The immunobiology of persistent intestinal infection by Campylobacter jejuni in the chicken

Infection of the intestinal tract of the chicken with Campylobacter jejuni is frequently prolonged with limited immune clearance from the caeca, the main site of colonisation. Previously it has been shown early infection of broiler chickens leads to a pro-inflammatory response, followed by regulatory and Th17 responses along with adaptive Th1 and Th2 cytokine responses. Here we show that infection up to 28 days post challenge leads to prolonged expression of IL-4 and high titre IgM and IgY serum antibody responses to C. jeuni, along with increased levels of total IgA in the gut of infected birds. Whilst early pro-inflammatory cytokine and chemokine responses largely wane, expression of both IL-10 and IL-17A remain high in the colonised caeca or caecal tonsils. Based on this and previous studies we hypothesize that the nature of the immune response to C.jeuni infection is one that allows persistence in the gut, but limits inflammation and invasive infection from the gut through maintaining the intestinal barrier and producing secretory antibody. This protects the birds from campylobacteriosis, but the persistence in the gut for the production lifetime of chickens remains an unsolved public health issue.