Japanese encephalitis vaccines: moving away from the mouse brain.

Japanese encephalitis (JE) is a severe disease that is widespread throughout Asia and is spreading beyond its traditional boundaries. Three vaccines are currently in use against JE but only one is available internationally, a mouse-brain-derived inactivated vaccine first used in the 1930s. Although this vaccine has been effective in reducing the incidence of JE, it is relatively expensive and has been linked to severe allergic and neurological reactions. Cell-culture-derived inactivated and attenuated vaccines have been developed but are only used in the People's Republic of China. Other vaccines currently in various stages of development are DNA vaccines, a chimeric yellow fever-JE viral vaccine, virus-like particle vaccines and poxvirus-based vaccines. Poxvirus-based vaccines and the chimeric yellow fever-JE vaccine have been tested in Phase I clinical trials. These new vaccines have the potential to significantly reduce the impact of JE in Asia, particularly if used in an oral vaccine delivery strategy.