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Title: NEOSPORA CANINUM ANTIGEN DEFINED BY ANTIGEN-DEPENDENT BOVINE CD4+ T CELLS

Author
item Tuo, Wenbin
item Fetterer, Raymond
item Jenkins, Mark
item Dubey, Jitender

Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/2004
Publication Date: 3/20/2005
Citation: Tuo, W., Fetterer, R.H., Jenkins, M.C., Dubey, J.P. 2005. Neospora caninum antigen defined by antigen-dependent bovine cd4+ t cells. Journal of Parasitology 91(3):564-568.

Interpretive Summary: Neospora caninum is an apicomplexan parasite that infects a wide range of animal species. Due to its high prevalence, neosporosis has been considered an important cause of pregnancy loss in cattle worldwide. The objective of this study was to identify N. caninum antigens as vaccine candidates using CD4+ T cells established from N. caninum immunized and challenged cows. N. caninum tachyzoite lysate was prepared from cultured N. caninum tachyzoites and separated into 6 fractions by DEAE anion exchange chromatography using High Pressure Liquid Chromatography (HPLC). T cell proliferation assay results showed that antigenic activity was associated with proteins from HPLC fractions 4 through 6. Fraction 5 exhibited the highest antigenic activity. Fractions 4 - 6 contained proteins that were recognized by a rabbit antiserum against N. caninum tachyzoites. Two proteins with molecular weights of ~16 and ~79 kDa were present only in fractions 4 - 6, which may be recognized by both CD4+ T cells and the rabbit antiserum. These studies indicate that antigen-specific T cells may be used to identify N. caninum antigens that may stimulate a protective immunity.

Technical Abstract: Neospora caninum is an apicomplexan parasite that infects a wide range of animal species. Due to its high prevalence, neosporosis has been considered an important cause of pregnancy loss in cattle worldwide. The objective of this study was to identify immunodominant N. caninum antigens as vaccine candidates using antigen-specific short-term CD4+ T cells established from N. caninum immunized and challenged cows. Whole soluble N. caninum tachyzoite lysate was prepared by sonication of in vitro cultured N. caninum tachyzoites. N. caninum tachyzoite lysate was separated into 6 fractions by DEAE anion exchange chromatography using High Pressure Liquid Chromatography (HPLC). CD4+ T cell proliferation assay results indicated that antigenic activity was associated with proteins from HPLC fractions 4 through 6 with fraction 5 exhibiting the highest antigenic activity. Fractions 4 - 6 contained distinctive protein bands that were recognized by a rabbit antiserum against live N. caninum tachyzoites. Clearly, two proteins with apparent molecular weights of ~16 and ~79 kDa were unique to fractions 4 - 6, which may be recognized by both CD4+ T cells and the rabbit antiserum. These studies indicate that antigen-specific T cells may be used to identify immunodominant N. caninum antigens that may elicit a protective T cells response. This research will enhance our understanding of bovine host cell-mediated immune defense mechanisms and may facilitate development of subunit vaccines against neosporosis.