Role of EspB in Experimental Human Enteropathogenic Escherichia coli Infection

Abstract

Enteropathogenic Escherichia coli (EPEC), a leading cause of diarrhea among infants in developing countries, induces dramatic alterations in host cell architecture that depend on a type III secretion system. EspB, one of the proteins secreted and translocated to the host cytoplasm via this system, is required for numerous alterations in host cell structure and function. To determine the role of EspB in virulence, we conducted a randomized, double-blind trial comparing the ability of wild-type EPEC and an isogenic ⌬espB mutant strain to cause diarrhea in adult volunteers. Diarrhea developed in 9 of 10 volunteers who ingested the wild-type strain but in only 1 of 10 volunteers who ingested the ⌬espB mutant strain. Marked destruction of the microvillous brush border adjacent to adherent organisms was observed in a jejunal biopsy from a volunteer who ingested the wild-type strain but not from two volunteers who ingested the ⌬espB mutant strain. Humoral and cell-mediated immune responses to EPEC antigens were stronger among recipients of the wild-type strain. In addition, four of the volunteers who ingested the wild-type strain had lymphoproliferative responses to EspB. These results demonstrate that EspB is a critical virulence determinant of EPEC infections and suggest that EspB contributes to an immune response.Enteropathogenic Escherichia coli (EPEC) strains cause serious diarrhea among infants in developing countries throughout the world (4). Because EPEC strains isolated from humans do not cause diarrhea in animals, EPEC pathogenicity and the role of EPEC virulence factors in disease can only be tested in volunteer studies (2,5,20,21). During human infections, typical EPEC strains display two phenotypes, localized adherence and the attaching-and-effacing effect, which are reproduced in tissue culture. Localized adherence is dependent upon a type IV fimbria known as the bundle-forming pilus, which is encoded by a cluster of fourteen genes on a large plasmid common to EPEC strains (28, 30). The attaching-and-effacing effect is characterized by profound changes in the architecture of the host cell, with loss of microvilli and accumulations of cytoskeletal proteins within a cup-like pedestal upon which the bacteria rest (17,18

In Vitro and In Vivo Model Systems for Studying Enteropathogenic Escherichia coli Infections

“…All but one individual developed diarrhea after consumption of the wild-type strain (Tacket et al 2000), whereas only one instance of diarrhea occurred in 10 individuals who consumed the espB mutant (Tacket et al 2000) and four out of 11 who consumed the intimin mutant (Donnenberg et al 1993). Due to the relative inability of most EPEC strains to colonize nonhuman hosts and cause diarrhea, clinical trials using adult volunteers are important to further our knowledge of EPEC pathogenesis in humans and to determine the role of specific virulence factors in EPEC-mediated disease (Tacket et al 2000). However, the use of human volunteer studies is not without its drawbacks as the diarrhea that develops is often not reproducible (Donnenberg et al 1993) and susceptibility among individual hosts is likely to vary based on differences in immune response and prior exposure to the pathogen.…”

“…Intestinal biopsies taken from human volunteers infected with wild-type EPEC show destruction of the epithelial brush border (Tacket et al 2000), a phenotype that is reproducible in tissue culture (Knutton et al 1987). All but one individual developed diarrhea after consumption of the wild-type strain (Tacket et al 2000), whereas only one instance of diarrhea occurred in 10 individuals who consumed the espB mutant (Tacket et al 2000) and four out of 11 who consumed the intimin mutant (Donnenberg et al 1993). Due to the relative inability of most EPEC strains to colonize nonhuman hosts and cause diarrhea, clinical trials using adult volunteers are important to further our knowledge of EPEC pathogenesis in humans and to determine the role of specific virulence factors in EPEC-mediated disease (Tacket et al 2000).…”

“…Intimin and EspB are essential for A/E lesion formation in tissue culture (Foubister et al 1994;Abe et al 1997) and intestinal damage in rabbits and mice infected with REPEC (Abe et al 1998;Marchès et al 2000) or C. rodentium, respectively (Schauer and Falkow 1993;Newman et al 1999;Deng et al 2004). Intestinal biopsies taken from human volunteers infected with wild-type EPEC show destruction of the epithelial brush border (Tacket et al 2000), a phenotype that is reproducible in tissue culture (Knutton et al 1987). All but one individual developed diarrhea after consumption of the wild-type strain (Tacket et al 2000), whereas only one instance of diarrhea occurred in 10 individuals who consumed the espB mutant (Tacket et al 2000) and four out of 11 who consumed the intimin mutant (Donnenberg et al 1993).…”

“…Adult volunteers have been used to verify the roles of intimin, EspB, and bundle-forming pili (BFP) in EPEC pathogenesis (Donnenberg et al 1993;Bieber et al 1998;Tacket et al 2000). BFP is an EPEC-specific virulence factor but intimin and EspB are found in the genomes of diverse A/E pathogen species (Tauschek et al 2002;Iguchi et al 2009;Ogura et al 2009;Petty et al 2010).…”

Identification and characterization of Cri1, a locus controlling mortality during Citrobacter rodentium infection in mice

“…[14][15][16][17] Whether these differences have a genetic basis is undetermined. On the other hand, differences in susceptibility to C. rodentium infection in mice were first described in 1977, when an abnormally high mortality rate was noted in the C3H/HeJ strain.…”