Jay W. Hooper

Smallpox vaccine–induced antibodies are necessary and sufficient for protection against monkeypox virus

Vaccination with live vaccinia virus affords long-lasting protection against variola virus, the agent of smallpox. Its mode of protection in humans, however, has not been clearly defined. Here we report that vaccinia-specific B-cell responses are essential for protection of macaques from monkeypox virus, a variola virus ortholog. Antibody-mediated depletion of B cells, but not CD4+ or CD8+ T cells, abrogated vaccine-induced protection from a lethal intravenous challenge with monkeypox virus. In addition, passive transfer of human vaccinia-neutralizing antibodies protected nonimmunized macaques from severe disease. Thus, vaccines able to induce long-lasting protective antibody responses may constitute realistic alternatives to the currently available smallpox vaccine (Dryvax).

Phase 1 Trials of rVSV Ebola Vaccine in Africa and Europe.

BACKGROUND The replication-competent recombinant vesicular stomatitis virus (rVSV)-based vaccine expressing a Zaire ebolavirus (ZEBOV) glycoprotein was selected for rapid safety and immunogenicity testing before its use in West Africa. METHODS We performed three open-label, dose-escalation phase 1 trials and one randomized, double-blind, controlled phase 1 trial to assess the safety, side-effect profile, and immunogenicity of rVSV-ZEBOV at various doses in 158 healthy adults in Europe and Africa. All participants were injected with doses of vaccine ranging from 300,000 to 50 million plaque-forming units (PFU) or placebo. RESULTS No serious vaccine-related adverse events were reported. Mild-to-moderate early-onset reactogenicity was frequent but transient (median, 1 day). Fever was observed in up to 30% of vaccinees. Vaccine viremia was detected within 3 days in 123 of the 130 participants (95%) receiving 3 million PFU or more; rVSV was not detected in saliva or urine. In the second week after injection, arthritis affecting one to four joints developed in 11 of 51 participants (22%) in Geneva, with pain lasting a median of 8 days (interquartile range, 4 to 87); 2 self-limited cases occurred in 60 participants (3%) in Hamburg, Germany, and Kilifi, Kenya. The virus was identified in one synovial-fluid aspirate and in skin vesicles of 2 other vaccinees, showing peripheral viral replication in the second week after immunization. ZEBOV-glycoprotein-specific antibody responses were detected in all the participants, with similar glycoprotein-binding antibody titers but significantly higher neutralizing antibody titers at higher doses. Glycoprotein-binding antibody titers were sustained through 180 days in all participants. CONCLUSIONS In these studies, rVSV-ZEBOV was reactogenic but immunogenic after a single dose and warrants further evaluation for safety and efficacy. (Funded by the Wellcome Trust and others; ClinicalTrials.gov numbers, NCT02283099, NCT02287480, and NCT02296983; Pan African Clinical Trials Registry number, PACTR201411000919191.).

A Recombinant Vesicular Stomatitis Virus Ebola Vaccine - Preliminary Report.

Background The worst Ebola virus disease (EVD) outbreak in history has resulted in more than 28,000 cases and 11,000 deaths. We present the final results of two phase 1 trials of an attenuated, replication‐competent, recombinant vesicular stomatitis virus (rVSV)–based vaccine candidate designed to prevent EVD. Methods We conducted two phase 1, placebo‐controlled, double‐blind, dose‐escalation trials of an rVSV‐based vaccine candidate expressing the glycoprotein of a Zaire strain of Ebola virus (ZEBOV). A total of 39 adults at each site (78 participants in all) were consecutively enrolled into groups of 13. At each site, volunteers received one of three doses of the rVSV‐ZEBOV vaccine (3 million plaque‐forming units [PFU], 20 million PFU, or 100 million PFU) or placebo. Volunteers at one of the sites received a second dose at day 28. Safety and immunogenicity were assessed. Results The most common adverse events were injection‐site pain, fatigue, myalgia, and headache. Transient rVSV viremia was noted in all the vaccine recipients after dose 1. The rates of adverse events and viremia were lower after the second dose than after the first dose. By day 28, all the vaccine recipients had seroconversion as assessed by an enzyme‐linked immunosorbent assay (ELISA) against the glycoprotein of the ZEBOV‐Kikwit strain. At day 28, geometric mean titers of antibodies against ZEBOV glycoprotein were higher in the groups that received 20 million PFU or 100 million PFU than in the group that received 3 million PFU, as assessed by ELISA and by pseudovirion neutralization assay. A second dose at 28 days after dose 1 significantly increased antibody titers at day 56, but the effect was diminished at 6 months. Conclusions This Ebola vaccine candidate elicited anti‐Ebola antibody responses. After vaccination, rVSV viremia occurred frequently but was transient. These results support further evaluation of the vaccine dose of 20 million PFU for preexposure prophylaxis and suggest that a second dose may boost antibody responses. (Funded by the National Institutes of Health and others; rVSV&Dgr;G‐ZEBOV‐GP ClinicalTrials.gov numbers, NCT02269423 and NCT02280408.)

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

BACKGROUND Safe and effective vaccines against Ebola could prevent or control outbreaks. The safe use of replication-competent vaccines requires a careful dose-selection process. We report the first safety and immunogenicity results in volunteers receiving 3 × 10(5) plaque-forming units (pfu) of the recombinant vesicular stomatitis virus-based candidate vaccine expressing the Zaire Ebola virus glycoprotein (rVSV-ZEBOV; low-dose vaccinees) compared with 59 volunteers who had received 1 ×10(7) pfu (n=35) or 5 × 10(7) pfu (n=16) of rVSV-ZEBOV (high-dose vaccinees) or placebo (n=8) before a safety-driven study hold. METHODS The Geneva rVSV-ZEBOV study, an investigator-initiated phase 1/2, dose-finding, placebo-controlled, double-blind trial conducted at the University Hospitals of Geneva, Switzerland, enrolled non-pregnant, immunocompetent, and otherwise healthy adults aged 18-65 years. Participants from the low-dose group with no plans to deploy to Ebola-aff5cted regions (non-deployable) were randomised 9:1 in a double-blind fashion using randomly permuted blocks of varying sizes to a single injection of 3 × 10(5) pfu or placebo, whereas deployable participants received single-injection 3 × 10(5) pfu open-label. Primary safety and immunogenicity outcomes were the incidence of adverse events within 14 days of vaccination and day-28 antibody titres, respectively, analysed by intention to treat. After viral oligoarthritis was observed in 11 of the first 51 vaccinees (22%) receiving 10(7) or 5 × 10(7) pfu, 56 participants were given a lower dose (3 × 10(5) pfu, n=51) or placebo (n=5) to assess the effect of dose reduction on safety and immunogenicity. This trial is ongoing with a follow-up period of 12 months; all reported results are from interim databases. This study is registered with ClinicalTrials.gov, number NCT02287480. FINDINGS Between Jan 5 and Jan 26, 2015, 43 non-deployable participants received low-dose rVSV-ZEBOV (3 × 10(5) pfu) or placebo in a double-blind fashion, whereas 13 deployable participants received 3 × 10(5) pfu open-label. Altogether, in the low-dose group, 51 participants received rVSV-ZEBOV and five received placebo. No serious adverse events occurred. At 3 × 10(5) pfu, early-onset reactogenicity remained frequent (45 [88%] of 51 compared with 50 [98%] of 51 high dose and two [15%] of 13 placebo recipients), but mild. Objective fever was present in one (2%) of 51 low-dose versus 13 (25%) of 51 high-dose vaccinees receiving at least 1 ×10(7) pfu (p<0·0001). Subjective fever (p<0·0001), myalgia (p=0·036), and chills (p=0·026) were significantly reduced and their time of onset delayed, reflecting significantly lower viraemia (p<0·0001) and blood monocyte-activation patterns (p=0·0233). Although seropositivity rates remained similarly high (48 [94%] of 51), day-28 EBOV-glycoprotein-binding and neutralising antibody titres were lower in low-dose versus high-dose vaccinees (geometric mean titres 344·5 [95% CI 229·7-516·4] vs 1064·2 [757·6-1495·1]; p<0·0001; and 35·1 [24·7-50·7] vs 127·0 [86·0-187·6]; p<0·0001, respectively). Furthermore, oligoarthritis again occurred on day 10 (median; IQR 9-14) in 13 (25%) of 51 low-dose vaccinees, with maculopapular, vesicular dermatitis, or both in seven (54%) of 13; arthritis was associated with increasing age in low-dose but not high-dose vaccinees. Two vaccinees presented with purpura of the lower legs; histological findings indicated cutaneous vasculitis. The presence of rVSV in synovial fluid and skin lesions confirmed causality. INTERPRETATION Reducing the dose of rVSV-ZEBOV improved its early tolerability but lowered antibody responses and did not prevent vaccine-induced arthritis, dermatitis, or vasculitis. Like its efficacy, the safety of rVSV-ZEBOV requires further definition in the target populations of Africa. FUNDING Wellcome Trust through WHO.

Active and Passive Vaccination against Hantavirus Pulmonary Syndrome with Andes Virus M Genome Segment-Based DNA Vaccine

ABSTRACT Hantavirus pulmonary syndrome (HPS) is a rapidly progressing human disease with one of the highest case fatality rates (30 to 50%) of any acute viral disease known. There are no vaccines, effective antiviral drugs, or immunologics to prevent or treat HPS. In an attempt to develop HPS medical countermeasures, we constructed an expression plasmid, pWRG/AND-M, that contains the full-length M genome segment of Andes virus (ANDV), a South American hantavirus. Transfection experiments in cell culture indicated that both the G1 and G2 glycoproteins are expressed from pWRG/AND-M. Rhesus macaques vaccinated by gene gun with pWRG/AND-M developed remarkably high levels of neutralizing antibodies that not only neutralized ANDV but also cross-neutralized other HPS-associated hantaviruses, including Sin Nombre virus. To determine if the antibodies elicited in the monkeys could confer protection, we performed a series of passive-transfer experiments using a recently described lethal HPS animal model (i.e., adult Syrian hamsters develop HPS and die within 10 to 15 days after challenge with ANDV). When injected into hamsters 1 day before challenge, sera from the vaccinated monkeys either provided sterile protection or delayed the onset of HPS and death. When injected on day 4 or 5 after challenge, the monkey sera protected 100% of the hamsters from lethal disease. These data provide a proof of concept for a gene-based HPS vaccine and also demonstrate the potential value of a postexposure immunoprophylactic to treat individuals after exposure, or potential exposure, to these highly lethal hantaviruses.

DNA Vaccination with the Hantaan Virus M Gene Protects Hamsters against Three of Four HFRS Hantaviruses and Elicits a High-Titer Neutralizing Antibody Response in Rhesus Monkeys

ABSTRACT Four hantaviruses—Hantaan virus (HTNV), Seoul virus (SEOV), Dobrava virus (DOBV) and Puumala virus—are known to cause hemorrhagic fever with renal syndrome (HFRS) in Europe and Asia. HTNV causes the most severe form of HFRS (5 to 15% case-fatality rate) and afflicts tens of thousands of people annually. Previously, we demonstrated that DNA vaccination with a plasmid expressing the SEOV M gene elicited neutralizing antibodies and protected hamsters against infection with SEOV and HTNV. Here, we report the construction and evaluation of a DNA vaccine that expresses the HTNV M gene products, G1 and G2. DNA vaccination of hamsters with the HTNV M gene conferred sterile protection against infection with HTNV, SEOV, and DOBV. DNA vaccination of rhesus monkeys with either the SEOV or HTNV M gene elicited high levels of neutralizing antibodies. These are the first immunogenicity data for hantavirus DNA vaccines in nonhuman primates. Because a neutralizing antibody response is considered a surrogate marker for protective immunity in humans, our protection data in hamsters combined with the immunogenicity data in monkeys suggest that hantavirus M gene-based DNA vaccines could protect humans against the most severe forms of HFRS.

Subunit Recombinant Vaccine Protects against Monkeypox

The smallpox vaccine Dryvax, a live vaccinia virus (VACV), protects against smallpox and monkeypox, but is contraindicated in immunocompromised individuals. Because Abs to VACV mediate protection, a live virus vaccine could be substituted by a safe subunit protein-based vaccine able to induce a protective Ab response. We immunized rhesus macaques with plasmid DNA encoding the monkeypox orthologs of the VACV L1R, A27L, A33R, and B5R proteins by the intradermal and i.m. routes, either alone or in combination with the equivalent recombinant proteins produced in Escherichia coli. Animals that received only DNA failed to produce high titer Abs, developed innumerable skin lesions after challenge, and died in a manner similar to placebo controls. By contrast, the animals vaccinated with proteins developed moderate to severe disease (20–155 skin lesions) but survived. Importantly, those immunized with DNA and boosted with proteins had mild disease with 15 or fewer lesions that resolved within days. DNA/protein immunization elicited Th responses and binding Ab titers to all four proteins that correlated negatively with the total lesion number. The sera of the immunized macaques recognized a limited number of linear B cell epitopes that are highly conserved among orthopoxviruses. Their identification may guide future efforts to develop simpler, safer, and more effective vaccines for monkeypox and smallpox.

Temporal Analysis of Andes Virus and Sin Nombre Virus Infections of Syrian Hamsters

ABSTRACT Andes virus (ANDV) and Sin Nombre virus (SNV) are rodent-borne hantaviruses that cause a highly lethal hemorrhagic fever in humans known as hantavirus pulmonary syndrome (HPS). There are no vaccines or specific drugs to prevent or treat HPS, and the pathogenesis is not understood. Syrian hamsters infected with ANDV, but not SNV, develop a highly lethal disease that closely resembles HPS in humans. Here, we performed a temporal pathogenesis study comparing ANDV and SNV infections in hamsters. SNV was nonpathogenic and viremia was not detected despite the fact that all animals were infected. ANDV was uniformly lethal with a mean time to death of 11 days. The first pathology detected was lymphocyte apoptosis starting on day 4. Animals were viremic and viral antigen was first observed in multiple organs by days 6 and 8, respectively. Levels of infectious virus in the blood increased 4 to 5 logs between days 6 and 8. Pulmonary edema was first detected ultrastructurally on day 6. Ultrastructural analysis of lung tissues revealed the presence of large inclusion bodies and substantial numbers of vacuoles within infected endothelial cells. Paraendothelial gaps were not observed, suggesting that fluid leakage was transcellular and directly attributable to infecting virus. Taken together, these data imply that HPS treatment strategies aimed at preventing virus replication and dissemination will have the greatest probability of success if administered before the viremic phase; however, because vascular leakage is associated with infected endothelial cells, a therapeutic strategy targeting viral replication might be effective even at later times (e.g., after disease onset).

Rescue of Hantaan virus minigenomes.

Hantavirus infections are a major public health concern worldwide. Their widespread geographical distribution and their ability to produce serious, often fatal, human disease underline the need for a system that allows manipulation of these viruses. We describe here the first successful establishment of a reverse genetics technology for Hantaan virus, the prototype of the genus Hantavirus. The system offers a unique opportunity to study the biology of hantaviruses, the pathogenesis of the diseases, and the efficacy of antiviral and prophylactic measures against hantavirus infections.

T Cells Are Not Required for Pathogenesis in the Syrian Hamster Model of Hantavirus Pulmonary Syndrome

ABSTRACT Andes virus (ANDV) is associated with a lethal vascular leak syndrome in humans termed hantavirus pulmonary syndrome (HPS). In hamsters, ANDV causes a respiratory distress syndrome closely resembling human HPS. The mechanism for the massive vascular leakage associated with HPS is poorly understood; however, T cell immunopathology has been implicated on the basis of circumstantial and corollary evidence. Here, we show that following ANDV challenge, hamster T cell activation corresponds with the onset of disease. However, treatment with cyclophosphamide or specific T cell depletion does not impact the course of disease or alter the number of surviving animals, despite significant reductions in T cell number. These data demonstrate, for the first time, that T cells are not required for hantavirus pathogenesis in the hamster model of human HPS. Depletion of T cells from Syrian hamsters did not significantly influence early events in disease progression. Moreover, these data argue for a mechanism of hantavirus-induced vascular permeability that does not involve T cell immunopathology.