Microencapsulated enterotoxigenic Escherichia coli and detached fimbriae for peroral vaccination of pigs.

The feasibility of peroral immunisation with microencapsulated Escherichia coli and detached fimbriae to prevent enterotoxigenic E. coli infections in pigs was examined. For this E. coli and fimbriae were microencapsulated into poly(lactide-co-glycolide) microspheres by spray-drying. Various microsphere formulations designed to deliver priming and booster doses were fed to new-born and weaned pigs. The pigs were challenged 19 days after the booster dose by peroral administration of an infective dose of the homologous E. coli. Serum IgA antibody titres and excretion of challenge E. coli, as indicators for colonisation, were determined. The data showed that no significant serum antibodies were induced, and E. coli colonisation was not reduced by the peroral administration of the various antigen-loaded microspheres. These results are in contradiction to some of the previously published experiments typically in rats or rabbits, where model antigens or unpractical immunisation procedures have frequently been used.