Ad5-Clostridium difficile-TA vaccine induces robust TA-specific CD8 T cell specific responses in contrast to Ad5-Null. WT BALB/c mice were IM injected (1010 vp/mouse) with Ad5-C. difficile-TA (n = 3) or Ad5-Null (n = 3). Mice were sacrificed at 14 dpi splenocytes prepared, and individually stimulated with 2 μg/well of peptide #63 or with mixture of peptides (#9, #13, #51, #55, #63, all 0.4 μg/well), stained and FACS sorted as described in Section 2. The bars represent mean ± SEM. Statistical analysis was completed using a two tailed homoscedatic Student’s t-test.