Search Results (281)

Background: Enterotoxigenic Escherichia coli (ETEC) is a zoonotic pathogen causing diarrhea and mortality in infants and livestock. Its numerous serotypes necessitate the urgent development of multivalent vaccines for effective prevention, thereby reducing public health and economic threats. Methods: Computational bioinformatics analyses were conducted on five major ETEC adhesins structural subunits (FaeG, FanC, FasA, FimF41a, and FedF). Dominant epitopes were selected and concatenated via flexible linkers, incorporating the PADRE sequence and LTb adjuvant to design a multi-epitope fusion antigen (MEFA). The recombinant MEFA protein was expressed in a prokaryotic system. Furthermore, molecular dynamics simulations, docking, and immune simulations assessed structural stability and immunogenicity. Immunoreactivity was tested by Western blot. Murine immunization evaluated antibody responses, lymphocyte proliferation, cytokine secretion, and protection against ETEC challenge. Results: Structural modeling showed an extended conformation, with docking and simulations indicating strong immune activation. Western blot confirmed MEFA immunoreactivity. MEFA induced high antigen-specific antibody titers, enhanced splenocyte proliferation, and increased IFN-γ and IL-4 secretion, indicating a Th2-biased response in mice. Vaccinated mice survived lethal ETEC challenge and maintained intestinal integrity. Conclusions: The MEFA candidate vaccine effectively induces robust humoral and cellular immune responses and provides protection against ETEC infection, representing a promising strategy for next-generation multivalent ETEC vaccines. Full article

Background/Objectives: Streptococcus suis (SS), an important zoonotic pathogen, has caused significant economic losses to the global pig industry. Existing commercial vaccines for SS mainly provide effective protection against a single serotype. Due to the existence of many serotypes and their robust immune evasion capabilities, the development of multi-component subunit vaccines or multi-epitope vaccines that provide effective cross-protection against different strains of SS is a key focus of current research. Methods: We applied two-dimensional electrophoresis (2-DE) and immunoblotting to screen for candidate immunogens among the immunogenic cell wall proteins of SS. BALB/c mice were immunized intradermally with a multi-component, multi-epitope vaccine. The vaccine’s safety and immunogenicity were assessed via clinical monitoring, antibody titer detection, cytokine assays, and survival curve analyses. Results: In this study, eight immunogenic cell wall proteins (GH25, Pk, PdhA, Ldh, ExoA, Pgk, MalX, and Dnak) were successfully identified using MALDI-TOF-MS, all of which could induce high IgG antibody titers. Based on the conservation and immunoprotection demonstrated by these eight protective antigenic proteins, PdhA, Ldh, and MalX were screened to construct a multi-component subunit vaccine as a candidate vaccine for providing cross-protection against SS isolates of multiple serotypes. Challenge studies showed that mice immunized with the multi-component subunit vaccine (PdhA, Ldh, and MalX) were protected against challenges with the SS2 virulent strain ZY05719 (62.5% protection) and the SSChz virulent strain CZ130302 (75% protection). Subsequently, we utilized immunoinformatics techniques to design a novel multi-epitope vaccine (MVPLM) derived from the immunogenic proteins PdhA, Ldh, and MalX. However, challenge tests revealed that the MVPLM offered limited protection against SS. Conclusions: These data demonstrate that a multi-component subunit vaccine composed of PdhA, Ldh, and MalX proteins shows promise as a candidate universal vaccine against multiple SS serotypes. Full article

Background: Dengue virus infection is a significant challenge for global health, with 100 million symptomatic cases, 2.3 million DALYs and 20,000 deaths annually. Dengue vaccines must provide long-lasting immunity against all four virus serotypes, especially in dengue-naïve individuals, in order to avoid the severe manifestations of secondary infections. Methods: This scoping review summarizes current evidence on licensed dengue vaccines and vaccine candidates, focusing on immunogenicity, efficacy, and safety outcomes. To identify relevant trials, in October 2023 we queried ClinicalTrials.gov using the search term “dengue vaccines” to identify past and present vaccine candidates; the search was repeated in February 2025. Vaccines were categorized into licensed (CYD-TDV and TAK-003), late-stage (TV003/TV005), and early-stage candidates (TDEN, DPIV, V180, TVDV). Results: CYD-TDV (Dengvaxia^®) showed moderate efficacy in large trials, with higher efficacy in seropositive than in seronegative individuals. Following commercialization, an increased hospitalization risk was discovered in the latter group. Due to these findings and impossibility of screening for prior exposure in endemic settings newer vaccines are now preferred and CYD-TDV production has recently been discontinued due to declining demand. TAK-003 (Qdenga^®) demonstrated high efficacy against virologically confirmed dengue (VCD) and dengue-related hospitalization. This vaccine was generally well tolerated and is currently recommended by scientific societies and national authorities for travelers and by WHO for routine use in adults and children in endemic settings. TV003 and TV005, developed by NIAID, showed strong immunogenicity and efficacy in phase II trials and human challenge models. Preliminary results show that a single-dose of TV003 has an efficacy of 79.6% in seronegatives and 89.2% in seropositives against VCD at a 2-year follow-up. Both formulations elicited tetravalent responses with an acceptable safety profile. Other vaccine strategies, including TDEN (live-attenuated), DPIV (purified inactivated), V180 (subunit), and TVDV (DNA-based) are still in early-phase development and suffer from waning antibody titers and limited efficacy in naïve subjects. Conclusions: The development of a safe and effective vaccine remains complex due to immunologic challenges. Currently, TAK-003 is regarded as the best option for broad implementation, while TV003 and TV005 remain promising candidates due to their shorter schedule and robust immunogenicity. Further research is needed to optimize vaccine strategies in seronegative populations, immunocompromised subjects, older adults, and travelers. Full article

Background: Helcococcus kunzii, a facultative anaerobe and Gram-positive coccus, has been documented as a cunning pathogen, mainly in immunocompromised individuals, as evidenced by recent clinical and microbiological reports. It has been associated with a variety of polymicrobial infections, comprising diabetic foot ulcers, prosthetic joint infections, osteomyelitis, endocarditis, and bloodstream infections. Despite its emerging clinical relevance, no licensed vaccine or targeted immunotherapy currently exists for H. kunzii, and its rising resistance to conventional antibiotics presents a growing public health concern. Objectives: In this study, we employed an integrated subtractive proteomics and immunoinformatics pipeline to design a multi-epitope subunit vaccine (MEV) candidate against H. kunzii. Initially, pan-proteome analysis identified non-redundant, essential, non-homologous, and virulent proteins suitable for therapeutic targeting. Methods/Results: From these, two highly conserved and surface-accessible proteins, cell division protein FtsZ and peptidoglycan glycosyltransferase FtsW, were selected as promising vaccine targets. Comprehensive epitope prediction identified nine cytotoxic T-lymphocyte (CTL), five helper T-lymphocyte (HTL), and two linear B-cell (LBL) epitopes, which were rationally assembled into a 397-amino-acid-long chimeric construct. The construct was designed using appropriate linkers and adjuvanted with the cholera toxin B (CTB) subunit (NCBI accession: AND74811.1) to enhance immunogenicity. Molecular docking and dynamics simulations revealed persistent and high-affinity ties amongst the MEV and essential immune receptors, indicating a durable ability to elicit an immune reaction. In silico immune dynamic simulations predicted vigorous B- and T-cell-mediated immune responses. Codon optimization and computer-aided cloning into the E. coli K12 host employing the pET-28a(+) vector suggested high translational efficiency and suitability for bacterial expression. Conclusions: Overall, this computationally designed MEV demonstrates favorable immunological and physicochemical properties, and presents a durable candidate for subsequent in vitro and in vivo validation against H. kunzii-associated infections. Full article

SSB proteins play essential roles in DNA replication, recombination, and repair in bacteria, archaea, and eukarya. This study investigates the transcript levels, identification, expression and purification, subcellular localization, and immune protective potential of the SSB-like proteins of Eimeria necatrix (EnSSB), exploring its role in the development of E. necatrix and its potential as a candidate antigen for a subunit vaccine against avian coccidiosis. The level of EnSSB gene transcription was highest in unsporulated oocysts (UO), followed by gametocytes (GAM) (p < 0.05). The gene consisted of an open reading frame of 1488 nucleotides encoding a protein of 495 amino acid residues with a predicted molecular weight of 53.31 kDa. EnSSB contained a SSB domain with a conserved OB (oligonucleotide/oligosaccharide binding) fold. The molecular mass of the native protein, as determined by Western blot analysis, was ~58 kDa in second-generation merozoites (MZ-2) and UO. In addition to the 58 kDa band, four other bands (~98 kDa, ~82 kDa, ~36 kDa and ~28 kDa) were detected in GAM. No bands were detected in MZ-3. Indirect immunofluorescence and immuno-electron microscopy localized EnSSB in the cytoplasm of macrogametocytes but not in wall-forming bodies and oocyst wall. Animal challenge experiments demonstrated that rEnSSB elicited robust IgY responses, increased splenic T lymphocytes and body weight gain, reduced intestinal lesion scores and oocyst shedding, and presented anticoccidial index (ACI) more than 160. These findings not only offer a foundation for understanding the role of EnSSB protein in regulating the development of E. necatrix, but also present a potential protective antigen of E. necatrix for the development of a subunit vaccine against avian coccidiosis. Full article

Human metapneumovirus (HMPV) is a major cause of acute respiratory tract infections, particularly in infants, young children, older adults, and immunocompromised individuals. Since its discovery in 2001, the virus has been recognized for its significant clinical and socioeconomic impact. Despite extensive research, no licensed vaccines or antiviral therapies are currently available for HMPV. This review aims to synthesize current knowledge on HMPV prevention and treatment, and to highlight promising avenues for future interventions. Several monoclonal antibodies (mAbs) targeting conserved epitopes of the HMPV fusion (F) protein have shown strong neutralizing activity in vitro and in animal models, although none have reached clinical trials. Vaccine development, including subunit, live attenuated, vector-based, and mRNA platforms, is progressing, with some candidates showing promise in adult populations. However, data in children, especially seronegative infants, remain limited. Antiviral research has explored repurposed drugs such as ribavirin and probenecid, along with novel agents like fusion inhibitors and T-cell-based immunotherapies, though none are yet approved. The development of safe, effective interventions—especially multivalent approaches targeting multiple respiratory viruses—remains a high priority. Continued research is essential to bridge the gap between preclinical promise and clinical application and to reduce the burden of HMPV infection worldwide. Full article

Objectives: The construction of subunit vaccines based on antigens that can induce strong cellular immunity is a widely accepted strategy to develop new tuberculosis vaccines. This study screens immunogens with potential for subunit vaccine development from seven candidate antigens and then verifies their vaccine efficacy. Design: C57BL/6 mice were immunized subcutaneously with purified PPE19, PPE50, FadD21, Rv1505c, Rv1506c, Rv2035, and Rv0976c proteins formulated with Freund’s adjuvant to evaluate both the antigen-specific Th1 cellular immune responses and IgG level. After the vaccination of mice with recombined pcDNA3.1 expressing Rv0976c, intravenous or aerosol infection with M. tb were further challenged to assess protective efficacy. Results: Purified PPE19, PPE50, FadD21, and Rv0976c proteins generated strong antigen-specific Th1 cellular immune responses in mice. Compared to Ag85A, Rv0976c also stimulated higher IgG antibody level in mice. In particular, Rv0976c stimulated high and specific IgG antibody levels in serum from TB patients. The vaccination of mice with DNA vaccines expressing Rv0976c, followed by intravenous challenge with Bacillus Calmette–Guerin (BCG) Pasteur or M. tb, resulted in significant levels of protection that are comparable to or better than that afforded by the two leading antigens, Ag85A and PPE18. Conclusions: These results indicated that Rv0976c was a better protective antigen. Future studies to combine Rv0976c with other antigens and evaluate its effectiveness as a booster of BCG or as a therapeutic vaccine are warranted. Full article

Coccidiosis is a major parasitic disease that suppresses poultry productivity and causes significant global economic losses. Currently, controlling Eimeria parasites relies primarily on the use of anticoccidial drugs or live vaccines. However, these conventional control strategies face the dual constraints of escalating drug resistance and unsustainable economic expenditures. In this study, the efficacy of a chimeric subunit vaccine comprising Eimeria maxima Elongation Factor-1α (EmEF1α) and chicken chemokine Ligand-1 (ChXCL1) was assessed for protection against experimental Eimeria maxima infection. The synthetic gene fragment ChXCL1-EmEF1α was ligated to the pET28a vector and expressed in vitro. Western blot analysis confirmed the successful expression of the recombinant ChXCL1-EmEF1α protein. Chickens immunized with the ChXCL1-EmEF1α exhibited a significantly stronger IgY response and higher secretion of IL-2 and IL-17 compared to those vaccinated with recombinant ChXCL1 alone or challenged solely with E. maxima. Furthermore, the ChXCL1-EmEF1α group demonstrated enhanced anticoccidial effects, including reduced intestinal lesions, higher body weight gain, and lower oocyst shedding compared to control groups. Following E. maxima challenge, the EmEF1α and ChXCL1-EmEF1α groups demonstrated robust protective efficacy, achieving high ACI values of 182 and 178, respectively. In contrast, the ChXCL1 and UC groups exhibited significantly lower ACI values (150 and 149, respectively), indicating minimal protection. This improvement was also reflected in the immune response, with significantly elevated levels of CD4⁺ and CD8⁺ T cells in the ChXCL1-EmEF1α-treated chickens. Moreover, ChXCL1 acts as an effective adjuvant when fused with EmEF1α, enhancing the vaccine’s anticoccidial efficacy. These results suggest that the ChXCL1-EmEF1α chimeric immunogen is a promising candidate for developing subunit vaccines against E. maxima infections. Full article

Background: It is still challenging to develop effective vaccines against tumorigenic human gammaherpesviruses such as Epstein–Barr virus (EBV). A major obstacle is the lack of a small animal model that reproduces the natural infection course of human gammaherpesviruses to allow for proper assessment of vaccine efficacy. Murine gammaherpesvirus 68 (MHV68) is a natural pathogen of wild rodents and laboratory mice and therefore can be used as a surrogate for human gammaherpesviruses to evaluate vaccination strategies. Methods: In this study, two mRNA vaccine candidates were generated, one encoding a fusion protein of the MHV68 gH with the gL (gHgL-mRNA) and the other expressing the MHV68 gB protein (gB-mRNA). The immunogenicity and protective efficacy of the mRNA vaccine candidates were evaluated in a mouse model of MHV68 infection. Results: The gHgL-mRNA but not the gB-mRNA candidate vaccine was able to induce neutralizing antibodies in mice, whereas both vaccines could elicit antigen-specific T-cell responses. Following MHV68 intranasal inoculation, complete blocking of the establishment of viral latency was observed in some mice immunized with individual gHgL-mRNA or gB-mRNA vaccines. Notably, co-immunization with the two mRNA vaccines appeared to be more effective than individual vaccines, achieving sterile immunity in 50% of the vaccinated mice. Conclusions: This study demonstrates that immunization with mRNA platform-based subunit vaccines is indeed capable of preventing MHV68 latent infection, thus validating a safe and efficacious vaccination strategy that may be applicable to human gammaherpesviruses. Full article

Vaccination is the most effective method to counteract infectious diseases in farmed fish. It secures aquaculture production and safeguards the wild stock and aquatic ecosystem from catastrophic contagious diseases. In vaccine development, recombinant subunit vaccines are favorable candidates since they can be economically produced in large quantities without growing many pathogens, as in inactivated or attenuated vaccine production. However, recombinant subunit vaccines are often weak or deficient in immunogenicity, resulting in inadequate defenses against infections. Technologies that can increase the immunogenicity of recombinant subunit vaccines are in desperate need. Enhanced green fluorescence protein (EGFP) has a low antigenicity and is susceptible to folding changes and losing fluorescence after fusing with other proteins. Using these valuable features of EGFP, we comprehend two amphipathic alpha-helical peptides, AH1 and AH3, derived from Hepatitis C virus and Influenza A virus, respectively, that can induce high immune responses of their fused EGFP in fish without affecting their folding. AH3-EGFP has the most elevated cell binding, significantly 62% and 36% higher than EGFP and AH1-EGFP, respectively. Immunizations with AH1-EGFP or AH3-EGFP significantly induced higher anti-EGFP antibody levels 300–500-fold higher than EGFP immunization after the boost injection in rainbow trout. Our results suggest that AH1 and AH3 effectively increase the immunogenicity of EGFP without influencing its structure. Further validation of their value in other recombinant proteins is necessary to demonstrate their broader utility in enhancing the immunogenicity of subunit vaccines. We also suggest that EGFP and its variants are promising candidates for initially screening proper immunogenicity-enhancing peptides or proteins to advance recombinant subunit vaccine development. Full article

Toxoplasma gondii is an intracellular protozoan found worldwide that is capable of infecting nearly all warm-blooded animals, including humans. Its parasitic success lies in its capacity to create chronic infections while avoiding immune detection, altering host immune responses, and disrupting programmed cell death pathways. This review examines the complex relationship between T. gondii and host immunity, focusing on how the parasite influences innate and adaptive immune responses to survive in immune-privileged tissues. We present recent findings on the immune modulation specific to various parasite strains, the immunopathology caused by imbalanced inflammation, and how the parasite undermines host cell death mechanisms such as apoptosis, necroptosis, and pyroptosis. These immune evasion tactics enable prolonged intracellular survival and pose significant challenges for treatment and vaccine development. We also review advancements in therapeutic strategies, including host-directed approaches, nanoparticle drug delivery, and CRISPR-based technologies, along with progress in vaccine development from subunit and DNA vaccines to live-attenuated candidates. This review emphasizes the importance of T. gondii as a model for chronic infections and points out potential avenues for developing innovative therapies and vaccines aimed at toxoplasmosis and similar intracellular pathogens. Full article

Background: Vaccines that stimulate systemic and mucosal immunity to a level required to prevent SARS-CoV-2 infection and transmission are an unmet need. Highly protective hepatitis B and human papillomavirus nanoparticle vaccines highlight the potential of multivalent nanoparticle vaccine platforms to provide enhanced immunity. Here, we report the construction and characterization of self-assembling 60-subunit icosahedral nanoparticle SARS-CoV-2 vaccines using the bacterial enzyme lumazine synthase (LuS). Methods and Results: Nanoparticles displaying prefusion-stabilized SARS-CoV-2 spike ectodomains fused to the surface-exposed amino terminus of LuS were designed using structure-guided approaches. Negative stain-electron microscopy studies of purified nanoparticles were consistent with self assembly into 60-mer nanoparticles displaying 20 spike trimers. After two intramuscular doses, these purified spike-LuS nanoparticles elicited significantly higher SARS-CoV-2 neutralizing activity than spike trimers in vaccinated mice. Furthermore, intramuscular DNA priming and intranasal boosting with a SARS-CoV-2 LuS nanoparticle vaccine stimulated mucosal IgA responses. Conclusion: These data identify LuS nanoparticles as highly immunogenic SARS-CoV-2 vaccine candidates and support the further development of this platform against SARS-CoV-2 and its emerging variants. Full article

Background/Objectives: Beak and feather disease virus (BFDV) is the causative agent of psittacine beak and feather disease (PBFD), affecting psittacine birds. There is currently no commercial vaccine or treatment for this disease. This study developed a novel BFDV coat protein mRNA vaccine encapsidated by TMV coat protein to form pseudovirions (PsVs) and tested its immunogenicity alongside BFDV coat protein (CP) subunit and DNA vaccine candidates. Methods: mRNA and BFDV CP subunit vaccine candidates were produced in Nicotiana benthamiana and subsequently purified using PEG precipitation and gradient ultracentrifugation, respectively. The DNA vaccine candidate was produced in E. coli cells harbouring a plasmid with a BFDV1.1mer pseudogenome. Immunogenicity of the vaccine candidates was evaluated in African grey parrot chicks. Results: Successful purification of TMV PsVs harbouring the mRNA vaccine, and of the BFDV-CP subunit vaccine, was confirmed by SDS-PAGE and western blot analysis. TEM analyses confirmed formation of TMV PsVs, while RT-PCR and RT-qPCR cDNA amplification confirmed encapsidation of the mRNA vaccine candidate within TMV particles. Restriction digests verified presence of the BFDV1.1mer genome in the plasmid. Four groups of 5 ten-week-old African grey parrot (Psittacus erithacus) chicks were vaccinated and received two boost vaccinations 2 weeks apart. Blood samples were collected from all four groups on day 14, 28 and 42, and sera were analysed using indirect ELISA, which showed that all vaccine candidates successfully elicited specific anti-BFDV-CP immune responses. The subunit vaccine candidate showed the strongest immune response, indicated by higher binding titres (>6400), followed by the mRNA and DNA vaccine candidates. Conclusions: The candidate vaccines present an important milestone in the search for a protective vaccine against PBFD, and their inexpensive manufacture could considerably aid commercial vaccine development. Full article

A novel bivalent oral vaccine candidate against H5N1 and H9N2 avian influenza virus (AIV) was developed using Lactobacillus surface display technology without genetic modification. The hemagglutinin subunit 1 (HA1) antigens from both subtypes were fused to the surface layer-binding domain of Lactobacillus crispatus K313, expressed in Escherichia coli, and purified. Wild-type Lactobacillus johnsonii H31, isolated from chicken intestine, served as a delivery vehicle by adsorbing and stably displaying the HA1 proteins on its surface. This approach eliminates the need for bacterial engineering while utilizing lactobacilli’s natural capacity to protect surface-displayed antigens, as evidenced by HA1’s protease resistance. Mouse immunization studies demonstrated induction of strong systemic IgG and mucosal IgA responses against both H5N1 and H9N2 HA1. The system offers several advantages, including safety through non-GMO probiotics, potential for multivalent vaccine expansion, and intrinsic antigen protection by lactobacilli. These findings suggest this platform could enable development of cost-effective, multivalent AIV vaccines. Full article

Background/Objectives: Contagious agalactia (CA) is a disease typically caused by Mycoplasma agalactiae, affecting small ruminants worldwide and being endemic in certain countries. CA causes severe economic losses due to mastitis, agalactia, and arthritis. As an alternative to existing immunoprophylactic measures, this study aimed to develop a recombinant subunit vaccine against M. agalactiae and evaluate its specific immune response in goats. Methods: Goats were divided into three groups: group 1 received recombinant proteins (P40 and MAG_1560), group 2 received formalin-inactivated M. agalactiae, and group 3 received Tris-buffered saline (negative control). All solutions were emulsified in Freund’s adjuvant. Animals were monitored for 181 days. IgG antibody production was assessed by ELISA, and peripheral blood mononuclear cells (PBMCs) were analyzed by real-time PCR for the expression of IL-1β, IFN-γ, IL-12, and MHC class II genes. Results: M. agalactiae-specific antibody response was observed for six months in the sera of animals from group 1. Analysis of cytokine gene expression revealed increased IL-1β mRNA levels over time in both experimental groups. In group 1, IFN-γ mRNA levels increased with P40 stimulation and decreased with MAG_1560. IL-12 mRNA expression decreased over time in group 1 with P40 stimulation, whereas group 2 showed increased IL-12 expression for both proteins. MHC-II expression was stimulated in both groups. Conclusions: The recombinant proteins induced antibody production and cytokine expression, demonstrating immunogenic potential and supporting their promise as vaccine candidates capable of eliciting both humoral and cellular immune responses against M. agalactiae. Full article