Comparative analysis of expression profiles of cytokines in Riemerella anatipestifer infection in ducks and chickens highlights the role of IL-17A in bacterial susceptibility

Abstract

Abstract Riemerella anatipestifer (R. anatipestifer) cause severe infection in ducks at up to 75% mortality, but corresponding infection in chickens is comparatively mild. In order to understand differences in susceptibility, both species infected with R. anatipestifer, then analyzed mortality, bacterial burden and expression profiles of cytokines in infected birds. As expected, ducks exhibited increased susceptibility to R. anatipestifer infection compared to chickens, as determined by mortality rate and bacterial burden. Interestingly, comparative expression analysis of immune- related genes in R. anatipestifer-infected tissues and -stimulated splenic lymphocytes obtained from both species revealed that IL-17A is strongly associated with Riemerella infection in only ducks. Moreover, marked expression of IL-6 which is associated with Th17 cell differentiation, but not TGF-β, was identified in infected tissues from ducks, but not those from chickens. Furthermore, treatment with 3,3′-diindolylmethane (DIM) and berberine (BBR) in ducks ameliorated the detrimental effects of R. anatipestifer infection, as determined by decreases in mortality rate and bacterial burden, as well as downregulation of IL-17A and IL-6 mRNA expression. Taken together, these results suggest that upregulation of IL-17A influenced susceptibility to R. anatipestifer infection and that anti-IL-17A agents could prove to be promising therapies for alleviating Riemerella infection.