The effect of dose on the safety and immunogenicity of the VSV Ebola candidate vaccine: a randomised double-blind, placebo-controlled phase 1/2 trial

Knowledge, attitudes, and practices and long-term immune response after rVSVΔG-ZEBOV-GP Ebola vaccination in healthcare workers in high-risk districts in Uganda

BACKGROUND

The rVSVΔG-ZEBOV-GP Ebola vaccine (rVSV-ZEBOV) has been used in response to Ebola disease outbreaks caused by Ebola virus (EBOV). Understanding Ebola knowledge, attitudes, and practices (KAP) and the long-term immune response following rVSV-ZEBOV are critical to inform recommendations on future use.

METHODS

We administered surveys and collected blood samples from healthcare workers (HCWs) from seven Ugandan healthcare facilities. Questionnaires collected information on demographic characteristics and KAP related to Ebola and vaccination. IgG ELISA, virus neutralization, and interferon gamma ELISpot measured immunological responses against EBOV glycoprotein (GP).

RESULTS

Overall, 37 % (210/565) of HCWs reported receiving any Ebola vaccination. Knowledge that rVSV-ZEBOV only protects against EBOV was low among vaccinated (32 %; 62/192) and unvaccinated (7 %; 14/200) HCWs. Most vaccinated (91 %; 192/210) and unvaccinated (92 %; 326/355) HCWs wanted to receive a booster or initial dose of rVSV-ZEBOV, respectively. Median time from rVSV-ZEBOV vaccination to sample collection was 37.7 months (IQR: 30.5, 38.3). IgG antibodies against EBOV GP were detected in 95 % (61/64) of HCWs with vaccination cards and in 84 % (162/194) of HCWs who reported receiving a vaccination. Geometric mean titer among seropositive vaccinees was 0.066 IU/mL (95 % CI: 0.058-0.076).

CONCLUSION

As Uganda has experienced outbreaks of Sudan virus and Bundibugyo virus, for which rVSV-ZEBOV does not protect against, our findings underscore the importance of continued education and risk communication to HCWs on Ebola and other viral hemorrhagic fevers. IgG antibodies against EBOV GP were detected in most vaccinated HCWs in Uganda 2─4 years after vaccination; however, the duration and correlates of protection warrant further investigation.

Replication, safety and immunogenicity of the vectored Ebola vaccine rVSV-ΔG-ZEBOV-GP in a sub-Saharan African paediatric population: A randomised controlled, open-label trial in children aged 1-12 years living in Lambaréné, Gabon

BACKGROUND

Unlike adults, children experienced stronger and longer vector replication in plasma and shedding in saliva following rVSVΔG-ZEBOV-GP vaccination. The resulting risks of immunosuppression or immune hyperactivation leading to increased Adverse Events (AEs) and altered antibody responses are concerns that have been addressed in the present manuscript.

METHODS

Children aged 1-12 years living in Gabon received either rVSVΔG-ZEBOV-GP (ERVEBO®) vaccine or the varicella-zoster virus (VZV) vaccine (VZV). The concentration of rVSVΔG vector in blood and saliva, the occurrence of AEs up to day 28; the anti-rVSVΔG-ZEBOV-GP and anti-VZV IgG antibody titres, neutralising and avidity functions of anti-rVSVΔG-ZEBOV-GP by day 365; were assessed in serum. (PACTR202005733552021) FINDINGS: In the rVSVΔG-ZEBOV-GP group, 70% and 7% of children had >0 copies/ml of rVSVΔG respectively in plasma by day 3 and in saliva by day 14 after vaccination, with no detection on day 28. Significantly higher but transient AEs occurred in the rVSVΔG-ZEBOV-GP group. Both vaccines induced seroconversion on day 28 and sustainable IgG antibody titres by day 365. Avidity and neutralisation functions of the anti-rVSVΔG-ZEBOV-GP antibodies peaked at day 28 and were maintained by day 365.

INTERPRETATION

The replication and shedding do not affect the favourable risk-benefit balance of the rVSVΔG-ZEBOV-GP in children.

An efficient plasmid-based system for the recovery of recombinant vesicular stomatitis virus encoding foreign glycoproteins

Viral glycoproteins mediate entry into host cells, thereby dictating host range and pathogenesis. In addition, they constitute the principal target of neutralizing antibody responses, making them important antigens in vaccine development. Recombinant vesicular stomatitis virus (VSV) encoding foreign glycoproteins can provide a convenient and safe surrogate system to interrogate the function, evolution, and antigenicity of viral glycoproteins from viruses that are difficult to manipulate or those requiring high biosafety level containment. However, the production of recombinant VSV can be technically challenging. In this work, we present an efficient and robust plasmid-based system for the production of recombinant VSV encoding foreign glycoproteins. We validate the system using glycoproteins from different viral families, including arenaviruses, coronaviruses, and hantaviruses, as well as highlight their utility for studying the effects of mutations on viral fitness. Overall, the methods described herein can facilitate the study of both native and recombinant VSV encoding foreign glycoproteins and can serve as the basis for the production of VSV-based vaccines.

An mRNA-LNP-based Lassa virus vaccine induces protective immunity in mice

The mammarenavirus Lassa virus (LASV) causes the life-threatening hemorrhagic fever disease, Lassa fever. The lack of licensed medical countermeasures against LASV underscores the urgent need for the development of novel LASV vaccines, which has been hampered by the requirement for a biosafety level 4 facility to handle live LASV. Here, we investigated the efficacy of mRNA-lipid nanoparticle (mRNA-LNP)-based vaccines expressing the LASV glycoprotein precursor (LASgpc) or nucleoprotein (LCMnp) of the prototypic mammarenavirus, lymphocytic choriomeningitis virus (LCMV), in mice. Two doses of LASgpc- or LCMnp-mRNA-LNP administered intravenously (i.v.) protected C57BL/6 mice from a lethal challenge with a recombinant (r) LCMV expressing a modified LASgpc (rLCMV/LASgpc2m) inoculated intracranially. Intramuscular (i.m.) immunization with two doses of LASgpc- or LCMnp-mRNA-LNP significantly reduced the viral load in C57BL/6 mice inoculated i.v. with rLCMV/LASgpc2m. High levels of viremia and lethality were observed in CBA mice inoculated i.v. with rLCMV/LASgpc2m, which were abrogated by i.m. immunization with two doses of LASgpc-mRNA-LNP. The protective efficacy of two i.m. doses of LCMnp-mRNA-LNP was confirmed in a lethal hemorrhagic disease model of FVB mice i.v. inoculated with wild-type rLCMV. In all conditions tested, negligible and high levels of LASgpc- and LCMnp-specific antibodies were detected in mRNA-LNP-immunized mice, respectively, but robust LASgpc- and LCMnp-specific CD8+ T cell responses were induced. Accordingly, plasma from LASgpc-mRNA-LNP-immunized mice did not exhibit neutralizing activity. Our findings and surrogate mouse models of LASV infection, which can be studied at a reduced biocontainment level, provide a critical foundation for the rapid development of mRNA-LNP-based LASV vaccines.IMPORTANCELassa virus (LASV) is a highly pathogenic mammarenavirus responsible for several hundred thousand infections annually in West African countries, causing a high number of lethal Lassa fever (LF) cases. Despite its significant impact on human health, clinically approved, safe, and effective medical countermeasures against LF are not available. The requirement of a biosafety level 4 facility to handle live LASV has been one of the main obstacles to the research and development of LASV countermeasures. Here, we report that two doses of mRNA-lipid nanoparticle-based vaccines expressing the LASV glycoprotein precursor (LASgpc) or nucleoprotein (LCMnp) of lymphocytic choriomeningitis virus (LCMV), a mammarenavirus genetically closely related to LASV, conferred protection to recombinant LCMV-based surrogate mouse models of lethal LASV infection. Notably, robust LASgpc- and LCMnp-specific CD8+ T cell responses were detected in mRNA-LNP-immunized mice, whereas no virus-neutralizing activity was observed.

Impact of Recombinant VSV-HIV Prime, DNA-Boost Vaccine Candidates on Immunogenicity and Viremia on SHIV-Infected Rhesus Macaques

Currently, no effective vaccine to prevent human immunodeficiency virus (HIV) infection is available, and various platforms are being examined. The vesicular stomatitis virus (VSV) vaccine vehicle can induce robust humoral and cell-mediated immune responses, making it a suitable candidate for the development of an HIV vaccine. Here, we analyze the protective immunological impacts of recombinant VSV vaccine vectors that express chimeric HIV Envelope proteins (Env) in rhesus macaques. To improve the immunogenicity of these VSV-HIV Env vaccine candidates, we generated chimeric Envs containing the transmembrane and cytoplasmic tail of the simian immunodeficiency virus (SIV), which increases surface Env on the particle. Additionally, the Ebola virus glycoprotein was added to the VSV-HIV vaccine particles to divert tropism from CD4 T cells and enhance their replications both in vitro and in vivo. Animals were boosted with DNA constructs that encoded matching antigens. Vaccinated animals developed non-neutralizing antibody responses against both the HIV Env and the Ebola virus glycoprotein (EBOV GP) as well as systemic memory T-cell activation. However, these responses were not associated with observable protection against simian-HIV (SHIV) infection following repeated high-dose intra-rectal SHIV SF162p3 challenges.

Heterologous cAd3-Ebola and MVA-EbolaZ vaccines are safe and immunogenic in US and Uganda phase 1/1b trials

Ebola virus disease (EVD) is a filoviral infection caused by virus species of the Ebolavirus genus including Zaire ebolavirus (EBOV) and Sudan ebolavirus (SUDV). We investigated the safety and immunogenicity of a heterologous prime-boost regimen involving a chimpanzee adenovirus 3 vectored Ebola vaccine [either monovalent (cAd3-EBOZ) or bivalent (cAd3-EBO)] prime followed by a recombinant modified vaccinia virus Ankara EBOV vaccine (MVA-EbolaZ) boost in two phase 1/1b randomized open-label clinical trials in healthy adults in the United States (US) and Uganda (UG). Trial US (NCT02408913) enrolled 140 participants, including 26 EVD vaccine-naïve and 114 cAd3-Ebola-experienced participants (April-November 2015). Trial UG (NCT02354404) enrolled 90 participants, including 60 EVD vaccine-naïve and 30 DNA Ebola vaccine-experienced participants (February-April 2015). All tested vaccines and regimens were safe and well tolerated with no serious adverse events reported related to study products. Solicited local and systemic reactogenicity was mostly mild to moderate in severity. The heterologous prime-boost regimen was immunogenic, including induction of durable antibody responses which peaked as early as two weeks and persisted up to one year after each vaccination. Different prime-boost intervals impacted the magnitude of humoral and cellular immune responses. The results from these studies demonstrate promising implications for use of these vaccines in both prophylactic and outbreak settings.

Refined innate plasma signature after rVSVΔG-ZEBOV-GP immunization is shared among adult cohorts in Europe and North America

Background

During the last decade Ebola virus has caused several outbreaks in Africa. The recombinant vesicular stomatitis virus-vectored Zaire Ebola (rVSVΔG-ZEBOV-GP) vaccine has proved safe and immunogenic but is reactogenic. We previously identified the first innate plasma signature response after vaccination in Geneva as composed of five monocyte-related biomarkers peaking at day 1 post-immunization that correlates with adverse events, biological outcomes (haematological changes and viremia) and antibody titers. In this follow-up study, we sought to identify additional biomarkers in the same Geneva cohort and validate those identified markers in a US cohort.

Methods

Additional biomarkers were identified using multiplexed protein biomarker platform O-link and confirmed by Luminex. Principal component analysis (PCA) evaluated if these markers could explain a higher variability of the vaccine response (and thereby refined the initial signature). Multivariable and linear regression models evaluated the correlations of the main components with adverse events, biological outcomes, and antibody titers. External validation of the refined signature was conducted in a second cohort of US vaccinees (n=142).

Results

Eleven additional biomarkers peaked at day 1 post-immunization: MCP2, MCP3, MCP4, CXCL10, OSM, CX3CL1, MCSF, CXCL11, TRAIL, RANKL and IL15. PCA analysis retained three principal components (PC) that accounted for 79% of the vaccine response variability. PC1 and PC2 were very robust and had different biomarkers that contributed to their variability. PC1 better discriminated different doses, better defined the risk of fever and myalgia, while PC2 better defined the risk of headache. We also found new biomarkers that correlated with reactogenicity, including transient arthritis (MCP-2, CXCL10, CXCL11, CX3CL1, MCSF, IL-15, OSM). Several innate biomarkers are associated with antibody levels one and six months after vaccination. Refined PC1 correlated strongly in both data sets (Geneva: r = 0.97, P < 0.001; US: r = 0.99, P< 0.001).

Conclusion

Eleven additional biomarkers refined the previously found 5-biomarker Geneva signature. The refined signature better discriminated between different doses, was strongly associated with the risk of adverse events and with antibody responses and was validated in a separate cohort.

Immunogenicity and safety of ebolavirus vaccines in healthy adults: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

This review aimed to systematically evaluate the immunogenicity and safety of the candidate Ebola virus vaccine (EVV).

METHODS

We searched five databases for randomized controlled trials (RCTs) evaluating the effects of EVV on healthy adults. The primary outcomes were relative risk (RR) of sero-conversion or sero-response of EVV in healthy adults between the groups that received EVV and the controls.

RESULTS

Twenty-nine RCTs (n = 23573) were included. There was a significant difference in RR of sero-conversion of EVV (RR 13.18; 95% CI 11.28-15.41; I2 = 33%; P < 0.01) between the two groups. There was a significant difference in RR of adverse events (AEs) of EVV (RR 1.49; 95% CI 1.27-1.74; I2 = 88%; P < 0.01), although no difference in RR of serious AE (SAE) between the two groups. Subgroup analysis showed that there was no significant difference in RR of AEs for DNAEBO, EBOV-GP, MVA, and rVSVN4CT1 vaccines, compared with controls.

CONCLUSIONS

The DNAEBO, EBOV-GP, MVA, and rVSVN4CT1 vaccines are likely to be safe and immunogenic, tending to support the vaccination against Ebola disease. These findings should provide much-needed evidence for public health policy makers to develop preventive measures based on disease prevalence features and socio-economic conditions.

The Utilization and Development of Viral Vectors in Vaccines as a Prophylactic Treatment Against Ebola Virus as an Emerging and Zoonotic Infectious Disease

Alongside the prescription of commonly used antivirals, such as acyclovir, remdesivir, oseltamivir, and ciprofloxacin, the most efficient way to prevent or treat communicable diseases is by vaccination. Vaccines have been the most efficient way to prevent or treat highly transmissible infectious agents, such as Ebola, Anthrax, and Dengue Fever. Most epidemics of these highly transmissible infectious agents occur in places, such as South America, Central America, Tropical Asia, and Africa, where the availability of resources and access to adequate healthcare are limited. However, recent events in history have proven that even with access to resources and proper healthcare, those in firstworld countries are not invincible when it comes to infectious diseases and epidemics. The Ebola virus outbreak in West Africa highlighted the gaps in therapeutic advancement and readiness and led to the rapid development of novel vaccine approaches. Viral vectors, in the case of the Ebola vaccine the Vesicular Stomatitis Virus (VSV), can be safely used to activate or initiate the innate adaptive immune response to protect against viral infection. When developed properly and with extensive study, novel vaccine approaches allow physicians and health experts to control the rate at which viruses spread or prevent transmission. This review will discuss the advantages of viral vector vaccines, their chemistry and development, and the pathophysiology of the Ebola virus to develop advantageous and efficacious treatments.

Global blood miRNA profiling unravels early signatures of immunogenicity of Ebola vaccine rVSVΔG-ZEBOV-GP

The vectored Ebola vaccine rVSVΔG-ZEBOV-GP elicits protection against Ebola Virus Disease (EVD). In a study of forty-eight healthy adult volunteers who received either the rVSVΔG-ZEBOV-GP vaccine or placebo, we profiled intracellular microRNAs (miRNAs) from whole blood cells (WB) and circulating miRNAs from serum-derived extracellular vesicles (EV) at baseline and longitudinally following vaccination. Further, we identified early miRNA signatures associated with ZEBOV-specific IgG antibody responses at baseline and up to one year post-vaccination, and pinpointed target mRNA transcripts and pathways correlated to miRNAs whose expression was altered after vaccination by using systems biology approaches. Several miRNAs were differentially expressed (DE) and miRNA signatures predicted high or low IgG ZEBOV-specific antibody levels with high classification performance. The top miRNA discriminators were WB-miR-6810, EV-miR-7151-3p, and EV-miR-4426. An eight-miRNA antibody predictive signature was associated with immune-related target mRNAs and pathways. These findings provide valuable insights into early blood biomarkers associated with rVSVΔG-ZEBOV-GP vaccine-induced IgG antibody responses.

Antibody responses to recombinant vesicular stomatitis virus-Zaire Ebolavirus vaccination for Ebola virus disease across doses and continents: 5-year durability

OBJECTIVES

To report 5-year persistence and avidity of antibodies produced by the live-attenuated recombinant vesicular stomatitis virus (rVSV) expressing the Zaire Ebolavirus (ZEBOV) glycoprotein (GP), known as rVSV-ZEBOV (Ervebo®).

METHODS

Healthy adults vaccinated with 300,000 or 10-50 million plaque-forming units of rVSV-ZEBOV in the WHO-coordinated trials of 2014-2015 were followed for up to 4 (Lambaréné, Gabon) and 5 (Geneva, Switzerland) years. We report seropositivity rates, geometric mean titres (GMTs), and population distribution of ZEBOV-GP ELISA IgG antibodies, neutralizing antibodies (pseudovirus and live-virus neutralization) and antibody avidity; the primary outcome was ZEBOV-GP ELISA IgG GMTs at 4 or 5 years compared with 1 year (Y1) after immunization.

RESULTS

Among the 168 eligible vaccinees (Geneva: 97 and Lambaréné: 71) enrolled 1 year post-immunization, 146 (87%) remained enrolled at 4 years (Geneva: n = 88, Lambaréné: n = 58), and 84 (87%, Geneva) at 5 years post-vaccination. ZEBOV-GP ELISA IgG GMTs plateaued, with no declining trend from 1 year through the last time point assessed (1147.8 [95% CI 874.3-1507.0] at Y1 versus 1548.1 [95% CI 1136.6-2108.5] at Y5 in Geneva volunteers receiving ≥10 million plaque-forming units of rVSV-ZEBOV), their avidity matching that of ZEBOV convalescents. Live-virus neutralizing antibodies were detected for shorter periods and in fewer vaccinees (53/95 [56%] at Y1 versus 35/84 [42%] at Y5 in Geneva volunteers, all dose levels).

DISCUSSION

Titres at Y1 emerged as a correlate of antibody persistence at Y5. The findings of persistent ZEBOV-GP ELISA IgG titres yet shorter-lasting, lower titres of live-virus neutralizing antibodies suggest the contribution of antibody-mediated protective mechanisms other than neutralization. Long-term clinical efficacy of rVSV-ZEBOV, however, requires further study.

Immunogenicity of mucosal COVID-19 vaccine candidates based on the highly attenuated vesicular stomatitis virus vector (VSVMT) in golden syrian hamster

COVID-19 is caused by coronavirus SARS-CoV-2. Current systemic vaccines generally provide limited protection against viral replication and shedding within the airway. Recombinant VSV (rVSV) is an effective vector which inducing potent and comprehensive immunities. Currently, there are two clinical trials investigating COVID-19 vaccines based on VSV vectors. These vaccines were developed with spike protein of WA1 which administrated intramuscularly. Although intranasal route is ideal for activating mucosal immunity with VSV vector, safety is of concern. Thus, a highly attenuated rVSV with three amino acids mutations in matrix protein (VSVMT) was developed to construct safe mucosal vaccines against multiple SARS-CoV-2 variants of concern. It demonstrated that spike protein mutant lacking 21 amino acids in its cytoplasmic domain could rescue rVSV efficiently. VSVMT indicated improved safeness compared with wild-type VSV as the vector encoding SARS-CoV-2 spike protein. With a single-dosed intranasal inoculation of rVSVΔGMT-SΔ21, potent SARS-CoV-2 specific neutralization antibodies could be stimulated in animals, particularly in term of mucosal and cellular immunity. Strikingly, the chimeric VSV encoding SΔ21 of Delta-variant can induce more potent immune responses compared with those encoding SΔ21 of Omicron- or WA1-strain. VSVMT is a promising platform to develop a mucosal vaccine for countering COVID-19.

A Highly Attenuated Panfilovirus VesiculoVax Vaccine Rapidly Protects Nonhuman Primates Against Marburg Virus and 3 Species of Ebola Virus

BACKGROUND

The family Filoviridae consists of several virus members known to cause significant mortality and disease in humans. Among these, Ebola virus (EBOV), Marburg virus (MARV), Sudan virus (SUDV), and Bundibugyo virus (BDBV) are considered the deadliest. The vaccine, Ervebo, was shown to rapidly protect humans against Ebola disease, but is indicated only for EBOV infections with limited cross-protection against other filoviruses. Whether multivalent formulations of similar recombinant vesicular stomatitis virus (rVSV)-based vaccines could likewise confer rapid protection is unclear.

METHODS

Here, we tested the ability of an attenuated, quadrivalent panfilovirus VesiculoVax vaccine (rVSV-Filo) to elicit fast-acting protection against MARV, EBOV, SUDV, and BDBV. Groups of cynomolgus monkeys were vaccinated 7 days before exposure to each of the 4 viral pathogens. All subjects (100%) immunized 1 week earlier survived MARV, SUDV, and BDBV challenge; 80% survived EBOV challenge. Survival correlated with lower viral load, higher glycoprotein-specific immunoglobulin G titers, and the expression of B-cell-, cytotoxic cell-, and antigen presentation-associated transcripts.

CONCLUSIONS

These results demonstrate multivalent VesiculoVax vaccines are suitable for filovirus outbreak management. The highly attenuated nature of the rVSV-Filo vaccine may be preferable to the Ervebo "delta G" platform, which induced adverse events in a subset of recipients.

Extracellular vesicle storm during the course of Ebola virus infection in primates

Introduction

Ebola virus (EBOV) is an RNA virus of the Filoviridae family that is responsible for outbreaks of hemorrhagic fevers in primates with a lethality rate as high as 90%. EBOV primarily targets host macrophages leading to cell activation and systemic cytokine storm, and fatal infection is associated with an inhibited interferon response, and lymphopenia. The EBOV surface glycoprotein (GP) has been shown to directly induce T cell depletion and can be secreted outside the virion via extracellular vesicles (EVs), though most studies are limited to epithelial cells and underlying mechanisms remain poorly elucidated.

Methods

To assess the role of GP on EBOV-induced dysregulation of host immunity, we first utilized EBOV virus-like particles (VLPs) expressing VP40 and NP either alone (Bald-VLP) or in conjunction with GP (VLP-GP) to investigate early inflammatory responses in THP-1 macrophages and in a murine model. We then sought to decipher the role of non-classical inflammatory mediators such as EVs over the course of EBOV infection in two EBOV-infected rhesus macaques by isolating and characterizing circulatory EVs throughout disease progression using size exclusion chromatography, nanoparticle tracking-analysis, and LC-MS/MS.

Results

While all VLPs could induce inflammatory mediators and recruit small peritoneal macrophages, pro-inflammatory cytokine and chemokine gene expression was exacerbated by the presence of GP. Further, quantification of EVs isolated from infected rhesus macaques revealed that the concentration of vesicles peaked in circulation at the terminal stage, at which time EBOV GP could be detected in host-derived exosomes. Moreover, comparative proteomics conducted across EV populations isolated from serum at various time points before and after infection revealed differences in host-derived protein content that were most significantly pronounced at the endpoint of infection, including significant expression of mediators of TLR4 signaling.

Discussion

These results suggest a dynamic role for EVs in the modification of disease states in the context of EBOV. Overall, our work highlights the importance of viral factors, such as the GP, and host derived EVs in the inflammatory cascade and pathogenesis of EBOV, which can be collectively further exploited for novel antiviral development.

Baseline gene signatures of reactogenicity to Ebola vaccination: a machine learning approach across multiple cohorts

Introduction

The rVSVDG-ZEBOV-GP (Ervebo®) vaccine is both immunogenic and protective against Ebola. However, the vaccine can cause a broad range of transient adverse reactions, from headache to arthritis. Identifying baseline reactogenicity signatures can advance personalized vaccinology and increase our understanding of the molecular factors associated with such adverse events.

Methods

In this study, we developed a machine learning approach to integrate prevaccination gene expression data with adverse events that occurred within 14 days post-vaccination.

Results and Discussion

We analyzed the expression of 144 genes across 343 blood samples collected from participants of 4 phase I clinical trial cohorts: Switzerland, USA, Gabon, and Kenya. Our machine learning approach revealed 22 key genes associated with adverse events such as local reactions, fatigue, headache, myalgia, fever, chills, arthralgia, nausea, and arthritis, providing insights into potential biological mechanisms linked to vaccine reactogenicity.

[Vaccines to prevent Ebola virus disease: current challenges and perspectives]

RELEVANCE

Ebola virus disease (EVD) is an acute infectious disease with an extremely high case fatality rate reaching up to 90%. EVD has become widely known since 2014-2016, when outbreak in West Africa occurred and led to epidemic, which caused travel-related cases on the territory of other continents. There are two vaccines against EVD, prequalified by WHO for emergency use, as well as a number of vaccines, approved by local regulators in certain countries. However, even with the availability of effective vaccines, the lack of data on immune correlates of protection and duration of protective immune response in humans and primates is limiting factor for effectively preventing the spread of EVD outbreaks.

AIMS

This review highlights experience of use of EVD vaccines during outbreaks in endemic areas, summarizes data on vaccine immunogenicity in clinical trials, and discusses perspectives for further development and use of effective EVD vaccines.

Nonclinical safety assessment and immunogenicity of rVSVInd(GML)-mspSGtc vaccine for SARS-CoV-2 in rabbits

The worldwide health, economic, and societal consequences of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic have been devastating. The primary strategy to prevent new infectious diseases is to vaccinate the majority of people worldwide. However, the significant hurdles that are faced include vaccine safety concerns and vaccine reluctance. Among the various types of vaccines, the recombinant vesicular stomatitis virus (rVSV) is a promising candidate owing to its safety and efficacy. Therefore, we investigated the toxicity, immunogenicity, and local tolerance of the rVSVInd(GML)-mspSGtc vaccine against SARS-CoV-2. New Zealand White (NZW) rabbits were administered single or three repeated intramuscular injections of rVSVInd(GML)-mspSGtc every 2 weeks, followed by a 4-week recovery period. Male and female rabbits were randomly assigned into three groups: a control group and two dose-level groups (1 × 109 and 4 × 109 PFU/mL). Treatment-related changes included a temporary increase in body temperature and local inflammation at the injection site. These findings indicated recovery or a trend toward recovery, with no overt systemic toxicity. Immunogenicity analysis results suggested that rVSVInd(GML)-mspSGtc elicited a robust dose-dependent immune response in terms of neutralizing antibodies and IgG antibodies against the SARS-CoV-2 spike protein. In addition, the immune response intensity was increased by repeated vaccine administration. In conclusion, both the approximate lethal dose and the no observed adverse effect level for rVSVInd(GML)-mspSGtc exceeded 4 × 109 PFU/mL in NZW rabbits. Overall, rVSVInd(GML)-mspSGtc induced no adverse effects at the maximum dosage tested; however, its efficacy warrants further clinical evaluation.

A review of criteria strictness in "Toxicity Grading Scale for Healthy Adult and Adolescent Volunteers Enrolled in Preventive Vaccine Clinical Trials"

To assess safety in vaccine development, stricter grading scales, such as the "Toxicity Grading Scale for Healthy Adult and Adolescent Volunteers Enrolled in Preventive Vaccine Clinical Trials" issued by the U.S. Food and Drug Administration (FDA grading scale), are required. However, concern exists that their strictness may lead to an overestimation of some adverse events (AEs). We analyzed the details of AEs in a phase I clinical trial of a preventive vaccine for infectious diseases. In this trial, we observed the high occurrence of Grade 1 or greater AEs in hemoglobin changes from baseline value, and hypernatremia, and hypokalemia by FDA grading scale. The range considered as non-AE according to the FDA grading scale shifted or became narrower when compared to reference intervals, especially for a Japanese cohort. For sodium grading, the criterion for hypernatremia was around 2 to mEq/L lower than the upper limit of most standards in several countries. Also, the criterion for hypokalemia was around 0.2 mEq/L higher than the lower limit of most standards. Regarding a decrease in hemoglobin from baseline, the criterion of "any decrease" used for a Grade 1 AE was too strict and we suggest this be omitted. Upper and lower limits of AE criteria for sodium and potassium should be equal to, or 10-20% above, the reference interval consistent with other toxicities determined by laboratory tests. Consideration should be given to the issues surrounding the criteria that determine AEs before conducting clinical trials.

YF17D-vectored Ebola vaccine candidate protects mice against lethal surrogate Ebola and yellow fever virus challenge

Ebola virus (EBOV) and related filoviruses such as Sudan virus (SUDV) threaten global public health. Effective filovirus vaccines are available only for EBOV, yet restricted to emergency use considering a high reactogenicity and demanding logistics. Here we present YF-EBO, a live YF17D-vectored dual-target vaccine candidate expressing EBOV glycoprotein (GP) as protective antigen. Safety of YF-EBO in mice was further improved over that of parental YF17D vaccine. A single dose of YF-EBO was sufficient to induce high levels of EBOV GP-specific antibodies and cellular immune responses, that protected against lethal infection using EBOV GP-pseudotyped recombinant vesicular stomatitis virus (rVSV-EBOV) in interferon-deficient (Ifnar^-/-) mice as surrogate challenge model. Concomitantly induced yellow fever virus (YFV)-specific immunity protected Ifnar^-/- mice against intracranial YFV challenge. YF-EBO could thus help to simultaneously combat both EBOV and YFV epidemics. Finally, we demonstrate how to target other highly pathogenic filoviruses such as SUDV at the root of the 2022 outbreak in Uganda.

Development and applications of mRNA treatment based on lipid nanoparticles

Nucleic acid-based therapies such as messenger RNA have the potential to revolutionize modern medicine and enhance the performance of existing pharmaceuticals. The key challenges of mRNA-based therapies are delivering the mRNA safely and effectively to the target tissues and cells and controlling its release from the delivery vehicle. Lipid nanoparticles (LNPs) have been widely studied as drug carriers and are considered to be state-of-the-art technology for nucleic acid delivery. In this review, we begin by presenting the advantages and mechanisms of action of mRNA therapeutics. Then we discuss the design of LNP platforms based on ionizable lipids and the applications of mRNA-LNP vaccines for prevention of infectious diseases and for treatment of cancer and various genetic diseases. Finally, we describe the challenges and future prospects of mRNA-LNP therapeutics.

Recombinant vesicular stomatitis virus-vectored vaccine induces long-lasting immunity against Nipah virus disease

The emergence of the novel henipavirus, Langya virus, received global attention after the virus sickened over three dozen people in China. There is heightened concern that henipaviruses, as respiratory pathogens, could spark another pandemic, most notably the deadly Nipah virus (NiV). NiV causes near-annual outbreaks in Bangladesh and India and induces a highly fatal respiratory disease and encephalitis in humans. No licensed countermeasures against this pathogen exist. An ideal NiV vaccine would confer both fast-acting and long-lived protection. Recently, we reported the generation of a recombinant vesicular stomatitis virus-based (rVSV-based) vaccine expressing the NiV glycoprotein (rVSV-ΔG-NiVBG) that protected 100% of nonhuman primates from NiV-associated lethality within a week. Here, to evaluate the durability of rVSV-ΔG-NiVBG, we vaccinated African green monkeys (AGMs) one year before challenge with an uniformly lethal dose of NiV. The rVSV-ΔG-NiVBG vaccine induced stable and robust humoral responses, whereas cellular responses were modest. All immunized AGMs (whether receiving a single dose or prime-boosted) survived with no detectable clinical signs or NiV replication. Transcriptomic analyses indicated that adaptive immune signatures correlated with vaccine-mediated protection. While vaccines for certain respiratory infections (e.g., COVID-19) have yet to provide durable protection, our results suggest that rVSV-ΔG-NiVBG elicits long-lasting immunity.

Combating Lassa Fever in West African Sub-Region: Progress, Challenges, and Future Perspectives

Lassa fever (LF) is a rodent-borne disease that threatens human health in the sub-region of West Africa where the zoonotic host of Lassa virus (LASV) is predominant. Currently, treatment options for LF are limited and since no preventive vaccine is approved for its infectivity, there is a high mortality rate in endemic areas. This narrative review explores the transmission, pathogenicity of LASV, advances, and challenges of different treatment options. Our findings indicate that genetic diversity among the different strains of LASV and their ability to circumvent the immune system poses a critical challenge to the development of LASV vaccines/therapeutics. Thus, understanding the biochemistry, physiology and genetic polymorphism of LASV, mechanism of evading host immunity are essential for development of effective LASV vaccines/therapeutics to combat this lethal viral disease. The LASV nucleoprotein (NP) is a novel target for therapeutics as it functions significantly in several aspects of the viral life cycle. Consequently, LASV NP inhibitors could be employed as effective therapeutics as they will potentially inhibit LASV replication. Effective preventive control measures, vaccine development, target validation, and repurposing of existing drugs, such as ribavirin, using activity or in silico-based and computational bioinformatics, would aid in the development of novel drugs for LF management.

Replicating-Competent VSV-Vectored Pseudotyped Viruses

Vesicular stomatitis virus (VSV) is prototype virus in the family of Rhabdoviridae. Reverse genetic platform has enabled the genetic manipulation of VSV as a powerful live viral vector. Replicating-competent VSV is constructed by replacing the original VSV glycoprotein gene with heterologous envelope genes. The resulting recombinant viruses are able to replicate in permissive cells and incorporate the foreign envelope proteins on the surface of the viral particle without changing the bullet-shape morphology. Correspondingly, the cell tropism of replicating-competent VSV is determined by the foreign envelope proteins. Replicating-competent VSVs have been successfully used for selecting critical viral receptors or host factors, screening mutants that escape therapeutic antibodies, and developing VSV-based live viral vaccines.

Understanding Immune Responses to Lassa Virus Infection and to Its Candidate Vaccines

Lassa fever (LF) is a deadly viral hemorrhagic fever disease that is endemic in several countries in West Africa. It is caused by Lassa virus (LASV), which has been estimated to be responsible for approximately 300,000 infections and 5000 deaths annually. LASV is a highly pathogenic human pathogen without effective therapeutics or FDA-approved vaccines. Here, we aim to provide a literature review of the current understanding of the basic mechanism of immune responses to LASV infection in animal models and patients, as well as to several of its candidate 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.

Lessons Learned from the Development and Roll-Out of the rVSVΔG-ZEBOV-GP Zaire ebolavirus Vaccine to Inform Marburg Virus and Sudan ebolavirus Vaccines

This review describes key aspects of the development of the rVSVΔG-ZEBOV-GP Ebola vaccine and key activities which are continuing to further expand our knowledge of the product. Extensive partnerships and innovative approaches were used to address the various challenges encountered during this process. The rVSVΔG-ZEBOV-GP Ebola vaccine was initially approved by the European Medicines Agency and prequalified by the World Health Organization in November 2019. It was approved by the United States Food and Drug Administration in December 2019 and approved in five African countries within 90 days of prequalification. The development resulted in the first stockpile of a registered Ebola vaccine that is available to support outbreak response. This also provides insights into how the example of rVSVΔG-ZEBOV-GP can inform the development of vaccines for Sudan ebolavirus, Marburg virus, and other emerging epidemic diseases in terms of the types of approaches and data needed to support product registration, availability, and the use of a filovirus vaccine.

Assays for the Evaluation of the Immune Response to Marburg and Ebola Sudan Vaccination-Filovirus Animal Nonclinical Group Anti-Marburg Virus Glycoprotein Immunoglobulin G Enzyme-Linked Immunosorbent Assay and a Pseudovirion Neutralization Assay

Since the discovery of the Marburg virus (MARV) in 1967 and Ebola virus (EBOV) in 1976, there have been over 40 reported outbreaks of filovirus disease with case fatality rates greater than 50%. This underscores the need for efficacious vaccines against these highly pathogenic filoviruses. Due to the sporadic and unpredictable nature of filovirus outbreaks, such a vaccine would likely need to be vetted through the U.S. Food and Drug Administration (FDA), following the Animal Rule or similar European Medicines Agency (EMA) regulatory pathway. Under the FDA Animal Rule, vaccine-induced immune responses correlating with survival of non-human primates (NHPs), or another well-characterized animal model, following lethal challenge, will need to be bridged for human immune response distributions in clinical trials. A correlate of protection has not yet been identified for the filovirus disease, but antibodies, specifically anti-glycoprotein (GP) antibodies, are believed to be critical in providing protection against the filovirus disease following vaccination and are thus a strong candidate for a correlate of protection. Thus, species-neutral methods capable of the detection and bridging of these antibody immune responses, such as methods to quantify anti-GP immunoglobulin G (IgG)-binding antibodies and neutralizing antibodies, are needed. Reported here is the development and qualification of two Filovirus Animal Nonclinical Group (FANG) anti-GP IgG Enzyme-Linked Immunosorbent Assays (ELISAs) to quantify anti-MARV and anti-Sudan virus (SUDV) IgG antibodies in human and NHP serum samples, as well as the development of pseudovirion neutralization assays (PsVNAs) to quantify MARV- and SUDV-neutralizing antibodies in human and NHP serum samples.

Immunovirotherapy Based on Recombinant Vesicular Stomatitis Virus: Where Are We?

Vesicular stomatitis virus (VSV), a negative-strand RNA virus of the Vesiculovirus genus, has demonstrated encouraging anti-neoplastic activity across multiple human cancer types. VSV is particularly attractive as an oncolytic agent because of its broad tropism, fast replication kinetics, and amenability to genetic manipulations. Furthermore, VSV-induced oncolysis can elicit a potent antitumor cytotoxic T-cell response to viral proteins and tumor-associated antigens, resulting in a long-lasting antitumor effect. Because of this multifaceted immunomodulatory property, VSV was investigated extensively as an immunovirotherapy alone or combined with other anticancer modalities, such as immune checkpoint blockade. Despite these recent opportunities to delineate synergistic and additive antitumor effects with existing anticancer therapies, FDA approval for the use of oncolytic VSV in humans has not yet been granted. This mini-review discusses factors that have prompted the use of VSV as an immunovirotherapy in human cancers and provides insights into future perspectives and research areas to improve VSV-based oncotherapy.

Effect of Recombinant Vesicular Stomatitis Virus–Zaire Ebola Virus Vaccination on Ebola Virus Disease Illness and Death, Democratic Republic of the Congo

We conducted a retrospective cohort study to assess the effect vaccination with the live-attenuated recombinant vesicular stomatitis virus–Zaire Ebola virus vaccine had on deaths among patients who had laboratory-confirmed Ebola virus disease (EVD). We included EVD-positive patients coming to an Ebola Treatment Center in eastern Democratic Republic of the Congo during 2018–2020. Overall, 25% of patients vaccinated before symptom onset died compared with 63% of unvaccinated patients. Vaccinated patients reported fewer EVD-associated symptoms, had reduced time to clearance of viral load, and had reduced length of stay at the Ebola Treatment Center. After controlling for confounders, vaccination was strongly associated with decreased deaths. Reduction in deaths was not affected by timing of vaccination before or after EVD exposure. These findings support use of preexposure and postexposure recombinant vesicular stomatitis virus–Zaire Ebola virus vaccine as an intervention associated with improved death rates, illness, and recovery time among patients with EVD.

Adenovirus-based vaccines-a platform for pandemic preparedness against emerging viral pathogens

Zoonotic viruses continually pose a pandemic threat. Infection of humans with viruses for which we typically have little or no prior immunity can result in epidemics with high morbidity and mortality. These epidemics can have public health and economic impact and can exacerbate civil unrest or political instability. Changes in human behavior in the past few decades-increased global travel, farming intensification, the exotic animal trade, and the impact of global warming on animal migratory patterns, habitats, and ecosystems-contribute to the increased frequency of cross-species transmission events. Investing in the pre-clinical advancement of vaccine candidates against diverse emerging viral threats is crucial for pandemic preparedness. Replication-defective adenoviral (Ad) vectors have demonstrated their utility as an outbreak-responsive vaccine platform during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Ad vectors are easy to engineer; are amenable to rapid, inexpensive manufacturing; are relatively safe and immunogenic in humans; and, importantly, do not require specialized cold-chain storage, making them an ideal platform for equitable global distribution or stockpiling. In this review, we discuss the progress in applying Ad-based vaccines against emerging viruses and summarize their global safety profile, as reflected by their widespread geographic use during the SARS-CoV-2 pandemic.

A highly attenuated Vesiculovax vaccine rapidly protects nonhuman primates against lethal Marburg virus challenge

BACKGROUND

Marburg virus (MARV), an Ebola-like virus, remains an eminent threat to public health as demonstrated by its high associated mortality rate (23-90%) and recent emergence in West Africa for the first time. Although a recombinant vesicular stomatitis virus (rVSV)-based vaccine (Ervebo) is licensed for Ebola virus disease (EVD), no approved countermeasures exist against MARV. Results from clinical trials indicate Ervebo prevents EVD in 97.5-100% of vaccinees 10 days onwards post-immunization.

METHODOLOGY/FINDINGS

Given the rapid immunogenicity of the Ervebo platform against EVD, we tested whether a similar, but highly attenuated, rVSV-based Vesiculovax vector expressing the glycoprotein (GP) of MARV (rVSV-N4CT1-MARV-GP) could provide swift protection against Marburg virus disease (MVD). Here, groups of cynomolgus monkeys were vaccinated 7, 5, or 3 days before exposure to a lethal dose of MARV (Angola variant). All subjects (100%) immunized one week prior to challenge survived; 80% and 20% of subjects survived when vaccinated 5- and 3-days pre-exposure, respectively. Lethality was associated with higher viral load and sustained innate immunity transcriptional signatures, whereas survival correlated with development of MARV GP-specific antibodies and early expression of predicted NK cell-, B-cell-, and cytotoxic T-cell-type quantities.

CONCLUSIONS/SIGNIFICANCE

These results emphasize the utility of Vesiculovax vaccines for MVD outbreak management. The highly attenuated nature of rVSV-N4CT1 vaccines, which are clinically safe in humans, may be preferable to vaccines based on the same platform as Ervebo (rVSV "delta G" platform), which in some trial participants induced vaccine-related adverse events in association with viral replication including arthralgia/arthritis, dermatitis, and cutaneous vasculitis.

Protective CD8+ T Cell Response Induced by Modified Vaccinia Virus Ankara Delivering Ebola Virus Nucleoprotein

The urgent need for vaccines against Ebola virus (EBOV) was underscored by the large outbreak in West Africa (2014–2016). Since then, several promising vaccine candidates have been tested in pre-clinical and clinical studies. As a result, two vaccines were approved for human use in 2019/2020, of which one includes a heterologous adenovirus/Modified Vaccinia virus Ankara (MVA) prime-boost regimen. Here, we tested new vaccine candidates based on the recombinant MVA vector, encoding the EBOV nucleoprotein (MVA-EBOV-NP) or glycoprotein (MVA-EBOV-GP) for their efficacy after homologous prime-boost immunization in mice. Our aim was to investigate the role of each antigen in terms of efficacy and correlates of protection. Sera of mice vaccinated with MVA-EBOV-GP were virus-neutralizing and MVA-EBOV-NP immunization readily elicited interferon-γ-producing NP-specific CD8+ T cells. While mock-vaccinated mice succumbed to EBOV infection, all vaccinated mice survived and showed drastically decreased viral loads in sera and organs. In addition, MVA-EBOV-NP vaccinated mice became susceptible to lethal EBOV infection after depletion of CD8+ T cells prior to challenge. This study highlights the potential of MVA-based vaccines to elicit humoral immune responses as well as a strong and protective CD8+ T cell response and contributes to understanding the possible underlying mechanisms.

Immunogenicity of rVSVΔG-ZEBOV-GP Ebola vaccination in exposed and potentially exposed persons in the Democratic Republic of the Congo

Despite more than 300,000 rVSVΔG-ZEBOV-glycoprotein (GP) vaccine doses having been administered during Ebola virus disease (EVD) outbreaks in the Democratic Republic of the Congo (DRC) between 2018 and 2020, seroepidemiologic studies of vaccinated Congolese populations are lacking. This study examines the antibody response at 21 d and 6 mo postvaccination after single-dose rVSVΔG-ZEBOV-GP vaccination among EVD-exposed and potentially exposed populations in the DRC. We conducted a longitudinal cohort study of 608 rVSVΔG-ZEBOV-GP-vaccinated individuals during an EVD outbreak in North Kivu Province, DRC. Participants provided questionnaires and blood samples at three study visits (day 0, visit 1; day 21, visit 2; and month 6, visit 3). Anti-GP immunoglobulin G (IgG) antibody titers were measured in serum by the Filovirus Animal Nonclinical Group anti-Ebola virus GP IgG enzyme-linked immunosorbent assay. Antibody response was defined as an antibody titer that had increased fourfold from visit 1 to visit 2 and was above four times the lower limit of quantification at visit 2; antibody persistence was defined as a similar increase from visit 1 to visit 3. We then examined demographics for associations with follow-up antibody titers using generalized linear mixed models. A majority of the sample, 87.2%, had an antibody response at visit 2, and 95.6% demonstrated antibody persistence at visit 3. Being female and of young age was predictive of a higher antibody titer postvaccination. Antibody response and persistence after Ebola vaccination was robust in this cohort, confirming findings from outside of the DRC.

Transcriptomic signatures induced by the Ebola virus vaccine rVSVΔG-ZEBOV-GP in adult cohorts in Europe, Africa, and North America: a molecular biomarker study

BACKGROUND

A recombinant vesicular stomatitis virus vector expressing the Zaire Ebola virus glycoprotein (rVSVΔG-ZEBOV-GP) vaccine has been reported as safe, immunogenic, and highly protective in a ring vaccination trial. We aimed to identify transcriptomic immune response biomarker signatures induced by vaccination and associated signatures with its immunogenicity and reactogenicity to better understand the potential mechanisms of action of the vaccine.

METHODS

354 healthy adult volunteers were vaccinated in randomised, double-blind, placebo-controlled trials in Europe (Geneva, Switzerland [November, 2014, to January, 2015]) and North America (USA [Dec 5, 2014, to June 23, 2015]), and dose-escalation trials in Africa (Lambaréné, Gabon [November, 2014, to January, 2015], and Kilifi, Kenya [December, 2014, to January, 2015]) using different doses of the recombinant vesicular stomatitis virus vector expressing the Zaire Ebola virus glycoprotein (rVSVΔG-ZEBOV-GP; 3 × 10⁵ to 1 × 10⁸ plaque-forming units [pfu]). Longitudinal transcriptomic responses (days 0, 1, 2, 3, 7, 14, and 28) were measured in whole blood using a targeted gene expression profiling platform (dual-colour reverse-transcriptase multiplex ligation-dependent probe amplification) focusing on 144 immune-related genes. The effect of time and dose on transcriptomic response was also assessed. Logistic regression with lasso regularisation was applied to identify host signatures with optimal discriminatory capability of vaccination at day 1 or day 7 versus baseline, whereas random-effects models and recursive feature elimination combined with regularised logistic regression were used to associate signatures with immunogenicity and reactogenicity.

FINDINGS

Our results indicated that perturbation of gene expression peaked on day 1 and returned to baseline levels between day 7 and day 28. The magnitude of the response was dose-dependent, with vaccinees receiving a high dose (≥9 × 10⁶ pfu) of rVSVΔG-ZEBOV-GP exhibiting the largest amplitude. The most differentially expressed genes that were significantly upregulated following vaccination consisted of type I and II interferon-related genes and myeloid cell-associated markers, whereas T cell, natural killer cell, and cytotoxicity-associated genes were downregulated. A gene signature associated with immunogenicity (common to all four cohorts) was identified correlating gene expression profiles with ZEBOV-GP antibody titres and a gene signatures associated with reactogenicity (Geneva cohort) was identified correlating gene expression profiles with an adverse event (ie, arthritis).

INTERPRETATION

Collectively, our results identify and cross-validate immune-related transcriptomic signatures induced by rVSVΔG-ZEBOV-GP vaccination in four cohorts of adult participants from different genetic and geographical backgrounds. These signatures will aid in the rational development, testing, and evaluation of novel vaccines and will allow evaluation of the effect of host factors such as age, co-infection, and comorbidity on responses to vaccines.

FUNDING

Innovative Medicines Initiative 2 Joint Undertaking.

Feasibility and safety of rVSV-ZEBOV vaccination of humanitarian health workers against Ebola virus disease: an observational study

BACKGROUND AND RATIONALE

Geneva University Hospitals were granted a temporary authorization to administer the recombinant live vesicular stomatitis virus rVSV-ZEBOV (Ervebo®) vaccine to expatriate humanitarian frontline workers (FLWs) prior to mission deployment.

OBJECTIVES

Our aims were to assess the feasibility of FLW vaccination before deployment and to report adverse events (AEs).

METHODS

FLWs received a single injection of rVSV-ZEBOV (>7.2E7 plaque forming unit) during their pre-deployment medical check-up at the Travel Medicine Clinic of the Geneva University Hospitals (Day 0). A safety questionnaire regarding potential AEs was emailed to FLWs on Days 3 and 21. Early and delayed AEs were those starting within 3 or 21 days of vaccination, respectively.

RESULTS

Between 1 August 2019 and 30 June 2020, 124 FLWs received the rVSV-ZEBOV vaccine. Eighty-six volunteers (86/124; 69%) received a concomitant vaccine. The response rate to the follow-up questionnaire was 88 and 55% at Days 3 and 21, respectively. Most respondents (105/109; 96.3%), experienced at least one AE, with a mean of three (±SD 1.75) AEs per person. The most common AE was injection site pain, followed by fever (53/109; 48.6%), fatigue (51/109; 46.7%) and myalgia (49/109; 44.9%). Most early AEs (360/377; 95.4%) resolved within 3 days, reflecting vaccine reactogenicity. Delayed AEs were reported by 6/69 (7.2%) subjects, the median time to symptom onset was 11 days (range: 5-14); half of them were joint-related AEs (3/6). Four serious adverse events (SAE) were observed: two cases of high grade fever, one rash and one case of arthritis. Two suspected unexpected serious adverse reactions were observed: one case of continuing recurrent transient dizziness and fatigue considered related to the vaccine; and one case of presbyopia that was deemed unrelated.

CONCLUSION

AEs to rVSV-ZEBOV were common but in general transient and were well tolerated, pre-deployment rVSV-ZEBOV vaccination in FLW is feasible and can be included with pre-mission check-up.

A vesicular stomatitis virus-based prime-boost vaccination strategy induces potent and protective neutralizing antibodies against SARS-CoV-2

The development of safe and effective vaccines to prevent SARS-CoV-2 infections remains an urgent priority worldwide. We have used a recombinant vesicular stomatitis virus (rVSV)-based prime-boost immunization strategy to develop an effective COVID-19 vaccine candidate. We have constructed VSV genomes carrying exogenous genes resulting in the production of avirulent rVSV carrying the full-length spike protein (S_F), the S1 subunit, or the receptor-binding domain (RBD) plus envelope (E) protein of SARS-CoV-2. Adding the honeybee melittin signal peptide (msp) to the N-terminus enhanced the protein expression, and adding the VSV G protein transmembrane domain and the cytoplasmic tail (Gtc) enhanced protein incorporation into pseudotype VSV. All rVSVs expressed three different forms of SARS-CoV-2 spike proteins, but chimeras with VSV-Gtc demonstrated the highest rVSV-associated expression. In immunized mice, rVSV with chimeric S protein-Gtc derivatives induced the highest level of potent neutralizing antibodies and T cell responses, and rVSV harboring the full-length msp-S_F-Gtc proved to be the superior immunogen. More importantly, rVSV-msp-S_F-Gtc vaccinated animals were completely protected from a subsequent SARS-CoV-2 challenge. Overall, we have developed an efficient strategy to induce a protective response in SARS-CoV-2 challenged immunized mice. Vaccination with our rVSV-based vector may be an effective solution in the global fight against COVID-19.

The COVID-19 pandemic has had unprecedented global health, economic and societal impact globally. Vaccinating the majority of the world’s population is the best way to help prevent new infections. Many vaccines have been developed to prevent various viral diseases that are currently in use around the world. This has generated a high demand for these vaccines, putting a strain on production capacity and delivery. With new variants of concern starting to dominate the human pandemic, new derivatives of the current vaccines may be necessary for continued protection from SARS-CoV-2 infection. We have developed a vaccine that uses a safe vesicular stomatitis virus-based delivery vehicle to present a key SARS-CoV-2 protein to our immune system in order to train it to recognize and prevent SARS-CoV-2 infection. Our vaccine completely protected vaccinated animals from SARS-CoV-2 infection and significantly reduced lung damage, a major hallmark of COVID-19.

Heterologous Prime-Boost Vaccination with a Peptide-Based Vaccine and Viral Vector Reshapes Dendritic Cell, CD4+ and CD8+ T Cell Phenotypes to Improve the Antitumor Therapeutic Effect

Simple Summary

Developing new therapeutic cancer vaccines is of paramount importance to counteract tumor escape observed after conventional therapies in certain types of cancer. We have previously shown that the combination of two different vaccine platforms, targeting tumor-specific antigens, resulted in potent immune responses in preclinical models. Here, we show that the heterologous prime-boost combination with a protein vaccine and a viral vector vesicular stomatitis virus immunologically reshapes the immune-excluded TC-1 tumor model as well as the inflamed MC-38 tumor model, leading to beneficial therapeutic efficacy. Furthermore, the treatment with a multi-epitope vaccine allowed us to appreciate the various repartition among three antigen-specific cytotoxic T-cell responses combined with the viral boost. The combination leads to improved efficacy in all animals and highlights the importance of combining tumor epitopes. Our vaccine strategy could be further extended to prophylactic cancer vaccines and beyond, for infectious diseases.

Abstract

Heterologous prime-boost settings with a protein vaccine and the viral vector vesicular stomatitis virus, both expressing tumor-associated antigens (KISIMA-TAA and VSV-GP-TAA), have been previously shown to generate potent antitumor immunity. In the cold TC-1 model (HPV antigen) and the immune-infiltrate MC-38 model (Adpgk, Reps1 and Rpl18 neo-antigens), we further investigated pivotal immune cells that educate CD8+ T cells. Heterologous prime-boost vaccination induced a superior antitumor response characterized by the increase in number and functionality of antigen-specific CD8+ T cells, recruitment of cross-presenting dendritic cells, and polarization of CD4+ T cells towards an antitumor Th1 phenotype within the tumor and tumor-draining lymph nodes, turning the cold TC-1 tumor into a hot, inflamed tumor. In the inflamed MC-38 tumor model, treatment combination markedly prolonged the overall survival of mice. Treatment with multi-epitope vaccines also induced high frequencies of multiple antigen specificities in the periphery and in the tumor. Prime-boost treatment reduced tumor-infiltrating regulatory CD4+ T cells whilst increasing cross-presenting dendritic cells in tumor-draining lymph nodes. In conclusion, heterologous prime-boost vaccination possesses the ability to induce a potent anti-tumor response in both immune-excluded and immune-infiltrated mouse tumor models. Additionally, this study highlights the design of a multi-epitope vaccine for cancer immunotherapy.

Baseline Asymptomatic Malaria Infection and Immunogenicity of Recombinant Vesicular Stomatitis Virus-Zaire Ebola Virus Envelope Glycoprotein

BACKGROUND

The effect of malaria infection on the immunogenicity of the recombinant vesicular stomatitis virus-Zaire Ebola virus envelope glycoprotein (GP) vaccine (rVSVΔG-ZEBOV-GP) (ERVEBO) is unknown.

METHODS

The Sierra Leone Trial to Introduce a Vaccine Against Ebola (STRIVE) vaccinated 7998 asymptomatic adults with rVSVΔG-ZEBOV-GP during the 2014-2016 Ebola epidemic. In STRIVE's immunogenicity substudy, participants provided blood samples at baseline and at 1, 6, and 9-12 months. Anti-GP binding and neutralizing antibodies were measured using validated assays. Baseline samples were tested for malaria parasites by polymerase chain reaction.

RESULTS

Overall, 506 participants enrolled in the immunogenicity substudy and had ≥1 postvaccination antibody titer. Of 499 participants with a result, baseline malaria parasitemia was detected in 73 (14.6%). All GP enzyme-linked immunosorbent assay (ELISA) and plaque reduction neutralization test (PRNT) geometric mean titers (GMTs) at 1, 6, and 9-12 months were above baseline, and 94.1% of participants showed seroresponse by GP-ELISA (≥2-fold rise and ≥200 ELISA units/mL), while 81.5% showed seroresponse by PRNT (≥4-fold rise) at ≥1 postvaccination assessment. In participants with baseline malaria parasitemia, the PRNT seroresponse proportion was lower, while PRNT GMTs and GP-ELISA seroresponse and GMTs showed a trend toward lower responses at 6 and 9-12 months.

CONCLUSION

Asymptomatic adults with or without malaria parasitemia had robust immune responses to rVSVΔG-ZEBOV-GP, persisting for 9-12 months. Responses in those with malaria parasitemia were somewhat lower.

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.

A Methyltransferase-Defective Vesicular Stomatitis Virus-Based SARS-CoV-2 Vaccine Candidate Provides Complete Protection against SARS-CoV-2 Infection in Hamsters

The current pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to dramatic economic and health burdens. Although the worldwide SARS-CoV-2 vaccination campaign has begun, exploration of other vaccine candidates is needed due to uncertainties with the current approved vaccines, such as durability of protection, cross-protection against variant strains, and costs of long-term production and storage. In this study, we developed a methyltransferase-defective recombinant vesicular stomatitis virus (mtdVSV)-based SARS-CoV-2 vaccine candidate. We generated mtdVSVs expressing SARS-CoV-2 full-length spike (S) protein, S1, or its receptor-binding domain (RBD). All of these recombinant viruses grew to high titers in mammalian cells despite high attenuation in cell culture. The SARS-CoV-2 S protein and its truncations were highly expressed by the mtdVSV vector. These mtdVSV-based vaccine candidates were completely attenuated in both immunocompetent and immunocompromised mice. Among these constructs, mtdVSV-S induced high levels of SARS-CoV-2-specific neutralizing antibodies (NAbs) and Th1-biased T-cell immune responses in mice. In Syrian golden hamsters, the serum levels of SARS-CoV-2-specific NAbs triggered by mtdVSV-S were higher than the levels of NAbs in convalescent plasma from recovered COVID-19 patients. In addition, hamsters immunized with mtdVSV-S were completely protected against SARS-CoV-2 replication in lung and nasal turbinate tissues, cytokine storm, and lung pathology. Collectively, our data demonstrate that mtdVSV expressing SARS-CoV-2 S protein is a safe and highly efficacious vaccine candidate against SARS-CoV-2 infection. IMPORTANCE Viral mRNA cap methyltransferase (MTase) is essential for mRNA stability, protein translation, and innate immune evasion. Thus, viral mRNA cap MTase activity is an excellent target for development of live attenuated or live vectored vaccine candidates. Here, we developed a panel of MTase-defective recombinant vesicular stomatitis virus (mtdVSV)-based SARS-CoV-2 vaccine candidates expressing full-length S, S1, or several versions of the RBD. These mtdVSV-based vaccine candidates grew to high titers in cell culture and were completely attenuated in both immunocompetent and immunocompromised mice. Among these vaccine candidates, mtdVSV-S induces high levels of SARS-CoV-2-specific neutralizing antibodies (Nabs) and Th1-biased immune responses in mice. Syrian golden hamsters immunized with mtdVSV-S triggered SARS-CoV-2-specific NAbs at higher levels than those in convalescent plasma from recovered COVID-19 patients. Furthermore, hamsters immunized with mtdVSV-S were completely protected against SARS-CoV-2 challenge. Thus, mtdVSV is a safe and highly effective vector to deliver SARS-CoV-2 vaccine.

Filovirus Neutralising Antibodies: Mechanisms of Action and Therapeutic Application

Filoviruses, especially Ebola virus, cause sporadic outbreaks of viral haemorrhagic fever with very high case fatality rates in Africa. The 2013–2016 Ebola epidemic in West Africa provided large survivor cohorts spurring a large number of human studies which showed that specific neutralising antibodies played a key role in protection following a natural Ebola virus infection, as part of the overall humoral response and in conjunction with the cellular adaptive response. This review will discuss the studies in survivors and animal models which described protective neutralising antibody response. Their mechanisms of action will be detailed. Furthermore, the importance of neutralising antibodies in antibody-based therapeutics and in vaccine-induced responses will be explained, as well as the strategies to avoid immune escape from neutralising antibodies. Understanding the neutralising antibody response in the context of filoviruses is crucial to furthering our understanding of virus structure and function, in addition to improving current vaccines & antibody-based therapeutics.

Construction and evaluation of DNA vaccine encoding Ebola virus glycoprotein fused with lysosome-associated membrane protein

Ebola virus (EBOV) of the genus Ebolavirus belongs to the family Filoviridae, which cause disease in both humans and non-human primates. Zaire Ebola virus accounts for the highest fatality rate, reaching 90%. Considering that EBOV has a high infection and fatality rate, the development of a highly effective vaccine has become a top public health priority. Glycoprotein (GP) plays a critical role during infection and protective immune responses. Herein, we developed an EBOV GP recombinant DNA vaccine that targets the major histocompatibility complex (MHC) class II compartment by fusing with lysosomal-associated membrane protein 1 (LAMP1). Through lysosome trafficking and antigen presentation transferring, the LAMP1 targeting strategy successfully improved both humoral and cellular EBOV-GP-specific immune responses. After three consecutive immunizations, the serum antibody titers, especially the neutralizing activity of mice immunized with the pVAX-LAMP/GPEBO vaccine were significantly higher than those of the other groups. Antigen-specific T cells showed positive activity against three dominant peptides, EAAVSHLTTLATIST, IGEWAFWETKKNLTR, and ELRTFSILNRKAIDF, with high affinity for MHC class II molecules predicted by IEDB-recommended. Preliminary safety observation denied histological alterations. DNA vaccine candidate pVAX-LAMP/GPEBO shows promise against Ebola epidemic and further evaluation is guaranteed.

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.

Vesicular Stomatitis Virus Chimeras Expressing the Oropouche Virus Glycoproteins Elicit Protective Immune Responses in Mice

Oropouche virus (OROV) infection of humans is associated with a debilitating febrile illness that can progress to meningitis or encephalitis. First isolated from a forest worker in Trinidad and Tobago in 1955, the arbovirus OROV has since been detected throughout the Amazon basin with an estimated 500,000 human infections over 60 years. Like other members of the family Peribunyaviridae, the viral genome exists as 3 single-stranded negative-sense RNA segments. The medium-sized segment encodes a viral glycoprotein complex (GPC) that is proteolytically processed into two viral envelope proteins, Gn and Gc, responsible for attachment and membrane fusion. There are no therapeutics or vaccines to combat OROV infection, and we have little understanding of protective immunity to infection. Here, we generated a replication competent chimeric vesicular stomatitis virus (VSV), in which the endogenous glycoprotein was replaced by the GPC of OROV. Serum from mice immunized by intramuscular injection with VSV-OROV specifically neutralized wild-type OROV, and using peptide arrays we mapped multiple epitopes within an N-terminal variable region of Gc recognized by the immune sera. VSV-OROV lacking this variable region of Gc was also immunogenic in mice producing neutralizing sera that recognize additional regions of Gc. Challenge of both sets of immunized mice with wild-type OROV shows that the VSV-OROV chimeras reduce wild-type viral infection and suggest that antibodies that recognize the variable N terminus of Gc afford less protection than those that target more conserved regions of Gc. IMPORTANCE Oropouche virus (OROV), an orthobunyavirus found in Central and South America, is an emerging public health challenge that causes debilitating febrile illness. OROV is transmitted by arthropods, and increasing mobilization has the potential to significantly increase the spread of OROV globally. Despite this, no therapeutics or vaccines have been developed to combat infection. Using vesicular stomatitis (VSV) as a backbone, we developed a chimeric virus bearing the OROV glycoproteins (VSV-OROV) and tested its ability to elicit a neutralizing antibody response. Our results demonstrate that VSV-OROV produces a strong neutralizing antibody response that is at least partially targeted to the N-terminal region of Gc. Importantly, vaccination with VSV-OROV reduces viral loads in mice challenged with wild-type virus. These data provide novel evidence that targeting the OROV glycoproteins may be an effective vaccination strategy to combat OROV infection.

Immunogenicity and safety of Ebola virus vaccines in healthy adults: a systematic review and network meta-analysis

Clinical development of Ebola virus vaccines (EVV) was accelerated by the West African Ebola virus epidemic which remains the deadliest in history. To compare and rank the EVV according to their immunogenicity and safety. A total of 21 randomized controlled trial, evaluating seven different vaccines with different doses, and 5,275 participants were analyzed. The rVSVΔG-ZEBOV-GP (2 × 10 ⁷) vaccine was more immunogenic (P-score 0.80). For pain, rVSVΔG-ZEBOV-GP (≤10 ⁵) had few events (P-score 0.90). For fatigue and headache, the DNA-EBOV (≤ 4 mg) was the best one with P-scores of 0.94 and 0.87, respectively. For myalgia, the ChAd3 (10 ¹⁰) had a lower risk (P-score 0.94). For fever, the Ad5.ZEBOV (≤ 8 × 10 ¹⁰) was the best one (P-score 0.80). The best vaccine to be used to stop future outbreak of Ebola is the rVSVDG-ZEBOV-GP vaccine at dose of 2 × 10⁷ PFU.

Development and Evaluation of an Ebola Virus Glycoprotein Mucin-Like Domain Replacement System as a New Dendritic Cell-Targeting Vaccine Approach against HIV-1

The development of efficient vaccine approaches against HIV infection remains challenging in the vaccine field. Here, we developed an Ebola virus envelope glycoprotein (EboGP)-based chimeric fusion protein system and demonstrated that replacement of the mucin-like domain (MLD) of EboGP with HIV C2-V3-C3 (134 amino acids [aa]) or C2-V3-C3-V4-C4-V5-C5 (243 aa) polypeptides (EbGPΔM-V3 and EbGPΔM-V3-V5, respectively) still maintained the efficiency of EboGP-mediated viral entry into human macrophages and dendritic cells (DCs). Animal studies using mice revealed that immunization with virus-like particles (VLPs) containing the above chimeric proteins, especially EbGPΔM-V3, induced significantly more potent anti-HIV antibodies than HIV gp120 alone in mouse serum and vaginal fluid. Moreover, the splenocytes isolated from mice immunized with VLPs containing EbGPΔM-V3 produced significantly higher levels of gamma interferon (IFN-γ), interleukin 2 (IL-2), IL-4, IL-5, and macrophage inflammatory protein 1α (MIP-1α). Additionally, we demonstrated that coexpression of EbGPΔM-V3 and the HIV Env glycoprotein in a recombinant vesicular stomatitis virus (rVSV) vector elicited robust anti-HIV antibodies that may have specifically recognized epitopes outside or inside the C2-V3-C3 region of HIV-1 gp120 and cross-reacted with the gp120 from different HIV strains. Thus, this study has demonstrated the great potential of this DC-targeting vaccine platform as a new vaccine approach for improving immunogen delivery and increasing vaccine efficacy.

IMPORTANCE Currently, there are more than 38.5 million reported cases of HIV globally. To date, there is no approved vaccine for HIV-1 infection. Thus, the development of an effective vaccine against HIV infection remains a global priority. This study revealed the efficacy of a novel dendritic cell (DC)-targeting vaccination approach against HIV-1. The results clearly show that the immunization of mice with virus-like particles (VLPs) and VSVs containing HIV Env and a fusion protein composed of a DC-targeting domain of Ebola virus GP with HIV C2-V3-C3 polypeptides (EbGPΔM-V3) could induce robust immune responses against HIV-1 Env and/or Gag in serum and vaginal mucosa. These findings provide a proof of concept of this novel and efficient DC-targeting vaccine approach in delivering various antigenic polypeptides of HIV-1 and/or other emergent infections to the host antigen-presenting cells to prevent HIV and other viral infections.

Effects of Gamma Irradiation of Human Serum Samples from rVSVΔG-ZEBOV-GP (V920) Ebola Virus Vaccine Recipients on Plaque-Reduction Neutralization Assays

Gamma irradiation (GI) is included in the CDC guidance on inactivation procedures to render a group of select agents and toxins nonviable. The Ebola virus falls within this group because it potentially poses a severe threat to public health and safety. To evaluate the impact of GI at a target dose of 50 kGy on neutralizing antibody titers induced by the rVSVΔG-ZEBOV-GP vaccine (V920), we constructed a panel of 48 paired human serum samples (GI-treated versus non-GI-treated) from healthy participants selected from a phase 3 study of V920 (study V920-012; NCT02503202). Neutralizing antibody titers were determined using a validated plaque-reduction neutralization test. GI of sera from V920 recipients was associated with approximately 20% reduction in postvaccination neutralizing antibody titers. GI was not associated with any change in pre-vaccination neutralizing antibody titers.

Postexposure Prophylaxis With rVSV-ZEBOV Following Exposure to a Patient With Ebola Virus Disease Relapse in the United Kingdom: An Operational, Safety, and Immunogenicity Report

Background

In October 2015, 65 people came into direct contact with a healthcare worker presenting with a late reactivation of Ebola virus disease (EVD) in the United Kingdom. Vaccination was offered to 45 individuals with an initial assessment of high exposure risk.

Methods

Approval for rapid expanded access to the recombinant vesicular stomatitis virus–Zaire Ebola virus (rVSV-ZEBOV) vaccine as an unlicensed emergency medicine was obtained from the relevant authorities. An observational follow-up study was carried out for 1 year following vaccination.

Results

Twenty-six of 45 individuals elected to receive vaccination between 10 and 11 October 2015 following written informed consent. By day 14, 39% had seroconverted, increasing to 87% by day 28 and 100% by 3 months, although these responses were not always sustained. Neutralizing antibody responses were detectable in 36% by day 14 and 73% at 12 months. Common side effects included fatigue, myalgia, headache, arthralgia, and fever. These were positively associated with glycoprotein-specific T-cell but not immunoglobulin (Ig) M or IgG antibody responses. No severe vaccine-related adverse events were reported. No one exposed to the virus became infected.

Conclusions

This paper reports the use of the rVSV-ZEBOV vaccine given as an emergency intervention to individuals exposed to a patient presenting with a late reactivation of EVD. The vaccine was relatively well tolerated, but a high percentage developed a fever ≥37.5°C, necessitating urgent screening for Ebola virus, and a small number developed persistent arthralgia.

High dose of vesicular stomatitis virus-vectored Ebola virus vaccine causes vesicular disease in swine without horizontal transmission

ABSTRACTThe recent impact of Ebola virus disease (EVD) on public health in Africa clearly demonstrates the need for a safe and efficacious vaccine to control outbreaks and mitigate its threat to global health. ERVEBO® is an effective recombinant Vesicular Stomatitis Virus (VSV)-vectored Ebola virus vaccine (VSV-EBOV) that was approved by the FDA and EMA in late 2019 for use in prevention of EVD. Since the parental virus VSV, which was used to construct VSV-EBOV, is pathogenic for livestock and the vaccine virus may be shed at low levels by vaccinated humans, widespread deployment of the vaccine requires investigation into its infectivity and transmissibility in VSV-susceptible livestock species. We therefore performed a comprehensive clinical analysis of the VSV-EBOV vaccine virus in swine to determine its infectivity and potential for transmission. A high dose of VSV-EBOV resulted in VSV-like clinical signs in swine, with a proportion of pigs developing ulcerative vesicular lesions at the nasal injection site and feet. Uninoculated contact control pigs co-mingled with VSV-EBOV-inoculated pigs did not become infected or display any clinical signs of disease, indicating the vaccine is not readily transmissible to naïve pigs during prolonged close contact. In contrast, virulent wild-type VSV Indiana had a shorter incubation period and was transmitted to contact control pigs. These results indicate that the VSV-EBOV vaccine causes vesicular illness in swine when administered at a high dose. Moreover, the study demonstrates the VSV-EBOV vaccine is not readily transmitted to uninfected pigs, encouraging its safe use as an effective human vaccine.

Development of Pandemic Vaccines: ERVEBO Case Study

Preventative vaccines are considered one of the most cost-effective and efficient means to contain outbreaks and prevent pandemics. However, the requirements to gain licensure and manufacture a vaccine for human use are complex, costly, and time-consuming. The 2013-2016 Ebola virus disease (EVD) outbreak was the largest EVD outbreak to date and the third Public Health Emergency of International Concern in history, so to prevent a pandemic, numerous partners from the public and private sectors combined efforts and resources to develop an investigational Zaire ebolavirus (EBOV) vaccine candidate (rVSVΔG-ZEBOV-GP) as quickly as possible. The rVSVΔG-ZEBOV-GP vaccine was approved as ERVEBOTM by the European Medicines Authority (EMA) and the United States Food and Drug Administration (FDA) in December 2019 after five years of development. This review describes the development program of this EBOV vaccine, summarizes what is known about safety, immunogenicity, and efficacy, describes ongoing work in the program, and highlights learnings applicable to the development of pandemic vaccines.