Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 1, 2000
Publication Date: N/A
Interpretive Summary: Coccidiosis is a major parasitic disease of poultry which costs a significant economic loss to the poultry industry worldwide. Ability to develop vaccine for coccidiosis would significantly reduce production loss due to this parasite and enhances US economy. In this study, ARS scientists studied intestinal lymphocyte response following coccidia infection to understand the nature of protective host immune response to this parasite. The results showed that coccidia infection induces changes in the percentages of thymus-derived lymphocytes in the intestine. There was a significant increase of interferon-gamma production and CD4 cells at the time of parasite reduction indicating that these types of host immune responses are important in the elimination of coccidia parasites. These results also indicate the importance of studying intestinal response to understand host immunity to coccidiosis. This study provide information on nthe nature of host protective immunity to avian coccidiosis and will enhance possibility of developing immunological control strategy against this infection.
The role of intestinal lymphocytes and IFN-gamma production in protective immunity to Eimeria tenella infection was evaluated in two inbred strains of chickens (SC and TK) that display different patterns of susceptibility to coccidiosis. Oral inoculation of either strain with E. tenella lead to parasite invasion of the intestinal cecum and cecal tonsils. Greater fecal oocyst shedding was seen in TK chickens. Flow cytometric analyses of ceca tonsil lymphocytes demonstrated greater numbers of CD4+ and TCR1+ cells in SC chickens and elevated numbers of CD8+ and TCR2+ cells in TK chickens following primary infection. IFN-gamma mRNA expression was significantly increased in cecal tonsil and intraepithelial lymphocytes at days 6 and 8 post-primary infection respectively in SC compared to TK chickens. While no differences were noted between cecal tonsil lymphocytes of the two strains following secondary infection, TK chickens showed elevated IFN-gamma transcript levels in intestinal intraepithelial lymphocytes at this time. Selective depletion of CD4+, but not CD8+, cecal tonsil lymphocytes in SC chickens resulted in a reduced IFN-gamma mRNA expression indicating that CD4+ cells are the primary source of this cytokine. Collectively, these results indicate that local lymphocyte responses and production of IFN-gamma are influenced by host genetic factors.