Systemic and mucosal immune responses of pigs to parenteral immunization with a pepsin-digested Serpulina hyodysenteriae bacterin

Serpulina hyodysenteriae infection of pigs, swine dysentery, causes a mucohemorrhagic diarrhoea resulting in significant economic losses to swine producers. The pathogenesis of this disease is poorly understood. Regardless, commercial vaccines have been developed and are in use. Thus, the present study was designed to examine cellular immune responses induced by parenteral S. hyodysenteriae vaccination. Significant antigen-specific interferon-γ (IFN-γ) and blastogenic responses were detected from peripheral blood lymphocytes isolated from vaccinated pigs. However, poor IFN-γ responses were detected from colonic lymph node lymphocytes from these same pigs despite significant antigen-specific blastogenic responses. In addition, peripheral blood IFN-γ responses were diminished by either in vitro depletion of CD4 expressing cells or by in vitro treatment with porcine IL-10. Colonic lymph node IFN-γ responses were not inhibited by treatment with porcine IL-10. Vaccination also resulted in increased percentages of both mucosal and peripheral blood CD8 single positive cells with concurrent decreases in percentages of CD4 single positive cells as compared to percentages of these same populations from non-vaccinated pigs. In conclusion, these studies show that parenteral S. hyodysenteriae vaccination results in cellular immune responses detectable both peripherally (systemic immunity) as well as at the site of infection (mucosal immunity). However, it appears that regulatory mechanisms affecting IFN-γ production in response to S. hyodysenteriae antigen differ between peripheral and colonic compartments.