University of Texas Medical Branch Galveston United States
Nearly 20 years ago, Nipah virus NiV emerged and was shown to be a previously unknown paramyxovirus, now classified along with Hendra virus HeV and Cedar virus within the Henipavirus genus. NiV causes febrile encephalitis and severe respiratory disease in humans with a fatality rate as high as 100 in some outbreaks. Genetic analysis has identified at least two strains of NiV responsible for outbreaks in different geographical areas. The Malaysia strain NiVM caused the initial outbreak of NiV from 1998-1999 in Malaysia and Singapore, in which over 270 people were infected with about 40 case fatality rate CFR with an additional 2014 outbreak in the Philippines with a CFR of approximately 52. The Bangladesh strain NiVB however has caused repeated outbreaks in Bangladesh and India between 2001 and 2018. The outbreaks of NiVB have had higher CFRs averaging about 75 with human-to-human transmission also observed. The observations that these two strains reportedly display differences in CFRs and human-to-human transmission are interesting, as there is 91.8 nucleotide homology between the genomes. Importantly, we have developed nonhuman primate NHP models for both NiVM and NiVB, and recently shown that NiVB is more pathogenic in African green monkeys AGM than NiVM under identical experimental conditions. Currently, there are no licensed vaccines for the prevention of NiV disease. Previously we developed single cycle recombinant vesicular stomatitis virus rVSV vaccine vectors expressing either the NiV F or NiV G proteins. These vaccines were evaluated 28 days after a single-dose vaccination in the NiV ferret model and were shown to completely protect ferrets from lethal challenge. An important consideration in regard to the pre-clinical animal studies conducted to date is that all of the studies assessed efficacy against the less pathogenic NiVM strain and not the more pathogenic NiVB strain.