Development and evaluation of a formalin-inactivated West Nile Virus vaccine (WN-VAX) for a human vaccine candidate

A formalin-inactivated West Nile Virus (WNV) vaccine (WN-VAX) derived from the WNV-NY99 strain was tested for its safety, efficacy, dilution limit for complete protection, and cross-neutralization. Safety tests performed with experimental animals, bacteria, or cultured cell lines showed no evidence of short- or long-term adverse effects. WN-VAX also protected 100% of 4-week-old mice against a lethal challenge from the WNV-NY99 strain after two doses of intraperitoneal inoculation-even when the vaccine was diluted to 3.2 ng/dose. Moreover, very limited cross-neutralization activity against Japanese encephalitis virus, Dengue virus, Murray Valley encephalitis virus, Yellow fever virus or St. Louis encephalitis virus was observed. Therefore, the WN-VAX satisfies the requirements for human trials planned to be done in Japan.