Induction of systemic and mucosal immune response in mice immunised with porins of Salmonella typhi

Porins, purified from Salmonella typhi strain 0901 provided 90% protection to BALB/c mice against a lethal dose (300 x LD50) of S. typhi Ty2 when given intraperitoneally. To measure the porin-induced cellular immune responses, macrophages and lymphocytes were isolated from spleen and lamina propria (LP) of porin immunised-challenge mice and of infected and control mice; T-cell phenotypes, lymphocyte proliferation and cytokine production were studied. The secretory IgA (sIgA) antibody level in the intestinal fluid was also measured to study mucosal immune response. After immunisation, the splenic lymphocytes exhibited a significant increase in total T-cell count and CD4+/CD8+ ratio, while the LP lymphocytes (LPL) exhibited an increase in CD4+/CD8+ ratio only. They also exhibited a significant increase in porin-specific proliferative response and cytokine levels (IL-1, IL-2, IFN-gamma and IL-4). After immunisation, sIgA antibody was also found to be increased. These results suggest that porins given intraperitoneally induce cellular and humoral immune responses both at systemic and mucosal levels.