TABLE 5.

Protection of BALB/c mice after passive immunization with immune serum to pneumococcal antigens^a

Serum specificity	Titerc	No. alive/total no.d	% Survival	P (versus MSA-immunized mice)d
Ctrlb	≤100	1/10	10	NA
PsaA	218,700	0/12	0	0.45
PpmA	72,900	0/12	0	0.45
PspA	140,929	9/12	75	0.0034*
T3 PS	8,100	10/12	83	0.0009*

^aNaive BALB/c mice were challenged with 1,000 CFU of live S. pneumoniae strain A66.1 (type 3) i.p. after passive immunization with pooled immune serum specific for the indicated pneumococcal antigens.

^bControl (Ctrl) mice were given S. pneumoniae after passive immunization with pooled serum from mice inoculated with MSA.

^cAntibody titers for each specific antigen in pooled immune sera were measured by ELISA. Absorbance values for MSA-immunized mice were arbitrarily assigned a relative titer for reactivity to each respective antigen of ≤100.

^dSurvival of mice was monitored for 15 days after challenge with S. pneumoniae. *, Statistically significant overall survival (P < 0.05) compared to the overall survival for control mice, as calculated by using the Fisher exact test. NA, not applicable.