Submitted to: Feed Information for News on the Web
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 4, 2004
Publication Date: N/A
Interpretive Summary: Avian coccidiosis is caused by at least 7 different Eimeria species and causes severe damage to the gut of chickens. Ability to develop effective control methods against avian coccidiosis will reduce economic loss of >$700 million. However, limited information concerning the nature of host immune mechanism in avian coccidiosis hinders rapid progress toward this goal. In order to understand host immune response to coccidiosis, we need to develop immunological methods to assess host immunity to parasites. In this article, ARS scientist describes new in vitro methods to measure host cell-mediated immunity. Availability of these methods will enhance our ability to measure host immunity to pathogens in commercial scale and increase basic understanding of host cell-mediated immunity to parasites.
Apicompexan protozoa of the genus Eimeria are a common cause of coccidiosis. Following ingestion of infective oocysts, coccidia parasites undergo a complex life cycle ultimately impairing the gastrointestinal tract and resulting in nutrient malabsorption, body weight loss and, in severe cases, death. Host immune responses to Eimeria are extremely complex and involve many different effector mechanisms of intestinal immune system. Because Eimeria undergo intracellular development inside host cells, antibodies do not play an important role in protection against coccidiosis. Rather, effector mechanisms involving local lymphocytes and their secreted soluble factors, cytokines, play an important role in defense against coccidiosis. Comprehensive understanding of local host-parasite interactions leading to protection is critical for the development of logical control strategy against coccidiosis. However, progress in this area has been slow due to limited availability of immunological methods to assess local immunity in chickens. To this end, new in vitro assays which enable the assessment of intestinal cell-mediated immunity to Eimeria have been developed. These assays are based on the measurement of soluble factors which are secreted by lymphocytes following activation by Eimeria. Although molecular methods to measure the expression of cytokine gene transcripts became available recently, in vitro immunoassays based on the cytokine-specific monoclonal antibodies will allow the measurement of secreted proteins in biological samples in a large scale for commercial application.