Characterization of a serine-to-asparagine substitution at position 123 in the Japanese encephalitis virus E protein
Amino acid position 123 in the E protein of Japanese encephalitis virus (JEV) determines viral growth properties and pathogenicity. The majority of JEV strains have a serine residue at this position (E123S); however, JEV with an asparagine residue (E123N) has also been isolated. To compare the growth properties and pathogenicity of E123S and E123N JEV, we produced recombinant JEV with a serine-to-asparagine substitution at position 123 (rJEV-Mie41-ES123N) in the E123S-type strain Mie/41/2002 background. The growth rate of rJEV-Mie41-ES123N was similar to that of Mie/41/2002 in mammalian and mosquito cell lines. Mouse challenge experiments showed that there was only a slight difference in neuroinvasiveness between the parent strain (Mie/41/2002) and rJEV-Mie41-ES123N. Thus, our results indicate that the Ser-to-Asn substitution in the JEV E protein has weak impact on viral growth properties in vitro or on pathogenicity in vivo.