Nucleotide sequence of the envelope glycoprotein of Negishi virus shows very close homology to louping ill virus.

Negishi virus, a member of the family Flaviviridae, was originally isolated in Japan, during an outbreak of Japanese encephalitis. Antigenically, however, Negishi virus resembles the tick-borne rather than the mosquito-borne flaviviruses. Monoclonal antibodies that bind louping ill virus showed a close antigenic relationship between louping ill and Negishi virus. The genes encoding the envelope glycoprotein of Negishi virus (strain 3248/49/P10) and louping ill virus (strain SB526) were cloned and sequenced. They showed a very close homology at both the nucleotide and deduced amino acid levels. Comparison with the known sequence of another strain of louping ill virus (strain 369/T2) and with other tick-borne flaviviruses showed that Negishi virus was more closely related to louping ill virus than to the other tick-borne viruses. The significance of this observation for virus evolution, virus distribution in the environment, and the potential use of nucleotide sequencing for rapid and precise identification of flaviviruses are discussed.