Intestinal Defensins and Their Role in Controlling Avian Salmonella and Campylobacter Infection

Defensins are small molecular weight proteins which are produced by a large variety of cells and play an important role in defence against microbial infection. We have recently identified 3 new defensin genes in the chicken genome in addition to the three previously known, and wish to assess the contribution of these genes to controlling microbial infections, in particular their effect on intestinal colonisation by Salmonella and Campylobacter. <P>
Defensin mRNA levels will be compared in the intestine, spleen and heterophils of uninfected and infected chickens of different lines and in birds which have been vaccinated, since it is known that bacterial lipopolysaccharide stimulates defensin production by the crypts. We will also express the defensin proteins to assess their direct effect on bacterial and other pathogens, especially Salmonella and Campylobacter of various serotypes. <P>This work will allow us to define the importance of defensins in controlling bacterial infections and colonisation, and identify whether variation in these genes is responsible for differences in genetic resistance. It will also make it possible to identify factors which will enhance defensin production, such as particular vaccine strains, and allow us to compare the antimicrobial effects of the chicken defensins with their mammalian counterparts.