Complete nucleotide sequence and cell-line multiplication pattern of the attenuated variant CH2195LA of Japanese encephalitis virus.

Strain-specific determinant of Japanese encephalitis virus (JEV) can be different among each virulence phenotype. We reported previously that the attenuated variant CH2195LA compared with the non-attenuated variant CH2195SA had four amino acid differences in E protein (E-85, E-306, E-331, and E-387) (Wu, S.-C., Lian, W.-C., Hsu, L.-C., Liau, M., 1997. Japanese encephalitis virus antigenic variants with characteristic differences in neutralization resistance and mouse virulence. Virus Res. 51, 173-181). Our present study determined the complete nucleotide sequences of these two variants and found another five amino acid changes in the nonstructural gene regions, including NS2A-215, NS3-350, NS4B-196, NS4B-197, and NS4B-198. The complete nucleotide sequences of the attenuated variant CH2195LA were compared with the non-attenuated variant CH2195SA and other 13 JEV strains. CH2195LA was mostly close to CH2195SA and JaOArS982, and phylogenetically distant to SA14-14-2, SA14-2-8, and RP-2ms of the attenuated JEV strains. The multiplication patterns for CH2195LA compared with CH2195SA in other seven cell lines were different from Vero cells. Relative fitness vector analysis based on a mixture of both variants during cell passage indicated the attenuated variant CH2195LA showed increased viral fitness in Vero cell adaptation. These results revealed that the attenuated variant CH2195LA was unique to culture in Vero cells.