Table 2.

Prior Immunity to LCMV or PV Can Lower VV Titer Independently of the Challenge Dose

Virus infections* Immune		VV Titer (mean log10 PFU/ml ± SEM)‡
		Acute VV infection virus dose		Spleen		Fat pads		Liver
		PFU
NAIVE		2 × 104		<1.4 ± 0.2		3.4 ± 0.7		2.9 ± 0.2
LCMV		2 × 104		<1.1 ± 0.05		<2.1 ± 0.1§		<2.3 ± 0.2§
PV		2 × 104		<1.0 ± 0		<2.6 ± 0.4§		<2.2 ± 0.1§
NAIVE		4 × 105		4.0 ± 0.3		4.8 ± 0.3		4.9 ± 0.3
PV		4 × 105		1.7 ± 0.3§		2.5 ± 0.5§		2.1 ± 0.2§
NAIVE		1 × 106		3.5 ± 0.2		5.8 ± 0.3		3.6 ± 0.3
LCMV		1 × 106		<1.0 ± 0§		<2.9 ± 0.05§		<2.0 ± 0.4§
PV		1 × 106		<1.4 ± 0.3§		<2.4 ± 0.5§		<2.0 ± 0§

^* The infection of mice was done as described in Materials and Methods.  

^‡ VV was titrated on ATCC vero cell monolayers using a 3-d plaque assay.  

^§ Statistically significant difference between naive and immunized mice (Student's t test, P < 0.05).