Serological subtypes of Escherichia coli colonization factor antigen II

Many of the enterotoxin-producing Escherichia coli strains causing diarrhea in humans possess one of two types of pili adhesins, the colonization factor antigens CFA/I and CFA/II. We identified two subtypes of CFA/II in two CFA/II bearing Escherichia coli strains (serotypes O6:H16 and O78:H12) by means of immunodiffusion analyses of heated extracts and hemagglutination inhibition tests. In addition to a shared antigenic structure on CFA/II from both strains, a specific antigenic determinant could be demonstrated on CFA/II from the O6:H16 strain. A protective effect against intestinal loop challenge with homologous bacteria in rabbits was noted for antibodies to both the shared and the subtype-specific structures of CFA/II.