Relationship between amino acid sequence diversity and antimicrobial activity of Japanese quail cathelicidins

Abstract

Background Japanese quail is a low-fat, meat-bird species exhibiting high disease resistance. Cathelicidins (CATHs) are host defense peptides conserved across numerous vertebrate species that play an important role in innate immunity. The activity of host defense peptides can be affected by amino acid substitutions. However, no polymorphisms in avian CATH genes have been reported to date. The aim of this study was to clarify the effect on antimicrobial activity of polymorphisms in CATHs. Results DNA for genomic analyses was extracted from the peripheral blood of 99 randomly selected quail from 6 inbred lines. A total of six, four, four, and six CjCATH3 , CjCATH2 , CjCATHB1 , and CjCATH1 alleles were identified, respectively. Nine haplotypes, including four that were strain specific, were identified in alleles from the CjCATH3 , CjCATH2 , CjCATHB1 , and CjCATH1 loci. In addition, two and one amino acid substitutions (I145F, Q148H, and P245H) predicted by PROVEAN and PolyPhen-2 to have deleterious effects were detected at CjCATH2 and B1, respectively. Synthetic CjCATH2 and B1 peptides exhibited greater antibacterial activity against Escherichia coli than chicken CATH2 and B1, respectively. Furthermore, CjCATHB1*04 peptide exhibited less-potent antimicrobial activity than other CjCATHB1 peptides examined. Conclusions This is the first report of amino acid substitutions accompanied by changes in antibacterial activity in avian CATHs. These findings could be employed as indicators of improvements in the innate immune response in poultry.