Colonization factor antigen CS3 fimbrial adhesin (CS3)

Colonization factor antigen CS3 (CS3) is a critical surface-exposed fimbrial adhesin found on Enterotoxigenic Escherichia coli (ETEC), which is a leading cause of traveler's diarrhea and significant childhood morbidity in developing nations (PubMed: 29158424). Unlike many other ETEC fimbriae that form rigid, rod-like structures, CS3 consists of thin, flexible fibrillae that facilitate the initial attachment of the bacteria to the human intestinal epithelium (PubMed: 25691586). This adhesion is a mandatory prerequisite for successful colonization and the subsequent delivery of heat-labile (LT) and heat-stable (ST) toxins that trigger diarrheal symptoms (UniProt: P0CK95). Because of its high prevalence among clinical ETEC isolates and its essential role in pathogenesis, CS3 is a primary target for broad-spectrum ETEC vaccine development (PubMed: 31606201). Current therapeutic strategies, such as the oral inactivated vaccine ETVAX, focus on eliciting a robust mucosal immune response, specifically secretory IgA antibodies that neutralize the adhesin. By blocking CS3-mediated attachment, these interventions effectively prevent bacterial colonization and the onset of clinical disease.

Other names

CS3 fimbriaeCS3 pilusMajor fimbrial subunit CstHCFA/II componentColonization factor antigen III

Immune exclusion via the induction of mucosal secretory IgA antibodies that bind to the CS3 adhesin, thereby preventing bacterial attachment to host intestinal epithelial cells.