CD4 and infection: Recent studies show that experimental subunit and whole-cell vaccines delivered intranasally (i.n.)elicit IL-17-producing CD4+ resident memory T cells (TRM) and mucosal antibodies that clear the infection from the entire murine respiratory tract (25–27), suggesting that inclusion of a Th1/17 polarizing adjuvant and mucosal vaccine delivery will improve aPV-mediated protection.