Association of three beta-defensin gene (AvBD4, AvBD5, AvBD14) polymorphisms with carrier-state susceptibility to salmonella in chickens

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.