Induction of memory responses following transcutaneous immunization requires presence of immunoadjuvantative cholera holotoxin

Abstract Vaccination induces both mucosal & systemic immune response. Polysaccharide antigen (PAg) which is T cell independent antigen does not stimulate production of memory responses. Cholera holotoxin (CT) is shown to be a potent immunoadjuvant. Transcutaneous immunization (TCI) is recently shown as an important alternative route of immunization to induce both systemic & mucosal immune responses. Induction of memory responses upon TCI with PAg is unkown. We evaluated if TCI with Vi & Vi-conjugate vaccine (Vi-DT)could induce anti-Vi specific memory responses in mice. Parenteral & TCI of Vi can not produce memory response. Splenic memory B cell IgG responses were induced by parenteral immunization with Vi-DT but not Vi, but were induced following TCI with Vi-DT/CT and Vi/CT. TC & parenteral immunization with Vi & Vi-DT induced serum anti-Vi IgG & IgA responses but more prominently along with CT & induced T cell independent PAg specific memory response in mice. Stool & lamina proprial lymphocyte (LPL) anti-Vi IgA responses were highest following TCI. Splenic antibody-secreting-cell (ASC) anti-Vi IgG responses were induced by parenteral immunization with Vi or Vi-DT, and by TCI with Vi/CT or Vi-DT/CT. Our results show that TCI induces both systemic & mucosal immune responses with PAg & use of CT as adjuvant induces this response more prominently. Memory responses only found when CT was used TC. This observation could assist in developing of vaccines providing long-term protection.