Table 1. Effects of specific E protein domain III BC loop amino acid substitutions on the recovery, antigenicity and/or mouse virulence phenotypes of a West Nile virus infectious clone based on the NY99 North American prototype strain.
| Neutralization Indexa and (Western blot reactivityb) with MAb: | Mouse neuroinvasiveness | |||||
|---|---|---|---|---|---|---|
| Residue | Substitution | Viability | 7H2 | 5H10 | 5C5 | LD50 (AST±sd)c |
| Wild type | -- | + | 3.0 (++) | 2.7 (++) | 2.4 (++) | 1.3 (9.8±1.7) |
| Y329 | F | - | nd (-) | nd (-) | nd (-) | nd |
| K | - | nd (-) | nd (-) | nd (-) | nd | |
| S | - | nd | nd | nd | nd | |
| T | - | nd | nd | nd | nd | |
| T330 | A | + | 3.1 (++) | 2.0 (++) | 2.1 (++) | 1.3 (8.4±0.7d) |
| I | + | 1.8 (-) | 1.2 (-) | 1.7 (+/-) | 1.3 (8.9±1.9) | |
| G331 | A | + | 2.1 (-) | 1.9 (-) | 1.8 (-) | >1000 (n/a) |
| T332 | A | + | 1.4 (+/-) | 1.3 (-) | 1.6 (+/-) | 0.3 (8.7±1.4) |
| K | + | 0.2 (-) | 0.4 (-) | 0.0 (-) | 12.6 (8.9±2.1) | |
| M | + | 1.0 (-) | 0.6 (+/-) | 1.0 (+) | 1.3 (8.5±1.1d) | |
| D333 | A | - | nd | nd | nd | nd |
| E | + | 1.5 (+/-) | 2.4 (+/-) | 1.7 (-) | 80 (10.1±2.2) | |
| N | + | 3.1 (+) | 1.6 (-) | 1.0 (-) | >1000 (10.0±2.8) | |
a
neutralization index is the log10 reduction in virus titer in the presence of MAb (100 ng per reaction) compared to a “virus only” control
b
see also Figure 3 for representative results
c
LD50 - 50% lethal dose following intraperitoneal inoculation, in pfu; AST±sd - average survival time ± standard deviation for all animals that died, in days; n/a - not applicable (no mice died in these groups)
d
AST significantly different to wild-type (Student t-test p < 0.05) nd - not determined