The nucleotide sequence of glycoprotein E of YL vaccine strain was cloned, sequenced and expressed in E. coli. Phylogenetic analysis of envelope (E) amino acid sequences of 18 JEVs in GenBank showed that the vaccine strain YL closer to the virulent strain HVI which is a Taiwanese isolate. We found only two amino acid mutations (K-138 and G-389) of E protein might lead viral attenuation in YL. In this study, we used pRSET vector system to construct three recombinant plasmids (pRSET/F1R1, pRSET/F2R2 and pRSET/F1R2), which encoded and expressed different or overlapping amino acid region of E protein. The antigenicity and hemagglutination activity of these recombinant proteins were examined by western blotting and hemagglutination test, respectively. Our results demonstrated that the recombinant protein of pRSET/F1R2 possesses predominant antigenicity and hemagglutination activity.

An extracellular protease, RpA, was identified from R. pickettii WP1 isolated from water supply system. The RpA metalloproteases is required for the pathogenicity of R. pickettii to mammalian cell lines.

We determined the complete nucleotide sequence of the YL strain of Japanese encephalitis virus and its amino acid sequence was deduced. Our results displayed that the genome of YL strain contained a single open reading frame of 10,296 nucleotides (nts) which was flanked by untranslated region (UTR) containing 95 bases at the 5'-end and 586 bases at the 3'-end, respectively. Comparison of sequences showed that the overall amino acid sequence and 3' UTR of YL were similar to those of the virulent strain JaGAr0l. However, some significant amino acid differences of viral envelope (E) protein were observed between YL and JaGAr01; the amino acid sequence of E protein in YL strain possessed RGG(387-389) tripeptide instead of RGD(387-389) in JaGAr01 and in other strains; and another amino acid is K(138) in YL, not E(138) found in others. These differences suggested that the YL strain impairs in viral attachment to the cell surface and loses neuroinvasiveness, and therefore this strain was used as a live attenuated vaccine.