Induction of local protective immunity to Eimeria acervulina by a Lactobacillus-based probiotic

Previously we have shown that resistance to Eimeria acervulina (EA) infection in broiler chickens was enhanced by a probiotic treatment. In the present studies, we examined cytokine and oocyst production under similar conditions using a commercial Lactobacillus-based probiotic. Day-old male broiler chicks were fed control or probiotic diets and were orally challenged with either 2x10(4) (Experiment 1) or 1x10(4) (Experiment 2) oocysts of EA at 3 weeks of age. For the first experiment, fecal oocyst shedding and IFN-gamma levels in the culture supernatants of ConA-stimulated spleen lymphocytes were evaluated. Humoral and local cell-mediated immunity in the second experiment were assessed by evaluating antibody and cytokine (IFN-gamma and IL-2) levels in sera and intestinal secretions on a 3-day interval post inoculation. Results showed small but significant (P<0.05) differences in cytokine levels and oocyst production but not antibody levels between the probiotic-treated and control groups. Collectively, these data suggest a positive impact of the probiotic on cellular immune responses of infected broilers as compared to control chickens resulting in enhanced resistance to EA as shown in reduced fecal oocyst shedding. The results showed an immunoregulatory effect of probiotic diets on the local cell-mediated immunity in poultry and provide a rationale for further study to investigate the beneficial effects of Lactobacillus-based probiotics in food animals.