Protection Against Marburg Virus Using a Recombinant VSV-Vaccine Depends on T and B Cell Activation

Divergent antibody recognition profiles are generated by protective mRNA vaccines against Marburg and Ravn viruses

The first-ever recent Marburg virus (MARV) outbreak in Ghana, West Africa and Equatorial Guinea has refocused efforts towards the development of therapeutics since no vaccine or treatment has been approved. mRNA vaccines were proven successful in a pandemic-response to severe acute respiratory syndrome coronavirus-2, making it an appealing vaccine platform to target highly pathogenic emerging viruses. Here, 1-methyl-pseudouridine-modified mRNA vaccines formulated in lipid nanoparticles (LNP) were developed against MARV and the closely-related Ravn virus (RAVV), which were based on sequences of the glycoproteins (GP) of the two viruses. Vaccination of guinea pigs with both vaccines elicited robust binding and neutralizing antibodies and conferred complete protection against virus replication, disease and death. The study characterized antibody responses to identify disparities in the binding and functional profiles between the two viruses and regions in GP that are broadly reactive. For the first time, the glycan cap is highlighted as an immunoreactive site for marburgviruses, inducing both binding and neutralizing antibody responses that are dependent on the virus. Profiling the antibody responses against the two viruses provided an insight into how antigenic differences may affect the response towards conserved GP regions which would otherwise be predicted to be cross-reactive and has implications for the future design of broadly protective vaccines. The results support the use of mRNA-LNPs against pathogens of high consequence.

Peripheral immune responses to filoviruses in a reservoir versus spillover hosts reveal transcriptional correlates of disease

Several filoviruses, including Marburg virus (MARV), cause severe disease in humans and nonhuman primates (NHPs). However, the Egyptian rousette bat (ERB, Rousettus aegyptiacus), the only known MARV reservoir, shows no overt illness upon natural or experimental infection, which, like other bat hosts of zoonoses, is due to well-adapted, likely species-specific immune features. Despite advances in understanding reservoir immune responses to filoviruses, ERB peripheral blood responses to MARV and how they compare to those of diseased filovirus-infected spillover hosts remain ill-defined. We thus conducted a longitudinal analysis of ERB blood gene responses during acute MARV infection. These data were then contrasted with a compilation of published primate blood response studies to elucidate gene correlates of filovirus protection versus disease. Our work expands on previous findings in MARV-infected ERBs by supporting both host resistance and disease tolerance mechanisms, offers insight into the peripheral immunocellular repertoire during infection, and provides the most direct known cross-examination between reservoir and spillover hosts of the most prevalently-regulated response genes, pathways and activities associated with differences in filovirus pathogenesis and pathogenicity.

Rhesus macaques show increased resistance to repeated SHIV intrarectal exposure following a heterologous regimen of rVSV vector vaccine expressing HIV antigen

Despite the human immunodeficiency virus (HIV) pandemic continuing worldwide for 40 years, no vaccine to combat the disease has been licenced for use in at risk populations. Here, we describe a novel recombinant vesicular stomatitis virus (rVSV) vector vaccine expressing modified HIV envelope glycoproteins and Ebola virus glycoprotein. Three heterologous immunizations successfully prevented infection by a different clade SHIV in 60% of non-human primates (NHPs). No trend was observed between resistance and antibody interactions. Resistance to infection was associated with high proportions of central memory T-cell CD69 and CD154 marker upregulation, increased IL-2 production, and a reduced IFN-γ response, offering insight into correlates of protection.

Transcriptional profiling of immune responses in NHPs after low-dose, VSV-based vaccination against Marburg virus

Infection with Marburg virus (MARV), the causative agent of Marburg virus disease (MVD), results in haemorrhagic disease and high case fatality rates (>40%) in humans. Despite its public health relevance, there are no licensed vaccines or therapeutics to prevent or treat MVD. A vesicular stomatitis virus (VSV)-based vaccine expressing the MARV glycoprotein (VSV-MARV) is currently in clinical development. Previously, a single 10 million PFU dose of VSV-MARV administered 1-5 weeks before lethal MARV challenge conferred uniform protection in nonhuman primates (NHPs), demonstrating fast-acting potential. Additionally, our group recently demonstrated that even a low dose VSV-MARV (1000 PFU) protected NHPs when given 7 days before MARV challenge. In this study, we longitudinally profiled the transcriptional responses of NHPs vaccinated with this low dose of VSV-MARV either 14 or 7 days before lethal MARV challenge. NHPs vaccinated 14 days before challenge presented with transcriptional changes consistent with an antiviral response before challenge. Limited gene expression changes were observed in the group vaccinated 7 days before challenge. After challenge, genes related to lymphocyte-mediated immunity were only observed in the group vaccinated 14 days before challenge, indicating that the length of time between vaccination and challenge influenced gene expression. Our results indicate that a low dose VSV-MARV elicits distinct immune responses that correlate with protection against MVD. A low dose of VSV-MARV should be evaluated in clinical rails as it may be an option to deliver beneficial public health outcomes to more people in the event of future outbreaks.

Characterization of the Cynomolgus Macaque Model of Marburg Virus Disease and Assessment of Timing for Therapeutic Treatment Testing

Marburg virus (MARV) causes severe disease and high mortality in humans. The objective of this study was to characterize disease manifestations and pathogenesis in cynomolgus macaques exposed to MARV. The results of this natural history study may be used to identify features of MARV disease useful in defining the ideal treatment initiation time for subsequent evaluations of investigational therapeutics using this model. Twelve cynomolgus macaques were exposed to a target dose of 1000 plaque-forming units MARV by the intramuscular route, and six control animals were mock-exposed. The primary endpoint of this study was survival to Day 28 post-inoculation (PI). Anesthesia events were minimized with the use of central venous catheters for periodic blood collection, and temperature and activity were continuously monitored by telemetry. All mock-exposed animals remained healthy for the duration of the study. All 12 MARV-exposed animals (100%) became infected, developed illness, and succumbed on Days 8-10 PI. On Day 4 PI, 11 of the 12 MARV-exposed animals had statistically significant temperature elevations over baseline. Clinically observable signs of MARV disease first appeared on Day 5 PI, when 6 of the 12 animals exhibited reduced responsiveness. Ultimately, systemic inflammation, coagulopathy, and direct cytopathic effects of MARV all contributed to multiorgan dysfunction, organ failure, and death or euthanasia of all MARV-exposed animals. Manifestations of MARV disease, including fever, systemic viremia, lymphocytolysis, coagulopathy, and hepatocellular damage, could be used as triggers for initiation of treatment in future therapeutic efficacy studies.

Preexisting Immunity Does Not Prevent Efficacy of Vesicular Stomatitis Virus-Based Filovirus Vaccines in Nonhuman Primates

Ebola virus (EBOV) and Marburg virus (MARV) made headlines in the past decade, causing outbreaks of human disease in previously nonendemic yet overlapping areas. While EBOV outbreaks can be mitigated with licensed vaccines and treatments, there is not yet a licensed countermeasure for MARV. Here, we used nonhuman primates (NHPs) previously vaccinated with vesicular stomatitis virus (VSV)-MARV and protected against lethal MARV challenge. After a resting period of 9 months, these NHPs were revaccinated with VSV-EBOV and challenged with EBOV, resulting in 75% survival. Surviving NHPs developed EBOV glycoprotein (GP)-specific antibody titers and no viremia or clinical signs of disease. The single vaccinated NHP succumbing to challenge showed the lowest EBOV GP-specific antibody response after challenge, supporting previous findings with VSV-EBOV that antigen-specific antibodies are critical in mediating protection. This study again demonstrates that VSVΔG-based filovirus vaccine can be successfully used in individuals with preexisting VSV vector immunity, highlighting the platform's applicability for consecutive outbreak response.

Emergence of Marburg virus: a global perspective on fatal outbreaks and clinical challenges

The Marburg virus (MV), identified in 1967, has caused deadly outbreaks worldwide, the mortality rate of Marburg virus disease (MVD) varies depending on the outbreak and virus strain, but the average case fatality rate is around 50%. However, case fatality rates have varied from 24 to 88% in past outbreaks depending on virus strain and case management. Designated a priority pathogen by the National Institute of Allergy and Infectious Diseases (NIAID), MV induces hemorrhagic fever, organ failure, and coagulation issues in both humans and non-human primates. This review presents an extensive exploration of MVD outbreak evolution, virus structure, and genome, as well as the sources and transmission routes of MV, including human-to-human spread and involvement of natural hosts such as the Egyptian fruit bat (Rousettus aegyptiacus) and other Chiroptera species. The disease progression involves early viral replication impacting immune cells like monocytes, macrophages, and dendritic cells, followed by damage to the spleen, liver, and secondary lymphoid organs. Subsequent spread occurs to hepatocytes, endothelial cells, fibroblasts, and epithelial cells. MV can evade host immune response by inhibiting interferon type I (IFN-1) synthesis. This comprehensive investigation aims to enhance understanding of pathophysiology, cellular tropism, and injury sites in the host, aiding insights into MVD causes. Clinical data and treatments are discussed, albeit current methods to halt MVD outbreaks remain elusive. By elucidating MV infection's history and mechanisms, this review seeks to advance MV disease treatment, drug development, and vaccine creation. The World Health Organization (WHO) considers MV a high-concern filovirus causing severe and fatal hemorrhagic fever, with a death rate ranging from 24 to 88%. The virus often spreads through contact with infected individuals, originating from animals. Visitors to bat habitats like caves or mines face higher risk. We tailored this search strategy for four databases: Scopus, Web of Science, Google Scholar, and PubMed. we primarily utilized search terms such as "Marburg virus," "Epidemiology," "Vaccine," "Outbreak," and "Transmission." To enhance comprehension of the virus and associated disease, this summary offers a comprehensive overview of MV outbreaks, pathophysiology, and management strategies. Continued research and learning hold promise for preventing and controlling future MVD outbreaks. GRAPHICAL ABSTRACT.

Single-dose VSV-based vaccine protects cynomolgus macaques from disease after Taï Forest virus infection

Taï Forest virus (TAFV) is a lesser-known ebolavirus that causes lethal infections in chimpanzees and is responsible for a single human case. Limited research has been done on this human pathogen; however, with the recent emergence of filoviruses in West Africa, further investigation and countermeasure development against this virus is warranted.We developed a vesicular stomatitis virus (VSV)-based vaccine expressing the TAFV glycoprotein as the viral antigen and assessed it for protective efficacy in nonhuman primates (NHPs). Following a single high-dose vaccination, NHPs developed antigen-specific binding and neutralizing antibodies as well as modest T cell responses. Importantly, all vaccinated NHPs were uniformly protected from disease after lethal TAFV challenge while the naïve control group succumbed to the disease. Histopathologic lesions consistent with filovirus disease were present in control NHPs but were not observed in vaccinated NHPs. Transcriptional analysis of whole blood samples obtained after vaccination and challenge was performed to gain insight into molecular underpinnings conferring protection. Differentially expressed genes (DEG) detected 7 days post-vaccination were enriched to processes associated with innate immunity and antiviral responses. Only a small number of DEG was detected in vaccinated NHPs post-challenge while over 1,000 DEG were detected in control NHPs at end-stage disease which mapped to gene ontology terms indicative of defense responses and inflammation. Taken together, this data demonstrates the effective single-dose protection of the VSV-TAFV vaccine, and its potential for use in outbreaks.

Rapid protection of nonhuman primates against Marburg virus disease using a single low-dose VSV-based vaccine

BACKGROUND

Marburg virus (MARV) is the causative agent of Marburg virus disease (MVD) which has a case fatality rate up to ∼90% in humans. Recently, there were cases reported in Guinea and Ghana highlighting this virus as a high-consequence pathogen potentially threatening global public health. There are no licensed treatments or vaccines available today. We used a vesicular stomatitis virus (VSV)-based vaccine expressing the MARV-Angola glycoprotein (VSV-MARV) as the viral antigen. Previously, a single dose of 1 × 10⁷ plaque-forming units (PFU) administered 7 days before challenge resulted in uniform protection from disease in cynomolgus macaques.

METHODS

As we sought to lower the vaccination dose to achieve a higher number of vaccine doses per vial, we administered 1 × 10⁵ or 1 × 10³ PFU 14 days or 1 × 10³ PFU 7 days before challenge to cohorts of cynomolgus macaques and investigated immunity as well as protective efficacy.

RESULTS

Vaccination resulted in uniform protection with no detectable viremia. Antigen-specific IgG responses were induced by both vaccine concentrations and were sustained until the study endpoint. Neutralizing antibody responses and antibody-dependent cellular phagocytosis were observed. The cellular response after vaccination was characterized by an early induction of NK cell activation. Additionally, antigen-specific memory T cell subsets were detected in all vaccination cohorts indicating that while the primary protective mechanism of VSV-MARV is the humoral response, a functional cellular response is also induced.

INTERPRETATION

Overall, this data highlights VSV-MARV as a viable and fast-acting MARV vaccine candidate suitable for deployment in emergency outbreak situations and supports its clinical development.

FUNDING

This work was funded by the Intramural Research Program NIAID, NIH.

Species-specific immunogenicity and protective efficacy of a vesicular stomatitis virus-based Sudan virus vaccine: a challenge study in macaques

BACKGROUND

The recent Sudan virus (SUDV) outbreak in Uganda highlights the need for rapid response capabilities, including development of vaccines against emerging viruses with high public health impact. We aimed to develop a Sudan virus-specific vaccine suitable for emergency use during outbreaks.

METHODS

We generated and characterised a vesicular stomatitis virus (VSV)-based vaccine, VSV- SUDV, and evaluated the protective efficacy following a single-dose vaccination against lethal SUDV infection in non-human primates (NHPs). We used male and female cynomolgus macaques (n=11) aged 6-11 years and weighing 3·8-9·0 kg. Animals received a 1 mL intramuscular injection for vaccination containing either 1 × 10⁷ plaque forming units (PFU) VSV-SUDV or 1 × 10⁷ PFU of a VSV-based vaccine against Marburg virus (control; five NHPs). NHPs were challenged intramuscularly 28 days after vaccination with 1 × 10⁴ TCID₅₀ SUDV-Gulu. We assessed anaesthetised NHPs on days 28, 21, 14, and 7 before challenge; days 0, 3, 6, 9, 14, 21, 28, and 35 after challenge; and at euthanasia (day 40 for survivors). As we repurposed NHPs from a successful VSV-Ebola virus (EBOV) vaccine efficacy study, we also investigated VSV-EBOV's cross-protective potential against SUDV challenge.

FINDINGS

Of the six NHPs given VSV-SUDV, none showed any signs of disease in response to the challenge. Four of the five NHPs in the control group developed characteristic clinical signs of Sudan virus diseases. SUDV glycoprotein-specific IgG concentrations peaked 14 days after vaccination (titre of >1:10 000) and reached their highest concentrations at 6 days after challenge (1:25 600-1:102 400). Although the NHPs developed cross-reactive humoral responses to SUDV after VSV-EBOV vaccination and EBOV challenge, there was little cross-protection.

INTERPRETATION

These data emphasise the need for species-specific vaccines for each human-pathogenic Ebolavirus. Furthermore, although previous VSV-EBOV immunity is boosted through VSV-SUDV vaccination, it only has a small effect on the immunogenicity and protective efficacy of VSV-SUDV vaccination against SUDV challenge.

FUNDING

Intramural Research Program, US National Institute of Allergy and Infectious Diseases, National Institutes of Health.

Marburg virus and the disease it causes

Over the 50 years since its discovery, many properties of the Marburg virus have been studied, but no reliable medical remedies of preventing and treating the infection it causes have been developed, although it can potentially cause large-scale epidemics. Marburg fever is relevant due to the risk of importation to other countries. The source of infection in nature is bats (reservoir) and monkeys (intermediate host), and the routes of transmission are aerosol, contact and alimentary. The mortality rate in recent outbreaks has reached 90%. In convalescents the causative agent was identified in tears, semen, and liver biopsies weeks and months after recovery. The lack of therapeutic and prophylactic antiviral drugs, high rates of mortality, infectivity, the ability of aerosol contamination, and a high epidemic potential all together define Marburg fever as a serious global threat to international health. The development of medical protection against this infection should be an urgent task of ensuring the biological safety of the population of the Russian Federation. The most promising ways to develop vaccines against Marburg fever are the construction of recombinants based on adenovirus, vesicular stomatitis virus or alphavirus replicon, DNA vaccines. A reliable protective effect of the chemotherapy drug remdesivir in combination with human antibodies, as well as an etiotropic drug with an antisense mechanism of action and an interferon inducer has been shown. In model experiments with pseudovirus, fundamentally new ways of developing pathogen inhibitors were found preventing its exit from cells, as well as the construction of anti-gene-binding Fab fragments that inhibit the synthesis of viral RNA.

Vesicular stomatitis virus-based vaccine targeting plasmodium blood-stage antigens elicits immune response and protects against malaria with protein booster strategy

Merozoite invasion of the erythrocytes in humans is a key step in the pathogenesis of malaria. The proteins involved in the merozoite invasion could be potential targets for the development of malaria vaccines. Novel viral-vector-based malaria vaccine regimens developed are currently under clinical trials. Vesicular stomatitis virus (VSV) is a single-stranded negative-strand RNA virus widely used as a vector for virus or cancer vaccines. Whether the VSV-based malarial vaccine is more effective than conventional vaccines based on proteins involved in parasitic invasion is still unclear. In this study, we have used the reverse genetics system to construct recombinant VSVs (rVSVs) expressing apical membrane protein 1 (AMA1), rhoptry neck protein 2 (RON2), and reticulocyte-binding protein homolog 5 (RH5), which are required for Plasmodium falciparum invasion. Our results showed that VSV-based viral vaccines significantly increased Plasmodium-specific IgG levels and lymphocyte proliferation. Also, VSV-PyAMA1 and VSV-PyRON2sp prime-boost regimens could significantly increase the levels of IL-2 and IFN-γ-producing by CD4⁺ and CD8⁺ T cells and suppress invasion in vitro. The rVSV prime-protein boost regimen significantly increase Plasmodium antigen-specific IgG levels in the serum of mice compared to the homologous rVSV prime-boost. Furthermore, the protective efficacy of rVSV prime protein boost immunization in the mice challenged with P. yoelii 17XL was better compared to traditional antigen immunization. Together, our results show that VSV vector is a novel strategy for malarial vaccine development and preventing the parasitic diseases.

An introduction to the Marburg virus vaccine consortium, MARVAC

The emergence of Marburg virus (MARV) in Guinea and Ghana triggered the assembly of the MARV vaccine "MARVAC" consortium representing leaders in the field of vaccine research and development aiming to facilitate a rapid response to this infectious disease threat. Here, we discuss current progress, challenges, and future directions for MARV vaccines.

Nonhuman Primates Are Protected against Marburg Virus Disease by Vaccination with a Vesicular Stomatitis Virus Vector-Based Vaccine Prepared under Conditions to Allow Advancement to Human Clinical Trials

Vaccines are needed to disrupt or prevent continued outbreaks of filoviruses in humans across Western and Central Africa, including outbreaks of Marburg virus (MARV). As part of a filovirus vaccine product development plan, it is important to investigate dose response early in preclinical development to identify the dose range that may be optimal for safety, immunogenicity, and efficacy, and perhaps demonstrate that using lower doses is feasible, which will improve product access. To determine the efficacious dose range for a manufacturing-ready live recombinant vesicular stomatitis virus vaccine vector (rVSV∆G-MARV-GP) encoding the MARV glycoprotein (GP), a dose-range study was conducted in cynomolgus macaques. Results showed that a single intramuscular injection with as little as 200 plaque-forming units (PFUs) was 100% efficacious against lethality and prevented development of viremia and clinical pathologies associated with MARV Angola infection. Across the vaccine doses tested, there was nearly a 2000-fold range of anti-MARV glycoprotein (GP) serum IgG titers with seroconversion detectable even at the lowest doses. Virus-neutralizing serum antibodies also were detected in animals vaccinated with the higher vaccine doses indicating that vaccination induced functional antibodies, but that the assay was a less sensitive indicator of seroconversion. Collectively, the data indicates that a relatively wide range of anti-GP serum IgG titers are observed in animals that are protected from disease implying that seroconversion is positively associated with efficacy, but that more extensive immunologic analyses on samples collected from our study as well as future preclinical studies will be valuable in identifying additional immune responses correlated with protection that can serve as markers to monitor in human trials needed to generate data that can support vaccine licensure in the future.

Bridging Animal and Human Data in Pursuit of Vaccine Licensure

The FDA Animal Rule was devised to facilitate approval of candidate vaccines and therapeutics using animal survival data when human efficacy studies are not practical or ethical. This regulatory pathway is critical for candidates against pathogens with high case fatality rates that prohibit human challenge trials, as well as candidates with low and sporadic incidences of outbreaks that make human field trials difficult. Important components of a vaccine development plan for Animal Rule licensure are the identification of an immune correlate of protection and immunobridging to humans. The relationship of vaccine-induced immune responses to survival after vaccination and challenge must be established in validated animal models and then used to infer predictive vaccine efficacy in humans via immunobridging. The Sabin Vaccine Institute is pursuing licensure for candidate filovirus vaccines via the Animal Rule and has convened meetings of key opinion leaders and subject matter experts to define fundamental components for vaccine licensure in the absence of human efficacy data. Here, filoviruses are used as examples to review immune correlates of protection and immunobridging. The points presented herein reflect the presentations and discussions during the second meeting held in October 2021 and are intended to address important considerations for developing immunobridging strategies.

Protection against Marburg Virus and Sudan Virus in NHP by an Adenovector-Based Trivalent Vaccine Regimen Is Correlated to Humoral Immune Response Levels

The Marburg virus (MARV) and Sudan virus (SUDV) belong to the filovirus family. The sporadic human outbreaks occur mostly in Africa and are characterized by an aggressive disease course with high mortality. The first case of Marburg virus disease in Guinea in 2021, together with the increased frequency of outbreaks of Ebola virus (EBOV), which is also a filovirus, accelerated the interest in potential prophylactic vaccine solutions against multiple filoviruses. We previously tested a two-dose heterologous vaccine regimen (Ad26.Filo, MVA-BN-Filo) in non-human primates (NHP) and showed a fully protective immune response against both SUDV and MARV in addition to the already-reported protective effect against EBOV. The vaccine-induced glycoprotein (GP)-binding antibody levels appear to be good predictors of the NHP challenge outcome as indicated by the correlation between antibody levels and survival outcome as well as the high discriminatory capacity of the logistic model. Moreover, the elicited GP-specific binding antibody response against EBOV, SUDV, and MARV remains stable for more than 1 year. Overall, the NHP data indicate that the Ad26.Filo, MVA-BN-Filo regimen may be a good candidate for a prophylactic vaccination strategy in regions at high risk of filovirus outbreaks.

Mining of Marburg Virus Proteome for Designing an Epitope-Based Vaccine

Marburg virus (MARV) is one of the most harmful zoonotic viruses with deadly effects on both humans and nonhuman primates. Because of its severe outbreaks with a high rate of fatality, the world health organization put it as a risk group 4 pathogen and focused on the urgent need for the development of effective solutions against that virus. However, up to date, there is no effective vaccine against MARV in the market. In the current study, the complete proteome of MARV (seven proteins) was analyzed for the antigenicity score and the virulence or physiological role of each protein where we nominated envelope glycoprotein (Gp), Transcriptional activator (VP30), and membrane-associated protein (VP24) as the candidates for epitope prediction. Following that, a vaccine construct was designed based on CTL, HTL, and BCL epitopes of the selected protein candidates and to finalize the vaccine construct, several amino acid linkers, β-defensin adjuvant, and PADRE peptides were incorporated. The generated potential vaccine was assessed computationally for several properties such as antigenicity, allergenicity, stability, and other structural features where the outcomes of these assessments nominated this potential vaccine to be validated for its binding affinity with two molecular targets TLR-8 and TLR-4. The binding score and the stability of the vaccine-receptor complex, which was deeply studied through molecular docking-coupled dynamics simulation, supported the selection of our designed vaccine as a putative solution for MARV that should be validated through future wet-lab experiments. Here, we describe the computational approach for designing and analysis of this potential vaccine.

A Cloned Recombinant Vesicular Stomatitis Virus-Vectored Marburg Vaccine, PHV01, Protects Guinea Pigs from Lethal Marburg Virus Disease

Marburg virus (MARV) is a negative-sense, single-stranded RNA virus that belongs to the Filoviridae family. Despite having caused numerous outbreaks of severe hemorrhagic fever with high case fatality rates, there are still no clinically approved therapeutics or vaccines to treat or prevent MARV disease. Recombinant vesicular stomatitis viruses (rVSVs) expressing heterologous viral glycoproteins have shown remarkable promise as live-attenuated vaccine vectors, with an rVSV-based Ebola virus vaccine having received regulatory approval in the United States and numerous other countries. Analogous rVSV vaccine vectors have also been developed for MARV and have shown efficacy in several preclinical studies conducted in nonhuman primates. Here, we used a guinea pig model to confirm the protective efficacy of a cloned, rVSV-based candidate vaccine, termed PHV01, expressing the MARV variant Angola glycoprotein. Our results demonstrated that a single dose (2 × 10⁶ PFU) of vaccine administered 28 days prior to challenge with a uniformly lethal dose of guinea-pig-adapted MARV variant Angola provided complete protection from death and disease. Moreover, protection was robust, with as little as 200 PFU of vaccine conferring significant protection. Not only does this study highlight the potential predictive value of the guinea pig model in the evaluation of MARV countermeasures, but it also demonstrates consistent and reproducible protection afforded by a clonal vaccine candidate. Indeed, this study identifies PHV01 as a suitable vaccine candidate for advanced development.

Contribution of magnetic particles in molecular diagnosis of human viruses

Viral diseases are the primary source of death, making a worldwide influence on healthcare, social, and economic development. Thus, diagnosis is the vital approach to the main aim of virus control and elimination. On the other hand, the prompt advancement of nanotechnology in the field of medicine possesses the probability of being beneficial to diagnose infections normally in labs as well as specifically. Nanoparticles are efficiently in use to make novel strategies because of permitting analysis at cellular in addition to the molecular scale. Henceforth, they assist towards pronounced progress concerning molecular analysis at the nanoscale. In recent times, magnetic nanoparticles conjugated through covalent bonds to bioanalytes for instance peptides, antibodies, nucleic acids, plus proteins are established like nanoprobes aimed at molecular recognition. These modified magnetic nanoparticles could offer a simple fast approach for extraction, purification, enrichment/concentration, besides viruses' recognition precisely also specifically. In consideration of the above, herein insight and outlook into the limitations of conventional methods and numerous roles played by magnetic nanoparticles to extract, purify, concentrate, and additionally in developing a diagnostic regime for viral outbreaks to combat viruses especially the ongoing novel coronavirus (COVID-19).

VSV-Based Vaccines Reduce Virus Shedding and Viral Load in Hamsters Infected with SARS-CoV-2 Variants of Concern

The continued progression of the COVID-19 pandemic can partly be attributed to the ability of SARS-CoV-2 to mutate and introduce new viral variants. Some of these variants with the potential to spread quickly and conquer the globe are termed variants of concern (VOC). The existing vaccines implemented on a global scale are based on the ancestral strain, which has resulted in increased numbers of breakthrough infections as these VOC have emerged. It is imperative to show protection against VOC infection with newly developed vaccines. Previously, we evaluated two vesicular stomatitis virus (VSV)-based vaccines expressing the SARS-CoV-2 spike protein alone (VSV-SARS2) or in combination with the Ebola virus glycoprotein (VSV-SARS2-EBOV) and demonstrated their fast-acting potential. Here, we prolonged the time to challenge; we vaccinated hamsters intranasally (IN) or intramuscularly 28 days prior to infection with three SARS-CoV-2 VOC-the Alpha, Beta, and Delta variants. IN vaccination with either the VSV-SARS2 or VSV-SARS2-EBOV resulted in the highest protective efficacy as demonstrated by decreased virus shedding and lung viral load of vaccinated hamsters. Histopathologic analysis of the lungs revealed the least amount of lung damage in the IN-vaccinated animals regardless of the challenge virus. This data demonstrates the ability of a VSV-based vaccine to not only protect from disease caused by SARS-CoV-2 VOC but also reduce viral shedding.

Immunogenicity of a Recombinant VSV-Vectored SARS-CoV Vaccine Induced Robust Immunity in Rhesus Monkeys after Single-Dose Immunization

Severe acute respiratory syndrome (SARS) is a highly contagious zoonotic disease caused by SARS coronavirus (SARS-CoV). Since its outbreak in Guangdong Province of China in 2002, SARS has caused 8096 infections and 774 deaths by December 31st, 2003. Although there have been no more SARS cases reported in human populations since 2004, the recent emergence of a novel coronavirus disease (COVID-19) indicates the potential of the recurrence of SARS and other coronavirus disease among humans. Thus, developing a rapid response SARS vaccine to provide protection for human populations is still needed. Spike (S) protein of SARS-CoV can induce neutralizing antibodies, which is a pivotal immunogenic antigen for vaccine development. Here we constructed a recombinant chimeric vesicular stomatitis virus (VSV) VSVΔG-SARS, in which the glycoprotein (G) gene is replaced with the SARS-CoV S gene. VSVΔG-SARS maintains the bullet-like shape of the native VSV, with the heterogeneous S protein incorporated into its surface instead of G protein. The results of safety trials revealed that VSVΔG-SARS is safe and effective in mice at a dose of 1 ​× ​10⁶ TCID₅₀. More importantly, only a single-dose immunization of 2 ​× ​10⁷ TCID₅₀ can provide high-level neutralizing antibodies and robust T cell responses to non-human primate animal models. Thus, our data indicate that VSVΔG-SARS can be used as a rapid response vaccine candidate. Our study on the recombinant VSV-vectored SARS-CoV vaccines can accumulate experience and provide a foundation for the new coronavirus disease in the future.

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A chimeric recombinant VSV-vectored virus expressing SARS-CoV spike protein, VSVΔG-SARS, was constructed.

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The S protein efficiently incorporated into the envelope of VSVΔG-SARS and mediated cell entry through human ACE2.

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VSVΔG-SARS induced high levels of neutralizing antibody and T cell responses in monkeys after single dose immunization.

Single Dose of a VSV-Based Vaccine Rapidly Protects Macaques From Marburg Virus Disease

Marburg virus (MARV) is a member of the filovirus family that causes hemorrhagic disease with high case fatality rates. MARV is on the priority list of the World Health Organization for countermeasure development highlighting its potential impact on global public health. We developed a vesicular stomatitis virus (VSV)-based vaccine expressing the MARV glycoprotein (VSV-MARV) and previously demonstrated uniform protection of nonhuman primates (NHPs) with a single dose. Here, we investigated the fast-acting potential of this vaccine by challenging NHPs with MARV 14, 7 or 3 days after a single dose vaccination with VSV-MARV. We found that 100% of the animals survived when vaccinated 7 or 14 days and 75% of the animal survived when vaccinated 3 days prior to lethal MARV challenge. Transcriptional analysis of whole blood samples indicated activation of B cells and antiviral defense after VSV-MARV vaccination. In the day -14 and -7 groups, limited transcriptional changes after challenge were observed with the exception of day 9 post-challenge in the day -7 group where we detected gene expression profiles indicative of a recall response. In the day -3 group, transcriptional analysis of samples from surviving NHPs revealed strong innate immune activation. In contrast, the animal that succumbed to disease in this group lacked signatures of antiviral immunity. In summary, our data demonstrate that the VSV-MARV is a fast-acting vaccine suitable for the use in emergency situations like disease outbreaks in Africa.

Therapeutic vaccination strategies against EBOV by rVSV-EBOV-GP: the role of innate immunity

Zaire Ebola virus (EBOV) is a member of the Filoviridae family. Infection with EBOV causes Ebola virus disease (EVD) characterized by excessive inflammation, lymphocyte death, coagulopathy, and multi-organ failure. In 2019, the FDA-approved the first anti-EBOV vaccine, rVSV-EBOV-GP (Ervebo® by Merck). This live-recombinant vaccine confers both prophylactic and therapeutic protection to nonhuman primates and humans. While mechanisms conferring prophylactic protection are well-investigated, those underlying protection conferred shortly before and after exposure to EBOV remain poorly understood. In this review, we review data from in vitro and in vivo studies analyzing early immune responses to rVSV-EBOV-GP and discuss the role of innate immune activation in therapeutic protection.

Vesicular Stomatitis Virus: From Agricultural Pathogen to Vaccine Vector

Vesicular stomatitis virus (VSV), which belongs to the Vesiculovirus genus of the family Rhabdoviridae, is a well studied livestock pathogen and prototypic non-segmented, negative-sense RNA virus. Although VSV is responsible for causing economically significant outbreaks of vesicular stomatitis in cattle, horses, and swine, the virus also represents a valuable research tool for molecular biologists and virologists. Indeed, the establishment of a reverse genetics system for the recovery of infectious VSV from cDNA transformed the utility of this virus and paved the way for its use as a vaccine vector. A highly effective VSV-based vaccine against Ebola virus recently received clinical approval, and many other VSV-based vaccines have been developed, particularly for high-consequence viruses. This review seeks to provide a holistic but concise overview of VSV, covering the virus's ascension from perennial agricultural scourge to promising medical countermeasure, with a particular focus on vaccines.

Systematic review of Marburg virus vaccine nonhuman primate studies and human clinical trials

BACKGROUND

Recent deadly outbreaks of Marburg virus underscore the need for an effective vaccine. A summary of the latest research is needed for this WHO priority pathogen. This systematic review aimed to determine progress towards a vaccine for Marburg virus.

METHODS

Article search criteria were developed to query PubMed for peer-reviewed articles from 1990 through 2019 on Marburg virus vaccine clinical trials in humans and pre-clinical studies in non-human primates (NHP). Abstracts were reviewed by two authors. Relevant articles were reviewed in full. Discrepancies were resolved by a third author. Data abstracted included year, author, title, vaccine construct, number of subjects, efficacy, and demographics. Assessment for risk of bias was performed using the Syrcle tool for animal studies, and the Cochrane Collaboration risk of bias tool for human studies.

RESULTS

101 articles were identified; 27 were related to Marburg vaccines. After full text review, 21 articles were selected. 215 human subjects were in three phase 1 clinical trials, and 203 NHP in 18 studies. Vaccine constructs were DNA plasmids, recombinant vesicular stomatitis virus (VSV) vectors, adenovirus vectors, virus-like particles (VLP), among others. Two human phase 1 studies of DNA vaccines had 4 adverse effects requiring vaccine discontinuation among 128 participants and 31-80% immunogenicity. In NHP challenge studies, 100% survival was seen in 6 VSV vectored vaccines, 2 DNA vaccines, 2 VLP vaccines, and in 1 adenoviral vectored vaccine.

CONCLUSION

In human trials, two Marburg DNA vaccines provided either low immunogenicity or a failure to elicit durable immunity. A variety of NHP candidate Marburg vaccines demonstrated favorable survival and immunogenicity parameters, to include VSV, VLP, and adenoviral vectored vaccines. Elevated binding antibodies appeared to be consistently associated with protection across the NHP challenge studies. Further human trials are needed to advance vaccines to limit the spread of this highly lethal virus.

To B or Not to B: Mechanisms of Protection Conferred by rVSV-EBOV-GP and the Roles of Innate and Adaptive Immunity

Zaire Ebola virus (EBOV) is a member of the Filoviridae family of negative sense, single-stranded RNA viruses. EBOV infection causes Ebola virus disease (EVD), characterized by coagulopathy, lymphopenia, and multi-organ failure, which can culminate in death. In 2019, the FDA approved the first vaccine against EBOV, a recombinant live-attenuated viral vector wherein the G protein of vesicular stomatitis virus is replaced with the glycoprotein (GP) of EBOV (rVSV-EBOV-GP, Ervebo^® by Merck). This vaccine demonstrates high efficacy in nonhuman primates by providing prophylactic, rapid, and post-exposure protection. In humans, rVSV-EBOV-GP demonstrated 100% protection in several phase III clinical trials in over 10,000 individuals during the 2013–2016 West Africa epidemic. As of 2020, over 218,000 doses of rVSV-EBOV-GP have been administered to individuals with high risk of EBOV exposure. Despite licensure and robust preclinical studies, the mechanisms of rVSV-EBOV-GP-mediated protection are not fully understood. Such knowledge is crucial for understanding vaccine-mediated correlates of protection from EVD and to aid the further design and development of therapeutics against filoviruses. Here, we summarize the current literature regarding the host response to vaccination and EBOV exposure, and evidence regarding innate and adaptive immune mechanisms involved in rVSV-EBOV-GP-mediated protection, with a focus on the host transcriptional response. Current data strongly suggest a protective synergy between rapid innate and humoral immunity.

Viral Emerging Diseases: Challenges in Developing Vaccination Strategies

In the last decades, a number of infectious viruses have emerged from wildlife or re-emerged, generating serious threats to the global health and to the economy worldwide. Ebola and Marburg hemorrhagic fevers, Lassa fever, Dengue fever, Yellow fever, West Nile fever, Zika, and Chikungunya vector-borne diseases, Swine flu, Severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and the recent Coronavirus disease 2019 (COVID-19) are examples of zoonoses that have spread throughout the globe with such a significant impact on public health that the scientific community has been called for a rapid intervention in preventing and treating emerging infections. Vaccination is probably the most effective tool in helping the immune system to activate protective responses against pathogens, reducing morbidity and mortality, as proven by historical records. Under health emergency conditions, new and alternative approaches in vaccine design and development are imperative for a rapid and massive vaccination coverage, to manage a disease outbreak and curtail the epidemic spread. This review gives an update on the current vaccination strategies for some of the emerging/re-emerging viruses, and discusses challenges and hurdles to overcome for developing efficacious vaccines against future pathogens.

Modified vaccinia Ankara vaccine expressing Marburg virus-like particles protects guinea pigs from lethal Marburg virus infection

We introduce a new vaccine platform against Marburg virus (MARV) combining the advantages of the immunogenicity of a highly attenuated vaccine vector (Modified Vaccinia Ankara, MVA) with the authentic conformation of virus-like particles (VLPs). Our vaccine, MVA–MARV–VLP, expresses the minimal components of MARV VLPs: the envelope glycoprotein GP and the matrix protein VP40. Electron microscopy confirmed self-assembly and budding of VLPs from infected cells. Prime/boost vaccination of guinea pigs with MVA–MARV–VLP-elicited MARV-specific binding and neutralizing antibody responses. Vaccination also induced Fc-mediated innate immune effector functions including activation of NK cells and antibody-dependent phagocytosis by neutrophils and monocytes. Inoculation of vaccinated animals with guinea pig-adapted MARV demonstrated 100% protection against death and disease with no viremia. Therefore, our vaccine platform, expressing two antigens resulting in assembly of VLPs in the native conformation in vaccinated hosts, can be used as a potent vaccine against MARV.

Viral Hemorrhagic Fevers Other than Ebola and Lassa

Viral hemorrhagic fevers represent a group of diseases caused by enveloped RNA viruses. The epidemiology is broadly variable, ranging from geographically localized to more diffuse infections. Viral hemorrhagic fevers are classified as category A bioweapon agents by the Centers for Disease Control and Prevention. Viral hemorrhagic fevers are severe febrile illnesses with hemorrhagic phenomena. Laboratory diagnosis takes place in highly specialized reference laboratories. Treatment is essentially supportive. In this article, we focus the attention on yellow fever and viral hemorrhagic fevers other than Ebola and Lassa virus diseases that have been described elsewhere in this issue.

Immune correlates of postexposure vaccine protection against Marburg virus

Postexposure immunization can prevent disease and reduce transmission following pathogen exposure. The rapid immunostimulatory properties of recombinant vesicular stomatitis virus (rVSV)-based vaccines make them suitable postexposure treatments against the filoviruses Ebola virus and Marburg virus (MARV); however, the mechanisms that drive this protection are undefined. Previously, we reported 60–75% survival of rhesus macaques treated with rVSV vectors expressing MARV glycoprotein (GP) 20–30 minutes after a low dose exposure to the most pathogenic variant of MARV, Angola. Survival in this model was linked to production of GP-specific antibodies and lower viral load. To confirm these results and potentially identify novel correlates of postexposure protection, we performed a similar experiment, but analyzed plasma cytokine levels, frequencies of immune cell subsets, and the transcriptional response to infection in peripheral blood. In surviving macaques (80–89%), we observed induction of genes mapping to antiviral and interferon-related pathways early after treatment and a higher percentage of T helper 1 (Th1) and NK cells. In contrast, the response of non-surviving macaques was characterized by hypercytokinemia; a T helper 2 signature; recruitment of low HLA-DR expressing monocytes and regulatory T-cells; and transcription of immune checkpoint (e.g., PD-1, LAG3) genes. These results suggest dysregulated immunoregulation is associated with poor prognosis, whereas early innate signaling and Th1-skewed immunity are important for survival.

Marburg virus pathogenesis - differences and similarities in humans and animal models

Marburg virus (MARV) is a highly pathogenic virus associated with severe disease and mortality rates as high as 90%. Outbreaks of MARV are sporadic, deadly, and often characterized by a lack of resources and facilities to diagnose and treat patients. There are currently no approved vaccines or treatments, and the chaotic and infrequent nature of outbreaks, among other factors, makes testing new countermeasures during outbreaks ethically and logistically challenging. Without field efficacy studies, researchers must rely on animal models of MARV infection to assess the efficacy of vaccines and treatments, with the limitations being the accuracy of the animal model in recapitulating human pathogenesis. This review will compare various animal models to the available descriptions of human pathogenesis and aims to evaluate their effectiveness in modeling important aspects of Marburg virus disease.

Single low-dose VSV-EBOV vaccination protects cynomolgus macaques from lethal Ebola challenge

Background

Ebola virus (EBOV), variant Makona, was the causative agent of the 2013–2016 West African epidemic responsible for almost 30,000 human infections and over 11,000 fatalities. During the epidemic, the development of several experimental vaccines was accelerated through human clinical trials. One of them, the vesicular stomatitis virus (VSV)-based vaccine VSV-EBOV, showed promising efficacy in a phase 3 clinical trial in Guinea and is currently used in the ongoing EBOV outbreak in the northeastern part of the Democratic Republic of the Congo (DRC). This vaccine expresses the EBOV-Kikwit glycoprotein from the 1995 outbreak as the immunogen.

Methods

Here we generated a VSV-based vaccine expressing the contemporary EBOV-Makona glycoprotein. We characterized the vaccine in tissue culture and analyzed vaccine efficacy in the cynomolgus macaque model. Subsequently, we determined the dose-dependent protective efficacy in nonhuman primates against lethal EBOV challenge.

Findings

We observed complete protection from disease with VSV-EBOV doses ranging from 1 × 10⁷ to 1 × 10¹ plaque-forming units. Some protected animals receiving lower vaccine doses developed temporary low-level EBOV viremia. Control animals developed classical EBOV disease and reached euthanasia criteria within a week after challenge. This study demonstrates that very low doses of VSV-EBOV uniformly protect macaques against lethal EBOV challenge.

Interpretation

Our study provides missing pre-clinical data supporting the use of reduced VSV-EBOV vaccine doses without decreasing protective efficacy and at the same time increase vaccine safety and availability - two critical concerns in public health response.

Funding

Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health.

Recombinant vesicular stomatitis virus vector vaccines for WHO blueprint priority pathogens

The devastating Ebola virus (EBOV) outbreak in West Africa in 2013-2016 has flagged the need for the timely development of vaccines for high-threat pathogens. To be better prepared for new epidemics, the WHO has compiled a list of priority pathogens that are likely to cause future outbreaks and for which R&D efforts are, therefore, paramount (R&D Blueprint: https://www.who.int/blueprint/priority-diseases/en/ ). To this end, the detailed characterization of vaccine platforms is needed. The vesicular stomatitis virus (VSV) has been established as a robust vaccine vector backbone for infectious diseases for well over a decade. The recent clinical trials testing the vaccine candidate VSV-EBOV against EBOV disease now have added a substantial amount of clinical data and suggest VSV to be an ideal vaccine vector candidate for outbreak pathogens. In this review, we discuss insights gained from the clinical VSV-EBOV vaccine trials as well as from animal studies investigating vaccine candidates for Blueprint pathogens.

Recent advances in marburgvirus research

Marburgviruses are closely related to ebolaviruses and cause a devastating disease in humans. In 2012, we published a comprehensive review of the first 45 years of research on marburgviruses and the disease they cause, ranging from molecular biology to ecology. Spurred in part by the deadly Ebola virus outbreak in West Africa in 2013-2016, research on all filoviruses has intensified. Not meant as an introduction to marburgviruses, this article instead provides a synopsis of recent progress in marburgvirus research with a particular focus on molecular biology, advances in animal modeling, and the use of Egyptian fruit bats in infection experiments.