibody titers and pseudovirus neutralization activity compared with the complex RBD variant (Complex/RBD) expressed in mammalian cells (293F) or glycoengineering-capable Pichia pastoris. The rate of H-MAN/RBD adsorption onto aluminum hydroxide (alum) adjuvant was significantly higher than that of Complex/RBD. It was assumed that H-MAN/RBD might carry more negative charges because of its phosphomannose-modified surfaces, leading to a higher rate of adsorption onto the positively charged alum and enhancing the immune response. To assess the impact of phosphomannose modification on antigen immunogenicity, a yeast strain was engineered to prepare a low-mannose RBD antigen (L-MAN/RBD); additionally, a yeast strain was constructed to generate a low-phosphomannose-modified RBD antigen (L-MAN-P/RBD). In conclusion, phosphomannose modification substantially enhanced the immunogenicity of RBD by altering the surface charges of the RBD antigen and facilitating its adsorption onto alum. These findings offer novel insights and strategies for vaccine design and immunotherapeutic approaches. Full article

The use of vaccines incorporating subunit proteins and viral components has significantly increased in recent decades, emphasizing the need for more effective and modular adjuvants. This study examined saponins from Saponaria officinalis, regarded as one of the most promising plant sources for developing an adjuvant platform using nanocomplex formation. A nanoparticle adjuvant containing saponins from Saponaria officinalis can be used to stimulate a humoral immune response; this ability was demonstrated using a model that included various viral proteins. The humoral immune response enhanced by saponin-containing adjuvants can increase from four to sixteen times, depending on the type of antigen used. Additionally, this response surpasses that triggered by antigens paired with aluminum hydroxide and is comparable to responses induced by adjuvants that contain Quil A. The further investigation of these platforms may yield a broader range of immunostimulants that can enhance vaccine effectiveness. Full article

Vaccine adjuvants are non-immunogenic agents that enhance or modulate immune responses to co-administered antigens and are essential to modern vaccines. Despite their importance, few are approved for human use. The rise of new pathogens and limited efficacy of some existing vaccines underscore the need for more advanced and effective formulations, particularly for vulnerable populations. Aluminum-based adjuvants are commonly used in vaccines and effectively promote humoral immunity. However, they mainly induce a Th2-biased response, making them suboptimal for diseases requiring cell-mediated immunity. In contrast, saponin-based adjuvants from the Quillajaceae family elicit a more balanced Th1/Th2 response and generate antigen-specific cytotoxic T cells (CTL). Due to ecological damage and limited availability caused by overharvesting Quillaja saponaria Molina barks, efforts have intensified to identify alternative plant-derived saponins with enhanced efficacy and lower toxicity. Quillaja brasiliensis (A.St.-Hil. and Tul.) Mart. (syn. Quillaja lancifolia D.Don), a related species native to South America, is considered a promising renewable source of Quillajaceae saponins. In this review, we highlight recent advances in vaccine adjuvant research, with a particular focus on saponins extracted from Q. brasiliensis leaves as a sustainable alternative to Q. saponaria saponins. These saponin fractions are structurally and functionally comparable, exhibiting similar adjuvant activity when they were formulated with different viral antigens. An alternative application involves formulating saponins into nanoparticles known as ISCOMs (immune-stimulating complexes) or ISCOM-matrices. These formulations significantly reduce hemolytic activity while preserving strong immunoadjuvant properties. Therefore, research advances using saponin-based adjuvants (SBA) derived from Q. brasiliensis and their incorporation into new vaccine platforms may represent a viable and sustainable solution for the development of more less reactogenic, safer, and effective vaccines, especially for diseases that require a robust cellular immunity. Full article

Background: Chitosan, a family of polysaccharides composed of glucosamine and N-acetyl glucosamine, is a promising adjuvant candidate for eliciting potent immune response. Methods: This study compared the adjuvant effects of chitosan to those of empty lipid nanoparticles (eLNPs) and aluminum hydroxide (alum) following administration of recombinant SARS-CoV-2 spike immunogen in adult mice. Mice received the adjuvanted recombinant protein vaccine in a prime-boost regimen with four weeks interval. Subsequent analyses included serological assessment of antibody responses, evaluation of T cell activity, immune cell recruitment and cytokine profiles at injection site. Results: Compared to alum, chitosan induced a more balanced Th1/Th2 response, akin to that observed with eLNPs, demonstrating its ability to modulate both the humoral and cellular immune pathways. Chitosan induced a different proinflammatory cytokine (e.g., IL-1⍺, IL-2, IL-6, and IL-7) and chemokine (e.g., Eotaxin, IP-10, MIP-1a) profile compared to eLNPs and alum at the injection site and in the draining lymph nodes. Moreover, chitosan potentiated the recruitment of innate immune cells, with neutrophils accounting for about 40% of the infiltrating cells in the muscle, representing a ~10-fold increase compared to alum and a comparable level to eLNPs. Conclusions: These findings collectively indicate that chitosan has the potential to serve as an effective adjuvant, offering comparable, and potentially superior, properties to those of currently approved adjuvants. Full article

Nanoclays have gained attention in biological applications due to their biocompatibility, low toxicity, and cost-effectiveness. Layered double hydroxides (LDHs) are synthetic nanoclays that have been used as adjuvants and antigen carriers in nanovaccines developed through passive bioconjugation. However, performing active bioconjugation to bind antigens covalently and generate subunit nanovaccines remains unexplored. In this study, we investigated the synthesis, functionalization, and active conjugation of LDH nanoparticles to produce subunit nanovaccines with peptides from SARS-CoV-2. The synthesis of Mg-Al LDHs via a coprecipitation and hydrothermal treatment rendered monodisperse particles averaging 100 nm. Their functionalization with (3-aminopropyl)triethoxysilane was better than it was with other organosilanes. Glutaraldehyde was used as a linker to bind lysine as a model biomolecule to establish the best conditions for reductive amination. Finally, two peptides, P₂ and P₅ (epitopes of the SARS-CoV-2 spike protein), were bound on the surface of the LDH to produce two subunit vaccine candidates, reaching peptide concentrations of 125 and 270 µg/mL, respectively. The particles were characterized using DLS, TEM, XRD, TGA, DSC, and FTIR. The cytotoxicity studies revealed that the conjugate with P₂ was non-toxic up to 250 µg/mL, while the immunogenicity studies showed that this conjugate induced similar IgG titers to those reached when aluminum hydroxide was used as an adjuvant. Full article

Background: Outer Membrane Vesicles (OMVs), nanosized particles derived from Gram-negative bacteria, are promising vaccine carriers due to innate immunogenicity and self-adjuvant properties. Yet the systematic evaluations of OMV-associated toxicity remain limited. Methods: We developed a CRISPR/Cas9-engineered Salmonella enterica serovar Typhimurium ΔmsbB mutant (Mut4_STM) to produce detoxified OMVs (Mut4_OMVs) with enhanced yield. Subcutaneous immunization of BALB/c mice with Mut4_OMVs to evaluate safety, and the adjuvant efficacy was also determined by injecting Mut4_OMVs with Yersinia pestis F1Vmut or Bacillus anthracis PA_D4 antigens, mixing formulation, respectively. Results: Mut4_OMVs showed a 9-fold protein yield increase over wild-type OMVs. While all mice injected with wild-type OMVs died, 100% survival was observed in those receiving Mut4_OMVs. However, dose-dependent pathological alterations became evident in specific organs as the administration dose escalated, such as induced splenic extramedullary hematopoiesis and renal edema. Despite residual toxicity, 2–3 doses of 10 μg Mut4_OMVs elicited antigen-specific antibody titers comparable to aluminum adjuvant controls and superior T-cell immune responses. Conclusion: While Mut4_OMVs retain potent adjuvant activity, their residual toxicity necessitates further biocompatibility optimization for safe vaccine applications. Full article