Enterotoxigenic Escherichia coli CS21 pilus contributes to adhesion to intestinal cells and to pathogenesis under in vivo conditions

Abstract

Colonization surface antigens (CSs) represent key virulence-associated factors of enterotoxigenic Escherichia coli (ETEC) strains. They are required for gut colonization, the first step of the diarrhoeal disease process induced by these bacteria. One of the most prevalent CSs is CS21, or longus, a type IV pili associated with bacterial self-aggregation, protection against environmental stresses, biofilm formation and adherence to epithelial cell lines. The objectives of this study were to assess the role of CS21 in adherence to primary intestinal epithelial cells and to determine if CS21 contributes to the pathogenesis of ETEC infection in vivo. We evaluated adherence of a CS21-expressing wild-type ETEC strain and an isogenic CS21-mutant strain to pig-derived intestinal cell lines. To determine the role of CS21 in pathogenesis we used the above ETEC strains in a neonatal mice challenge infection model to assess mortality. Quantitative adherence assays confirmed that ETEC adheres to primary intestinal epithelial cells lines in a CS21-dependent manner. In addition, the CS21-mediated ETEC adherence to cells was specific as purified LngA protein, the CS21 major subunit, competed for binding with the CS21-expressing ETEC while specific anti-LngA antibodies blocked adhesion to intestinal cells. Neonatal DBA/2 mice died after intra-stomach administration of CS21-expressing strains while lack of CS21 expression drastically reduced the virulence of the wild-type ETEC strain in this animal model. Collectively these results further support the role of CS21 during ETEC infection and add new evidence on its in vivo relevance in pathogenesis.

Murine immunization with CS21 pili or LngA major subunit of enterotoxigenic Escherichia coli (ETEC) elicits systemic and mucosal immune responses and inhibits ETEC gut colonization

“…This suggested that anti-CS21 and anti-LngA immune responses may inhibit CS21-mediated ETEC binding to intestinal cells and may block gut colonization. Evidence that anti-LngA antibodies inhibited CS21-dependent ETEC adherence to intestinal cells was previously demonstrated in vitro (Guevara et al 2013). …”

“…A 16-gene cluster, essential in the biosynthesis of CS21, includes structural and regulatory genes (Gomez-Duarte et al 2007). The CS21 structural subunit gene lngA encodes a 22 kDa mature protein implicated in CS21-mediated ETEC specific adherence to intestinal cells (Guevara et al 2013). CS21 also mediated bacterial self-aggregation believed to promote resistance to environmental stress factors (including antimicrobials) (Clavijo et al 2010, Cruz-Córdova et al 2014, Guevara et al 2013, Mazariego-Espinosa et al 2010).…”

Colonization Factors in Enterotoxigenic Escherichia coli Strains in Travelers to Mexico, Guatemala, and India Compared with Children in Houston, Texas

“…24 In their experimental animal model, Guevara and others confirmed the role of CS21 in the pathogenesis of ETEC diarrhea. 25 More recently, the ETEC isolates with CS21 has been linked with self-aggregation, biofilm formation, and adherence to intestinal cells among Bangladeshi children with diarrhea. 26 Apart from CS21, the other two CFs that were more frequently expressed were CS6 (25%) and CS3 (17%).…”

Recent advances in adherence and invasion of pathogenic Escherichia coli

“…Guevara et al recently investigated one colonization factors, the CS21 pilus, and its role in adherence and pathogenesis in vivo (29). They found that ETEC CS21 (Longus) adherence to primary intestinal cells was inhibited by anti-LngA sera and the purified LngA protein.…”