WEST NILE VIRUS ENVELOPE PROTEINS - NUCLEOTIDE-SEQUENCE ANALYSIS OF STRAINS DIFFERING IN MOUSE NEUROINVASIVENESS

Several neuroinvasive and non-neuroinvasive West Nile (WN) viruses wer e characterized by nucleotide sequencing of their envelope (E) protein regions. Prolonged passage in mosquito cells caused loss of neuroinva siveness and acquisition of an N-linked glycosylation site, which is u tilized. Limited passage in cell culture also caused glycosylation but not attenuation, suggesting that glycosylation may not be directly re sponsible for attenuation and that a second mutation (L-68 --> P) may also be involved. A monoclonal anti body-neutralization escape mutant with a substitution at residue 307, a site common to other flavivirus escape mutants, was also attenuated. A partially neuroinvasive reverta nt regained the parental E sequence, implying that determinants outsid e of the E region may also influence attenuation. Data suggest that th e neuroinvasive determinants may be similar to those for other flavivi ruses. Also, sequence comparison with the WN virus (Nigeria) strain re vealed considerable divergence of the E protein at the nucleotide and amino acid levels.