Adjuvanticidade de Bacillus toyonensis e Saccharomyces boulardii em vacinas avaliadas em murinos e ovinos

Abstract

Probiotics modulate the immune response and can increase the effectiveness of vaccines The aim of this study was to assess the effects of Bacillus toyonensis and Saccharomyces boulardii on the immune response of mice and sheep vaccinated with recombinant and conventional vaccines. Three experiments were performed in mice and two experiments in sheep. In the first experiment with mice, one group of animals was supplemented orally with 1 × 106 viable spores of B. toyonensis per gram of food throughout the experimental period while other group was submitted to probiotic treatment only 7 days prior to the initial vaccination. In the second experiment, whilst one group followed the same regimen as in the first experiment (every day during the experiment), another group received the inoculation with 1 × 106 viable spores of B. toyonensis by subcutaneously on day 0 and day 21. In both experiments, mice were vaccinated Bovine herpesvirus type 5 (BoHV-5) recombinant glycoprotein D. In the third experiment with mice, one group was submitted to oral administration of B. toyonensis, as described for the other experiments, however, the animals were vaccinated with the C fragment of the tetanus toxin (TTFC) adsorbed on B. subtilis spores by the mucosal (nasal) route. Regarding the experiments with sheep, on the first experimental test, sheep were supplemented by oral route with 3 × 108 viable spores of B. toyonensis for 5 days prior to the vaccinations with Clostridium perfringens recombinant epsilon toxin (rETX). In the second experiment, one group received the same dose as in the first experiment, but another group was exposed to the same dosage of S. boulardii. A third group received a combination of these microorganisms. In all the groups the administration of probiotics was made orally 5 days prior to the vaccinations against Clostridium chauvoei. The humoral and cellular immune response was evaluated by indirect ELISA, serum neutralization and by detection of cytokines in splenocytes and peripheral blood mononuclear cells (PBMCs). The groups of mice supplemented with spores of B. toyonensis (regardless of the regimen experiment) have presented high serum antibody levels (total IgG, IgG1, and IgG2a) with neutralizing capacity and higher mRNA transcript levels of IL-4, IL-12, and IFN-γ in splenocytes when compared to the controls. The supplementation of B. toyonensis in mice vaccinated with TTFC-adsorbed B. subtilis spores modulated the humoral immune response of mice, increased fecal IgA, total IgG and IgG2c serum levels and cellular immune response by stimulating the production of high levels of IL-6, IL-10, and IFN-γ in splenocytes. In the experiments with sheep it was observed that groups exposed to B. toyonensis and vaccinated with rETX presented higher total IgG, IgG1, and IgG2 levels as well as sheep supplemented either with B. toyonensis or S. boulardii, in comparison with controls. The PBMCs from supplemented sheep of both experiments presented higher mRNA transcript levels of IL-2, IFN-γ and Bcl6. In conclusion, the short-term probiotic supplementation was sufficient to modulate the immune response. The results indicate these probiotics were able to stimulate immunity and improve the response to vaccines in murine and sheep.