A bivalent vaccine confers immunogenicity and protection against Shigella flexneri and enterotoxigenic Escherichia coli infections in mice.
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ABSTRACT:
SUBMITTER: Medeiros PHQS
PROVIDER: S-EPMC7101394 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:An invasive strain of Shigella flexneri 2a (SC608) has been developed as a vector for the expression and delivery of heterologous antigens. SC608 is an aspartate semialdehyde dehydrogenase (asd) derivative of SC602 (icsA iuc), a well-characterized live attenuated vaccine strain which has undergone several clinical trials in human volunteers. When administered orally at a single 10(4) (CFU) dose, SC602 is both immunogenic and efficacious against shigellosis. Using asd-based plasmid vectors, we designed SC608 to express the enterotoxigenic Escherichia coli (ETEC) fimbrial subunit CfaB (CFA/I structural subunit) alone or in combination with the E. coli B subunit of heat-labile enterotoxin (LTB). The expression of each heterologous protein in SC608 was verified by immunoblot analysis. Each strain was comparable to the parent strain, SC602, in a HeLa cell invasion assay. After intranasal immunizations of guinea pigs, serum and mucosal immune responses were detected against both Shigella lipopolysaccharide and heterologous ETEC antigens by enzyme-linked immunosorbent assay and ELISPOT analysis. All immunized animals were subsequently protected against a challenge with wild-type S. flexneri 2a in a keratoconjunctivitis Sereny test. Serum antibodies generated against LTB and CfaB demonstrated antitoxin and agglutination activities, respectively. These results suggest that CfaB and LTB expressed in SC608 retain important conformational epitopes that are required for the generation of antibodies that have functional activities. These initial experiments demonstrate that a fully invasive Shigella vaccine strain can be engineered to deliver antigens from other diarrheal pathogens.
| S-EPMC538972 | biostudies-literature
Project description:A multivalent live oral vaccine against both Shigella spp. and enterotoxigenic Escherichia coli (ETEC) is being developed based on the hypothesis that protection can be achieved if attenuated shigellae express ETEC fimbrial colonization factors and genetically detoxified heat-labile toxin from a human ETEC isolate (LTh). Two detoxified derivatives of LTh, LThK63 and LThR72, were engineered by substitution-serine to lysine at residue 63, or lysine to arginine at residue 72. The genes encoding these two derivatives were cloned separately on expression plasmids downstream from the CFA/I operon. Following electroporation into S. flexneri 2a vaccine strain CVD 1204, coexpression of CFA/I and LThK63 or LThR72 was demonstrated by Western blot analysis, GM(1) binding assays, and agglutination with anti-CFA/I antiserum. Hemagglutination and electron microscopy confirmed surface expression of CFA/I. Guinea pigs immunized intranasally on days 0 and 15 with CVD 1204 expressing CFA/I and LThK63 or LThR72 exhibited high titers of both serum immunoglobulin G (IgG) and mucosal secretory IgA anti-CFA/I; 40% of the animals produced antibodies directed against LTh. All immunized guinea pigs also produced mucosal IgA (in tears) and serum IgG anti-S. flexneri 2a O antibodies. Furthermore, all immunized animals were protected from challenge with wild-type S. flexneri 2a. This prototype Shigella-ETEC hybrid vaccine demonstrates the feasibility of expressing multiple ETEC antigens on a single plasmid in an attenuated Shigella vaccine strain and engendering immune responses against both the heterologous antigens and vector strain.
| S-EPMC101689 | biostudies-literature
Project description:The genes that encode the enterotoxigenic Escherichia coli (ETEC) CS4 fimbriae, csaA, -B, -C, -E, and -D', were isolated from strain E11881A. The csa operon encodes a 17-kDa major fimbrial subunit (CsaB), a 40-kDa tip-associated protein (CsaE), a 27-kDa chaperone-like protein (CsaA), a 97-kDa usher-like protein (CsaC), and a deleted regulatory protein (CsaD'). The predicted amino acid sequences of the CS4 proteins are highly homologous to structural and assembly proteins of other ETEC fimbriae, including CS1 and CS2, and to CFA/I in particular. The csaA, -B, -C, -E operon was cloned on a stabilized plasmid downstream from an osomotically regulated ompC promoter. pGA2-CS4 directs production of CS4 fimbriae in both E. coli DH5alpha and Shigella flexneri 2a vaccine strain CVD 1204, as detected by Western blot analysis and bacterial agglutination with anti-CS4 immune sera. Electron-microscopic examination of Shigella expressing CS4 confirmed the presence of fimbriae on the bacterial surface. Guinea pigs immunized with CVD 1204(pGA2-CS4) showed serum and mucosal antibody responses to both the Shigella vector and the ETEC fimbria CS4. Among the seven most prevalent fimbrial antigens of human ETEC, CS4 is the last to be cloned and sequenced. These findings pave the way for CS4 to be included in multivalent ETEC vaccines, including an attenuated Shigella live-vector-based ETEC vaccine.
| S-EPMC148885 | biostudies-literature
Project description:To construct a prototype hybrid vaccine against Shigella and enterotoxigenic Escherichia coli (ETEC), the genes encoding the production of ETEC CS2 and CS3 fimbriae were isolated and expressed in attenuated Shigella flexneri 2a guaBA strain CVD 1204. The CS2 cotA to -D genes, isolated from ETEC strain C91F, and the CS3 cstA to -H genes, subcloned from plasmid pCS100, were cloned into ~15-copy-number-stabilized pGA1 behind the osmotically regulated ompC promoter, resulting in high expression of both fimbriae. Under nonselective in vitro growth conditions, pGA1-CS2 and pGA1-CS3 were stable in CVD 1204, exhibiting a plasmid loss of only approximately 1% per duplication. Expression of CS2 and CS3 reduced the invasiveness of Shigella for HeLa cells and slowed the intracellular growth rate. Guinea pigs immunized intranasally with CVD 1204(pGA1-CS2) or CVD 1204(pGA1-CS3), or with a mixture of these strains, developed secretory immunoglobulin A (IgA) in tears and serum IgG antibodies against Shigella lipopolysaccharide, CS2, and CS3 antigens. Moreover, the animals were protected against keratoconjunctivitis following conjunctival challenge with virulent S. flexneri 2a strain 2457T. Animals immunized with Shigella expressing CS2 or CS3 developed serum antibodies that agglutinated Shigella as well as an ETEC strain bearing the homologous fimbriae, whereas animals immunized with combined CVD 1204(pGA1-CS2) and CVD 1204(pGA1-CS3) developed antibodies that agglutinated all three test strains. These observations support the feasibility of a multivalent vaccine against shigellosis and ETEC diarrhea consisting of multiple Shigella live vectors expressing relevant ETEC antigens.
| S-EPMC98271 | biostudies-literature
Project description:We have identified and characterized a secreted protein, designated Pic, which is encoded on the chromosomes of enteroaggregative Escherichia coli (EAEC) 042 and Shigella flexneri 2457T. The product of the pic gene is synthesized as a 146.5-kDa precursor molecule which is processed at the N and C termini during secretion, allowing the release of a mature protein (109.8 kDa) into the culture supernatant. The deduced amino acid sequence of Pic shows high homology to autotransporter proteins, particularly a subgroup termed the SPATEs (serine protease autotransporters of the Enterobacteriaceae). Present in all members of this subgroup is a motif similar to the active sites of certain serine proteases. Pic catalyzes gelatin degradation, which can be abolished by disruption of the predicted proteolytic active site. Functional analysis of the Pic protein implicates this factor in mucinase activity, serum resistance, and hemagglutination. Our data suggest that Pic may be a multifunctional protein involved in enteric pathogenesis.
| S-EPMC96930 | biostudies-literature
Project description:The molecular basis for the survival of bacteria under extreme conditions in which growth is inhibited is a question of great current interest. A preliminary study was carried out to determine residue pattern conservation among the antiporters of enteric bacteria, responsible for extreme acid sensitivity especially in Escherichia coli and Shigella flexneri. Here we found the molecular evidence that proved the relationship between E. coli and S. flexneri. Multiple sequence alignment of the gadC coded acid sensitive antiporter showed many conserved residue patterns at regular intervals at the N-terminal region. It was observed that as the alignment approaches towards the C-terminal, the number of conserved residues decreases, indicating that the N-terminal region of this protein has much active role when compared to the carboxyl terminal. The motif, FHLVFFLLLGG, is well conserved within the entire gadC coded protein at the amino terminal. The motif is also partially conserved among other antiporters (which are not coded by gadC) but involved in acid sensitive/resistance mechanism. Phylogenetic cluster analysis proves the relationship of Escherichia coli and Shigella flexneri. The gadC coded proteins are converged as a clade and diverged from other antiporters belongs to the amino acid-polyamine-organocation (APC) superfamily.
| S-EPMC2255067 | biostudies-literature
Project description:We have identified a new gene, glpX, belonging to the glp regulon of Escherichia coli, located directly downstream of the glpK gene. The transcription of glpX is inducible with glycerol and sn-glycerol-3-phosphate and is constitutive in a glpR mutant. glpX is the third gene in the glpFKX operon. The function of GlpX remains unknown. GlpX has an apparent molecular weight of 40,000 on sodium dodecyl sulfate-polyacrylamide gels. In addition to determining the E. coli glpX sequence, we also sequenced the corresponding glpFKX region originating from Shigella flexneri, which after transfer into E. coli was instrumental in elucidating the function of glpF in glycerol transport (D. P. Richey and E. C. C. Lin, J. Bacteriol. 112:784-790, 1972). Sequencing of the glpFKX region of this hybrid strain revealed an amber mutation instead of the tryptophan 215 codon in glpF. The most striking difference between the E. coli and S. flexneri DNA was found directly behind glpK, where two repetitive (REP) sequences were present in S. flexneri, but not in the E. coli sequence. The presence or absence of these REP sequences had no effect on transport or on growth on glycerol. Not including the REP sequence-containing region, only 1.1% of a total of 2,167 bp sequenced was different in the two sequences. Comparison of the sequence with those in the EMBL data library revealed a 99% identity between the last third of glpX and the first part of a gene called mvrA. We show that the cloned mvrA gene (M. Morimyo, J. Bacteriol. 170:2136-2142, 1988) originated from the 88-min region of the Escherichia coli chromosome and not, as reported, from the 7-min region and that the gene product identified as MvrA is in fact encoded by a gene distal to glpX.
| S-EPMC207378 | biostudies-other
Project description:BackgroundEnterotoxigenic Escherichia coli (ETEC) are common causes of diarrheal morbidity and mortality in developing countries for which there is currently no vaccine. Heterogeneity in classical ETEC antigens known as colonization factors (CFs) and poor efficacy of toxoid-based approaches to date have impeded development of a broadly protective ETEC vaccine, prompting searches for novel molecular targets.MethodologyUsing a variety of molecular methods, we examined a large collection of ETEC isolates for production of two secreted plasmid-encoded pathotype-specific antigens, the EtpA extracellular adhesin, and EatA, a mucin-degrading serine protease; and two chromosomally-encoded molecules, the YghJ metalloprotease and the EaeH adhesin, that are not specific to the ETEC pathovar, but which have been implicated in ETEC pathogenesis. ELISA assays were also performed on control and convalescent sera to characterize the immune response to these antigens. Finally, mice were immunized with recombinant EtpA (rEtpA), and a protease deficient version of the secreted EatA passenger domain (rEatApH134R) to examine the feasibility of combining these molecules in a subunit vaccine approach.Principal findingsEtpA and EatA were secreted by more than half of all ETEC, distributed over diverse phylogenetic lineages belonging to multiple CF groups, and exhibited surprisingly little sequence variation. Both chromosomally-encoded molecules were also identified in a wide variety of ETEC strains and YghJ was secreted by 89% of isolates. Antibodies against both the ETEC pathovar-specific and conserved E. coli antigens were present in significantly higher titers in convalescent samples from subjects with ETEC infection than controls suggesting that each of these antigens is produced and recognized during infection. Finally, co-immunization of mice with rEtpA and rEatApH134R offered significant protection against ETEC infection.ConclusionsCollectively, these data suggest that novel antigens could significantly complement current approaches and foster improved strategies for development of broadly protective ETEC vaccines.
| S-EPMC4309559 | biostudies-literature
Project description:BackgroundEnterotoxigenic Escherichia coli (ETEC) and shigella are two major pathogens that cause moderate-to-severe diarrhoea in children younger than 5 years. Diarrhoea is associated with an increased risk of stunting, which puts children at risk of death due to other infectious diseases.MethodsWe modelled ETEC-related and shigella-related mortality and the effect of moderate-to-severe diarrhoea episodes to determine the number of children with stunting due to these infections in 79 low-income and lower middle-income countries. We applied population attributable risk for increased number of deaths due to other infectious diseases in children who are stunted. We calculated 95% uncertainty intervals (UIs) for the point estimates.FindingsIn children younger than 5 years, we estimate 196 million (95% UI 135-269) episodes of ETEC and shigella diarrhoea occur annually, resulting in 3·5 million (0·8-5·4) cases of moderate-to-severe stunting and 44 400 (29 400-59 800) total ETEC deaths and 63 100 (44 000-81 900) total shigella deaths in 2015. Additional infectious disease mortality due to stunting resulted in increases of 24% (8-34; for ETEC) and 28% (10-39; for shigella) over direct deaths due to diarrhoeal episodes. The distribution of mortality and morbidity varied geographically, with African Region and Eastern Mediterranean Region countries bearing the greatest burden.InterpretationThe expanded effects of non-fatal ETEC and shigella-related diarrhoeal episodes can have lasting consequences. Prevention of these infections could reduce the risk of direct death and stunting and deaths due to other infectious diseases. Understanding the countries and populations with the highest disease risk helps to target interventions for the most vulnerable populations.FundingThe Bill & Melinda Gates Foundation.
| S-EPMC6379821 | biostudies-literature
Project description:Shigellosis remains a major cause of diarrheal disease in developing countries and causes substantial morbidity and mortality in children. Vaccination represents a promising preventive measure to fight the burden of the disease, but despite enormous efforts, an efficacious vaccine is not available to date. The use of an innovative biosynthetic Escherichia coli glycosylation system substantially simplifies the production of a multivalent conjugate vaccine to prevent shigellosis. This bioconjugation approach has been used to produce the Shigella dysenteriae type O1 conjugate that has been successfully tested in a phase I clinical study in humans. In this report, we describe a similar approach for the production of an additional serotype required for a broadly protective shigellosis vaccine candidate. The Shigella flexneri 2a O-polysaccharide is conjugated to introduced asparagine residues of the carrier protein exotoxin A (EPA) from Pseudomonas aeruginosa by co-expression with the PglB oligosaccharyltransferase. The bioconjugate was purified, characterized using physicochemical methods and subjected to preclinical evaluation in rats. The bioconjugate elicited functional antibodies as shown by a bactericidal assay for S. flexneri 2a. This study confirms the applicability of bioconjugation for the S. flexneri 2a O-antigen, which provides an intrinsic advantage over chemical conjugates due to the simplicity of a single production step and ease of characterization of the homogenous monomeric conjugate formed. In addition, it shows that bioconjugates are able to raise functional antibodies against the polysaccharide antigen.
| S-EPMC6704370 | biostudies-literature