Colonization factor CS5 (CS5) (CS5)

Colonization factor CS5 is a major surface-exposed fimbrial protein found on Enterotoxigenic Escherichia coli (ETEC), which is a leading cause of diarrhea in children in developing countries and travelers (Svennerholm et al., 2014). It belongs to the CFA/IV (Colonization Factor Antigen IV) group and is frequently co-expressed with CS6 on the bacterial surface (Wolf, 1997). CS5 facilitates the initial attachment of the bacteria to the human intestinal mucosa, a critical step for subsequent toxin delivery and the development of clinical symptoms (Qadri et al., 2005). The structure of CS5 consists of major and minor subunits that form a pilus structure extending from the bacterial cell wall (Knutton et al., 1989). Because of its essential role in pathogenesis and its high prevalence among clinical ETEC isolates, CS5 is a primary target for the development of oral vaccines, such as ETVAX (Lundgren et al., 2014). These vaccines aim to induce mucosal IgA antibodies that bind to the CS5 fimbriae and sterically hinder the attachment of ETEC to intestinal epithelial cells (Leung et al., 2020). Targeting CS5 provides a strategy to prevent the onset of symptoms by inhibiting colonization rather than treating the infection after it has established. Clinical trials have demonstrated that vaccines targeting CS5 are generally safe and can induce significant immune responses in both adults and children (Qadri et al., 2020).

Other names

CS5 fimbriaeCS5 pilusCFA/IV component CS5Coli surface antigen 5

Induction of mucosal secretory IgA antibodies that bind to the CS5 fimbriae, thereby sterically hindering the attachment of ETEC to intestinal epithelial cells and preventing colonization.