METHODS: In this study we have designed new live-attenuated vaccine vectors based on recombinant vesicular stomatitis viruses (rVSV) expressing NiV glycoproteins (G or F) or nucleoprotein (N) and evaluated their protective efficacy in Syrian hamsters, an established NiV animal disease model. We further characterized the humoral immune response to vaccination in hamsters using ELISA and neutralization assays and performed serum transfer studies.
RESULTS: Vaccination of Syrian hamsters with a single dose of the rVSV vaccine vectors resulted in strong humoral immune responses with neutralizing activities found only in those animals vaccinated with rVSV expressing NiV G or F proteins. Vaccinated animals with neutralizing antibody responses were completely protected from lethal NiV disease, whereas animals vaccinated with rVSV expressing NiV N showed only partial protection. Protection of NiV G or F vaccinated animals was conferred by antibodies, most likely the neutralizing fraction, as demonstrated by serum transfer studies. Protection of N-vaccinated hamsters was not antibody-dependent indicating a role of adaptive cellular responses for protection.
CONCLUSIONS: The rVSV vectors expressing Nipah virus G or F are prime candidates for new 'emergency vaccines' to be utilized for NiV outbreak management.
METHODS: We produced two NiV vaccine candidates using the licensed VSV-EBOV vaccine as a backbone and tested its efficacy against lethal homologous and heterologous NiV challenge with Nipah virus Bangladesh and Nipah virus Malaysia, respectively, in the African green monkey model.
FINDINGS: The VSV-EBOV vaccine expressing NiV glycoprotein G (VSV-NiVG) induced high neutralising antibody titers and afforded complete protection from homologous and heterologous challenge. The VSV-EBOV vaccine expressing NiV fusion protein F (VSV-NiVF) induced a lower humoral response and afforded complete homologous protection, but only partial heterologous protection. Both vaccines reduced virus shedding from the upper respiratory tract, and virus replication in the lungs and central nervous system. None of the protected animals vaccinated with VSV-NiVG or VSV-NiVF showed histological lesions in the CNS, but one VSV-NiVF-vaccinated animal that was not protected developed severe meningoencephalitis.
INTERPRETATION: The VSV-NiVG vaccine offers broad protection against NiV disease.
FUNDING: This study was supported by the Intramural Research Program, NIAID, NIH.