Non-infectious antigen for laboratory diagnosis of Japanese encephalitis.

Sucrose-acetone suckling mouse brain antigens of Na-kayama NIH, JaGAr-01 and Peking-1 strains of Japanese encephalitis (JE) virus treated with beta-propiolactone (BPL) retained their ability to specifically react in haemagglutination inhibition (HI) tests with antibody to JE virus, as demonstrated with convalescent sera. BPL treatment abolished the infectivity but did not affect the haemagglutinating activity of the virus of the pH optimum of the haemagglutination (HA) test.