Major fimbrial subunit FanC (FanC)

The Escherichia coli K99 pilus FanC subunit is the major structural protein of the F5 (K99) fimbriae, which are essential virulence factors in enterotoxigenic E. coli (ETEC) (UniProt P18103). These pili facilitate the attachment of the bacteria to the small intestinal epithelium of neonatal calves, lambs, and piglets by binding to specific glycolipid receptors, such as N-glycolylneuraminic acid-containing GM3 gangliosides (QED Bioscience). This adhesion is a critical first step in the pathogenesis of neonatal diarrhea, allowing the bacteria to colonize the gut and release enterotoxins (NIH, PMC4048151). Because FanC is the primary component of the pilus filament, it is a major target for immunological interventions (NIH, PMC5791551). Therapeutic strategies primarily focus on preventing colonization through the use of maternal vaccines that induce protective antibodies in colostrum or the administration of oral monoclonal antibodies to newborns (Merck Animal Health). By blocking the FanC-mediated attachment, these treatments effectively prevent the onset of severe dehydration and mortality associated with ETEC infections in livestock (PubMed, 3919874).

Other names

K99 fimbrial proteinF5 fimbrial subunitFanC proteinK99 major pilinK99 surface antigen

Antibodies bind to the FanC subunit, sterically hindering the interaction between the K99 pilus and host intestinal glycolipid receptors (Neu5Gc-GM3), thereby preventing bacterial colonization.