IMMUNIZATION OF CHICKENS TO REDUCE INTESTINAL COLONIZATION WITH CAMPYLOBACTER-JEJUNI

1. Systemic and intestinal antibody titres were measured in chickens f ollowing subcutaneous, intraperitoneal (IF), oral (po) and combined IP /po administration of antigen, in soluble, emulsified or microparticul ate form. Antigens tested included keyhole limpet haemocyanin (KLH), k illed Campylobacter jejuni whole cells and purified campylobacter flag ellin protein. 2. The effect of immunisation with purified flagellin p rotein or with killed C. jejuni whole cells in reducing intestinal col onisation was assessed. The ability of newlyhatched chicks to respond to immunisation was limited, possibly because of the immaturity of the immune system rather than maternal suppression of an immune response. Only 5 of 13 birds that were first immunised when 1-d-old with KLH sh owed a systemic response, even after 4 immunisations, whereas 10 of 11 birds that were first immunised at 24 d-old responded systemically. 3 . In an immunisation and challenge experiment, birds that were immunis ed twice intraperitoneally, at 16 and 29 d-old, with killed C. jejuni whole cells, had fewer C. jejuni, in the caecal contents than unimmuni sed control birds. This reduction in intestinal colonisation, to less than 2% of bacterial numbers in control birds, was associated with an increase in specific Ige in intestinal secretions. There was no signif icant increase in specific IgA or IgM in intestinal secretions followi ng immunisation and challenge. 4. These results indicate that immunisa tion can reduce the level of intestinal infection with C. jejuni. The protection may be enhanced by developing improved methods of immunisat ion that stimulate production of increased titres of specific antibody in intestinal secretions, particularly specific IgA antibody.