Chicken AvBD4

1. Chicken salmonellosis is a common zoonotic infectious disease transmitted both vertically and horizontally. Avian beta-defensins (gallinacins) play an important role in the innate defence of the host and provide broad-spectrum immunity against multiple pathogens. 2. To detect the relationship between immune genes and salmonella carrier status and susceptibility to salmonellosis in chickens, polymorphisms with carrier-state susceptibility to salmonella and, hence, developing salmonellosis, were investigated in three avian beta-defensin genes (AvBD4, AvBD5, and AvBD14) in a Chinese local chicken breed, based on a case-control study. 3. Fifteen, twenty and nineteen SNPs were found in AvBD4, AvBD5 and AvBD14, respectively. Among the 54 total SNPs, four resulted in non-synonymous substitution of amino acid changes. Five SNPs in AvBD5 and four SNPs in AvBD14 were significantly associated with salmonellosis susceptibility (P < 0.05). Using the PHASE program, thirteen, ten and twelve major haplotypes were constructed in AvBD4, AvBD5 and AvBD14. Logistic regression analysis revealed that five haplotypes in AvBD5 and six haplotypes in AvBD14 were significantly associated with salmonellosis susceptibility, but no significant haplotype in AvBD4 was detected. A total of six strongly susceptible haplotypes with odds ratio (OR) values greater than 2.0 and four strongly resistant haplotypes with OR value less than 0.5 were revealed in the three genes examined. 4. These results suggested that the AvBD5 and AvBD14 genes may play an important role in the susceptibility to salmonellosis in chickens.

The aim of this study was to determine the effect of vaccinations for avian infectious bronchitis with Newcastle disease (IB/ND) and Marek's disease (MD) on the expression of toll-like receptors (TLR) that recognize viral RNA and microbial DNA, and AvBD in chick kidneys. Day-old chicks were vaccinated with MD or IB/ND vaccines or received no treatment (control group). The gene expression of TLR and AvBD in the kidneys of 3-day-old chicks and 10-day-old chicks was examined using real-time PCR. The localization of AvBD2 and AvBD4 was examined by immunohistochemistry at day three only. At 3 days of age, the expression of TLR7 and TLR21 was significantly higher in the IB/ND group (but not in the MD group) than in the control group. Conversely, at 10 days of age there was no significant difference in the expression of the three TLR between groups. In the 3-day-old chicks the expression levels of AvBD4, 5, 6, and 7 were higher in the MD group than in the control group. Furthermore, at this age, the expression levels of other AvBD were not significantly different between the control and vaccination (MD and IB/ND) groups. At 10 days of age, no AvBD expression was affected by MD and IB/ND vaccinations. Immunohistochemistry results localized AvBD2 in the leukocytes in the interstitial tissue and AvBD4 in the surface of microvillus epithelial cells of renal tubules, and in the epithelial cells of the collecting ducts and ureter. The localization of AvBD2 and AvBD4 was identified in all chicks. We suggest that the expression of innate immune molecules (including TLR and AvBD) in kidneys could be modulated by MD and IB/ND vaccination when performed at the day-old stage. Although the effects of both vaccinations may subside within 10 days, the enhanced expression of those innate immune molecules may support the innate immunodefense function in the kidneys of young chicks.

Coccidiosis is a disease caused by Eimeria, which represents the first parasitic disease in poultry farming. Among them, E. tenella is a virulent species which specifically colonizes the caecum. The inflammatory response to infection is associated to numerous host proteases including cysteine cathepsins that can be deleterious for tissue and innate immunity integrity. Here, germ-free and conventional chickens were used as models to find out whether the microbiota could modify the intestinal expression of host cysteine cathepsins during coccidiosis. The basal caecal peptidase activity primarily relies on host proteases rather than proteases from the commensal flora. While mRNA levels of E. tenella cathepsins B and L remained unchanged in germ-free and conventional broilers, an overall increase in endopeptidase activity of cysteine cathepsins was found in E. tenella-infected caeca in both experimental models (P < 0.005). A significant decrease in avian cystatin C transcription was also observed in infected conventional, but not in infected germ-free broilers. Despite an unchanged mRNA level of avian cathepsin L (CatL), its protein expression raised following infection, in parallel with an increased transcription of antimicrobial β-defensins (AvBD1, AvBD2, AvBD4, AvBD6, and AvBD7). Taken together, data support that host CatL is post-translationally upregulated during E. tenella infection, and thus may be involved in the alteration of the gut proteolytic balance. Furthermore, CatL may participate to inflammation occurring during coccidiosis through its known ability to proteolytically inactivates up-regulated avian β-defensins that are key molecules of innate immunity.