CD4 and infection: To evaluate a potential protective role of vaccine elicited CD4 T cells, mice were immunized with either IBT-V02 or BSA, and CD4 T cells were depleted 72 h prior to and 48 h post-infection with 1 × 107 CFU of USA300 (NRS384) using an anti-CD4 monoclonal antibody (mAb clone GK1.5).