Title: Differential gene expression profiles of ß-defensins in the crop, intestine, and spleen using a necrotic enteritis model in two commercial broiler chicken lines Authors
Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 15, 2012
Publication Date: June 25, 2012
Citation: Hong, Y., Lillehoj, H.S., Song, W., Lee, S.H. 2012. Differential gene expression profiles of ß-defensins in the crop, intestine, and spleen using a necrotic enteritis model in two commercial broiler chicken lines. Poultry Science. 91(5):1081-1088. Interpretive Summary: Defensins are antimicrobial peptides of relatively small molecules with less than 100 amino acids and contribute to the antimicrobial action of granulocytes, mucosal host defense in the gut and epithelial host defense in the skin and elsewhere. Although mammals possess at least 2 different kinds of defensins, a- and ß-defensins, chickens have only one type. Chicken ß-defensins represent important effector molecules of host innate immune system and their timely production is vital in immediate defense against invading pathogens such as bacteria, virus and parasites considering birds’ exposure to dirty environment right after hatch. There is very limited information on chicken defensins although they are known to be important host defense molecules. In this study, ARS scientists and scientists at the Choong Ang University of South Korea collaborated to study their role in necrotic enteritis (NE) disease model in poultry commercial meat-type chickens. In the United States, NE is among the most important infectious diseases in chickens and recently NE has re-emerged as a significant problem as a result of restrictions on use of in-feed antibiotics, modern practices of high-density housing conditions, and re-use of litter. The results of this study showed that some avian ß-defensin (AvBD) are induced in necrotic enteritis (NE). Among the 14 ß-defensin types examined, there was a tissue-specific expression of AvBD transcripts which indicate the role of some AvBD in NE. The findings of this study provide a groundwork for future investigation on the role of defensins in poultry diseases and will help our understanding of effector mechanisms of host defense in poultry.
Technical Abstract: Changes in the expression levels of avian ß-defensin (AvBD) mRNAs were evaluated in necrotic enteritis (NE) disease model in two genetically disparate commercial broiler chicken lines, R and C. NE was initiated in the intestinal track by a previously established co-infection model using oral Eimeria maxima (E. maxima) infection followed by Clostridium perfringens (C. perfringens) challenge. Among the 14 ß-defensin types examined, there was a tissue-specific expression of AvBD transcripts: AvBD1, AvBD7, and AvBD9 in the crop, AvBD8, AvBD10, and AvBD13 in the intestine and AvBD1 and AvBD7 in the spleen. Two different commercial broiler chicken lines showed differential gene expression patterns of AvBD transcripts following coinfection with E. maxima and C. perfringens with R line generally showing higher expression levels than C strain chickens. Both chicken strains showed enhanced gene expression levels of pro-inflammatory cytokines such as IL-1ß, IL-6, IL-17F and TNFSF15 in spleen, and TNFSF15 in intestine whereas only IL-17F was increased in intestine in R line chickens following NE infection compared to their uninfected counterparts. Although the exact interactions between defensins and cytokines in determining the nature of host innate immune responses to the pathogens of NE in chickens remains to be investigated, the differences in gene expression levels of ß-defensin and pro-inflammatory cytokines in the intestine and spleen could explain the genetically determined disease resistance and susceptibility to NE in two commercial broiler chickens.