Table 2.

The presence of West Nile virus (WNV) -neutralizing antibodies in the sera of immunized mice following challenge with WNV

Vaccination	WNV challenge	Date of sera harvest	Neutralizing antibody titre
No treatment	–		< 1 : 20
p458	–	7 days after third immunization	< 1 : 20
p458-Ep15	–	7 days after third immunization	1 : 80
p458-Ep15	104 PFU	10 days after challenge	1 : 2560
p458	104 PFU	10 days after challenge	1 : 160

Three-week-old mice were immunized as previously described. Seven days after the last immunization, the mice were bled and challenged intraperitoneally with 10⁴ plaque-forming units (PFU) of the WNV-ISR98 strain. Ten days after challenge, the mice were bled, sera from each group were pooled and tested for WNV neutralization capability, as measured by plaque reduction neutralization test 50% as described in the Materials and methods.