Table 2.

Serologic responses among immune and non-immune house sparrows after experimental inoculation with West Nile virus

		Pre-inoculation	Viremia profiles		14 days post-inoculation
Experimental group, time PI*	N	PRNT90† range	% viremic	Peak range (PFU‡/mL serum)	PRNT90 titer range	% ≥ 4-fold increase
Non-immune controls	18	< 10	100	104.5–10.2	40–2,560	–
Naturally- immune	7	10–320	0	< 101.7	80–2,560§	38
Experimentally immune, 6 mo PI	10	10–80	10	101.7–2.4	80–2,560	80
Experimentally immune, 12 mo PI	10	< 10–80	0	< 101.7	20–2,560	80
Experimentally immune, 24 mo PI	10	10–320	0	< 101.7	40–2,560	60
Experimentally immune, 36 mo PI	41	10–640	0	< 101.7	80–20,480	73

^*PI = post-inoculation.

^†PRNT₉₀ = endpoint 90% neutralization titer (PRNT₉₀ < 10 is considered seronegative).

^‡PFU = plaque forming units.

^§Post-inoculation PRNT₉₀ titers for the naturally immune group were determined at one month PI, and 21 birds were included in this analysis.