CHARACTERIZATION OF A HIGHLY ATTENUATED JAPANESE ENCEPHALITIS-VIRUS GENERATED FROM MOLECULARLY CLONED CDNA

Six recombinant Japanese encephalitis virus (JEV) isolates were recove red from infectious RNAs transcribed by T7 RNA polymerase from molecul arly cloned cDNA templates. Three of the recombinant viruses had chara cteristics similar to the wild-type parent virus, JaOArS982. The other 3 recombinant viruses exhibited an attenuated phenotype in mice. An a virulent recombinant virus, IC47, was characterized and compared with the wild-type parent virus and a virulent recombinant virus, IC37. IC4 7 produced smaller plaques than parent or IC37 viruses and exhibited n o viremia or neuroinvasion in young adult mice inoculated subcutaneous ly and no mortality when inoculated intracerebrally. IC47 was also imm unogenic and protective in the murine model. The probable basis for at tenuation, revealed by nucleotide sequence analysis, was a single amin o acid substitution at position 138 (Glu to Lys) in the E protein.