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Infection and Immunity, December 2004, p. 6987-6993, Vol. 72, No. 12
0019-9567/04/$08.00+0     DOI: 10.1128/IAI.72.12.6987-6993.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Induction of Cationic Chicken Liver-Expressed Antimicrobial Peptide 2 in Response to Salmonella enterica Infection

Claire L. Townes, Georgios Michailidis, Christopher J. Nile, and Judith Hall^*

School of Cell and Molecular Biosciences, University of Newcastle upon Tyne, Newcastle upon Tyne, United Kingdom

Received 6 April 2004/ Returned for modification 4 May 2004/ Accepted 4 July 2004

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.

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* Corresponding author. Mailing address: School of Cell and Molecular Biosciences, Kings Walk, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU, United Kingdom. Phone: 44 191 222 8346. Fax: 44 191 222 8684. E-mail: Judith.hall{at}ncl.ac.uk.

Editor: F. C. Fang

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Infection and Immunity, December 2004, p. 6987-6993, Vol. 72, No. 12
0019-9567/04/$08.00+0     DOI: 10.1128/IAI.72.12.6987-6993.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

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