Search Results (246)

Background/Objectives: SARS-CoV-2, the causative agent of COVID-19, has been responsible for more than seven million deaths worldwide since its emergence. The Bacillus Calmette–Guérin (BCG) vaccine, used for over 100 years to prevent tuberculosis, induces a Th1-prominent immune response that is important for protection against Mycobacterium tuberculosis, other mycobacteria, and intracellular pathogens. BCG has also been shown to induce innate immune memory and heterologous protection against non-related infections. Additionally, BCG has been used as a vector to express heterologous proteins, showing protective effects against various diseases, particularly respiratory viral infections, including SARS-CoV-2. In this report, we constructed two recombinant BCG strains as potential vaccine candidates based on the receptor-binding domain (RBD) of the Spike antigen: one expressing only the RBD protein (rBCG-RBD) and another expressing the RBD protein in fusion with the LTB (Escherichia coli Labile Toxin subunit B) adjuvant (rBCG-LTB-RBD). Methods: We evaluated the induction of SARS-CoV-2-specific humoral and cellular immune responses using these vaccine candidates in a prime–boost strategy with a booster dose using the rRBD protein (produced in cell culture) and the Alum adjuvant. Antisera were evaluated for neutralization of the Wuhan and Omicron SARS-CoV-2 pseudotyped virus. Results: Either immunization scheme (rBCG-RBD/rRBD or rBCG-LTB-RBD/rRBD) induced high IgG antibody titers, with antibody neutralization against a Wuhan SARS-CoV-2 pseudotyped virus after 10 weeks. The antibody levels induced by rBCG-RBD/rRBD were maintained for up to 9 months. Interestingly, only the sera from mice receiving the prime–boost with rBCG-LTB-RBD/rRBD showed cross-reactive neutralization against the Omicron SARS-CoV-2 pseudotyped virus. Immunization with rBCG-RBD or rBCG-LTB-RBD and a rRBD booster dose promoted the induction of specific CD4+ and CD8+ T cells producing Th1/Th2 cytokines (IL-4, TNF-α and IFN-γ). Conclusions: Our study highlights the potential of the prime–boost immunization strategy using rBCG-RBD/rRBD to induce long-term immunity and rBCG-LTB-RBD/rRBD to induce cross-protection against different variants, both of which could serve as promising vaccine candidates. Full article

Mucosal-associated invariant T (MAIT) cells exist in high numbers in the body and have a unique and highly conserved T cell receptor (TCR). They can be activated in a TCR-dependent manner by ligands presented on the monomorphic protein MHC class I-related protein 1 (MR1) which is found on many cell types, including professional antigen presenting cells (APCs) and epithelial cells. This has sparked interest in the potential to exploit the MR1-MAIT cell axis for the development of vaccines against infectious disease. Within this context an MR1 ligand, typically 5-(2-oxopropylideneamino)-d-ribitylaminouracil (5-OP-RU), is administered with or without a Toll-like receptor (TLR) ligand or cytokine in a pan vaccination approach that would prime the immune response to provide protection against a variety of bacterial and viral pathogens. This strategy has led to enhanced protection in murine models of Legionella longbeachae, Francisella tularensis, Klebsiella pneumoniae, Streptococcus pneumoniae and influenza infection. However, studies against Mycobacterium tuberculosis infection have proven less successful. The second vaccination approach involves pairing the MR1 ligand with more conventional antigens that could activate CD4⁺ and/or CD8⁺ T cells. This approach has been successful in murine models of cholera, influenza, and SARS-CoV-2, including in the context of subunit vaccines. However, there are several challenges when using MR1-MAIT cell-mediated vaccine adjuvants. These include the inherent instability of 5-OP-RU and the need for more advanced studies to better understand how the use of MR1 ligands would translate to applications in humans. This review will discuss these aspects and highlight the mechanistic studies that have been undertaken to understand how MAIT cells might elicit their effects within the context of MAIT cell-mediated vaccines for infectious disease. Full article

Outcomes of influenza virus infection vary widely across individuals, reflecting not only viral genetics and host factors but also the composition and function of the airway microbiome. Over the past few years, mechanistic work has clarified how specific commensals (for example, Staphylococcus epidermidis and Streptococcus oralis) restrict influenza replication by priming epithelial interferon-λ programs, reshaping intracellular metabolite pools (notably polyamines), dampening host protease activity, and maintaining barrier integrity; meanwhile, pathobionts (notably Staphylococcus aureus and Streptococcus pneumoniae) can enhance viral fitness via secreted proteases and neuraminidases that activate hemagglutinin and remodel sialylated glycoconjugates and mucus, setting the stage for secondary bacterial disease. Recent studies also highlight the gut–lung axis: gut microbiota-derived short-chain fatty acids (SCFAs), especially acetate, protect tight junctions and modulate antiviral immunity in influenza models. Together, these insights motivate translational strategies—from intranasal live biotherapeutics (LBPs) to metabolite sprays and decoy/dual neuraminidase approaches—that complement vaccines and antivirals. We synthesize recent evidence and outline a framework for leveraging the airway microbiome to prevent infection, blunt severity, and reduce transmission. Key priorities include strain-level resolution of commensal effects, timing/dosing windows for metabolites and LBPs, and microbiome-aware clinical pathways for anticipating and averting bacterial coinfection. Overall, the airway microbiome emerges as a tractable lever for influenza control at the site of viral entry, with several candidates moving toward clinical testing. Full article

Background: Developing an effective vaccine is crucial for the prevention and control of AIDS. Viral vector-based vaccines, particularly those utilizing homologous or heterologous prime-boost strategies, represent an important direction in current HIV vaccine research. Methods: In this study, replication-defective chimeric adenovirus Ad5F35 and modified vaccinia virus Ankara (rMVA) vector vaccines expressing the HIV-1 AEgp145 were successfully constructed, designated as Ad5F35-AEgp145 and rMVA-AEgp145, respectively. Sixty BALB/c mice were randomly divided into three groups: Ad5F35 alone, rMVA prime/Ad5F35 boost, and PBS control. The mice were immunized intramuscularly at weeks 0 and 3, and humoral and cellular immune responses were assessed at 4, 8, 12, and 16 weeks after the initial immunization. Results: The homologous Ad5F35 and heterologous rMVA/Ad5F35 vaccination regimens elicited comparable levels of HIV Env-specific cellular immune responses, peaking at 2100 ± 222 SFCs/million splenocytes and 2200 ± 619 SFCs/million splenocytes, respectively (p > 0.05). Compared to the heterologous regimen, the homologous Ad5F35 regimen induced significantly higher levels of gp120-binding antibodies at weeks 4 and 8 post-initial immunization, with geometric mean titers of 1:25,600 ± 7011 versus 1:1280 ± 150.7 and 1:10,240 ± 4048 versus 1:2560 ± 391.9, respectively. Furthermore, neutralizing activity at week 8 was significantly higher in the homologous group, with a 50% neutralization titers of 1:45 compared to 1:12 in the heterologous group (p < 0.01). Conclusion: This study demonstrates that the Ad5F35-AEgp145 vaccine, whether administered alone or in combination with rMVA-AEgp145, effectively induces strong and comparable cellular immune responses targeting HIV-1 Env in mice. While both regimens are effective, homologous immunization elicits moderately higher levels of antibody responses. These findings provide an important foundation for the further investigation of vector-based HIV vaccine formulations. Full article

Background: Emerging immune-evasive viral variants threaten the efficacy of current vaccines, underscoring the need for strategies that elicit broad and durable protection. Heterologous prime–boost regimens combining distinct vaccine platforms can enhance humoral and cellular immunity through complementary mechanisms. Methods: Using an intramuscular immunization scheme aligned with clinical vaccination practice, CD-1 mice received homologous or heterologous prime–boost regimens combining a replication-deficient Orf virus (Parapoxvirus orf, ORFV)-based spike vaccine (ORFV-S) with the licensed adjuvanted recombinant protein vaccine VidPrevtyn Beta. Spike-specific humoral and cellular immune responses were assessed. Results: ORFV-S alone induced potent and broad spike-specific IgG responses and achieved the strongest ACE2-binding inhibition across variants of concern. ORFV-S priming followed by VidPrevtyn Beta boosting markedly enhanced the magnitude and cross-variant breadth of antibody responses compared with homologous protein vaccination. Both homologous ORFV-S and heterologous regimens incorporating ORFV-S elicited strong CD4⁺ and CD8⁺ T-cell responses, whereas VidPrevtyn Beta alone induced only modest T-cell activity, demonstrating that ORFV-S effectively complements protein-based vaccines. Conclusions: The ORFV-S vector represents a potent vaccine platform capable of inducing broad humoral and cellular immunity. Its use in heterologous prime–boost combinations enhances both antibody magnitude and breadth beyond homologous protein vaccination, supporting its application in vaccination strategies against evolving viral pathogens. 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

Background/Objective: The poultry industry requires extensive vaccination of chickens against IBV in an effort to prevent the disease in animals and significant economic losses. Current vaccination strategies often lack effectiveness, and the continual emergence of new IBV variants makes disease control increasingly challenging. We have developed an inactivated vaccine for poultry containing nine different antigens (Nobilis Multriva), including two IBDV strains, two ARV strains, one NDV strain, one AMPV strain, one EDSV strain and two IBV strains: M41 (genotype GI-1) and 4–91 (genotype GI-13). In this study, the IB efficacy of this novel inactivated vaccine was investigated against homologous and heterologous IBV strains. Methods: Inactivated IBV vaccine containing the M41 and 4–91 strains (Nobilis Multriva) was administered intramuscularly, either alone or following vaccine priming, in SPF and commercial chickens. Birds were challenged with homologous and heterologous IBV strains at defined ages (peak of lay, mid-lay and end of lay). Vaccine efficacy was evaluated through serological assays, clinical observations, and monitoring of egg production post-challenge. Results: This vaccine provided excellent broad protection against different IBV strains circulating in different parts of the world, including IBV M41, 4–91, QX, Q1 and Var2. Furthermore, the vaccine provided long-lasting IBV serological response against IB M41 and IB 4–91 until at least 96 weeks of age in SPF and commercial layers and breeder birds. This vaccine will allow farmers to reduce the number of vaccination moments, thereby minimizing stress to the birds, while also decreasing labor demands and the risk of human error, ultimately contributing to lower overall vaccination costs. Conclusions: Given its demonstrated broad cross-protection and sustained serological responses, this nine-valent inactivated vaccine (Nobilis Multriva) represents a key component of an effective vaccination regimen for controlling IBV infections in the poultry industry. Full article

Background/Objectives: Tuberculosis (TB) remains the leading cause of death from a single infectious agent worldwide. In line with the World Health Organization’s (WHO) goal to end TB by 2035, the rapid development and clinical implementation of new, effective vaccines is urgently needed. To support global TB control efforts, we developed a novel candidate subunit multistage vaccine. Methods: This vaccine incorporates multiple Mycobacterium tuberculosis antigens expressed during both dormant and active stages of infection, fused into a single recombinant protein (ESAT6-CFP10-Ag85A-Rv2660c-Rv1813c). The antigen was encapsulated in biodegradable poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles along with the pattern recognition receptor (PRR) agonists monophosphoryl lipid A (MPLA) and muramyl dipeptide (MDP), which function as adjuvants. Results: Using a mixed intramuscular/nasal prime-boost regimen, the vaccine elicited a mixed Th1/Th17 cell-mediated immune response, as well as a robust humoral response characterized by sustained systemic IgG (lasting at least one year) and prominent local secretory IgA. The vaccine demonstrated protective efficacy as a prophylactic booster following BCG priming in both murine and guinea pig models and was also effective in a therapeutic setting in a murine infection model. Conclusions: The results of this study provide empirical evidence that multistage tuberculosis vaccines represent a promising strategy for achieving global TB control. 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/Objectives: Flaviviruses, including West Nile virus (WNV), pose global health challenges due to their worldwide distribution, pathogenicity, and lack of effective treatments or vaccines. Today, WNV is considered the most important causative agent of viral encephalitis worldwide. This study investigated the different forms of the main WNV antigen—the preM/E protein—in the context of its immunogenic and protective properties. Methods: The recombinant adenovirus type 2 (rAd2) vectors expressing different forms of the WNV preM/E genes were obtained using standard molecular biology techniques. Immunogenicity in mice was assessed by enzyme-linked immunosorbent assay (ELISA) and virus neutralization assay. Immunological efficacy was evaluated in a mouse viral challenge model. Results: The rAd2 vector expressing the West Nile virus preM/E gene with mutations in the fusion loop exhibited robust immunogenicity when administered intramuscularly either once or in a homologous prime-boost regimen. This antigen form, as part of an adenoviral vector, protected mice from death in viral challenge experiments, providing 100% survival following WNV challenge. Conclusions: We believe that a vaccination strategy involving a recombinant adenoviral vector based on human adenovirus type 2 and the WNV antigen represented by the preM/E gene with mutations in the fusion loop may be a promising approach for combating West Nile virus infection. Full article

Background: The development of an effective HIV-1 vaccine remains a major challenge due to HIV-1’s extraordinary diversity, high mutation rate, and the rarity of broadly neutralizing antibody (bnAb) precursors. To address these challenges, we have previously immunized rabbits with mRNA-LNPs encoding for HIV-1 envelope glycoproteins (Envs), together with mRNA-LNPs encoding for HIV-1 Gag, which likely mediated the generation of virus-like particles presenting HIV-1 Envs to the immune system in vivo. Methods: Here, we investigated whether an escalating dose (ED) immunization using mRNA-LNP priming, followed by boosts with synthetic, protein-based, virus-like particles (synVLPs) displaying HIV-1 SOSIP trimers via SpyTag/SpyCatcher conjugation (group 1), could improve the quality and durability of the antibody responses compared to conventional bolus immunization (group 2). Previous studies have shown that, in contrast to single bolus immunization, the ED priming strategy could enhance B cell activation and prolong affinity maturation, resulting in higher-quality antibody responses. Results: Upon vaccination, rabbits from both groups developed strong homologous anti-Env antibody responses, with an increasing ability of sera from immunized rabbits to bind Envs following subsequent boosts. Antibodies in rabbit sera bound heterologous Envs, but there was no statistically significant difference in binding between the two groups. Overall, antibody responses were comparable across all animals and declined similarly over time in both groups, indicating that neither the adjuvants nor the ED priming led to any marked differences within this small sample size. Neutralization activity against homologous tier-2 HIV-1_AD8 (mRNA prime) and tier-2 HIV-1₁₀₅₉ (protein boost) was generally low across both groups; however, a higher neutralization titer was observed for the ED group against HIV-1_AD8 following the final boost. One of the rabbits from the bolus group exhibited exceptionally high neutralization titers that correlated with elevated Env-specific binding against HIV-1₁₀₅₉. Conclusions: These results highlight the challenges in eliciting broad and potent neutralizing antibody (nAb) responses. Our findings underscore the need for the continued development and refinement of immunogen design and delivery strategies to guide the elicitation of nAb. Full article

Background/Objectives: Varicellovirus bovinealpha1 and Varicellovirus bovinealpha5 (BoAHV-1 and BoAHV-5), respectively, are widely distributed pathogens that cause distinct clinical conditions in cattle including infectious bovine rhinotracheitis, infectious pustular vulvovaginitis/balanoposthitis, and meningoencephalitis. Due to the establishment of viral latency, controlling these infections is challenging, and vaccination remains the most effective strategy. In this study, vaccine candidates targeting both BoAHV-1 and BoAHV-5 were developed. Methods: A synthetic gene encoding immunodominant epitopes from the gB and gD proteins and tegument phosphoprotein of BoAHV-1 and BoAHV-5 was designed to produce a multi-epitope recombinant antigen, expressed both in a prokaryotic system (RecBoAHV) and by a modified vaccinia Ankara (MVA-BoAHV) viral vector. The binding affinity of MHC-I to bovine leukocyte antigens (BoLA) was predicted using the NetMHCpan tool (version 4.1). The immunogenicity of the vaccine candidates was evaluated in rabbit and mouse models, using prime-boost immunization protocols. Sera from bovines naturally infected with BoAHV-1 and/or BoAHV-5 were used to evaluate the chimeric protein antigenicity. Immune responses were assessed by indirect ELISA and Western blot. Results: The recombinant multi-epitope protein was effectively recognized by IgG and IgM antibodies in sera from cattle naturally infected with BoAHV-1 or BoAHV-5, confirming the antigenic specificity. Both RecBoAHV and MVA-RecBoAHV induced strong and specific humoral immune responses in rabbits following a homologous prime-boost regimen. In mice, both homologous and heterologous prime-boost protocols revealed robust immunogenicity, particularly after the second booster dose. Conclusions: These findings highlight the immunogenic potential of the RecBoAHV multi-epitope vaccine candidates for controlling BoAHV-1 and BoAHV-5 infections. Further characterization of these vaccine formulations is currently underway in bovine, the target specie. Full article

Cases of confirmed tick-borne encephalitis (TBE) have increased dramatically over the last 30 years, highlighting growing endemicity across Eurasia. Two preventative vaccines, Encepur^® (Bavarian Nordic A/S, Hellerup, Denmark) and FSME-Immun^® (Pfizer Ireland Pharmaceuticals, Cork, Ireland), are licensed in Europe. For both vaccines, primary immunisation consists of a three-dose regimen, administered over approximately one year using “Conventional” dosing schedules. Both vaccines can also be administered using “Rapid” schedules, which shorten the interval between the first two doses but still take around a year to complete. Currently, only Encepur offers an approved “Express” schedule, whereby all three priming doses are given within 21 days. The effectiveness of TBE vaccination is markedly higher in individuals who receive ≥3 doses, compared with those who receive only one or two doses, indicating the importance of series completion. Moreover, seropositivity takes several weeks to develop after vaccination. As such, individuals are advised to initiate vaccination before peak tick season to allow sufficient time to develop protective immunity during periods of highest risk. Despite these considerations, vaccine uptake and series completion remain suboptimal in TBE-endemic regions. Furthermore, many vaccinees—including travellers with limited time before departure and residents of endemic areas—do not initiate vaccination until peak tick season, when risk is greatest. Broader use of Encepur’s Express schedule may help to address these challenges. The Express schedule’s 21-day timeframe may help to increase series completion by reducing drop-offs associated with prolonged dosing intervals. Additionally, it can support timely protection by enabling series completion, with sufficient time post-vaccination to develop protective immunity, all within a single-risk season, even among late initiators. In this narrative review, we evaluate the safety and immunogenicity of Encepur’s Express schedule and discuss its potential utility across a broader range of vaccinees. These insights may help inform TBE vaccine recommendations and support efforts towards improving vaccination strategies amid increasing TBE risk. Full article

Background: In response to the emergence of immune-evasive variants of SARS-CoV-2, this study explores a novel heterologous vaccination strategy using a microparticulate formulation approach that is delivered via oral dissolving film (ODF) formulations into the buccal cavity. Heterologous administration has the potential to generate cross-reactive antibodies, which can be especially beneficial against viruses with ever-mutating variants. Moreover, the microparticulate oral dissolving film-based vaccine approach is a non-invasive vaccine delivery platform. Methods: The vaccine design incorporated whole inactivated Delta and Omicron variants of the virus, administered at prime and booster doses, respectively, effectively encapsulated in a Poly(lactic-co-glycolic) acid (PLGA) polymer matrix, and adjuvanted with Alum to enhance immune activation. Following vaccination, serum, mucosal, and tissue samples were analyzed to evaluate humoral and cellular immune responses against the model antigen, as well as other variants such as Alpha and Beta variants, to understand the cross-reactive response. Result: In vitro evaluations confirmed the vaccine’s safety and its ability to stimulate immune responses. On administering microparticulate oral dissolving films to mice, whole inactivated delta and omicron variant-specific antibodies were observed in serum samples along with neutralizing titers in terminal week. The formulated vaccine showed significant secretory IgA antibody levels in mucosal samples. Moreover, CD4⁺ and CD8a cellular responses were observed in tissue samples of spleen and lymph nodes, along with antibodies (IgG, IgA, and IgM) detected in lung supernatant samples. Humoral and cellular cross-reactive antibodies were observed in the samples. Conclusions: This approach offers a promising platform for developing next-generation vaccines capable of inducing broad immunity. Full article

Rational design of capripoxvirus-based vaccine vectors can be achieved by knockout of immunomodulatory genes. In this study, the effect of knockout of the immunomodulatory genes LSDV005, LSDV008 and LSDV066 on the replication of Lumpy skin disease virus in cell cultures and the immune response to an integrated foreign antigen were assessed. The knockout of genes was performed by homologous recombination under conditions of temporary dominant selection. It was found that single knockout of the LSDV005 gene and the LSDV008 gene did not affect the replicative activity of recombinant viruses in vitro (Atyrau-5 and Atyrau-B). Both single knockout of the LSDV066 gene and in combination with knockout of LSDV005 or LSDV008 led to a decrease in the replicative activity of recombinant LSDVs. The recombinant Atyrau-5J(IL18) with LSDV005 gene knockout induced production of antibodies to the integrated antigen in mice. Prime-boost vaccination with all studied recombinants increased the level of interferon-γ. In addition, during immunization with the recombinant Atyrau-5J(IL18) secretion of interleukin-2 was significantly increased. The study of the functions of immunomodulatory genes and their effect on the expression of inserted sequences of foreign antigens is promising for the creation of highly effective polyvalent vector vaccines for animals. Full article