NEOSPORA CANINUM ANTIGENS DEFINED BY ANTIGEN-DEPENDENT BOVINE CD4⁺ T CELLS Available to Purchase

Neosporosis is an important cause of pregnancy loss in cattle worldwide. The objective of the present study was to identify Neospora caninum antigens as vaccine candidates using antigen-specific, short-term CD4⁺ T cells established from N. caninum–immunized and –challenged cows. Whole N. caninum tachyzoite lysate was separated into 6 fractions by DEAE anion-exchange chromatography using high-pressure liquid chromatography (HPLC). The CD4⁺ T-cell proliferation assay results indicated that antigenic activity was associated with proteins from HPLC fractions 4–6, with fraction 5 exhibiting the highest antigenic activity. Also, SDS-PAGE analysis revealed a 16-kDa protein in fractions 4–6 that was recognized by anti–N. caninum antibodies. This 16-kDa protein was absent in other fractions, and it may be a target of a T-cell response in cattle. Further identification of immunogenic proteins of N. caninum may facilitate development of subunit vaccines against neosporosis.