Chicken AvBD12

Salmonella typhimurium and Campylobacter jejuni pose significant risks to human health and poultry are a major vector for infection. Comparative in vivo infection models were performed to compare the avian host immune response to both bacterial species. Forty-five commercial broiler chickens were orally challenged with either C. jejuni or S. typhimurium whilst 60 similar control birds were mock challenged in parallel. Birds were sacrificed at 0, 6, 20 and 48 h post-infection and cloacal swabs, blood and tissue samples taken. Peripheral blood leukocytes were isolated for flow cytometric analyses and RNA was extracted for gene expression profiling. Colonisation patterns were markedly different between the two bacterial species, with systemic colonisation of Campylobacter outside the gastrointestinal tract. Salmonella infection induced significant changes in circulating heterophil and monocyte/macrophage populations, whilst Campylobacter infection had no effect on the heterophil numbers but caused a significant early increase in circulating monocytes/macrophages. Toll-like receptor 1 (TLR1) gene expression was decreased, and avian beta-defensin (AvBD) gene expression (AvBD3, AvBD10 and AvBD12) was significantly increased in response to Salmonella infection (P < 0.05). In contrast, Campylobacter infection induced increased TLR21 gene expression but significantly reduced expression of seven antimicrobial peptide (AMP) genes (AvBD3, AvBD4, AvBD8, AvBD13, AvBD14, CTHL2 and CTHL3; P < 0.05). Considered together, microbiological, cellular and gene expression profiles indicate that the innate immune system responds differently to Salmonella and to Campylobacter infection. Furthermore, reduction in the expression of AMPs may play a role in the persistence of high level colonisation of the host by Campylobacter.

Campylobacter is a bacterium that colonizes the lower gastrointestinal tract of poultry and may influence the intestinal environment to promote its survival. The objective of this study was to characterize the effects of Campylobacter challenge on the mRNA abundance of nutrient transporters and host defense peptides (HDP), such as the avian β-defensins (AvBD) and liver expressed antimicrobial peptide 2 (LEAP2). On the day of hatch, broiler chicks were challenged with one of three (106, 107, 108 colony-forming units, cfu) levels of Campylobacter jejuni. Quantitative PCR analysis revealed that there were dose-, tissue-, and age-specific changes in gene expression for both nutrient transporters and HDP. Expression of zinc transporter 1 (ZnT1) mRNA increased on d 7 in the duodenum, ileum, and cecum of birds challenged with 106 cfu of C. jejuni. At d 14, there was upregulation of the amino acid transporter bo,+AT mRNA in the duodenum, jejunum, and ileum of birds challenged with 106 cfu of C. jejuni. Other transporters such as EAAT3, GLUT2, SGLT1, and ZnT1 showed upregulation of mRNA in the ileum of the 106 cfu challenged group. There was a delayed response of the HDP to the C. jejuni challenge, with only a few HDP changed at d 7 but all HDP changed at d 14. At d 7, there was upregulation of AvBD10 mRNA in the duodenum of the 106 cfu challenged group but downregulation of AvBD10 in the ileum and AvBD12 and LEAP2 in the cecum of the 108 cfu challenged group. At d 14, there was upregulation of AvBD1, AvBD6, AvBD8, AvBD10, AvBD11, AvBD12, and AvBD13 mRNA in the ileum and cecum of the 106 cfu challenged group but not the 107 and 108 cfu challenged groups compared to control. These results indicated that at a low dose (106 cfu) of C. jejuni, intestinal cells increased nutrient transporter and AvBD mRNA abundance to try to counter the infection, but that at higher doses the cellular response was suppressed.

The aim of this study was to determine the mechanism by which expression of avian β-defensins (AvBD) in the follicular theca tissue was regulated. It was examined whether their expression was stimulated directly by LPS or indirectly through proinflammatory cytokines (IL-1β and IL-6) induced by LPS. Theca tissues of ovarian follicles were collected from White Leghorn hens. The specimens of those theca tissues were cultured in TCM-199 culture medium and stimulated by lipopolysaccharide from Salmonella minnesota (LPS), recombinant chicken IL-1β, or recombinant chicken IL-6. In the first experiment, changes in the expression of IL-1β, IL-6, AvBD10, and AvBD12 in response to LPS stimulation were examined by quantitative reverse-transcription PCR. The AvBD10 and 12 had been known to be expressed in the theca. In the second experiment, changes in the expression of AvBD10 and 12 in response to recombinant chicken IL-1β or IL-6 stimulation were examined by quantitative reverse-transcription PCR. Density of AvBD12 protein after IL-1β stimulation that showed changes in the gene expression was analyzed by Western blotting. In the first experiment, LPS was able to induce IL-1β and IL-6, but not AvBD10 or AvBD12. In the second experiment, IL-1β was able to upregulate significantly the expression of AvBD12 mRNA and protein. However, IL-6 did not exert significant effects on the expression of AvBD10 and AvBD12. It is suggested that LPS may stimulate theca cells to produce proinflammatory cytokines, whereas, in turn, IL-1β stimulates those cells to synthesize AvBD12, which may be able to attack infectious gram-negative bacteria.