Saccharomyces cerevisiae (YT001) supplementation for the control of Haemonchus contortus and modulation of the immune response of sheep.

Studies aiming at the development and evaluation of alternative methods to minimise losses caused by the gastrointestinal nematode Haemonchus contortus are extremely important. Such research is essential, given the high morbidity rates among sheep and the significant mortality rates of lambs, allied to the low efficacy of commercial products for the control of this parasite. The purpose of this study was to evaluate the effect of the Saccharomyces cerevisiae (YT001 - YEASTECH) on the control of H. contortus and its modulation of the immune response in experimentally infected sheep. Eighteen sheep were divided into two groups. Group 1, the control group, comprised animals infected with H. contortus and supplemented with distilled water, while Group 2, the treated group, consisted of animals infected and supplemented with S. cerevisiae (400 million cfu/day of suspension for 49 days). The following parasitological parameters were evaluated: number of eggs per gram of faeces, number of infective larvae (L3) recovered per faecal culture, and parasitic load of the abomasum. The following immunological parameters were quantified: immunoglobulin (Ig)A in the mucous secretions and serum IgG; cytokines interleukin (IL)-4, IL-5 and IL-10; number of eosinophils in the abomasal mucosa and groups of cells positive for the markers: MHCII, CD4+CD25+, CD5+CD8+, WC4, CD5+CD4+, CD8+CD11b+ and CD5+WC1 by whole blood flow cytometry. The results revealed a significant decrease (P<0.05) in the number of larvae and significantly higher serum IgG levels (P<0.05) in the group supplemented with S. cerevisiae. The supplemented animals showed significantly larger numbers of eosinophils (P<0.05), as well as more cells positive for MHCII, CD4+CD25+, CD5+CD8+ than the control animals. This study confirmed the beneficial action of S. cerevisiae on the host immune response to H. contortus, as evidenced mainly by the smaller number of L3 recovered from the faeces of sheep supplemented with S. cerevisiae.

Experimental Leishmania (L.) amazonensis leishmaniasis: characterization and immunogenicity of subcellular fractions.

A technique developed in Trypanosoma cruzi biochemical studies was successfully used to fractionate Leishmania (Leishmania) amazonensis promastigotes. Ultrastructural analyses revealed a membrane fraction (MF) associated to subpellicular microtubules, a ribosomal-rich microsomal fraction (MicF), and a flagellar fraction (FF) free of associated membrane. All fractions proved to be immunogenic through delayed type hypersensitivity reaction assays. Therefore, a protocol was designed to test whether these fractions could elicit a protective response in mice infected by L. (L), amazonensis. The protocol consisted of a BCG injection (as cellular immunity inducer), followed by cyclophosphamide (once its cytotoxic effect is over, this immunosuppressor can increase the number of circulating leukocytes), then an injection with one of the fractions followed by a challenge. When compared to infected control animals, mice injected with any of the fractions presented a smaller footpad swelling, especially those injected with MicF or FF. Macroscopically, immunized mice under modulation by BCG presented no swelling. Histopathological studies performed on day 120 revealed fewer amastigotes and more intense inflammation in lesions of MicF and FF injected mice. Animals injected with MF presented an intermediate pattern. Parasite quantification corroborated these results. The results show that all fractions are potent immunostimulators, but MicF and FF have the strongest protective ability.