Other studies have previously shown pigs with a primary virulent infection are protected against challenge with L. intracellularis without bacterial shedding after challenge [9] and [10] and reduced or no L. intracellularis in tissue samples from the pigs re-inoculated at 12 weeks of age [10]. Serum IgG did not appear to correlate with protection while re-inoculated pigs responded to L. intracellularis challenge with a significantly increased IFN-γ response, which indicated induction of a cell-mediated immunity (CMI) memory recall response, with CD8+ and CD4+CD8+ double positive lymphocytes as main IFN-γ producers [11].
Here we present the outcome of L. intracellularis challenge infection in pigs vaccinated with Enterisol®ileitis (VAC) and compare acute phase protein responses, and humoral and CMI responses with non-vaccinated challenge control pigs (CC) and pigs protected against L. intracellularis re-infection (RE).