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.

Bioreactor production of rVSV-based vectors in Vero cell suspension cultures.

The Vero cell line is the most used continuous cell line in viral vaccine manufacturing. This adherent cell culture platform requires the use of surfaces to support cell growth, typically roller bottles, or microcarriers. We have recently compared the production of rVSV-ZEBOV on Vero cells between microcarrier and fixed-bed bioreactors. However, suspension cultures are considered superior with regard to process scalability. Therefore, we further explore the Vero suspension system for recombinant vesicular stomatitis virus (rVSV)-vectored vaccine production. Previously, this suspension cell line was only able to be cultivated in a proprietary medium. Here, we expand the adaptation and bioreactor cultivation to a serum-free commercial medium. Following small-scale optimization and screening studies, we demonstrate bioreactor productions of highly relevant vaccines and vaccine candidates against Ebola virus disease, HIV, and coronavirus disease 2019 in the Vero suspension system. rVSV-ZEBOV, rVSV-HIV, and rVSVInd -msp-SF -Gtc can replicate to high titers in the bioreactor, reaching 3.87 × 107 TCID50 /ml, 2.12 × 107 TCID50 /ml, and 3.59 × 109 TCID50 /ml, respectively. Furthermore, we compare cell-specific productivities, and the quality of the produced viruses by determining the ratio of total viral particles to infectious viral particles.

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.

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.

Optimization of Single-Dose VSV-Based COVID-19 Vaccination in Hamsters.

The ongoing COVID-19 pandemic has resulted in global effects on human health, economic stability, and social norms. The emergence of viral variants raises concerns about the efficacy of existing vaccines and highlights the continued need for the development of efficient, fast-acting, and cost-effective vaccines. Here, we demonstrate the immunogenicity and protective efficacy of two vesicular stomatitis virus (VSV)-based vaccines encoding the SARS-CoV-2 spike protein either alone (VSV-SARS2) or in combination with the Ebola virus glycoprotein (VSV-SARS2-EBOV). Intranasally vaccinated hamsters showed an early CD8+ T cell response in the lungs and a greater antigen-specific IgG response, while intramuscularly vaccinated hamsters had an early CD4+ T cell and NK cell response. Intranasal vaccination resulted in protection within 10 days with hamsters not showing clinical signs of pneumonia when challenged with three different SARS-CoV-2 variants. This data demonstrates that VSV-based vaccines are viable single-dose, fast-acting vaccine candidates that are protective from COVID-19.

Prior vaccination with recombinant Vesicular Stomatitis Virus - Zaire Ebolavirus vaccine is associated with improved survival among patients with Ebolavirus infection.

The second largest Ebolavirus disease (EVD) outbreak ever recorded is currently ongoing in Eastern Democratic Republic of the Congo (DRC). This is the first outbreak for which the recombinant Vesicular Stomatitis Virus - Zaire Ebolavirus (rVSV-ZEBOV) candidate vaccine has been widely administered, using a ring vaccination strategy. We examined whether prior vaccination with rVSV-ZEBOV impacts viral load, organ impairment, and survival among patients with EVD admitted to Ebola Treatment Units (ETUs) in the DRC. We conducted a retrospective observational study of patients admitted to the ETUs in Butembo and Katwa, Eastern DRC, between 30 March and 10 August 2019. We included 257 patients, of whom 44 had been vaccinated prior to admission and 213 were unvaccinated. Vaccinated patients were admitted to hospital sooner than unvaccinated patients (median 2 days (IQR 1.8-4) versus 4 days (IQR 3-6), p < 0.001). Vaccinated patients had a lower viral load at admission compared to those who were unvaccinated: 6.0 log10 cp/mL (IQR 5.0-7.1) versus 6.9 log10 cp/mL (IQR 5.4-7.6), p = 0.017. In a longitudinal analysis of daily viral load measurements, vaccinated patients had an overall viremia 1.32 log10 cp/mL (95% CI 0.58-2.1) lower than unvaccinated patients over the course of their infection. Acute kidney injury at admission was less common in vaccinated patients: OR 0.44 (95% CI 0.20-0.94), p = 0.027. Mortality in vaccinated patients was 10/44 (23%) compared to 117/213 (55%) unvaccinated patients (OR 0.24, 95% CI 0.11-0.51, p < 0.001). In conclusion, prior rVSV-ZEBOV vaccination was associated with reduced severity of infection and improved survival among patients with confirmed EVD treated at ETUs in Eastern DRC. These findings support the efficacy of the rVSV-ZEBOV vaccine in modulating EVD severity.

Titration methods for rVSV-based vaccine manufacturing.

The recombinant Vesicular Stomatitis Virus (rVSV) is an emerging platform for viral vector-based vaccines. Promising results have been reported in clinical trials for the rVSV-ZEBOV vaccine for Ebola virus disease prevention. In this study, we describe the titration tools elaborated to assess the titre of rVSV-ZEBOV productions. • A streamlined Median Tissue Culture Infectious Dose (TCID50) assay to determine the infectious titer of this vaccine was established. • A digital polymerase chain reaction (dPCR) assay to assess the total number of viral particles present in cell-free culture supernatants of rVSV productions was developed. • These assays are used to titre rVSV-ZEBOV samples and characterize the ratio of total particles to infectious units for monitoring process robustness and product quality attributes and can be used to titre samples generated in the production of further rVSV vectors.

Serum-free production of rVSV-ZEBOV in Vero cells: Microcarrier bioreactor versus scale-X™ hydro fixed-bed.

Ebola virus disease outbreaks have repeatedly occurred on the African continent over the last decades, with more serious outbreaks in recent years. Being highly transmissible and associated to high fatality rates, it constitutes a serious threat to public health. Vaccination, however, may allow for efficient control of its propagation. The most promising Ebola vaccine candidate to date, rVSV-ZEBOV, relies on a recombinant vesicular stomatitis virus construct, in which the native viral glycoprotein is replaced by the glycoprotein of Ebola virus (Zaire). However, its cell-based manufacturing process is still lengthy and cumbersome, thus urging the implementation of a new and more efficient bioprocess. To address these issues, serum-free production of rVSV-ZEBOV in Vero cells has been studied with the aim to test an alternative upstream process. Until viable options of suspension cell culture are available, Vero cell cultures still rely on adherent bioprocesses and have thus been developed in this work. Particularly, a bioprocess developed with standard microcarrier bioreactor technology was successfully transferred to the novel single-use scale-X™ hydro fixed-bed.

Being Pregnant during the Kivu Ebola Virus Outbreak in DR Congo: The rVSV-ZEBOV Vaccine and Its Accessibility by Mothers and Infants during Humanitarian Crises and in Conflict Areas.

The Ebola virus disease (EVD) outbreak that began in Kivu province of the Democratic Republic of the Congo (DRC) in July 2018 is the second largest in history. It is also the largest and most deadly of the ten Ebola outbreaks to occur in DRC, the country where Ebola was first identified during the 1976 Yambuku outbreak. The Kivu region is one of the most challenging locations in which to organize humanitarian assistance. It is an active conflict zone in which numerous armed groups are conducting violent acts, often directed against the inhabitants, healthcare and relief workers and peacekeepers. EVD has been especially problematic in pregnancy-previous outbreaks both in DRC and other countries have resulted in very high mortality rates among pregnant women and especially their infants, with maternal mortality in some outbreaks reaching over 90% and perinatal mortality 100%. The development and implementation of the Merck rVSV-ZEBOV vaccine for Ebola infection has been a tremendous public health advance in preventing EVD, being used successfully in both the West Africa Ebola epidemic and the Équateur DRC Ebola outbreak. But from the start of the Kivu outbreak, policy decisions had resulted in excluding pregnant and lactating women and their infants from receiving it during extensive ring vaccination efforts. In June 2019, this policy was reversed, 10 months after the start of the outbreak. Pregnant and lactating women are now permitted not only the rVSV-ZEBOV vaccine in the continuing Kivu outbreak but also the newly implemented Ad26.ZEBOV/MVA-BN vaccine.

Ebola epidemic in war-torn Democratic Republic of Congo, 2018: Acceptability and patient satisfaction of the recombinant Vesicular Stomatitis Virus - Zaire Ebolavirus Vaccine.

BACKGROUND: The current Ebola outbreak in Eastern Democratic Republic of the Congo (DRC) is the second largest in history and the first in which the recombinant Vesicular Stomatitis Virus - Zaire Ebolavirus (rVSV-ZEBOV) vaccine has been used at scale. We assessed side-effects, satisfaction, and attitudes toward the new vaccine. METHODS: Cross-sectional survey questionnaire from a convenience sample of 90 vaccine recipients and 96 community controls in Eastern DRC. RESULTS: Side-effects were reported in 75/90 (83%) vaccine recipients but only 5 (7%) and 4 (5%) reported arthralgia and rash, respectively. 76/90 (84%) vaccinees were classified as "promoters" (would recommend vaccine to others) and 6/90 (7%) as "detractors." 69/96 (72%) of unvaccinated community controls would wish to be vaccinated if supply were available. 153/186 (82%) would accept vaccination for family members. CONCLUSIONS: The rVSV-ZEBOV vaccine was well tolerated, with high acceptability in the community during the current outbreak in the DRC.

Production of rVSV-ZEBOV in serum-free suspension culture of HEK 293SF cells.

Ebola virus disease is an urgent international priority. Promising results for several vaccine candidates have been reported in non-human primate studies and clinical trials with the most promising being the rVSV-ZEBOV vaccine. In this study, we sought to produce rVSV-ZEBOV in HEK 293SF cells in suspension and serum-free media. The purpose of this study was to establish a process using the HEK 293SF production platform, optimise the production titre, demonstrate scalability and the efficiency of the generated material to elicit an immune reaction in an animal model. Critical process parameters were evaluated to maximize production yield and process robustness and the following operating conditions: 1-2 × 106 cells/mL grown in HyClone HyCell TransFx-H media infected at an MOI of 0.001 with a temperature shift to 34 °C during the production phase and a harvest of the product after 48 h. Using these conditions, scalability in a 3.5 L controlled bioreactor was shown reaching a titre of 1.19 × 108 TCID50/mL at the peak of production, the equivalent of 4165 doses of vaccine per litre. The produced virus was shown to be thermostable in the culture media and, when concentrated, purified and administered to mice, demonstrated the ability to induce a ZEBOV-specific immune response.

Durability of single-dose rVSV-ZEBOV vaccine responses: what do we know?

INTRODUCTION: The live-attenuated recombinant vesicular stomatitis virus vaccine expressing the glycoprotein (GP) of Zaire Ebola virus (rVSV-ZEBOV) has proven immunogenic in humans and effective in field studies. Yet long-term durability of vaccine responses is unknown. AREAS COVERED: We survey the evidence available in the literature for the durability of human responses to rVSV-ZEBOV. We also review determinants of initial responses and of their persistence. EXPERT COMMENTARY: Persistence of EBOV-GP-specific antibody responses is strong at 2 years - currently the longest post-vaccination interval studied - after a single injection. Vaccine dose predicts persistence of seropositivity, though the magnitude of antibody responses at later time points becomes less dose-dependent. Vaccine-related arthritis is a significant predictor of both persistence and magnitude of the antibody response.

Systems Vaccinology Identifies an Early Innate Immune Signature as a Correlate of Antibody Responses to the Ebola Vaccine rVSV-ZEBOV.

Predicting vaccine efficacy remains a challenge. We used a systems vaccinology approach to identify early innate immune correlates of antibody induction in humans receiving the Ebola vaccine rVSV-ZEBOV. Blood samples from days 0, 1, 3, 7, and 14 were analyzed for changes in cytokine levels, innate immune cell subsets, and gene expression. Integrative statistical analyses with cross-validation identified a signature of 5 early innate markers correlating with antibody titers on day 28 and beyond. Among those, IP-10 on day 3 and MFI of CXCR6 on NK cells on day 1 were independent correlates. Consistently, we found an early gene expression signature linked to IP-10. This comprehensive characterization of early innate immune responses to the rVSV-ZEBOV vaccine in humans revealed immune signatures linked to IP-10. These results suggest correlates of vaccine-induced antibody induction and provide a rationale to explore strategies for augmenting the effectiveness of vaccines through manipulation of IP-10.

Dose-dependent T-cell Dynamics and Cytokine Cascade Following rVSV-ZEBOV Immunization.

BACKGROUND: The recent West African Ebola epidemic led to accelerated efforts to test Ebola vaccine candidates. As part of the World Health Organisation-led VSV Ebola Consortium (VEBCON), we performed a phase I clinical trial investigating rVSV-ZEBOV (a recombinant vesicular stomatitis virus-vectored Ebola vaccine), which has recently demonstrated protection from Ebola virus disease (EVD) in phase III clinical trials and is currently in advanced stages of licensing. So far, correlates of immune protection are incompletely understood and the role of cell-mediated immune responses has not been comprehensively investigated to date. METHODS: We recruited 30 healthy subjects aged 18-55 into an open-label, dose-escalation phase I trial testing three doses of rVSV-ZEBOV (3×105 plaque-forming units (PFU), 3×106 PFU, 2×107 PFU) (ClinicalTrials.gov; NCT02283099). Main study objectives were safety and immunogenicity, while exploratory objectives included lymphocyte dynamics, cell-mediated immunity and cytokine networks, which were assessed using flow cytometry, ELISpot and LUMINEX assay. FINDINGS: Immunization with rVSV-ZEBOV was well tolerated without serious vaccine-related adverse events. Ebola virus-specific neutralizing antibodies were induced in nearly all individuals. Additionally, vaccinees, particularly within the highest dose cohort, generated Ebola glycoprotein (GP)-specific T cells and initiated a cascade of signaling molecules following stimulation of peripheral blood mononuclear cells with Ebola GP peptides. INTERPRETATION: In addition to a benign safety and robust humoral immunogenicity profile, subjects immunized with 2×107 PFU elicited higher cellular immune responses and stronger interlocked cytokine networks compared to lower dose groups. To our knowledge these data represent the first detailed cell-mediated immuneprofile of a clinical trial testing rVSV-ZEBOV, which is of particular interest in light of its potential upcoming licensure as the first Ebola vaccine. VEBCON trial Hamburg, Germany (NCT02283099).