TABLE 1.

Detection of CfaB-specific ASC by ELISPOT assays with mice subjected to different immunization regimens

Vaccination regimena	No. of CfaB-specific ASC/106 splenocytesb
	Spleen	PP	MLN
Nonimmunized	0	0	0
pRECFA	10 ± 0.4	0	0
HG3	0	0	0
pRE4 + HG3	0	0	0
pRECFA + HG3	130 ± 4*	7 ± 0*	20 ± 0.8*

^aVaccination regimens: non-immunized mice; pRECFA, mice immunized with two i.m. doses of pRECFA (100 μg/dose); HG3, mice immunized with two p.o. doses (10¹⁰ CFU/dose) of the HG3 strain; pRE4 + HG3, mice immunized with two doses of pRE4 followed 2 weeks later by two booster doses with the HG3 strain; pRECFA + HG3, mice subjected to the standard primer-booster immunization regimen, with a 2-week interval between the priming and boosting immunizations.

^bCfaB-specific ASC were detected after incubation of the cells with alkaline phosphatase-conjugated goat anti-mouse IgG (spleen) or goat anti-mouse IgA (Peyer's patches and mesenteric lymph nodes). All cells were harvested 2 weeks after the last immunization dose either from groups that were vaccinated with a single vaccine type or from groups that were subjected to primer-booster regimens. The results are based on one determination and are expressed as means ± SE. *, statistically significant (P < 0.05) differences compared with corresponding results for mouse groups immunized with pRECFA.