Genome sequence and attenuating mutations in West Nile virus isolate from Mexico

Abstract

The complete genome sequence of a Mexican West Nile virus isolate, TM171-03, included 46 nucleotide (0.42%) and 4 amino acid (0.11%) differences from the NY99 prototype. Mouse virulence differences between plaque-purified variants of TM171-03 with mutations at the E protein glycosylation motif suggest the emergence of an attenuating mutation.

Figure 1

Western blot showing differing mobility of E proteins from nine plaque-purified variants of West Nile virus (WNV) strain TM-171 Mex03. Nucleotide sequencing of strains in lanes 5 to 9 indicated the presence of an "NYS" glycosylation motif at residues 154 to 156 of E, while strains in lanes 1 to 4 encoded "NYP." Antigens were separated in a nonreducing 5%/10% discontinuous sodium dodecyl sulfate–polyacrylamide gel, transferred to 0.2 μm nitrocellulose and detected with WNV-specific monoclonal antibody 7H2 (6).

Figure 2

Neighbor-joining phylogenetic tree based on complete genome sequences of West Nile virus strains. Strain TM171-03 is indicated in bold text. The topology of maximum parsimony and maximum likelihood trees was essentially identical. Bayesian analysis also confirmed the close relationship between TM171-03 and NY00-grouse3282 sequences (data not shown). Bootstrap values are shown for major branches (500 replicates). GenBank accession numbers for sequences used to construct the tree are indicated on the branches.