The specificity of antibody in chickens immunised to reduce intestinal colonisation with Campylobacter jejuni

Poultry consumption has been identified as a major risk factor for human in fection with Campylobacter jejuni in developed countries. C. jejuni is pres ent in the gastrointestinal tract of broiler chickens at the time of slaugh ter, and faecal contamination of carcases during processing results in sign ificant campylobacter loads on carcases. One approach to reducing the level of carcase contamination with C.jejuni is to control campylobacter infecti on in broiler chickens. To this end, the study described here investigated the specificity of antibody in serum and intestinal secretions of chickens that had been immunised with campylobacter antigens and then challenged wit h viable bacteria. The immunodominant antigens in the serum of birds that s howed a 2-log reduction in caecal colonisation with C. jejuni included flag ellin protein (61-63 Kd) and three additional antigens of 67, 73.5 and 77.5 Kd. Only flagellin and the 67 Kd antigen were recognised by IgG antibody i n gastrointestinal secretions of the same birds. Antibody from chickens imm unised with purified native flagellin protein recognised flagellin protein and the 67 Kd antigen in Western blots probed with serum, but only the flag ellin proteins (61-63 Kd) in Westerns probed with gastrointestinal secretio ns. Analysis of the specificity of the response to flagellin protein using recombinant clones that expressed regions of the flagellin gene suggests th at epitopes in each region of the flagellin protein were immunogenic. Of th e immunodominant antigens, only flagellin appeared to be surface-exposed on viable C. jejuni, although conformational epitopes of flagellin appeared t o be sensitive to the method of antigen purification. The results of this s tudy suggest that flagellin and possibly the 67 Kd antigen may be valuable for immunological control of intestinal infection with C.jejuni in chickens , but that further work is required to purify these as vaccine candidates b y using methods that preserve conformational epitopes. (C) 1998 Elsevier Sc ience B.V. All rights reserved.