Characterization of a Bivalent Vaccine Capable of Inducing Protection Against Both Ebola and Cross-clade H5N1 Influenza in Mice

Background. Ebola virus (EBOV) is a lethal pathogen that causes up to 90% mortality in humans, whereas H5N1 avian influenza has a 60% fatality rate. Both viruses are considered pandemic threats. The objective was to evaluate the protective efficacy of a bivalent, recombinant vesicular stomatitis virus vaccine expressing both the A/Hanoi/30408/2005 H5N1 hemagglutinin and the EBOV glycoprotein (VSVΔG-HA-ZGP) in a lethal mouse model of infection. Methods. Mice were vaccinated 28 days before or 30 minutes after a lethal challenge with mouse-adapted EBOV or selected H5N1 influenza viruses from clades 0, 1, and 2. Animals were monitored for weight loss and survival, in addition to humoral and cell-mediated responses after immunization. Results. A single VSVΔG-HA-ZGP injection was efficacious when administered 28 days before a homologous H5N1 and/or mouse-adapted EBOV challenge, as well as a heterologous H5N1 challenge. Postexposure protection was only observed in vaccinated animals challenged with homologous H5N1 and/or mouse-adapted EBOV. Analysis of the adaptive immune response postvaccination revealed robust specific T- and B-cell responses, including a potent hemagglutinin inhibition antibody response against all H5N1 strains tested. Conclusions. The results highlight the ability of vesicular stomatitis virus-vectored vaccines to rapidly confer protection against 2 unrelated pathogens and stimulate cross-protection against H5N1 influenza viruses.