Affiliation:
1. School of Cell and Molecular Biosciences, University of Newcastle upon Tyne, Newcastle upon Tyne, United Kingdom
Abstract
ABSTRACT
Cationic antimicrobial peptides constitute part of the innate immune system and provide an essential role in the defense against infection. At present there is a paucity of information regarding the antimicrobial profile of the chicken (
Gallus gallus
). Using in silico studies, an expressed sequence tag (EST) clone was identified which encodes a novel cationic antimicrobial peptide, chicken liver-expressed antimicrobial peptide 2 (cLEAP-2). The predicted amino acid sequence composed a prepropeptide, and the active peptide contained four conserved cysteine amino acids. The gene was localized to chromosome 13, and analysis of the genome revealed three exons separated by two introns. The cLEAP-2 gene was expressed in a number of chicken epithelial tissues including the small intestine, liver, lung, and kidney. Northern analysis identified liver-specific cLEAP-2 splice variants, suggesting some degree of tissue-specific regulation. To investigate whether cLEAP-2 expression was constitutive or induced in response to microbial infection, 4-day-old birds were orally infected with
Salmonella
. Analyses of cLEAP-2 expression by semiquantitative reverse transcription-PCR indicated that cLEAP-2 mRNA was upregulated significantly in the small intestinal tissues and the liver, indicative of direct and systemic responses. The antimicrobial activity of cLEAP-2 against
Salmonella
was analyzed in vitro with a time-kill assay and recombinant cLEAP-2. Interestingly
Salmonella enterica
serovar Typhimurium SL1344 showed increased susceptibility to the active cationic peptide (amino acids 37 to 76) compared to
S. enterica
serovar Typhimurium C5 and
Salmonella enteritidis
. Taken together, these data suggest that cationic cLEAP-2 is part of the innate host defense mechanisms of the chicken.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology