Rappuoli R

References (16)

Title : Sequence type 1 group B Streptococcus, an emerging cause of invasive disease in adults, evolves by small genetic changes - Flores_2015_Proc.Natl.Acad.Sci.U.S.A_112_6431
Author(s) : Flores AR , Galloway-Pena J , Sahasrabhojane P , Saldana M , Yao H , Su X , Ajami NJ , Holder ME , Petrosino JF , Thompson E , Margarit YRI , Rosini R , Grandi G , Horstmann N , Teatero S , McGeer A , Fittipaldi N , Rappuoli R , Baker CJ , Shelburne SA
Ref : Proc Natl Acad Sci U S A , 112 :6431 , 2015
Abstract : The molecular mechanisms underlying pathogen emergence in humans is a critical but poorly understood area of microbiologic investigation. Serotype V group B Streptococcus (GBS) was first isolated from humans in 1975, and rates of invasive serotype V GBS disease significantly increased starting in the early 1990s. We found that 210 of 229 serotype V GBS strains (92%) isolated from the bloodstream of nonpregnant adults in the United States and Canada between 1992 and 2013 were multilocus sequence type (ST) 1. Elucidation of the complete genome of a 1992 ST-1 strain revealed that this strain had the highest homology with a GBS strain causing cow mastitis and that the 1992 ST-1 strain differed from serotype V strains isolated in the late 1970s by acquisition of cell surface proteins and antimicrobial resistance determinants. Whole-genome comparison of 202 invasive ST-1 strains detected significant recombination in only eight strains. The remaining 194 strains differed by an average of 97 SNPs. Phylogenetic analysis revealed a temporally dependent mode of genetic diversification consistent with the emergence in the 1990s of ST-1 GBS as major agents of human disease. Thirty-one loci were identified as being under positive selective pressure, and mutations at loci encoding polysaccharide capsule production proteins, regulators of pilus expression, and two-component gene regulatory systems were shown to affect the bacterial phenotype. These data reveal that phenotypic diversity among ST-1 GBS is mainly driven by small genetic changes rather than extensive recombination, thereby extending knowledge into how pathogens adapt to humans.
ESTHER : Flores_2015_Proc.Natl.Acad.Sci.U.S.A_112_6431
PubMedSearch : Flores_2015_Proc.Natl.Acad.Sci.U.S.A_112_6431
PubMedID: 25941374

Title : Neisseria meningitidis is structured in clades associated with restriction modification systems that modulate homologous recombination - Budroni_2011_Proc.Natl.Acad.Sci.U.S.A_108_4494
Author(s) : Budroni S , Siena E , Dunning Hotopp JC , Seib KL , Serruto D , Nofroni C , Comanducci M , Riley DR , Daugherty SC , Angiuoli SV , Covacci A , Pizza M , Rappuoli R , Moxon ER , Tettelin H , Medini D
Ref : Proc Natl Acad Sci U S A , 108 :4494 , 2011
Abstract : Molecular data on a limited number of chromosomal loci have shown that the population of Neisseria meningitidis (Nm), a deadly human pathogen, is structured in distinct lineages. Given that the Nm population undergoes substantial recombination, the mechanisms resulting in the evolution of these lineages, their persistence in time, and the implications for the pathogenicity of the bacterium are not yet completely understood. Based on whole-genome sequencing, we show that Nm is structured in phylogenetic clades. Through acquisition of specific genes and through insertions and rearrangements, each clade has acquired and remodeled specific genomic tracts, with the potential to impact on the commensal and virulence behavior of Nm. Despite this clear evidence of a structured population, we confirm high rates of detectable recombination throughout the whole Nm chromosome. However, gene conversion events were found to be longer within clades than between clades, suggesting a DNA cleavage mechanism associated with the phylogeny of the species. We identify 22 restriction modification systems, probably acquired by horizontal gene transfer from outside of the species/genus, whose distribution in the different strains coincides with the phylogenetic clade structure. We provide evidence that these clade-associated restriction modification systems generate a differential barrier to DNA exchange consistent with the observed population structure. These findings have general implications for the emergence of lineage structure and virulence in recombining bacterial populations, and they could provide an evolutionary framework for the population biology of a number of other bacterial species that show contradictory population structure and dynamics.
ESTHER : Budroni_2011_Proc.Natl.Acad.Sci.U.S.A_108_4494
PubMedSearch : Budroni_2011_Proc.Natl.Acad.Sci.U.S.A_108_4494
PubMedID: 21368196
Gene_locus related to this paper: neigo-pip , neima-metx , neime-ESD , neime-NMA2216 , neime-NMB0276 , neime-NMB1877

Title : Structure and dynamics of the pan-genome of Streptococcus pneumoniae and closely related species - Donati_2010_Genome.Biol_11_R107
Author(s) : Donati C , Hiller NL , Tettelin H , Muzzi A , Croucher NJ , Angiuoli SV , Oggioni M , Dunning Hotopp JC , Hu FZ , Riley DR , Covacci A , Mitchell TJ , Bentley SD , Kilian M , Ehrlich GD , Rappuoli R , Moxon ER , Masignani V
Ref : Genome Biol , 11 :R107 , 2010
Abstract : BACKGROUND: Streptococcus pneumoniae is one of the most important causes of microbial diseases in humans. The genomes of 44 diverse strains of S. pneumoniae were analyzed and compared with strains of non-pathogenic streptococci of the Mitis group.
RESULTS: Despite evidence of extensive recombination, the S. pneumoniae phylogenetic tree revealed six major lineages. With the exception of serotype 1, the tree correlated poorly with capsular serotype, geographical site of isolation and disease outcome. The distribution of dispensable genes--genes present in more than one strain but not in all strains--was consistent with phylogeny, although horizontal gene transfer events attenuated this correlation in the case of ancient lineages. Homologous recombination, involving short stretches of DNA, was the dominant evolutionary process of the core genome of S. pneumoniae. Genetic exchange occurred both within and across the borders of the species, and S. mitis was the main reservoir of genetic diversity of S. pneumoniae. The pan-genome size of S. pneumoniae increased logarithmically with the number of strains and linearly with the number of polymorphic sites of the sampled genomes, suggesting that acquired genes accumulate proportionately to the age of clones. Most genes associated with pathogenicity were shared by all S. pneumoniae strains, but were also present in S. mitis, S. oralis and S. infantis, indicating that these genes are not sufficient to determine virulence.
CONCLUSIONS: Genetic exchange with related species sharing the same ecological niche is the main mechanism of evolution of S. pneumoniae. The open pan-genome guarantees the species a quick and economical response to diverse environments.
ESTHER : Donati_2010_Genome.Biol_11_R107
PubMedSearch : Donati_2010_Genome.Biol_11_R107
PubMedID: 21034474

Title : Identification of protective and broadly conserved vaccine antigens from the genome of extraintestinal pathogenic Escherichia coli - Moriel_2010_Proc.Natl.Acad.Sci.U.S.A_107_9072
Author(s) : Moriel DG , Bertoldi I , Spagnuolo A , Marchi S , Rosini R , Nesta B , Pastorello I , Corea VA , Torricelli G , Cartocci E , Savino S , Scarselli M , Dobrindt U , Hacker J , Tettelin H , Tallon LJ , Sullivan S , Wieler LH , Ewers C , Pickard D , Dougan G , Fontana MR , Rappuoli R , Pizza M , Serino L
Ref : Proc Natl Acad Sci U S A , 107 :9072 , 2010
Abstract : Extraintestinal pathogenic Escherichia coli (ExPEC) are a common cause of disease in both mammals and birds. A vaccine to prevent such infections would be desirable given the increasing antibiotic resistance of these bacteria. We have determined the genome sequence of ExPEC IHE3034 (ST95) isolated from a case of neonatal meningitis and compared this to available genome sequences of other ExPEC strains and a few nonpathogenic E. coli. We found 19 genomic islands present in the genome of IHE3034, which are absent in the nonpathogenic E. coli isolates. By using subtractive reverse vaccinology we identified 230 antigens present in ExPEC but absent (or present with low similarity) in nonpathogenic strains. Nine antigens were protective in a mouse challenge model. Some of them were also present in other pathogenic non-ExPEC strains, suggesting that a broadly protective E. coli vaccine may be possible. The gene encoding the most protective antigen was detected in most of the E. coli isolates, highly conserved in sequence and found to be exported by a type II secretion system which seems to be nonfunctional in nonpathogenic strains.
ESTHER : Moriel_2010_Proc.Natl.Acad.Sci.U.S.A_107_9072
PubMedSearch : Moriel_2010_Proc.Natl.Acad.Sci.U.S.A_107_9072
PubMedID: 20439758
Gene_locus related to this paper: ecoli-Aes , ecoli-rutD , ecoli-bioh , ecoli-C0410 , ecoli-C2429 , ecoli-C2451 , ecoli-C4836 , ecoli-dlhh , ecoli-entf , ecoli-fes , ecoli-IROD , ecoli-IROE , ecoli-pldb , ecoli-ptrb , ecoli-yafa , ecoli-yaim , ecoli-ybff , ecoli-ycfp , ecoli-ycjy , ecoli-yeiG , ecoli-YFBB , ecoli-yghX , ecoli-yhet , ecoli-yjfp , ecoli-YNBC , ecoli-ypfh , ecoli-yqia , ecoli-Z1930 , ecoli-YfhR , ecout-q1r7l6 , yerpe-YBTT

Title : Genome analysis of multiple pathogenic isolates of Streptococcus agalactiae: implications for the microbial pan-genome - Tettelin_2005_Proc.Natl.Acad.Sci.U.S.A_102_13950
Author(s) : Tettelin H , Masignani V , Cieslewicz MJ , Donati C , Medini D , Ward NL , Angiuoli SV , Crabtree J , Jones AL , Durkin AS , DeBoy RT , Davidsen TM , Mora M , Scarselli M , Margarit y Ros I , Peterson JD , Hauser CR , Sundaram JP , Nelson WC , Madupu R , Brinkac LM , Dodson RJ , Rosovitz MJ , Sullivan SA , Daugherty SC , Haft DH , Selengut J , Gwinn ML , Zhou L , Zafar N , Khouri H , Radune D , Dimitrov G , Watkins K , O'Connor KJ , Smith S , Utterback TR , White O , Rubens CE , Grandi G , Madoff LC , Kasper DL , Telford JL , Wessels MR , Rappuoli R , Fraser CM
Ref : Proc Natl Acad Sci U S A , 102 :13950 , 2005
Abstract : The development of efficient and inexpensive genome sequencing methods has revolutionized the study of human bacterial pathogens and improved vaccine design. Unfortunately, the sequence of a single genome does not reflect how genetic variability drives pathogenesis within a bacterial species and also limits genome-wide screens for vaccine candidates or for antimicrobial targets. We have generated the genomic sequence of six strains representing the five major disease-causing serotypes of Streptococcus agalactiae, the main cause of neonatal infection in humans. Analysis of these genomes and those available in databases showed that the S. agalactiae species can be described by a pan-genome consisting of a core genome shared by all isolates, accounting for approximately 80% of any single genome, plus a dispensable genome consisting of partially shared and strain-specific genes. Mathematical extrapolation of the data suggests that the gene reservoir available for inclusion in the S. agalactiae pan-genome is vast and that unique genes will continue to be identified even after sequencing hundreds of genomes.
ESTHER : Tettelin_2005_Proc.Natl.Acad.Sci.U.S.A_102_13950
PubMedSearch : Tettelin_2005_Proc.Natl.Acad.Sci.U.S.A_102_13950
PubMedID: 16172379
Gene_locus related to this paper: strag-ESTA , strag-GBS0040 , strag-GBS0107 , strag-GBS1828 , strag-pepx , strag-q3dah6 , strag-SAG0246 , strag-SAG0383 , strag-SAG0679 , strag-SAG0680 , strag-SAG0785 , strag-SAG0912 , strag-SAG1562 , strag-SAG2132

Title : Complete genome sequence and comparative genomic analysis of an emerging human pathogen, serotype V Streptococcus agalactiae - Tettelin_2002_Proc.Natl.Acad.Sci.U.S.A_99_12391
Author(s) : Tettelin H , Masignani V , Cieslewicz MJ , Eisen JA , Peterson S , Wessels MR , Paulsen IT , Nelson KE , Margarit I , Read TD , Madoff LC , Wolf AM , Beanan MJ , Brinkac LM , Daugherty SC , DeBoy RT , Durkin AS , Kolonay JF , Madupu R , Lewis MR , Radune D , Fedorova NB , Scanlan D , Khouri H , Mulligan S , Carty HA , Cline RT , Van Aken SE , Gill J , Scarselli M , Mora M , Iacobini ET , Brettoni C , Galli G , Mariani M , Vegni F , Maione D , Rinaudo D , Rappuoli R , Telford JL , Kasper DL , Grandi G , Fraser CM
Ref : Proc Natl Acad Sci U S A , 99 :12391 , 2002
Abstract : The 2,160,267 bp genome sequence of Streptococcus agalactiae, the leading cause of bacterial sepsis, pneumonia, and meningitis in neonates in the U.S. and Europe, is predicted to encode 2,175 genes. Genome comparisons among S. agalactiae, Streptococcus pneumoniae, Streptococcus pyogenes, and the other completely sequenced genomes identified genes specific to the streptococci and to S. agalactiae. These in silico analyses, combined with comparative genome hybridization experiments between the sequenced serotype V strain 2603 V/R and 19 S. agalactiae strains from several serotypes using whole-genome microarrays, revealed the genetic heterogeneity among S. agalactiae strains, even of the same serotype, and provided insights into the evolution of virulence mechanisms.
ESTHER : Tettelin_2002_Proc.Natl.Acad.Sci.U.S.A_99_12391
PubMedSearch : Tettelin_2002_Proc.Natl.Acad.Sci.U.S.A_99_12391
PubMedID: 12200547
Gene_locus related to this paper: strag-ESTA , strag-GBS0040 , strag-GBS1828 , strag-pepx , strag-SAG0108 , strag-SAG0246 , strag-SAG0383 , strag-SAG0521 , strag-SAG0679 , strag-SAG0680 , strag-SAG0681 , strag-SAG0785 , strag-SAG0912 , strag-SAG1040 , strag-SAG1562 , strag-SAG2132

Title : Complete genome sequence of Neisseria meningitidis serogroup B strain MC58 - Tettelin_2000_Science_287_1809
Author(s) : Tettelin H , Saunders NJ , Heidelberg J , Jeffries AC , Nelson KE , Eisen JA , Ketchum KA , Hood DW , Peden JF , Dodson RJ , Nelson WC , Gwinn ML , Deboy R , Peterson JD , Hickey EK , Haft DH , Salzberg SL , White O , Fleischmann RD , Dougherty BA , Mason T , Ciecko A , Parksey DS , Blair E , Cittone H , Clark EB , Cotton MD , Utterback TR , Khouri H , Qin H , Vamathevan J , Gill J , Scarlato V , Masignani V , Pizza M , Grandi G , Sun L , Smith HO , Fraser CM , Moxon ER , Rappuoli R , Venter JC
Ref : Science , 287 :1809 , 2000
Abstract : The 2,272,351-base pair genome of Neisseria meningitidis strain MC58 (serogroup B), a causative agent of meningitis and septicemia, contains 2158 predicted coding regions, 1158 (53.7%) of which were assigned a biological role. Three major islands of horizontal DNA transfer were identified; two of these contain genes encoding proteins involved in pathogenicity, and the third island contains coding sequences only for hypothetical proteins. Insights into the commensal and virulence behavior of N. meningitidis can be gleaned from the genome, in which sequences for structural proteins of the pilus are clustered and several coding regions unique to serogroup B capsular polysaccharide synthesis can be identified. Finally, N. meningitidis contains more genes that undergo phase variation than any pathogen studied to date, a mechanism that controls their expression and contributes to the evasion of the host immune system.
ESTHER : Tettelin_2000_Science_287_1809
PubMedSearch : Tettelin_2000_Science_287_1809
PubMedID: 10710307
Gene_locus related to this paper: neigo-pip , neima-metx , neimb-q9k0t9 , neime-ESD , neime-NMA2216 , neime-NMB0276 , neime-NMB0868 , neime-NMB1828 , neime-NMB1877

Title : Action site and cellular effects of cytotoxin VacA produced by Helicobacter pylori - Papini_1998_Folia.Microbiol.(Praha)_43_279
Author(s) : Papini E , Satin B , de Bernard M , Molinari M , Arico B , Galli C , Telford JR , Rappuoli R , Montecucco C
Ref : Folia Microbiol (Praha) , 43 :279 , 1998
Abstract : Cells treated with the VacA toxin from Helicobacter pylori develop large membrane-bound vacuoles that originate from the late endocytotic pathway. Using different experimental approaches, we showed that VacA can induce vacuoles by acting within the cell cytosol. Moreover, separation of VacA-induced vacuoles at an early stage of formation, using a novel isopycnic density ultracentrifugation method, allowed us to show that they resemble a hybrid compartment, containing elements of both late endosomes and lysosomes. Functional defects of the endocytotic pathway were also studied before any macroscopic vacuolation is evident. VacA-intoxicated cells degrade extracellular ligands with reduced efficiency and, at the same time, they secrete acidic hydrolases into the extracellular medium, normally sorted to lysosomes. All these findings indicate that VacA translocates into the cell cytosol where it causes a lesion of the late endosomal/lysosomal compartments, such that protein trafficking across this crucial cross-point is altered with consequences that may be relevant to the pathogenesis of gastroduodenal ulcers.
ESTHER : Papini_1998_Folia.Microbiol.(Praha)_43_279
PubMedSearch : Papini_1998_Folia.Microbiol.(Praha)_43_279
PubMedID: 9717255

Title : Selective increase of the permeability of polarized epithelial cell monolayers by Helicobacter pylori vacuolating toxin - Papini_1998_J.Clin.Invest_102_813
Author(s) : Papini E , Satin B , Norais N , de Bernard M , Telford JL , Rappuoli R , Montecucco C
Ref : J Clinical Investigation , 102 :813 , 1998
Abstract : The effects of the vacuolating toxin (VacA) released by pathogenic strains of Helicobacter pylori on several polarized epithelial monolayers were investigated. Trans-epithelial electric resistance (TER) of monolayers formed by canine kidney MDCK I, human gut T84, and murine mammary gland epH4, was lowered by acid-activated VacA. Independent of the cell type and of the starting TER value, VacA reduced it to a minimal value of 1,000-1,300 Omega x cm2. TER decrease was paralleled by a three- to fourfold increase of [14C]-mannitol (molecular weight 182.2) and a twofold increase of [14C]-sucrose (molecular weight 342.3) transmonolayer flux. On the contrary, transmembrane flux of the proinflammatory model tripeptide [14C]-N-formyl-Met-Leu-Phe (molecular weight 437.6), of [3H]-inuline (molecular weight 5,000) and of HRP (molecular weight 47,000) did not change. These data indicate that VacA increases paracellular epithelial permeability to molecules with molecular weight < 350-440. Accordingly, the epithelial permeability of Fe3+ and Ni2+ ions, essential for H. pylori survival in vivo, was also increased by VacA. High-resolution immunofluorescence and SDS-PAGE analysis failed to reveal alterations of junctional proteins ZO-1, occludin, cingulin, and E-cadherin. It is proposed that induction by VacA of a selective permeabilization of the epithelial paracellular route to low molecular weight molecules and ions may serve to supply nutrients, which favor H. pylori growth in vivo.
ESTHER : Papini_1998_J.Clin.Invest_102_813
PubMedSearch : Papini_1998_J.Clin.Invest_102_813
PubMedID: 9710450

Title : Identification of the Helicobacter pylori VacA toxin domain active in the cell cytosol - de Bernard_1998_Infect.Immun_66_6014
Author(s) : de Bernard M , Burroni D , Papini E , Rappuoli R , Telford J , Montecucco C
Ref : Infect Immun , 66 :6014 , 1998
Abstract : Cells exposed to Helicobacter pylori toxin VacA develop large vacuoles which originate from massive swelling of membranous compartments at late stages of the endocytic pathway. When expressed in the cytosol, VacA induces vacuolization as it does when added from outside. This and other evidence indicate that VacA is a toxin capable of entering the cell cytosol, where it displays its activity. In this study, we have used cytosolic expression to identify the portion of the toxin molecule responsible for the vacuolating activity. VacA mutants with deletions at the C and N termini were generated, and their activity was analyzed upon expression in HeLa cells. We found that the vacuolating activity of VacA resides in the amino-terminal region, the whole of which is required for its intracellular activity.
ESTHER : de Bernard_1998_Infect.Immun_66_6014
PubMedSearch : de Bernard_1998_Infect.Immun_66_6014
PubMedID: 9826387

Title : Cell vacuolization induced by Helicobacter pylori VacA toxin: cell line sensitivity and quantitative estimation - de Bernard_1998_Toxicol.Lett_99_109
Author(s) : de Bernard M , Moschioni M , Papini E , Telford J , Rappuoli R , Montecucco C
Ref : Toxicol Lett , 99 :109 , 1998
Abstract : A major virulence factor released by Helicobacter pylori is a protein toxin, termed VacA, which induces the formation of large intracellular vacuoles characterised by a lumenal acidic pH. Consequently they accumulate membrane permeable weak bases. The increase in neutral red uptake by intoxicated cells is the only known in vitro procedure to estimate quantitatively the activity of VacA. With the goal to standardize this assay, several parameters were evaluated: cell type, serum concentration, cell density and toxin concentration. Among the different cell types tested, HeLa cells were found to be the most sensitive to VacA. Results show that several factors contribute to VacA activity and that optimal vacuolation is achieved at non-confluent cell density, in the presence of low serum concentrations.
ESTHER : de Bernard_1998_Toxicol.Lett_99_109
PubMedSearch : de Bernard_1998_Toxicol.Lett_99_109
PubMedID: 9817082

Title : TPA and butyrate increase cell sensitivity to the vacuolating toxin of Helicobacter pylori - de Bernard_1998_FEBS.Lett_436_218
Author(s) : de Bernard M , Moschioni M , Papini E , Telford JL , Rappuoli R , Montecucco C
Ref : FEBS Letters , 436 :218 , 1998
Abstract : The Helicobacter pylori toxin VacA induces large membrane-bound vacuolar compartments of late endosomal/lysosomal origin. Pre-treatment of cells with TPA and butyrate enhances the toxin induced vacuolisation up to 20 times, depending on the cell line, whereas other differentiating factors such as DMSO, EGF, valeric and retinoic acid have no effect. The higher toxin sensitivity induced by TPA does not result from an increased surface binding or endocytosis. The effect of TPA is apparent after several hours from addition and is inhibited by a PKC specific inhibitor. These data suggest that expression of cellular proteins, other than the toxin receptor(s), influences the vacuolating activity of VacA and may contribute to the sensitivity of different cell lines. The present findings define the most sensitive in vitro assay of the activity of VacA.
ESTHER : de Bernard_1998_FEBS.Lett_436_218
PubMedSearch : de Bernard_1998_FEBS.Lett_436_218
PubMedID: 9781682

Title : The acid activation of Helicobacter pylori toxin VacA: structural and membrane binding studies - Molinari_1998_Biochem.Biophys.Res.Commun_248_334
Author(s) : Molinari M , Galli C , de Bernard M , Norais N , Ruysschaert JM , Rappuoli R , Montecucco C
Ref : Biochemical & Biophysical Research Communications , 248 :334 , 1998
Abstract : The cell vacuolating activity of the protein toxin VacA, released by Helicobacter pylori, is strongly increased in vitro by exposure to acidic pH followed by neutralization. This short acid exposure does not increase significantly the binding of VacA to cell or to lipid membranes. However, membrane photolabeling with photoactivatable radioactive phospholipids and ANS binding studies show that VacA transiently exposed to pH equal or lower than 5 changes conformation and exposes on its surface hydrophobic segments. Both the 32 and the 58 kDa subunits of the toxin insert in the lipid bilayer and interact with the fatty acid chains of phospholipids. Membrane binding and penetration are enhanced by incubating target cells or liposomes with the toxin at mild acidic pH values, similar to those present around H. pylori on the stomach mucosa. These findings are discussed with respect to the critical step in cell intoxication consisting in the translocation of the active toxin domain into the cell cytosol. We suggest that membrane translocation takes place at the plasma membrane level.
ESTHER : Molinari_1998_Biochem.Biophys.Res.Commun_248_334
PubMedSearch : Molinari_1998_Biochem.Biophys.Res.Commun_248_334
PubMedID: 9675136

Title : Selective inhibition of Ii-dependent antigen presentation by Helicobacter pylori toxin VacA - Molinari_1998_J.Exp.Med_187_135
Author(s) : Molinari M , Salio M , Galli C , Norais N , Rappuoli R , Lanzavecchia A , Montecucco C
Ref : J Exp Med , 187 :135 , 1998
Abstract : A major virulence factor in the stomach chronic infection by Helicobacter pylori is a protein toxin (VacA), which alters cell membrane trafficking of late endosomal/prelysosomal compartments. Its role in the chronic infection established by H. pylori is unknown. To test the possibility that VacA alters antigen processing taking place in prelysosomal compartments, we have used the well-established model of antigen processing and presentation consisting of tetanus toxoid-specific human (CD4(+)) T cells stimulated by autologous antigen-pulsed Epstein-Barr virus-transformed B cells. We found that VacA interferes with proteolytic processing of tetanus toxin and toxoid and specifically inhibits the Ii-dependent pathway of antigen presentation mediated by newly synthesized major histocompatibility complex (MHC) class II, while leaving unaffected the presentation pathway dependent on recycling MHC class II. The results presented here suggest that VacA may contribute to the persistence of H. pylori by interfering with protective immunity and that this toxin is a new useful tool in the study of the different pathways of antigen presentation.
ESTHER : Molinari_1998_J.Exp.Med_187_135
PubMedSearch : Molinari_1998_J.Exp.Med_187_135
PubMedID: 9419220

Title : Helicobacter pylori toxin VacA induces vacuole formation by acting in the cell cytosol - de Bernard_1997_Mol.Microbiol_26_665
Author(s) : de Bernard M , Arico B , Papini E , Rizzuto R , Grandi G , Rappuoli R , Montecucco C
Ref : Molecular Microbiology , 26 :665 , 1997
Abstract : Cells exposed to Helicobacter pylori toxin VacA develop large vacuoles that originate from massive swelling of membranous compartments of late stages of the endocytic pathway. To determine if the toxin is active from the cell cytosol, cells were either microinjected with toxin or transfected with plasmids encoding VacA. Both procedures cause formation of intracellular vacuoles. Cytosolic localization of the toxin was assessed by indirect immunofluorescence with specific antibodies and by expression of an active green fluorescence protein (GFP)-VacA chimera. Vacuoles induced by internally produced VacA are morphologically and functionally identical to those induced by externally added toxin. It is concluded that VacA is a toxin acting intracellularly by altering a cytosol-exposed target, possibly involved in the control of membrane trafficking.
ESTHER : de Bernard_1997_Mol.Microbiol_26_665
PubMedSearch : de Bernard_1997_Mol.Microbiol_26_665
PubMedID: 9427397

Title : Diphtheria toxin and its mutant crm 197 differ in their interaction with lipids - Papini_1987_FEBS.Lett_215_73
Author(s) : Papini E , Colonna R , Schiavo G , Cusinato F , Tomasi M , Rappuoli R , Montecucco C
Ref : FEBS Letters , 215 :73 , 1987
Abstract : The interaction of diphtheria toxin and its enzymatically deficient mutants crm 176 and crm 197 with liposomes has been studied by turbidity measurement and hydrophobic photolabelling with photoactivatable phosphatidylcholines. Diphtheria toxin and crm 176 at neutral pH bind to the surface of lipid bilayers while crm 197 also appears to interact with the fatty acid chains of phospholipids. All proteins undergo a change in conformation over the same range of acidic pH and become able to insert in the lipid bilayer. The tighter lipid interaction of crm 197 may account for its higher cell association constant. The possibility is discussed that the binding of diphtheria toxin to cells is mediated by both a protein receptor and an interaction with the head group of phospholipids.
ESTHER : Papini_1987_FEBS.Lett_215_73
PubMedSearch : Papini_1987_FEBS.Lett_215_73
PubMedID: 3569541