Abstract
The complete genomic sequence of one human isolate of West Nile virus (WNV) and the partial genomic sequences of 14 other strains from India isolated in the period 1955-1982 from different hosts and geographical areas were determined. Phylogenetic analyses based on complete and partial genomic sequences (921 nt of the C-prM-E region) revealed that WNV could be classified into five distinct groups that differed from each other by 20-25% at the complete genome level and by 20-26% using partial sequences. Of the Indian isolates, 13 formed a distinct genetic lineage, lineage 5, whereas two isolates, one from a human patient (1967) and another from a bat (1968), were related closely to lineage 1 strains. The complete genomic sequence of the Indian isolate, 804994, showed 20-22% genetic divergence from the previously proposed lineage 1 and 2 strains and 24-25% divergence from isolates of the newly proposed lineages 3 (Rabensburg isolate 97-103 of 1997) and 4 (Russian isolate LEIV-Krnd88-190 of 1998). Similarly, the partial genomic sequences of the Indian isolates showed 21-26% divergence from lineage 1 and 2 strains and from the Rabensburg (97-103) and Russian (LEIV-Krnd88-190) isolates. Cross-neutralization using strain-specific polyclonal antibodies against lineage 1 strain Eg-101 and representative Indian strains suggests substantial antigenic variation. This study documents circulation of WNV strains typical to India for 27 years and the introduction of lineage 1 strains during 1967-1968. These results indicate strongly that WNV should be classified into five genetic lineages, with Indian viruses constituting the distinct genetic lineage 5.
Published Version
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