Desenvolvimento de insumos imunobiológicos para o controle de Haemonchus contortus em ovinos

Abstract

Developing alternatives for the control of the gastrointestinal nematode of ruminants, Haemonchus contortus, is a necessary challenge for the continuity of sheep flocks around the world. The aim of this study was to evaluate the immunological and nematicide effects of the probiotics Saccharomyces cerevisiae and Saccharomyces boulardii in sheep experimentally infected with de Haemonchus contortus, and to verify the immunogenicity of synthetic peptides selected by analyzing the genome of H. contortus in mice. In the first study, 18 sheep divided into a treatment group were used: animals supplemented with S. cerevisiae and infected with H. contortus, and a control group: animals infected without supplementation. In the second study, 24 sheep divided into a group supplemented with S. boulardii, a control group, and a Naive group (not infected and not supplemented). For the treatments, 40 mL of yeast suspension was used at a concentration of 1x10 7 CFU / mL, daily for 49 days. Parasitological parameters were evaluated: number of H. contortus eggs in the feces (OPG), number of infective larvae (L3) recovered by fecal cultures and the parasitic load of the abomasum. For immunological parameters, the following were quantified: immunoglobulins IgA in mucus and serum IgG; cytokines IL-4, IL-5 and IL-10; number of eosinophils in the abomasum mucosa and groups of cells positive for the markers: MHCII, CD4 + CD25 +, CD5 + CD8 +, WC4, CD5 + CD4 + and CD5 + WC1 by total peripheral blood flow cytometry. For the evaluation of the immunogenicity of the peptides, 40 mice were used, divided into four groups, of which one group remained as a control, and the other three were vaccinated with two doses, with an interval of 21 days, of their respective vaccine containing 20 µg of the peptide in 100µl of PBS and adsorbed on 10% Al(OH)3, subcutaneously. Individual blood samples were taken weekly to evaluate, by indirect ELISA, the immunogenicity of the peptides. The results of the experiments with Saccharomyces demonstrated a significant decrease (p <0.05) in the number of larvae in the S. cerevisiae group and a 48% reduction in the OPG of the group treated with S. boulardii. In both treatments, significantly higher levels of serum IgG (p <0.05) and positive cells for MHCII were observed. In the S. cerevisiae group, there was also a significantly higher number of eosinophils (p <0.05) in the mucosa, as well as in the number of CD4 + CD25 +, CD5 + CD8 + cells. The three peptides tested were shown to be immunogenic from the second dose. Thus, this study showed the beneficial local and systemic probiotic action of Saccharomyces cerevisiae and Saccharomyces boulardii in the immune response of sheep infected with H. contortus, and nematicide action demonstrated mainly by the reduction in the number of L3 and eggs recovered from the feces of supplemented sheep. In addition, the peptides tested are promising for the development of a new vaccine for the control of haemoncose.