Serological response to type 1-like somatic fimbriae in diarrheal infection due to classical enteropathogenic Escherichia coli

Fimbriae from enteropathogenic Escherichia coli strain E2349/69 (0127:H6) and its plasmid-minus derivative, MAR20, were purified and characterized as type 1-like by their physicochemical and hemagglutination patterns. Sera from adult volunteers challenged with the diarrheagenic parent strain and the attenuated plasmid-minus derivative were examined to detect an immune response, using the purified fimbriae as antigens in an enzyme linked immunosorbent assay (ELISA) and immunoblot assay. An anti-fimbrial response was evident in sera of 7 of 10 volunteers fed the diarrheagenic parent strain E2348 but also in 8 of 9 individuals fed the attenuated, plasmid-cured, derivative MAR20. The antibody response appeared specific in that the sera failed to react in an ELISA and by immunoblot assay with type 1 fimbriae from other E. coli. These findings suggest that the type 1 fimbriae of this representative EPEC strain are antigenically distinct. The results of this investigation provide the first evidence of seroconversion to type 1-like fimbriae in infections caused by diarrheagenic E. coli.