Search Results (40)

Background/Objectives: In preparation for a potential pandemic caused by the H5N1 highly pathogenic avian influenza (HPAI) virus, pre-pandemic vaccines against several viral clades have been developed and stocked worldwide. Although these vaccines are well tolerated, their immunogenicity and cross-reactivity with viruses of different clades can be improved. Methods: To address this aspect, we generated recombinant influenza vaccines against H5-subtype viruses using two different strains of highly attenuated vaccinia virus (VACV) vectors. Results: rLC16m8-mcl2.2 hemagglutinin (HA) and rLC16m8-mcl2.3.4 HA consisted of a recombinant LC16m8 vector encoding the HA protein from clade 2.2 or clade 2.3.4 viruses (respectively); rDIs-mcl2.2 HA consisted of a recombinant DIs vector encoding the HA protein from clade 2.2. A single dose of rLC16m8-mcl2.2 HA showed rapid (1 week after vaccination) and long-term protection (20 months post-vaccination) in mice against the HPAI H5N1 virus. Moreover, cynomolgus macaques immunized with rLC16m8-mcl2.2 HA exhibited long-term protection when challenged with a heterologous clade of the HPAI H5N1 virus. Although the DIs strain is unable to grow in most mammalian cells, rDIs-mcl2.2 HA also showed rapid and long-lasting effects against HPAI H5N1 virus infection. Notably, the protective efficacy of rDIs-mcl2.2 HA was comparable to that of rLC16m8-mcl2.2 HA. Furthermore, these vaccines protected animals previously immunized with VACVs from a lethal challenge with the HPAI H5N1 virus. Conclusions: These results suggest that both rLC16m8-mcl2.2 HA and rDIs-mcl2.2 HA are effective in preventing HPAI H5N1 virus infection, and rDIs-mcl2.2 HA is a promising vaccine candidate against H5 HA-subtype viruses. Full article

Background: The Epstein-Barr virus (EBV) is intricately linked to a range of human malignancies, with EBV latent membrane protein 2A (LMP2A) emerging as a potential target antigen for immunotherapeutic strategies in the treatment of nasopharyngeal carcinoma (NPC). Methods: The modified vaccinia virus Ankara (MVA) is universally used in vector vaccine research because of its excellent safety profile and highly efficient recombinant gene expression. Here, we constructed a novel MVA-LMP2A recombinant virus and investigated its specific immune response induction and oncolytic effect. Results: An immunization dose of 2 × 10⁷ PFU induced the highest specific immune response, which was no longer increased by boost injections after four doses. Three weeks post-final immunization, the specific immune response reached its peak. The MVA-LMP2A vaccine-induced LMP2A-specific cytotoxic T lymphocytes (CTLs), which exhibited substantial efficacy against target cells and effectively inhibited tumor growth. Conclusions: Thus, the MVA-LMP2A recombinant virus effectively induces strong LMP2A-specific cellular and humoral immune responses and anti-tumor activity. This work provides a promising therapeutic strategy for developing NPC candidate vaccines, as well as a reference for the treatment of EBV LMP2-associated malignancies. Full article

Background/Objectives: Marburg virus (MARV) is the etiological agent of Marburg Virus Disease (MVD), a rare but severe hemorrhagic fever disease with high case fatality rates in humans. Smaller outbreaks have frequently been reported in countries in Africa over the last few years, and confirmed human cases outside Africa are, so far, exclusively imported by returning travelers. Over the previous years, MARV has also spread to non-endemic African countries, demonstrating its potential to cause epidemics. Although MARV-specific vaccines are evaluated in preclinical and clinical research, none have been approved for human use. Modified Vaccinia virus Ankara (MVA), a well-established viral vector used to generate vaccines against emerging pathogens, can deliver multiple antigens and has a remarkable clinical safety and immunogenicity record, further supporting its evaluation as a vaccine against MARV. The rapid availability of safe and effective MVA-MARV vaccine candidates would expand the possibilities of multi-factored intervention strategies in endemic countries. Methods: We have used an optimized methodology to rapidly generate and characterize recombinant MVA candidate vaccines that meet the quality requirements to proceed to human clinical trials. As a proof-of-concept for the optimized methodology, we generated two recombinant MVAs that deliver either the MARV glycoprotein (MVA-MARV-GP) or the MARV nucleoprotein (MVA-MARV-NP). Results: Infections of human cell cultures with recombinant MVA-MARV-GP and MVA-MARV-NP confirmed the efficient synthesis of MARV-GP and MARV-NP proteins in mammalian cells, which are non-permissive for MVA replication. Prime-boost immunizations in C57BL/6J mice readily induced circulating serum antibodies binding to recombinant MARV-GP and MARV-NP proteins. Moreover, the MVA-MARV-candidate vaccines elicited MARV-specific T-cell responses in C57BL/6J mice. Conclusions: We confirmed the suitability of our two backbone viruses MVA-mCherry and MVA-GFP in a proof-of-concept study to rapidly generate candidate vaccines against MARV. However, further studies are warranted to characterize the protective efficacy of these recombinant MVA-MARV vaccines in other preclinical models and to evaluate them as vaccine candidates in humans. Full article

The use of Vaccinia virus (VACV) as a preventive vaccine against variola, the etiological agent of smallpox, led to the eradication of smallpox as a human disease. The L1 protein, a myristylated transmembrane protein present on the surface of mature virions, plays a significant role in infection and morphogenesis, is well-conserved in all orthopoxviruses, and is the target of neutralizing antibodies. DNA recombinant vaccines expressing this protein were successfully used, but they showed lower efficacy in non-human and human primates when used alone, and viral-vectored fowlpox vaccines were already proved to increase immunogenicity when used as a boost. Here, we constructed a novel fowlpox-based recombinant (FP_tPA-L1R), in which the tissue plasminogen activator signal sequence was linked to the 5′ end of the L1R gene to drive the L1 protein into the cellular secretion pathway. FP_tPA-L1R expresses a functional heterologous protein that can be immunoprecipitated by hyperimmune rabbit serum. The protein shows cytoplasmic and membrane subcellular localizations and long-lasting expression in CEF, non-human primate Vero and human MRC-5 cells. The tissue plasminogen activator signal sequence can thus contribute significantly to the expression of the L1 protein and may enhance the immunogenicity of a putative DNA/FP prime–boost vaccine. Full article

Chlamydia trachomatis remains a major global health problem with increasing infection rates, requiring innovative vaccine solutions. Modified Vaccinia Virus Ankara (MVA) is a well-established, safe and highly immunogenic vaccine vector, making it a promising candidate for C. trachomatis vaccine development. In this study, we evaluated two novel MVA-based recombinant vaccines expressing spCTH522 and CTH522:B7 antigens. Our results show that while both vaccines induced CD4⁺ T-cell responses in C57BL/6J mice, they failed to generate antigen-specific systemic CD8⁺ T cells. Only the membrane-anchored CTH522 elicited strong IgG2b and IgG2c antibody responses. In an HLA transgenic mouse model, both recombinant MVAs induced Th1-directed CD4⁺ T cell and multifunctional CD8⁺ T cells, while only the CTH522:B7 vaccine generated antibody responses, underscoring the importance of antigen localization. Collectively, our data indicate that distinct antigen formulations can induce different immune responses depending on the mouse strain used. This research contributes to the development of effective vaccines by highlighting the importance of careful antigen design and the selection of appropriate animal models to study specific vaccine-induced immune responses. Future studies should investigate whether these immune responses provide protection in humans and should explore different routes of immunization, including mucosal and systemic immunization. Full article

Aging is associated with a decline in immune system functionality. So-called immunosenescence may impair the successful vaccination of elderly people. Thus, improved vaccination strategies also suitable for an aged immune system are required. Modified Vaccinia virus Ankara (MVA) is a highly attenuated and replication-deficient vaccinia virus that has been established as a multipurpose viral vector for vaccine development against various infections. We characterized a recombinant MVA expressing a prefusion-stabilized version of SARS-CoV-2 S protein (MVA-ST) in an aged-hamster model for COVID-19. Intramuscular MVA-ST immunization resulted in protection from disease and severe lung pathology. Importantly, this protection was correlated with a potent activation of SARS-CoV-2 specific T-cells and neutralizing antibodies. Our results suggest that MVA vector vaccines merit further evaluation in preclinical models to contribute to future clinical development as candidate vaccines in elderly people to overcome the limitations of age-dependent immunosenescence. Full article

Smallpox was eradicated in less than 200 years after Edward Jenner’s practice of cowpox variolation in 1796. The forty-three years of us living free of smallpox, beginning in 1979, never truly separated us from poxviruses. The recent outbreak of monkeypox in May 2022 might well warn us of the necessity of keeping up both the scientific research and public awareness of poxviruses. One of them in particular, the vaccinia virus (VACV), has been extensively studied as a vector given its broad host range, extraordinary thermal stability, and exceptional immunogenicity. Unceasing fundamental biological research on VACV provides us with a better understanding of its genetic elements, involvement in cellular signaling pathways, and modulation of host immune responses. This enables the rational design of safer and more efficacious next-generation vectors. To address the new technological advancement within the past decade in VACV research, this review covers the studies of viral immunomodulatory genes, modifications in commonly used vectors, novel mechanisms for rapid generation and purification of recombinant virus, and several other innovative approaches to studying its biology. Full article

Influenza, a respiratory disease mainly caused by influenza A and B, viruses of the Orthomyxoviridae, is still a burden on our society’s health and economic system. Influenza A viruses (IAV) circulate in mammalian and avian populations, causing seasonal outbreaks with high numbers of cases. Due to the high variability in seasonal IAV triggered by antigenic drift, annual vaccination is necessary, highlighting the need for a more broadly protective vaccine against IAV. The safety tested Modified Vaccinia virus Ankara (MVA) is licensed as a third-generation vaccine against smallpox and serves as a potent vector system for the development of new candidate vaccines against different pathogens. Here, we generated and characterized recombinant MVA candidate vaccines that deliver the highly conserved internal nucleoprotein (NP) of IAV under the transcriptional control of five newly designed chimeric poxviral promoters to further increase the immunogenic properties of the recombinant viruses (MVA-NP). Infections of avian cell cultures with the recombinant MVA-NPs demonstrated efficient synthesis of the IAV-NP which was expressed under the control of the five new promoters. Prime-boost or single shot immunizations in C57BL/6 mice readily induced circulating serum antibodies’ binding to recombinant IAV-NP and the robust activation of IAV-NP-specific CD8+ T cell responses. Moreover, the MVA-NP candidate vaccines protected C57BL/6 mice against lethal respiratory infection with mouse-adapted IAV (A/Puerto Rico/8/1934/H1N1). Thus, further studies are warranted to evaluate the immunogenicity and efficacy of these recombinant MVA-NP vaccines in other IAV challenge models in more detail. Full article

The COVID-19 pandemic has underscored the importance of swift responses and the necessity of dependable technologies for vaccine development. Our team previously developed a fast cloning system for the modified vaccinia virus Ankara (MVA) vaccine platform. In this study, we reported on the construction and preclinical testing of a recombinant MVA vaccine obtained using this system. We obtained recombinant MVA expressing the unmodified full-length SARS-CoV-2 spike (S) protein containing the D614G amino-acid substitution (MVA-Sdg) and a version expressing a modified S protein containing amino-acid substitutions designed to stabilize the protein a in a pre-fusion conformation (MVA-Spf). S protein expressed by MVA-Sdg was found to be expressed and was correctly processed and transported to the cell surface, where it efficiently produced cell–cell fusion. Version Spf, however, was not proteolytically processed, and despite being transported to the plasma membrane, it failed to induce cell–cell fusion. We assessed both vaccine candidates in prime-boost regimens in the susceptible transgenic K18-human angiotensin-converting enzyme 2 (K18-hACE2) in mice and in golden Syrian hamsters. Robust immunity and protection from disease was induced with either vaccine in both animal models. Remarkably, the MVA-Spf vaccine candidate produced higher levels of antibodies, a stronger T cell response, and a higher degree of protection from challenge. In addition, the level of SARS-CoV-2 in the brain of MVA-Spf inoculated mice was decreased to undetectable levels. Those results add to our current experience and range of vaccine vectors and technologies for developing a safe and effective COVID-19 vaccine. Full article

Infectious bronchitis (IB) is an acute respiratory disease of chickens caused by the avian coronavirus Infectious Bronchitis Virus (IBV). Modified Live Virus (MLV) vaccines used commercially can revert to virulence in the field, recombine with circulating serotypes, and cause tissue damage in vaccinated birds. Previously, we showed that a mucosal adjuvant system, QuilA-loaded Chitosan (QAC) nanoparticles encapsulating plasmid vaccine encoding for IBV nucleocapsid (N), is protective against IBV. Herein, we report a heterologous vaccination strategy against IBV, where QAC-encapsulated plasmid immunization is followed by Modified Vaccinia Ankara (MVA) immunization, both expressing the same IBV-N antigen. This strategy led to the initiation of robust T-cell responses. Birds immunized with the heterologous vaccine strategy had reduced clinical severity and >two-fold reduction in viral burden in lachrymal fluid and tracheal swabs post-challenge compared to priming and boosting with the MVA-vectored vaccine alone. The outcomes of this study indicate that the heterologous vaccine platform is more immunogenic and protective than a homologous MVA prime/boost vaccination strategy. Full article

Here, we investigate the potential of CD70 co-expression during viral vector boost vaccination to improve an antigen-specific T cell response. To determine the chance of activating antigen-specific T cells by CD70, we used the HBV core antigen as a model antigen in a heterologous protein-prime, Modified Vaccinia virus Ankara (MVA) boost vaccination scheme. Both the HBV core and a CD70 expression cassette were co-expressed upon delivery by an MVA vector under the same promoter linked by a P2A site. To compare immunogenicity with and without CD70 co-expression, HBV-naïve, C57BL/6 (wt) mice and HBV-transgenic mice were prime-vaccinated using recombinant HBV core antigen followed by the MVA vector boost. Co-expression of CD70 increased the number of vaccine-induced HBV core-specific CD8 T cells by >2-fold and improved their effector functions in HBV-naïve mice. In vaccinated HBV1.3tg mice, the number and functionality of HBV core-specific CD8 T cells was slightly increased upon CD70 co-expression in low-viremic, but not in high-viremic animals. CD70 co-expression did not impact liver damage as indicated by ALT levels in the serum, but increased the number of vaccine-induced, proliferative T cell clusters in the liver. Overall, this study indicates that orchestrated co-expression of CD70 and a vaccine antigen may be an interesting and safe means of enhancing antigen-specific CD8 T cell responses using vector-based vaccines, although in our study it was not sufficient to break immune tolerance. Full article

As demonstrated by the 2015 Zika virus outbreak in the Americas, emerging and re-emerging arboviruses are public health threats that warrant research investment for the development of effective prophylactics and therapeutics. Many arboviral diseases are underreported, neglected, or of low prevalence, yet they all have the potential to cause outbreaks of local and international concern. Here, we show the production of virus-like particles (VLPs) using a rapid and efficient recombinant vaccinia virus (VACV) expression system for five tick- and mosquito-borne arboviruses: Powassan virus (POWV), Heartland virus (HRTV), severe fever with thrombocytopenia syndrome virus (SFTSV), Bourbon virus (BRBV) and Mayaro virus (MAYV). We detected the expression of arbovirus genes of interest by Western blot and observed the expression of VLPs that resemble native virions under transmission electron microscopy. We were also able to improve the secretion of POWV VLPs by modifying the signal sequence within the capsid gene. This study describes the use of a rapid VACV platform for the production and purification of arbovirus VLPs that can be used as subunit or vectored vaccines, and provides insights into the selection of arbovirus genes for VLP formation and genetic modifications to improve VLP secretion and yield. Full article

The feline immunodeficiency virus (FIV) is a retrovirus with global impact and distribution, affecting both domestic and wild cats. This virus can cause severe and progressive immunosuppression culminating in the death of felids. Since the discovery of FIV, only one vaccine has been commercially available. This vaccine has proven efficiency against FIV subtypes A and D, whereas subtype B (FIV-B), found in multiple continents, is not currently preventable by vaccination. We, therefore, developed and evaluated a vaccine prototype against FIV-B using the recombinant viral vector modified vaccinia virus Ankara (MVA) expressing the variable region V1–V3 of the FIV-B envelope protein. We conducted preclinical tests in immunized mice (C57BL/6) using a prime-boost protocol with a 21 day interval and evaluated cellular and humoral responses as well the vaccine viability after lyophilization and storage. The animals immunized with the recombinant MVA/FIV virus developed specific splenocyte proliferation when stimulated with designed peptides. We also detected cellular and humoral immunity activation with IFN-y and antibody production. The data obtained in this study support further development of this immunogen and testing in cats. Full article

Oncolytic virotherapy has emerged as a novel form of cancer immunotherapy. Oncolytic viruses (OVs) can directly infect and lyse the tumor cells, and modulate the beneficial immune microenvironment. Vaccinia virus (VACV) is a promising oncolytic vector because of its high safety, easy gene editing, and tumor intrinsic selectivity. To further improve the safety, tumor-targeting ability, and OV-induced cancer-specific immune activation, various approaches have been used to modify OVs. The recombinant oncolytic VACVs with deleting viral virulence factors and/or arming various therapeutic genes have displayed better therapeutic effects in multiple tumor models. Moreover, the combination of OVs with other cancer immunotherapeutic approaches, such as immune checkpoint inhibitors and CAR-T cells, has the potential to improve the outcome in cancer patients. This will open up new possibilities for the application of OVs in cancer treatment, especially for personalized cancer therapies. Full article

Epstein–Barr virus (EBV) was discovered in 1964 in the cell line of Burkitt lymphoma and became first known human oncogenic virus. EBV belongs to the Herpesviridae family, and is present worldwide as it infects 95% of people. Infection with EBV usually happens during childhood when it remains asymptomatic; however, in adults, it can cause an acute infection known as infectious mononucleosis. In addition, EBV can cause wide range of tumors with origins in B lymphocytes, T lymphocytes, and NK cells. Its oncogenicity and wide distribution indicated the need for vaccine development. Research on mice and cultured cells as well as human clinical trials have been in progress for a few decades for both prophylactic and therapeutic EBV vaccines. The main targets of the vaccines are EBV envelope glycoproteins such as gp350 and EBV latent genes. The long wait for the EBV vaccine is due to the complexity of the EBV replication cycle and the wide range of its host cells. Although some strategies such as the use of dendritic cells and recombinant Vaccinia viral vectors have shown success, ongoing clinical trials using mRNA-based vaccines as well as new delivery systems as nanoparticles are yet to show the best choice of vaccine target and its production strategy. Full article