Submitted to: Coccidiosis International Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: September 30, 1998
Publication Date: N/A
Technical Abstract: Previous studies from our laboratory showed that T lymphocytes play a critical role in protection against coccidiosis. Depletion of lymphocytes expressing the CD8 or TCR2, but not CD4, antigens abrogated development of resistance to E. acervulina. Since cell-mediated immunity is regulated by various cytokines, parasite-induced cytokine production was also assessed. Sporozoites and merozoites elicited high levels of IFN-gamma and TNF in vitro and E. acervulina-infected chickens showed IFN-gamma and TGF-beta 4 mRNA in the duodenum. When the production of these cytokines in two genetically disparate chicken strains differing in disease susceptibility to E. acervulina was compared, different kinetics were observed. Since IFN-gamma plays a critical role in many intracellular parasitic infections, the role of IFN-gamma in avian coccidiosis was next investigated. A chicken cDNA encoding IFN-gamma was expressed in CHCC-OU2 chicken cells and recombinant chicken IFN-gamma(rchIFN-gamma) produced. Recombinant IFN- gamma showed potent macrophage activating activity and and inhibited intracellular development of E. tenella in CHCC-OU2 cells. However, IFN-gamma-mediated protective immunity in vivo was independent of NO production since pretreatment of chickens with an inhibitor of inducible NO synthase did not alter oocyst production, weight loss or intestinal lesions compared to untreated controls. These results indicate that various cytokines are involved in the immunoregulation of host response to Eimeria.