Biological activities of the structural proteins of Japanese encephalitis virus.

Structural proteins V1, V2 and V3 of Japanese encephalitis virus (JEV) were isolated and purified by means of polyacrylamide gel electrophoresis (PAGE) in the presence of sodium dodecyl sulfate (SDS) and extracted from the sliced gel. The purified and renatured V3 envelope protein was found to bind to receptors for JEV on red blood cells. V3 also bound to haemagglutination inhibition (HI) antibodies from anti-JEV sera. In addition, V3 protein induced neutralizing antibodies against JEV when injected into mice. These facts strongly suggest that V3 protein carries the antigenic epitope(s) that elicit neutralizing antibodies and react with HI antibodies. We conclude the V3 plays an important role in virus infection. V2 protein did not exhibit these biological activities, but antibody against V1 protein, not contaminated with V3 protein, showed slight virus neutralizing activity. Possible implications of these results are discussed.