INTRAPERITONEAL IMMUNIZATION PROMOTES LOCAL INTESTINAL IMMUNITY IN CHICKENS

The limited success in stimulating protective immunity in the intestin e by traditional vaccination approaches has led to the search for nove l strategies to improve intestinal immunity. In mammalian species we h ave demonstrated that whereas oral immunization produces poor intestin al responses, immunization by the intraperitoneal route using appropri ate formulations is an effective means of priming the intestinal lymph oid tissue for an enhanced mucosal response to orally administered ant igen. In the experiments reported here we extend these findings to chi ckens and compare the intestinal IgA response to a non-replicating ant igen administered by the oral route alone or in oil emulsion formulati ons administered subcutaneously or intraperitoneally with or without o ral boosting. Despite repeated daily dosing, oral immunization of unpr imed animals produced only a small intestinal response. However, primi ng by the intraperitoneal route with antigen in either Freund's adjuva nt or a biodegradable oil-in-water emulsion (Auspharm adjuvant) result ed in a markedly improved response, especially when additional oral bo osting was given. The data also demonstrate that Quil A, a saponin der ivative, further boosts the response when co-administered with the oil emulsion intraperitoneally. This study illustrates the efficacy of sy stemic immunization by the intraperitoneal route in priming for an int estinal IgA response in chickens.