AvBD1 nucleotide polymorphisms, peptide antimicrobial activities and microbial colonisation of the broiler chicken gut

Abstract

BackgroundThe importance of poultry as a global source of protein underpins the chicken genome and associated SNP data as key tools in selecting and breeding healthy robust birds with improved disease resistance. SNPs affecting host peptides involved in the innate defences tend to be rare, but three non-synonymous SNPs in the avian β-defensin (AvBD1) gene encoding the variant peptides NYH, SSY and NYY were identified that segregated specifically to three lines of commercial broiler chickens Line X (LX), Line Y(LY) and Line Z. The impacts of such amino acid changes on peptide antimicrobial properties were analysed in vitro and described in relation to the caecal microbiota and gut health of LX and LY birds.ResultsTime-kill and radial immune diffusion assays indicated all three peptides to have antimicrobial properties against gram negative and positive bacteria with a hierarchy of NYH > SSY > NYY. Calcein leakage assays supported AvBD1 NYH as the most potent membrane permeabilising agent although no significant differences in secondary structure were identified to explain this. However, distinct claw regions, identified by 3D modelling and proposed to play a key role in microbial membrane attachment, and permeation, were more distinct in the NYH model. In vivo AvBD1 synthesis was detected in the bird gut epithelia. Analyses of the caecal gut microbiota of young day 4 birds suggested trends in Lactobacilli sp. colonisation at days 4 (9% LX vs × 30% LY) and 28 (20% LX vs 12% LY) respectively, but these were not statistically significant (P > 0.05).ConclusionAmino acid changes altering the killing capacity of the AvBD1 peptide were associated with two different bird lines, but such changes did not impact significantly on caecal gut microbiota.

Expression of Toll‐like receptors and host defence peptides in the cecum of chicken challenged with Eimeria tenella

“…In the present study, the expression of associated HDPs showed a significant increase in the cecum of E. tenella infected chickens. HDP in the gastrointestinal tract of chickens are mainly expressed by enterocytes and Paneth cells, and play crucial roles in controlling microbiota and protecting from the pathogenic bacteria in the gastrointestinal tract of chickens 52,53 . CATH, an important HDP in chicken, not only has rapid antimicrobial activity against a broad range of bacteria, but also regulates the immune responses of host cells 24 .…”

“…HDP in the gastrointestinal tract of chickens are mainly expressed by enterocytes and Paneth cells, and play crucial roles in controlling microbiota and protecting from the pathogenic bacteria in the gastrointestinal tract of chickens. 52,53 CATH, an important HDP in chicken, not only has rapid antimicrobial activity against a broad range of bacteria, but also regulates the immune responses of host cells. 24 However, studies on CATH activity against protozoa, especially E. tenella, are lacking.…”

The Impact of Hydrated Aluminosilicates Supplemented in Litter and Feed on Chicken Growth, Muscle Traits and Gene Expression in the Intestinal Mucosa

“…The decrease in the gene expression may lead to changes in innate immunity and modification of the intestinal microbiota. As a consequence, this may lead to an increase in the host’s susceptibility to disease [ 57 ]. In the expression analysis, we showed that in group 2, where the minerals in the feed and the halloysite were added to the litter, the expression increased numerically.…”