Comparative innate immune gene expression in chicken intestine after in vivo challenge with commensal (Campylobacter) and pathogenic (Salmonella) bacteria

Abstract

Campylobacter jejuni is a commensal bacterium in chickens and a major cause of food poisoning in humans. It is unknown whether the intestinal immune response has a role in establishing the commensal state. The innate immune responses of 4 week‐old broiler chickens to C. jejuni challenge (108 bacteria) were studied and compared with an avian pathogen, Salmonella enterica. Challenged and control birds were sacrificed 6 hours post‐challenge, RNA was extracted and cDNA synthesised. Selected genes involved in pathogen detection and innate immune response to bacterial infection were profiled in the caecum by quantitative real‐time PCR.A significant increase in the expression of TLR21 was observed after challenge with both types of bacteria (P < 0.05) compared to control birds. TLR4 expression was increased 4‐fold after C. jejuni challenge only (P = 0.02). IL6 was increased in response to both commensal and pathogenic challenges (P < 0.02). In contrast, IL8 mRNA expression was decreased 4‐fold in response to C. jejuni but increased 5‐fold to S. enterica challenge (P = 0). Antimicrobial peptides were differentially expressed in both models. Specifically, AvBD6 was increased by 24‐fold in response to S. enterica infection (P = 0).Results indicate that C. jejuni induces early innate immune gene expression changes, some similar to and others distinct from pathogenic challengeFunding: FIRM, Ireland