Coli surface antigens 1 and 3 of colonization factor antigen II-positive enterotoxigenic Escherichia coli: morphology, purification, and immune responses in humans

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Abstract
Enterotoxigenic E. coli (ETEC) of serotype O6:H16, biotype A, bearing colonization factor antigen II (CFA/II) possesses 2 distinct coli surface antigens, CS1 and CS3; CFA/II-positive ETEC of serotype O8:H9 manifests only CS3. By immune electron microscopy, the morphological characteristics of CS3 were investigated on bacterial cells and after purification. CS3 consisted of thin (2 nm), flexible, wiry, fibrillar fimbriae, visible on bacteria (O6:H16, biotype A, and O8:H9 strains) and in the pure state. CS1 existed as wider (6 nm), a rigid fimbriae on the surface of O6:H16, biotype A, strains. By the use of antisera to CS1 and CS3 in immune electron microscopy, immunodiffusion in gel and immunoblotting techniques, CS1 and CS3 were found to be immunologically and morphologically distinct. Of 9 volunteers who developed diarrhea after challenge with an O139:H28 ETEC strain bearing CS1 and CS3, 6 had significant serological rises to purified CS1 and CS3 antigens, suggesting that both antigens are elaborated in vivo, play a role in pathogenesis and stimulate an immune response.