A team of U.S. and U.K. researchers have shown that an experimental West Nile virus (WNV) vaccine shows promise in protecting humans from the arbovirus. The study abstract appeared online April 14 in the early edition of the Proceedings of the National Academy of Sciences of the United States of America.

According to the scientists, the vaccine is a “live, attenuated recombinant vaccine constructed from an infectious clone of yellow fever (YF) 17D virus in which the premembrane and envelope genes of 17D have been replaced by the corresponding genes of WN virus.” In other words, they replaced structural genes of a weakened yellow fever virus (which is closely related to WNV) with those of WNV, making a new attenuated “chimeric” virus that is designed to stimulate immunity against WNV without causing disease.

“All subjects developed neutralizing antibodies to WN or YF, respectively, and the majority developed specific T-cell (cell-mediated immunity) responses,” signifying protection, said the scientists in the study. “ChimeriVax-WN02 rapidly elicits strong immune responses after a single dose, and is a promising candidate warranting further evaluation for prevention of WN disease.”

Acambis has been developing this human vaccine. The Horse reported earlier in 2006 on safety and efficacy studies conducted on an equine chimera WNV vaccine that was based on the technology of Acambis and made by Intervet. For more information about the equine vaccine under development see www.TheHorse.com/ViewArticle.aspx?ID=6475