21 research outputs found
Attaching and effacing (A/E) lesion formation by enteropathogenic E. coli on human intestinal mucosa is dependent on non-LEE effectors
Enteropathogenic E. coli (EPEC) is a human pathogen that causes acute and chronic pediatric diarrhea. The hallmark of EPEC infection is the formation of attaching and effacing (A/E) lesions in the intestinal epithelium. Formation of A/E lesions is mediated by genes located on the pathogenicity island locus of enterocyte effacement (LEE), which encode the adhesin intimin, a type III secretion system (T3SS) and six effectors, including the essential translocated intimin receptor (Tir). Seventeen additional effectors are encoded by genes located outside the LEE, in insertion elements and prophages. Here, using a stepwise approach, we generated an EPEC mutant lacking the entire effector genes (EPEC0) and intermediate mutants. We show that EPEC0 contains a functional T3SS. An EPEC mutant expressing intimin but lacking all the LEE effectors but Tir (EPEC1) was able to trigger robust actin polymerization in HeLa cells and mucin-producing intestinal LS174T cells. However, EPEC1 was unable to form A/E lesions on human intestinal in vitro organ cultures (IVOC). Screening the intermediate mutants for genes involved in A/E lesion formation on IVOC revealed that strains lacking non-LEE effector/s have a marginal ability to form A/E lesions. Furthermore, we found that Efa1/LifA proteins are important for A/E lesion formation efficiency in EPEC strains lacking multiple effectors. Taken together, these results demonstrate the intricate relationships between T3SS effectors and the essential role non-LEE effectors play in A/E lesion formation on mucosal surfaces
Functional analysis of lymphostatin homologues in enterohaemorrhagic Escherichia coli.
Enteropathogenic Escherichia coli contain a large chromosomal gene (lifA) that encodes lymphostatin, a predicted 365 kDa protein that inhibits the mitogen-activated proliferation of peripheral blood lymphocytes and lamina propria mononuclear cells and the synthesis of proinflammatory cytokines. Non-O157 serotypes of enterohaemorrhagic E. coli (EHEC) contain a highly homologous gene, designated efa1 (EHEC factor for adherence), which influences adherence to epithelial cells in vitro and intestinal colonization in calves. Serotype O157:H7 EHEC strains contain a truncated version of this gene (efa1') and a pO157-encoded homologue of lifA/efa1 (toxB). Here we report for the first time that efa1 inhibits mitogen-activated proliferation of bovine peripheral blood lymphocytes by EHEC O103:H2, but that E. coli K-12 strains expressing the N-terminal and central portions of the protein lack activity. While a Shiga toxin-negative E. coli O157:H7 strain was shown to possess lymphostatin-like activity, deletion of efa1' or toxB, singly or in combination, failed to significantly relieve the inhibitory effect
Functional analysis of lymphostatin homologues in enterohaemorrhagic Escherichia coli.
Enteropathogenic Escherichia coli contain a large chromosomal gene (lifA) that encodes lymphostatin, a predicted 365 kDa protein that inhibits the mitogen-activated proliferation of peripheral blood lymphocytes and lamina propria mononuclear cells and the synthesis of proinflammatory cytokines. Non-O157 serotypes of enterohaemorrhagic E. coli (EHEC) contain a highly homologous gene, designated efa1 (EHEC factor for adherence), which influences adherence to epithelial cells in vitro and intestinal colonization in calves. Serotype O157:H7 EHEC strains contain a truncated version of this gene (efa1') and a pO157-encoded homologue of lifA/efa1 (toxB). Here we report for the first time that efa1 inhibits mitogen-activated proliferation of bovine peripheral blood lymphocytes by EHEC O103:H2, but that E. coli K-12 strains expressing the N-terminal and central portions of the protein lack activity. While a Shiga toxin-negative E. coli O157:H7 strain was shown to possess lymphostatin-like activity, deletion of efa1' or toxB, singly or in combination, failed to significantly relieve the inhibitory effect
Subunit vaccines based on intimin and Efa-1 polypeptides induce humoral immunity in cattle but do not protect against intestinal colonisation by enterohaemorrhagic Escherichia coli O157:H7 or O26:H-.
Enterohaemorrhagic Escherichia coli (EHEC) infections in humans are an important public health concern and are commonly acquired via contact with ruminant faeces. Cattle are a key control point however cross-protective vaccines for the control of EHEC in the bovine reservoir do not yet exist. The EHEC serogroups that are predominantly associated with human infection in Europe and North America are O157 and O26. Intimin and EHEC factor for adherence (Efa-1) play important roles in intestinal colonisation of cattle by EHEC and are thus attractive candidates for the development of subunit vaccines. Immunisation of calves with the cell-binding domain of intimin subtypes beta or gamma via the intramuscular route induced antigen-specific serum IgG1 and, in some cases salivary IgA responses, but did not reduce the magnitude or duration of faecal excretion of EHEC O26:H- (Int(280)-beta) or EHEC O157:H7 (Int(280)-gamma) upon subsequent experimental challenge. Similarly, immunisation of calves via the intramuscular route with the truncated Efa-1 protein (Efa-1') from EHEC O157:H7 or a mixture of the amino-terminal and central thirds of the full-length protein (Efa-1-N and M) did not protect against intestinal colonisation by EHEC O157:H7 (Efa-1') or EHEC O26:H- (Efa-1-N and M) despite the induction of humoral immunity. A portion of the serum IgG1 elicited by the truncated recombinant antigens in calves was confirmed to recognise native protein exposed on the bacterial surface. Calves immunised with a mixture of Int(280)-gamma and Efa-1' or an EHEC O157:H7 bacterin via the intramuscular route then boosted via the intranasal route with the same antigens using cholera toxin B subunit as an adjuvant were also not protected against intestinal colonisation by EHEC O157:H7. These studies highlight the need for further studies to develop and test novel vaccines or treatments for control of this important foodborne pathogen
Subunit vaccines based on intimin and Efa-1 polypeptides induce humoral immunity in cattle but do not protect against intestinal colonisation by enterohaemorrhagic Escherichia coli O157:H7 or O26:H-
Enterohaemorrhagic Escherichia coli (EHEC) infections in humans are an important public health concern and are commonly acquired via contact with ruminant faeces. Cattle are a key control point however cross-protective vaccines for the control of EHEC in the bovine reservoir do not yet exist. The EHEC serogroups that are predominantly associated with human infection in Europe and North America are O157 and O26. Intimin and EHEC factor for adherence (Efa-1) play important roles in intestinal colonisation of cattle by EHEC and are thus attractive candidates for the development of subunit vaccines. Immunisation of calves with the cell-binding domain of intimin subtypes β or γ via the intramuscular route induced antigen-specific serum IgG1 and, in some cases salivary IgA responses, but did not reduce the magnitude or duration of faecal excretion of EHEC O26:H- (Int280-β) or EHEC O157:H7 (Int280-γ) upon subsequent experimental challenge. Similarly, immunisation of calves via the intramuscular route with the truncated Efa-1 protein (Efa-1′) from EHEC O157:H7 or a mixture of the amino-terminal and central thirds of the full-length protein (Efa-1-N and M) did not protect against intestinal colonisation by EHEC O157:H7 (Efa-1′) or EHEC O26:H- (Efa-1-N and M) despite the induction of humoral immunity. A portion of the serum IgG1 elicited by the truncated recombinant antigens in calves was confirmed to recognise native protein exposed on the bacterial surface. Calves immunised with a mixture of Int280-γ and Efa-1′ or an EHEC O157:H7 bacterin via the intramuscular route then boosted via the intranasal route with the same antigens using cholera toxin B subunit as an adjuvant were also not protected against intestinal colonisation by EHEC O157:H7. These studies highlight the need for further studies to develop and test novel vaccines or treatments for control of this important foodborne pathogen