Submitted to: Journal of Eukaryotic Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 19, 1996
Publication Date: N/A
Interpretive Summary: Coccidiosis, an economically important disease of chickens, turkeys, and game birds, costs the U.S. poultry approximately $300 million annually. The primary means of control of the disease, anticoccidial drugs, are becoming less effective than before as the parasites show increasing resistance to the drugs. As a result, alternative measures against coccidiosis, including immunological and biological control, are gaining in importance. One strategy for controlling coccidiosis by biological means is to prevent invasion of the host bird by the coccidia. Each species of coccidia invades only a limited, defined area of the intestine, suggesting that specific characteristics of the cells in each area regulate cellular invasion. The current study showed that metabolic products from cecal cells significantly enhance invasion by coccidia that normally invade the ceca, whereas metabolic products of other cells had no effect on invasion. Purification and testing of the enhancing metabolic products should allow clarification of cellular invasion at the molecular level. An understanding of the mechanisms of invasion will provide the basis for the development of strategies to markedly reduce parasite invasion without lowering the productivity of the host bird.
The effect of conditioned media from various cell cultures on cellular invasion by sporozoites of the turkey coccidium, Eimeria adenoeides, was examined. Conditioned medium from turkey kidney cells and baby hamster kidney cells failed to alter invasion of either turkey or hamster cell cultures. However, medium from the turkey cecal cells significantly enhanced invasion over control medium in all cell types that were tested. Retentates of conditioned medium from the turkey cecal cells that were passed through microconcentrators having molecular weight cutoffs of 50 to 300 kilodaltons similarly enhanced invasion over retentates from control medium. However, retentates from microconcentrators with a cutoff of 1000 kilodaltons f ailed to enhance invasion. Pretreatment in conditioned medium, followed by washing of the sporozoites prior to inoculation into cultures, did not result in enhanced invasion. Moreover, when the interval between inoculation of the sporozoites into the cells and the fixation of the cultures was reduced to less than 3 hr, no enhancement of invasion occurred. Conditioned medium from the turkey cecal cells grown in the presence of 35S-translabel contained several high molecular weight bands that were not present in conditioned media from other cell types.