Abstract
Interleukin 6 (IL-6) is an immunoregulatory cytokine involved in various inflammatory and immune responses. To investigate the effects of single nucleotide polymorphisms (SNPs) and haplotypes of IL-6 on resistance to Eimeria tenella (E. tenella), SNPs in the 5′ regulatory region of IL-6 were detected with direct sequencing, and the effects of SNPs and haplotypes on resistance to E. tenella were analyzed by the least square model in Jinghai yellow chickens. Nineteen SNPs were identified in the 5′ regulation region of IL-6, among which three SNPs were newly discovered. The SNP association analysis results showed that nine of the SNPs were significantly associated with E. tenella resistance indexes; the A-483G locus was significantly associated with the GSH-Px, IL-2, and IL-17 indexes (p < 0.05); the C-447G locus was significantly associated with the SOD, GSH-Px, IL-17, and IL-2 indexes (p < 0.05); and the G-357A locus had significant effects on the CAT and IL-16 indexes (p < 0.05). Haplotype analysis showed that H2H3 and H2H5 were favorable haplotype combinations with good coccidium resistance. Furthermore, we used qRT-PCR and observed that the expression of IL-6 in the infection group was higher than that in the control group in the liver, proventriculus, small intestine, thymus, kidney, and bursa of Fabricius and extremely significantly different than that in the cecum especially (p < 0.01). In summary, SNPs and haplotypes in the 5′ regulatory region of IL-6 have important effects on E. tenella resistance, and the results will provide a reference for molecular marker selection of E. tenella resistance in Jinghai yellow chickens.
Highlights
Coccidiosis is one of the intestinal parasitic diseases caused by the genus Eimeria, which seriously affects poultry production and animal welfare [1,2]
The RNA-seq technique was used to sequence the cecum tissue of an E. tenella-infected group and a noninfected group on the 7th day post-infection, and the results revealed that the differentially expressed genes (DEGs) included Interleukin 6 (IL-6), IL-12β, and TGFB2, which were significantly enriched during coccidiosis infection [13]
By sequencing and sequence alignment, a total of nineteen single nucleotide polymorphisms (SNPs) sites were identified in the 50 regulation region of IL-6 and three genotypes were detected in each site, among which three SNPs were newly discovered (C-447G, G-357A, A-663G) [18]
Summary
Coccidiosis is one of the intestinal parasitic diseases caused by the genus Eimeria, which seriously affects poultry production and animal welfare [1,2]. Coccidiostats, live vaccines and strict hygiene control are the main measures to prevent coccidiosis in poultry production [5]. Problems such as drug residues in food-producing animals, coccidiosis resistance, and vaccine safety still cannot be solved [6]. IL-6 performs protective functions in the healing of damaged tissues, participating in the acute phase immune response and coagulation in chickens [9]. Rose-John et al [11]
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