Comparative evaluation of pathogenicity of three isolates of vesicular stomatitis virus (Indiana serotype) in pigs.

Vesicular stomatitis (VS) is a notifiable disease of livestock affecting cattle, horses, pigs and humans. Vesicular stomatitis virus (VSV) serotypes Indiana and New Jersey are endemic to Central America; however, they also cause sporadic and scattered outbreaks in various countries in South and North America, including the USA. In order to develop an effective experimental challenge model for VSV, we compared the pathogenicity of three VSV serotype Indiana isolates in 36 4-5 week-old pigs. Two bovine isolates of Central American origin and one equine isolate from the USA were used for the experimental infections. Each pig was inoculated with a single isolate by both the intradermal and intranasal routes. Clinical signs of VSV infection were recorded daily for 10 days post-inoculation (days p.i.). Nasal and tonsillar swab samples and blood were collected to monitor immune responses, virus replication and shedding. Post-challenge, characteristic signs of VS were observed, including vesicles on the nasal planum and coronary bands, lameness, loss of hoof walls and pyrexia. Pigs inoculated with the Central American isolates showed consistently more severe clinical signs in comparison to the pigs infected with the USA isolate. Genomic RNA was isolated from the original challenge virus stocks, sequenced and compared to VSV genomes available in GenBank. Comparative genome analysis demonstrated significant differences between the VSV isolate from the USA and the two Central American isolates. Our results indicate that the Central American isolates of VSV serotype Indiana used in this study are more virulent in swine than the USA VSV serotype Indiana isolate and represent good candidate challenge strains for future VSV studies.

Addition of αGal HyperAcute™ technology to recombinant avian influenza vaccines induces strong low-dose antibody responses.

Highly pathogenic avian influenza represents a severe public health threat. Over the last decade, the demand for highly efficacious vaccines against avian influenza viruses has grown, especially after the 2013 H7N9 outbreak in China that resulted in over 600 human cases with over 200 deaths. Currently, there are several H5N1 and H7N9 influenza vaccines in clinical trials, all of which employ traditional oil-in-water adjuvants due to the poor immunogenicity of avian influenza virus antigens. In this study, we developed potent recombinant avian influenza vaccine candidates using HyperAcute™ Technology, which takes advantage of naturally-acquired anti-αGal immunity in humans. We successfully generated αGal-positive recombinant protein and virus-like particle vaccine candidates of H5N1 and H7N9 influenza strains using either biological or our novel CarboLink chemical αGal modification techniques. Strikingly, two doses of 100 ng αGal-modified vaccine, with no traditional adjuvant, was able to induce a much stronger humoral response in αGT BALB/c knockout mice (the only experimental system readily available for testing αGal in vivo) than unmodified vaccines even at 10-fold higher dose (1000 ng/dose). Our data strongly suggest that αGal modification significantly enhances the humoral immunogenicity of the recombinant influenza vaccine candidates. Use of αGal HyperAcute™ technology allows significant dose-sparing while retaining desired immunogenicity. Our success in the development of highly potent H5N1 and H7N9 vaccine candidates demonstrated the potential of αGal HyperAcute™ technology for the development of vaccines against other infectious diseases.

Safety and immunogenicity of the rVSV∆G-ZEBOV-GP Ebola virus vaccine candidate in healthy adults: a phase 1b randomised, multicentre, double-blind, placebo-controlled, dose-response study.

BACKGROUND: The 2014 Zaire Ebola virus outbreak highlighted the need for a safe, effective vaccine with a rapid onset of protection. We report the safety and immunogenicity of the recombinant vesicular stomatitis virus-Zaire Ebola virus envelope glycoprotein vaccine (rVSV∆G-ZEBOV-GP) across a 6 log10 dose range in two sequential cohorts. METHODS: In this phase 1b double-blind, placebo-controlled, dose-response study we enrolled and randomly assigned healthy adults (aged 18-61 years) at eight study sites in the USA to receive a single injection of vaccine or placebo, administered by intramuscular injection. In cohort 1, participants were assigned to receive 3 × 103, 3 × 104, 3 × 105, or 3 × 106 PFU doses of rVSV∆G-ZEBOV-GP or placebo. In cohort 2, participants were assigned to receive 3 × 106, 9 × 106, 2 × 107, or 1 × 108 PFU doses of rVSV∆G-ZEBOV-GP or placebo. Participants were centrally allocated by the study statistician to vaccine groups or placebo through computer-generated randomisation lists. The primary safety outcome was incidence of adverse events within 14 days in the modified intention-to-treat population (all randomly assigned participants who received vaccine or placebo), and the primary outcome for immunogenicity was IgG ELISA antibody titres at day 28 in the per-protocol population. Surveillance was enhanced for arthritis and dermatitis through to day 56. This study is registered with ClinicalTrials.gov, number NCT02314923. FINDINGS: Between Dec 26, 2014, and June 8, 2015, 513 participants were enrolled and randomly assigned; one was not immunised because of unsuccessful phlebotomy. In cohort 1, 256 participants received vaccine (3 × 103 [n=64], 3 × 104 [n=64], 3 × 105 [n=64], or 3 × 106 PFU [n=64]) and 74 received placebo. In cohort 2, 162 participants received vaccine (3 × 106 [n=20], 9 × 106 [n=47], 2 × 107 [n=47], or 1 × 108 PFU [n=48]) and 20 received placebo. Most adverse events occurred in the first day after vaccination, and were mild to moderate in intensity, of a short duration, and more frequent at high vaccine doses (9 × 106 PFU and greater). At the 2 × 107 PFU dose (used in phase 3 trials), the most common local adverse events versus placebo within the first 14 days were arm pain (57·4% [27 of 47] vs 7·4% [seven of 94]) and local tenderness (59·6% [28 of 47] vs 8·5% [eight of 94]). The most common systemic adverse events at the 2 × 107 PFU dose versus placebo, occurring in the first 14 days, were headache (46·8% [22 of 47] vs 27·7% [26 of 94]), fatigue (38·3% [18 of 47] vs 19·1% [18 of 94]), myalgia (34·0% [16 of 47] vs 10·6% [10 of 94]), subjective fever (29·8% [14 of 47] vs 2·1% [two of 94]), shivering or chills (27·7% [13 of 47] vs 7·4% [seven of 94]), sweats (23·4% [11 of 47] vs 3·2% [three of 94]), joint aches and pain (19·1% [nine of 47] vs 7·4% [seven of 94]), objective fever (14·9% [seven of 47] vs 1·1% [one of 94]), and joint tenderness or swelling (14·9% [seven of 47] vs 2·1% [two of 94]). Self-limited, post-vaccination arthritis occurred in 4·5% (19 of 418) of vaccinees (median onset 12·0 days [IQR 10-14]; median duration 8·0 days [6-15]) versus 3·2% (three of 94) of controls (median onset 15·0 days [6-20]; median duration 47·0 days [37-339]), with no apparent dose relationship. Post-vaccination dermatitis occurred in 5·7% (24 of 418) of vaccinees (median onset 9·0 days [IQR 2-12]; median duration 7·0 days [4-9]) versus 3·2% (three of 94) of controls (median onset 5·0 days [3-53]; median duration 33·0 days [5-370]). A low-level, transient, dose-dependent viraemia occurred in concert with early reactogenicity. Antibody responses were observed in most participants by day 14. IgG and neutralising antibody titres were dose-related (p=0·0003 for IgG ELISA and p<0·0001 for the 60% plaque-reduction neutralisation test [PRNT60] by linear trend). On day 28 at the 2 × 107 PFU dose, the geometric mean IgG ELISA endpoint titre was 1624 (95% CI 1146-2302) and seroconversion was 95·7% (95% CI 85·5-98·8); the geometric mean neutralising antibody titre by PRNT60 was 250 (176-355) and seroconversion was 95·7% (85·5-98·8). These robust immunological responses were sustained for 1 year. INTERPRETATION: rVSV∆G-ZEBOV-GP was well tolerated and stimulated a rapid onset of binding and neutralising antibodies, which were maintained through to day 360. The immunogenicity results support selection of the 2 × 107 PFU dose. FUNDING: Biomedical Advanced Research and Development Authority, US Department of Health and Human Services.