Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 27, 1994
Publication Date: N/A
Interpretive Summary: Avian coccidiosis is one of the major poultry diseases that cost the poultry industry major economic losses. Vaccines for coccidiosis are not available and prophylatic medication is costly due to development of drug resistance. Therefore, development of new control measures are necessary. In order to develop immunological control strategy, ARS scientists are investigating how the host immune system interacts with parasites. This study shows that parasites invade lymphocytes and recruit various kinds of host lymphocytes into the intestine following infection. Understanding these host- parasite interactions will enhance our ability to develop a better vaccine.
To better understand host cell-parasite interactions during coccidial infection, duodenal tissues were removed from: 1) SC chickens 24 h post primary infection (ppi) with 2x107 oocysts, 2) TK chickens 24,48, and 72 h ppi with 2.5x107 normal or irradiated oocysts, and 3) SC and TK chickens at 24,48 and 72 h post secondary infection with 2.5x107 oocysts. Tissues were imbedded in freezing compound, frozen, sectioned, and stained with monoclonal antibodies to identify CD4+,CD8+,lg+,Bu1a+ lymphocytes, macrophages, and parasites. At 24 h after all infections, sporozoites were seen primarily in CD8+ cells, and macrophages. Large numbers of CD8+ cells were seen in the sections at all times after the infections and were frequently in contact with infected epithelial cells. Meront development at 48 h ppi was extensive with normal oocysts and sparse with irradiated oocysts, but moderate during a secondary infection. These results suggest that sporozoites are transported primarily by CD8+ cells and/or macrophages and that CD8+ cells may mediate host immunity to coccidian parasites.