High Profile Diseases - West Nile Virus

Mark Slifka (ONPRC)

West Nile virus (WNV) is a mosquito-borne flavivirus that has become endemic in the United States. From 1999–2012, there have been 37,088 reported cases of WNV and 1,549 deaths, resulting in a 4.2% case-fatality rate. Despite development of effective WNV vaccines for horses, there is no licensed vaccine to prevent human WNV infection. Several vaccines have been tested in preclinical studies, and to date there have been eight clinical trials, with promising results in terms of safety and induction of antiviral immunity. Although mass vaccination is unlikely to be cost effective, implementation of a targeted vaccine program may be feasible if a safe and effective vaccine can be brought to market.

NHP provide an important resource for WNV vaccine development due to the similarities of NHP and human immune response to this viral pathogen. This attribute allows direct comparisons of vaccine antigens, delivery systems and adjuvants that may predict the potency and specificity of responses and potential correlates of protection prior to the clinical development stage. Although NHP do not typically present with clinical signs of disease after experimental WNV infection, recent studies (B.E. Verstrepen et al. PLoS Neg Trop Dis 2014;8:e2797) have found that rhesus macaques and common marmosets are susceptible to infection with a virulent European strain of WNV (WNV-Ita09) and present with higher levels of viremia/RNAemia than that observed in previous studies that used the WNV-NY99 strain of virus. Both models of WNV infection are deserving of further study, especially in terms of testing the efficacy of future WNV vaccines and therapeutics.