Identification of T-cell epitopes of the intracellular parasite Babesia bovis by immunopeptidomic analysis of BoLA-II presented peptides.

Immunity to the bovine parasite Babesia bovis requires both innate and adaptive mechanisms that include macrophages, CD4+ T cells and neutralizing antibodies. Therefore, the development of new vaccines that replace the use of attenuated strains should include antigens and delivery systems targeting both arms of the immune response. Bioinformatic pipelines for the prediction of B-cell epitopes have been widely used by many research groups. However, despite intensive efforts, only a limited number of T-cell epitopes have been identified so far for B. bovis. Here, we report for the first time the characterization of the B. bovis BoLA II immunopeptidome derived from bovine macrophages pulsed with infected erythrocytes. This parasite-bovine host cell interaction model allowed the identification of 28 previously uncharacterized naturally presented BoLA II peptides of the parasite. In vitro validation of a subset of peptides resulted in the identification of a glyceraldehyde-3-phosphate dehydrogenase derived T-cell epitope that induced the release of IFN-γ from CD4+ lymphocytes from B. bovis infected animals. Altogether these results demonstrate the discovery of new potential candidate antigens for a B. bovis recombinant vaccine. This peptide dataset could also be used to enrich bioinformatic algorithms for future predictions involving other infectious diseases of cattle.