engleski

Levamisole synergizes experimental F4ac+ Escherichia coli oral vaccine in stimulating ileal Peyer's patch T cells in weaned pigs

Abstract We have recently found that priming by levamisole of weaned pigs experimentally vaccinated against post-weaning colibacillosis (PWC) contributes to immune protection from challenge-induced clinical disease through stimulation of the mesenteric lymph node cells that participate in the cell-mediated immunity. With the objective to better understand the mechanisms by which levamisole induces protective mucosal cell-mediated immune response to vaccination against PWC, we tested by both flow cytometry and immunohistochemical in situ staining whether the drug synergizes experimental F4ac+ Escherichia coli oral vaccine in stimulating T-cells also in the jejunal lamina propria (JLP) and ileal Peyer’ s patch (IPP) upon virulent challenge. Commercial crossbred pigs weaned at four weeks were used and allocated into two equal groups. The experimental group was intramuscularly primed with the drug at an immunostimulatory dose of 2.5 mg/kg given daily, in three consecutive days, and controls received saline according to the same schedule. Both groups were orally vaccinated with the vaccinal E. coli strain on day zero and challenged with the virulent E. coli strain 7 days later. All pigs were killed on post challenge day 6. The results obtained by immunophenotyping of isolated cells show that priming by levamisole of the vaccinated weaned pigs selectively recruits and activate T-cells in the IPP, a primary lymphoid organ generating B-lymphocytes. Since the pig IPP is normally populated with up to 5% of CD3+ T-cells and as the CD6 is an activation antigen expressed exclusively by T-cells in swine, significantly higher number of CD3+ (P  0.01) and CD6+ (P  0.001) cells observed within the IPP follicles of the primed vaccinated versus un-primed vaccinated challenge-infected pigs suggest enhanced T-cell-mediated immunity in this B-cell compartment induced by the potentiating action of the drug and vaccine. The results of the quantitative phenotypic analysis of isolated cells were confirmed by immunohistochemical in situ staining. The ability of levamisole to influence interaction between activated CD6+ T-cells and B-cells in the IPP of the primed vaccinated weaned pigs, and the possibility that this interaction play a role in regulating B-cell maturation within the IPP follicles are discussed.

levamisole; weaned pigs; colibacillosis; mucosal immunity

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