Enterotoxigenic Escherichia coli colonization factor antigen I fimbrial antigen (CFA/I fimbrial antigen)

Enterotoxigenic Escherichia coli colonization factor antigen I fimbrial antigen (CFA/I fimbrial antigen) is a surface adhesive pilus (fimbria) expressed by ETEC, a pathogenic E. coli strain that causes acute watery diarrhea, especially in children and travelers. CFA/I fimbriae consist of a major stalk subunit (CfaB) and a minor tip adhesin (CfaE), forming helical filaments mediating robust, host-specific adhesion to glycosphingolipid receptors on the intestinal epithelium. This adhesive interaction initiates colonization and subsequent pathogenicity, making CFA/I a critical virulence factor and a validated target for vaccine and anti-adhesion therapeutic development. CFA/I belongs to the class 5 fimbriae family, shares structural features with other bacterial pili, and displays antigenic variation in exposed regions to evade host immunity. Blockade of CFA/I—by antibodies or vaccine-induced immune responses—prevents bacterial attachment, colonization, and disease progression. Expression profiling and immunoassays detect CFA/I as a diagnostic marker in clinical ETEC isolates. Notable challenges include antigenic variability and coverage, as well as the absence of approved small-molecule drugs targeting this antigen directly.

Other names

Colonization factor antigen ICFA/I fimbriaeCFA/I pilusCFA/I fimbrial proteinClass 5 fimbriaeCFA/ICFA/I pilin

Adhesion inhibition (blocking interaction between CFA/I fimbriae and host glycosphingolipids); Immune neutralization by antibody binding to CfaB or CfaE and preventing adhesion/colonization; Vaccine-induced immune memory against CFA/I tip or stalk proteins