Differential immune-related gene expression in two genetically disparate chicken lines during infection by Eimeria maxima.

Two M5.1 and M15.2 B complex congenic lines of Fayoumi chickens were evaluated for body weight loss and faecal oocyst counts as parameters of avian coccidiosis. M5.1 chickens exhibited resistance to E. maxima compared with M15.2. To correlate the differential responses of the M5.1 and M15.2 lines to E. maxima infection with cellular immune responses, the expression levels of mRNAs encoding 14 immune-related molecules were measured by quantitative RT-PCR in intestinal intraepithelial lymphocytes (IELs) and splenocytes at 0, 3, 4, and 5 days following parasite infection. Intestinal IELs from M5.1 chickens expressed higher levels of transcripts encoding interferon gamma (IFNG), interleukin-lbeta (1L1B), IL6, IL8, IL12, IL15, IL17A, inducible nitric oxide synthase (iNOS), and lipopolysaccharide-induced tumour necrosis a factor (LITAF), and lower levels of mRNAs for IFNA, IL10, IL17D, NK-lysin (NKL), and tumour necrosis factor superfamily 15 (TNFSF15) at 3 days post infection, compared with the M15.2 line. In the spleen, E. maxima infection was associated with higher expression levels of IFNA, and IL15 and lower levels of IL6, IL17D, and IL12 in M5.1 compared to M15.2 birds. Using an intestinal IEL cDNA microarray, the differential dynamics of gene expression in the gut of M5.1 and M15.2 chickens following experimental coccidiosis were evident. In particular, the genes encoding lymphotactin and parathymosin were expressed at significantly higher levels in M5.1 compared with M15.2 line chickens. In conclusion, genetic determinants within the chicken major histocompatibility complex (MHC) B complex influence resistance to E. maxima infection by controlling the local and systemic expression of immune-related cytokine and chemokine genes.