Role of Escherichia coli type 1 pilus in colonization of porcine ileum and its protective nature as a vaccine antigen in controlling colibacillosis.

This study was designed to evaluate the role of Escherichia coli type 1 pili in adherence of the organism to porcine small intestines and the efficacy of pili as a vaccine antigen in controlling neonatal colibacillosis. Our results demonstrated that an E. coli phase cloned to express type 1 pili readily attached to the small intestines of colostrum-deprived newborn pigs. Immunofluorescent staining of intestine sections revealed the presence of E. coli expressing type 1 pili only on the brush border, suggesting involvement of type 1 pili in the colonization process. Administration of anti-type 1 serum to newborn pigs prior to challenge reduced the level of gut-associated E. coli sixfold compared with controls. Purified type 1 pilus vaccine induced significant protection against colibacillosis in newborn pigs following challenge with E. coli expressing type 1 pili. Pigs born to vaccinated gilts scoured less and gained more weight than pigs born to control gilts. Our results demonstrate that type 1 pili are a virulence factor, as well as an effective vaccine antigen.