Differences in biological activity of the V3 envelope protein of two Japanese encephalitis virus strains

Two stains Nakayama-NIH and JaGAr-01 of Japanese encephalitis virus (JEV) distinctly differ in their virulence. Amino acid analysis of the V3 viral protein revealed different serine and tyrosine contents in JaGAr-01 V3 as compared to Nakayama -NIH V3. SDS-PAGE purified renatured JaGAr- and Nakayama-V3 proteins could absorb cross-reactive neutralizing antibodies present in anti-nakayama and anti-JaGAr hyperimmune sera. They also absorbed strain specific antibodies of anti-JaGAr and anti-Nakayama sera, respectively. These observations clearly suggest that both JEV strain specific and cross reactive antigenic determinants are present on V3 protein molecules. Antibody against purified Nakayama V3 protein neutralized Nakayama-NIH virus, but had little neutralizing activity against JaGAr-01 virus. The phenomenon is less pronounced when antibodies against Nakayama-NIH virions are used rather than those against purified homologous V3. This suggests that the antigenicity of the purified V3 protein differs from that of the intact virus envelope.