Protective Efficacy of a Bivalent Recombinant Vesicular Stomatitis Virus Vaccine in the Syrian Hamster Model of Lethal Ebola Virus Infection

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Abstract
Outbreaks of filoviral hemorrhagic fever occur sporadically and unpredictably across wide regions in central Africa and overlap with the occurrence of other infectious diseases of public health importance. As a proof of concept we developed a bivalent recombinant vaccine based on vesicular stomatitis virus (VSV) expressing the Zaire ebolavirus (ZEBOV) and Andes virus (ANDV) glycoproteins (VSVΔG/Dual) and evaluated its protective efficacy in the common lethal Syrian hamster model. Hamsters were vaccinated with VSVΔG/Dual and were lethally challenged with ZEBOV or ANDV. Time to immunity and postexposure treatment were evaluated by immunizing hamsters at different times prior to and post ZEBOV challenge. A single immunization with VSVΔG/Dual conferred complete and sterile protection against lethal ZEBOV and ANDV challenge. Complete protection was achieved with an immunization as close as 3 days prior to ZEBOV challenge, and 40% of the animals were even protected when treated with VSVΔG/Dual one day postchallenge. In comparison to the monovalent VSV vaccine, the bivalent vaccine has slightly reduced postexposure efficacy most likely due to its restricted lymphoid organ replication. Bivalent VSV vectors are a feasible approach to vaccination against multiple pathogens.