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1.
Infect Immun ; 88(2)2020 01 22.
Artigo em Inglês | MEDLINE | ID: mdl-31712269

RESUMO

Helicobacter pylori colonizes the stomach in about half of the world's population. H. pylori strains containing the cag pathogenicity island (cag PAI) are associated with a higher risk of gastric adenocarcinoma or peptic ulcer disease than cag PAI-negative strains. The cag PAI encodes a type IV secretion system (T4SS) that mediates delivery of the CagA effector protein as well as nonprotein bacterial constituents into gastric epithelial cells. H. pylori-induced nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation and interleukin-8 (IL-8) secretion are attributed to T4SS-dependent delivery of lipopolysaccharide metabolites and peptidoglycan into host cells, and Toll-like receptor 9 (TLR9) activation is attributed to delivery of bacterial DNA. In this study, we analyzed the bacterial energetic requirements associated with these cellular alterations. Mutant strains lacking Cagα, Cagß, or CagE (putative ATPases corresponding to VirB11, VirD4, and VirB4 in prototypical T4SSs) were capable of T4SS core complex assembly but defective in CagA translocation into host cells. Thus, the three Cag ATPases are not functionally redundant. Cagα and CagE were required for H. pylori-induced NF-κB activation, IL-8 secretion, and TLR9 activation, but Cagß was dispensable for these responses. We identified putative ATP-binding motifs (Walker-A and Walker-B) in each of the ATPases and generated mutant strains in which these motifs were altered. Each of the Walker box mutant strains exhibited properties identical to those of the corresponding deletion mutant strains. These data suggest that Cag T4SS-dependent delivery of nonprotein bacterial constituents into host cells occurs through mechanisms different from those used for recruitment and delivery of CagA into host cells.


Assuntos
Antígenos de Bactérias/genética , Antígenos de Bactérias/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Células Epiteliais/microbiologia , Helicobacter pylori/genética , Helicobacter pylori/metabolismo , Sistemas de Secreção Tipo IV/genética , Sistemas de Secreção Tipo IV/metabolismo , Transporte Biológico , DNA Bacteriano/metabolismo , Humanos , Interleucina-8/metabolismo , Lipopolissacarídeos/metabolismo , NF-kappa B/metabolismo , Peptidoglicano/metabolismo , Receptor Toll-Like 9/metabolismo , Fatores de Virulência/genética , Fatores de Virulência/metabolismo
2.
Elife ; 82019 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-31210639

RESUMO

Bacterial type IV secretion systems (T4SSs) are molecular machines that can mediate interbacterial DNA transfer through conjugation and delivery of effector molecules into host cells. The Helicobacter pylori Cag T4SS translocates CagA, a bacterial oncoprotein, into gastric cells, contributing to gastric cancer pathogenesis. We report the structure of a membrane-spanning Cag T4SS assembly, which we describe as three sub-assemblies: a 14-fold symmetric outer membrane core complex (OMCC), 17-fold symmetric periplasmic ring complex (PRC), and central stalk. Features that differ markedly from those of prototypical T4SSs include an expanded OMCC and unexpected symmetry mismatch between the OMCC and PRC. This structure is one of the largest bacterial secretion system assemblies ever reported and illustrates the remarkable structural diversity that exists among bacterial T4SSs.


Assuntos
Helicobacter pylori/metabolismo , Sistemas de Secreção Tipo IV/química , Proteínas da Membrana Bacteriana Externa/química , Proteínas da Membrana Bacteriana Externa/ultraestrutura , Modelos Moleculares , Sistemas de Secreção Tipo IV/ultraestrutura
3.
mBio ; 10(3)2019 05 14.
Artigo em Inglês | MEDLINE | ID: mdl-31088930

RESUMO

Helicobacter pylori colonizes about half of humans worldwide, and its presence in the gastric mucosa is associated with an increased risk of gastric adenocarcinoma, gastric lymphoma, and peptic ulcer disease. H. pylori strains carrying the cag pathogenicity island (cagPAI) are associated with increased risk of disease progression. The cagPAI encodes the Cag type IV secretion system (CagT4SS), which delivers the CagA oncoprotein and other effector molecules into human gastric epithelial cells. We visualized structures of native and mutant CagT4SS machines on the H. pylori cell envelope by cryoelectron tomography. Individual H. pylori cells contain multiple CagT4SS nanomachines, each composed of a wheel-shaped outer membrane complex (OMC) with 14-fold symmetry and an inner membrane complex (IMC) with 6-fold symmetry. CagX, CagY, and CagM are required for assembly of the OMC, whereas strains lacking Cag3 and CagT produce outer membrane complexes lacking peripheral components. The IMC, which has never been visualized in detail, is configured as six tiers in cross-section view and three concentric rings surrounding a central channel in end-on view. The IMC contains three T4SS ATPases: (i) VirB4-like CagE, arranged as a hexamer of dimers at the channel entrance; (ii) a hexamer of VirB11-like Cagα, docked at the base of the CagE hexamer; and (iii) VirD4-like Cagß and other unspecified Cag subunits, associated with the stacked CagE/Cagα complex and forming the outermost rings. The CagT4SS and recently solved Legionella pneumophila Dot/Icm system comprise new structural prototypes for the T4SS superfamily.IMPORTANCE Bacterial type IV secretion systems (T4SSs) have been phylogenetically grouped into two subfamilies. The T4ASSs, represented by the Agrobacterium tumefaciens VirB/VirD4T4SS, include "minimized" machines assembled from 12 VirB- and VirD4-like subunits and compositionally larger systems such as the Helicobacter pylori CagT4SS T4BSSs encompass systems closely related in subunit composition to the Legionella pneumophila Dot/IcmT4SS Here, we present structures of native and mutant H. pylori Cag machines determined by in situ cryoelectron tomography. We identify distinct outer and inner membrane complexes and, for the first time, visualize structural contributions of all three "signature" ATPases of T4SSs at the cytoplasmic entrance of the translocation channel. Despite their evolutionary divergence, the CagT4SS aligns structurally much more closely to the Dot/IcmT4SS than an available VirB/VirD4 subcomplex. Our findings highlight the diversity of T4SSs and suggest a structural classification scheme in which T4SSs are grouped as minimized VirB/VirD4-like or larger Cag-like and Dot/Icm-like systems.


Assuntos
Proteínas de Bactérias/genética , Helicobacter pylori/genética , Sistemas de Secreção Tipo IV/genética , Sistemas de Secreção Tipo IV/ultraestrutura , Antígenos de Bactérias/genética , Microscopia Crioeletrônica , Ilhas Genômicas , Humanos
4.
J Proteomics ; 202: 103374, 2019 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-31063819

RESUMO

Helicobacter pylori infection and a high salt diet are each risk factors for gastric cancer. In this study, we tested the hypothesis that environmental salt concentration influences the composition of the H. pylori exoproteome. H. pylori was cultured in media containing varying concentrations of sodium chloride, and aliquots were fractionated and analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). We identified proteins that were selectively released into the extracellular space, and we identified selectively released proteins that were differentially abundant in culture supernatants, depending on the environmental salt concentration. We also used RNA-seq analysis to identify genes that were differentially expressed in response to environmental salt concentration. The salt-responsive proteins identified by proteomic analysis and salt-responsive genes identified by RNA-seq analysis were mostly non-concordant, but the secreted toxin VacA was salt-responsive in both analyses. Western blot analysis confirmed that VacA levels in the culture supernatant were increased in response to high salt conditions, and quantitative RT-qPCR experiments confirmed that vacA transcription was upregulated in response to high salt conditions. These results indicate that environmental salt concentration influences the composition of the H. pylori exoproteome, which could contribute to the increased risk of gastric cancer associated with a high salt diet. SIGNIFICANCE: Helicobacter pylori-induced alterations in the gastric mucosa have been attributed, at least in part, to the actions of secreted H. pylori proteins. In this study, we show that H. pylori growth in high salt concentrations leads to increased levels of a secreted VacA toxin. Salt-induced alterations in the composition of the H. pylori exoproteome is relevant to the increased risk of gastric cancer associated with consumption of a high salt diet.

5.
J Mol Biol ; 431(10): 1956-1965, 2019 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-30954575

RESUMO

Helicobacter pylori colonizes the human stomach and contributes to the development of gastric cancer and peptic ulcer disease. H. pylori secretes a pore-forming toxin called vacuolating cytotoxin A (VacA), which contains two domains (p33 and p55) and assembles into oligomeric structures. Using single-particle cryo-electron microscopy, we have determined low-resolution structures of a VacA dodecamer and heptamer, as well as a 3.8-Å structure of the VacA hexamer. These analyses show that VacA p88 consists predominantly of a right-handed beta-helix that extends from the p55 domain into the p33 domain. We map the regions of p33 and p55 involved in hexamer assembly, model how interactions between protomers support heptamer formation, and identify surfaces of VacA that likely contact membrane. This work provides structural insights into the process of VacA oligomerization and identifies regions of VacA protomers that are predicted to contact the host cell surface during channel formation.

6.
mBio ; 10(2)2019 03 19.
Artigo em Inglês | MEDLINE | ID: mdl-30890606

RESUMO

The gastric bacterium Helicobacter pylori causes a persistent infection that is directly responsible for gastric ulcers and gastric cancer in some patients and protective against allergic and other immunological disorders in others. The two outcomes of the Helicobacter-host interaction can be modeled in mice that are infected as immunocompetent adults and as neonates, respectively. Here, we have investigated the contribution of the Helicobacter immunomodulator VacA to H. pylori-specific local and systemic immune responses in both models. We found that neonatally infected mice are colonized at higher levels than mice infected as adults and fail to generate effector T-cell responses to the bacteria; rather, T-cell responses in neonatally infected mice are skewed toward Foxp3-positive (Foxp3+) regulatory T cells that are neuropilin negative and express RORγt. We found these peripherally induced regulatory T cells (pTregs) to be enriched, in a VacA-dependent manner, not only in the gastric mucosa but also in the lungs of infected mice. Pulmonary pTreg accumulation was observed in mice that have been infected neonatally with wild-type H. pylori but not in mice that have been infected as adults or mice infected with a VacA null mutant. Finally, we traced VacA to gastric lamina propria myeloid cells and show that it suppressed interleukin-23 (IL-23) expression by dendritic cells and induced IL-10 and TGF-ß expression in macrophages. Taken together, the results are consistent with the idea that H. pylori creates a tolerogenic environment through its immunomodulator VacA, which skews T-cell responses toward Tregs, favors H. pylori persistence, and affects immunity at distant sites.IMPORTANCE Helicobacter pylori has coexisted with humans for at least 60.000 years and has evolved persistence strategies that allow it to evade host immunity and colonize its host for life. The VacA protein is expressed by all H. pylori strains and is required for high-level persistent infection in experimental mouse models. Here, we show that VacA targets myeloid cells in the gastric mucosa to create a tolerogenic environment that facilitates regulatory T-cell differentiation, while suppressing effector T-cell priming and functionality. Tregs that are induced in the periphery during H. pylori infection can be found not only in the stomach but also in the lungs of infected mice, where they are likely to affect immune responses to allergens.


Assuntos
Proteínas de Bactérias/metabolismo , Diferenciação Celular , Mucosa Gástrica/patologia , Helicobacter pylori/imunologia , Membrana Mucosa/patologia , Células Mieloides/efeitos dos fármacos , Linfócitos T Reguladores/fisiologia , Animais , Células Dendríticas/imunologia , Modelos Animais de Doenças , Infecções por Helicobacter/patologia , Infecções por Helicobacter/fisiopatologia , Helicobacter pylori/metabolismo , Evasão da Resposta Imune , Interleucina-10/metabolismo , Interleucina-23/metabolismo , Pulmão/patologia , Macrófagos/imunologia , Camundongos , Fator de Crescimento Transformador beta/metabolismo
7.
Infect Immun ; 87(4)2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30692181

RESUMO

Helicobacter pylori VacA is a secreted pore-forming toxin that induces cell vacuolation in vitro and contributes to the pathogenesis of gastric cancer and peptic ulcer disease. We observed that purified VacA has relatively little effect on the viability of AGS gastric epithelial cells, but the presence of exogenous weak bases such as ammonium chloride (NH4Cl) enhances the susceptibility of these cells to VacA-induced vacuolation and cell death. Therefore, we tested the hypothesis that NH4Cl augments VacA toxicity by altering the intracellular trafficking of VacA or inhibiting intracellular VacA degradation. We observed VacA colocalization with LAMP1- and LC3-positive vesicles in both the presence and absence of NH4Cl, indicating that NH4Cl does not alter VacA trafficking to lysosomes or autophagosomes. Conversely, we found that supplemental NH4Cl significantly increases the intracellular stability of VacA. By conducting experiments using chemical inhibitors, stable ATG5 knockdown cell lines, and ATG16L1 knockout cells (generated using CRISPR/Cas9), we show that VacA degradation is independent of autophagy and proteasome activity but dependent on lysosomal acidification. We conclude that weak bases like ammonia, potentially generated during H. pylori infection by urease and other enzymes, enhance VacA toxicity by inhibiting toxin degradation.


Assuntos
Proteínas de Bactérias/metabolismo , Células Epiteliais/citologia , Mucosa Gástrica/citologia , Infecções por Helicobacter/microbiologia , Helicobacter pylori/metabolismo , Autofagia/efeitos dos fármacos , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/toxicidade , Linhagem Celular , Sobrevivência Celular , Células Epiteliais/efeitos dos fármacos , Células Epiteliais/microbiologia , Mucosa Gástrica/efeitos dos fármacos , Mucosa Gástrica/microbiologia , Helicobacter pylori/química , Helicobacter pylori/genética , Humanos , Concentração de Íons de Hidrogênio , Muramidase/química , Muramidase/metabolismo , Estabilidade Proteica , Transporte Proteico , Proteólise
8.
J Allergy Clin Immunol ; 143(4): 1496-1512.e11, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30240703

RESUMO

BACKGROUND: Transmaternal exposure to tobacco, microbes, nutrients, and other environmental factors shapes the fetal immune system through epigenetic processes. The gastric microbe Helicobacter pylori represents an ancestral constituent of the human microbiota that causes gastric disorders on the one hand and is inversely associated with allergies and chronic inflammatory conditions on the other. OBJECTIVE: Here we investigate the consequences of transmaternal exposure to H pylori in utero and/or during lactation for susceptibility to viral and bacterial infection, predisposition to allergic airway inflammation, and development of immune cell populations in the lungs and lymphoid organs. METHODS: We use experimental models of house dust mite- or ovalbumin-induced airway inflammation and influenza A virus or Citrobacter rodentium infection along with metagenomics analyses, multicolor flow cytometry, and bisulfite pyrosequencing, to study the effects of H pylori on allergy severity and immunologic and microbiome correlates thereof. RESULTS: Perinatal exposure to H pylori extract or its immunomodulator vacuolating cytotoxin confers robust protective effects against allergic airway inflammation not only in first- but also second-generation offspring but does not increase susceptibility to viral or bacterial infection. Immune correlates of allergy protection include skewing of regulatory over effector T cells, expansion of regulatory T-cell subsets expressing CXCR3 or retinoic acid-related orphan receptor γt, and demethylation of the forkhead box P3 (FOXP3) locus. The composition and diversity of the gastrointestinal microbiota is measurably affected by perinatal H pylori exposure. CONCLUSION: We conclude that exposure to H pylori has consequences not only for the carrier but also for subsequent generations that can be exploited for interventional purposes.

9.
Gastroenterology ; 156(1): 175-186.e2, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30296434

RESUMO

BACKGROUND & AIMS: Previous studies reported an association of the bacteria Helicobacter pylori, the primary cause of gastric cancer, and risk of colorectal cancer (CRC). However, these findings have been inconsistent, appear to vary with population characteristics, and may be specific for virulence factor VacA. To more thoroughly evaluate the potential association of H pylori antibodies with CRC risk, we assembled a large consortium of cohorts representing diverse populations in the United States. METHODS: We used H pylori multiplex serologic assays to analyze serum samples from 4063 incident cases of CRC, collected before diagnosis, and 4063 matched individuals without CRC (controls) from 10 prospective cohorts for antibody responses to 13 H pylori proteins, including virulence factors VacA and CagA. The association of seropositivity to H pylori proteins, as well as protein-specific antibody level, with odds of CRC was determined by conditional logistic regression. RESULTS: Overall, 40% of controls and 41% of cases were H pylori-seropositive (odds ratio [OR], 1.09; 95% CI, 0.99-1.20). H pylori VacA-specific seropositivity was associated with an 11% increased odds of CRC (OR, 1.11; 95% CI, 1.01-1.22), and this association was particularly strong among African Americans (OR, 1.45; 95% CI, 1.08-1.95). Additionally, odds of CRC increased with level of VacA antibody in the overall cohort (P = .008) and specifically among African Americans (P = .007). CONCLUSIONS: In an analysis of a large consortium of cohorts representing diverse populations, we found serologic responses to H pylori VacA to associate with increased risk of CRC risk, particularly for African Americans. Future studies should seek to understand whether this marker is related to virulent H pylori strains carried in these populations.


Assuntos
Anticorpos Antibacterianos/imunologia , Proteínas de Bactérias/imunologia , Neoplasias Colorretais/microbiologia , Infecções por Helicobacter/microbiologia , Helicobacter pylori/imunologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Anticorpos Antibacterianos/sangue , Biomarcadores/sangue , Estudos de Casos e Controles , Neoplasias Colorretais/sangue , Neoplasias Colorretais/epidemiologia , Feminino , Infecções por Helicobacter/sangue , Infecções por Helicobacter/epidemiologia , Helicobacter pylori/patogenicidade , Interações Hospedeiro-Patógeno , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Fatores de Risco , Estudos Soroepidemiológicos , Estados Unidos/epidemiologia , Virulência , Adulto Jovem
10.
Mol Cell Proteomics ; 18(2): 352-371, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30455363

RESUMO

Helicobacter pylori is the strongest risk factor for gastric cancer. Initial interactions between H. pylori and its host originate at the microbial-gastric epithelial cell interface, and contact between H. pylori and gastric epithelium activates signaling pathways that drive oncogenesis. One microbial constituent that increases gastric cancer risk is the cag pathogenicity island, which encodes a type IV secretion system that translocates the effector protein, CagA, into host cells. We previously demonstrated that infection of Mongolian gerbils with a carcinogenic cag + H. pylori strain, 7.13, recapitulates many features of H. pylori-induced gastric cancer in humans. Therefore, we sought to define gastric proteomic changes induced by H. pylori that are critical for initiation of the gastric carcinogenic cascade. Gastric cell scrapings were harvested from H. pylori-infected and uninfected gerbils for quantitative proteomic analyses using isobaric tags for relative and absolute quantitation (iTRAQ). Quantitative proteomic analysis of samples from two biological replicate experiments quantified a total of 2764 proteins, 166 of which were significantly altered in abundance by H. pylori infection. Pathway mapping identified significantly altered inflammatory and cancer-signaling pathways that included Rab/Ras signaling proteins. Consistent with the iTRAQ results, RABEP2 and G3BP2 were significantly up-regulated in vitro, ex vivo in primary human gastric monolayers, and in vivo in gerbil gastric epithelium following infection with H. pylori strain 7.13 in a cag-dependent manner. Within human stomachs, RABEP2 and G3BP2 expression in gastric epithelium increased in parallel with the severity of premalignant and malignant lesions and was significantly elevated in intestinal metaplasia and dysplasia, as well as gastric adenocarcinoma, compared with gastritis alone. These results indicate that carcinogenic strains of H. pylori induce dramatic and specific changes within the gastric proteome in vivo and that a subset of altered proteins within pathways with oncogenic potential may facilitate the progression of gastric carcinogenesis in humans.


Assuntos
Proteínas de Transporte/metabolismo , Infecções por Helicobacter/complicações , Helicobacter pylori/patogenicidade , Neoplasias Gástricas/microbiologia , Proteínas de Transporte Vesicular/metabolismo , Animais , Linhagem Celular , Modelos Animais de Doenças , Regulação Neoplásica da Expressão Gênica , Gerbillinae , Infecções por Helicobacter/microbiologia , Humanos , Mucosa Intestinal/metabolismo , Mucosa Intestinal/microbiologia , Masculino , Mapas de Interação de Proteínas , Proteômica , Neoplasias Gástricas/metabolismo , Regulação para Cima
11.
Infect Immun ; 87(2)2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30510104

RESUMO

Helicobacter pylori CagA is a secreted effector protein that contributes to gastric carcinogenesis. Previous studies showed that there is variation among H. pylori strains in the steady-state levels of CagA and that a strain-specific motif downstream of the cagA transcriptional start site (the +59 motif) is associated with both high levels of CagA and premalignant gastric histology. The cagA 5' untranslated region contains a predicted stem-loop-forming structure adjacent to the +59 motif. In the current study, we investigated the effect of the +59 motif and the adjacent stem-loop on cagA transcript levels and cagA mRNA stability. Using site-directed mutagenesis, we found that mutations predicted to disrupt the stem-loop structure resulted in decreased steady-state levels of both the cagA transcript and the CagA protein. Additionally, these mutations resulted in a decreased cagA mRNA half-life. Mutagenesis of the +59 motif without altering the stem-loop structure resulted in reduced steady-state cagA transcript and CagA protein levels but did not affect cagA transcript stability. cagA transcript stability was not affected by increased sodium chloride concentrations, an environmental factor known to augment cagA transcript levels and CagA protein levels. These results indicate that both a predicted stem-loop structure and a strain-specific +59 motif in the cagA 5' untranslated region influence the levels of cagA expression.


Assuntos
Antígenos de Bactérias/genética , Proteínas de Bactérias/genética , DNA Bacteriano/ultraestrutura , Infecções por Helicobacter/genética , Helicobacter pylori/genética , Estabilidade de RNA/genética , RNA Mensageiro/ultraestrutura , Antígenos de Bactérias/metabolismo , Proteínas de Bactérias/metabolismo , Humanos , Mutagênese Sítio-Dirigida
12.
Cancer Epidemiol Biomarkers Prev ; 27(10): 1186-1194, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-30038049

RESUMO

Background: Antibody responses to Streptococcus gallolyticus subspecies gallolyticus (SGG) proteins, especially pilus protein Gallo2178, have been consistently associated with colorectal cancer risk. Previous case-control studies and prospective studies with up to 8 years of follow-up, however, were unable to decipher the temporality of antibody responses to SGG in the context of the long-term multistep development of colorectal cancer. In this study, we analyzed a large U.S. colorectal cancer cohort consortium with follow-up beyond 10 years for antibody responses to SGG.Methods: We applied multiplex serology to measure antibody responses to 9 SGG proteins in participants of 10 prospective U.S. cohorts (CLUE, CPSII, HPFS, MEC, NHS, NYUWHS, PHS, PLCO, SCCS, and WHI) including 4,063 incident colorectal cancer cases and 4,063 matched controls. Conditional logistic regression was used to assess whether antibody responses to SGG were associated with colorectal cancer risk, overall and by time between blood draw and diagnosis.Results: Colorectal cancer risk was increased among those with antibody responses to Gallo2178, albeit not statistically significant [OR, 1.23; 95% confidence interval (CI), 0.99-1.52]. This association was stronger for cases diagnosed <10 years after blood draw (OR, 1.40; 95% CI, 1.09-1.79), but was not found among cases diagnosed ≥10 years after blood draw (OR, 0.79; 95% CI, 0.50-1.24).Conclusions: In a large cohort consortium, we reproduced the association of antibody responses to SGG Gallo2178 with colorectal cancer risk for individuals diagnosed within 10 years after blood draw.Impact: This timing-specific finding suggests that antibody responses to SGG are associated with increased colorectal cancer risk only after tumorigenesis has begun. Cancer Epidemiol Biomarkers Prev; 27(10); 1186-94. ©2018 AACR.


Assuntos
Anticorpos Antibacterianos/sangue , Formação de Anticorpos/imunologia , Proteínas de Bactérias/imunologia , Neoplasias Colorretais/imunologia , Infecções Estreptocócicas/complicações , Streptococcus gallolyticus subspecies gallolyticus/imunologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Anticorpos Antibacterianos/imunologia , Estudos de Casos e Controles , Neoplasias Colorretais/sangue , Neoplasias Colorretais/microbiologia , Neoplasias Colorretais/patologia , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Prognóstico , Estudos Prospectivos , Infecções Estreptocócicas/microbiologia , Adulto Jovem
13.
PeerJ ; 6: e4803, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29796347

RESUMO

Helicobacter pylori requires genetic agility to infect new hosts and establish long-term colonization of changing gastric environments. In this study, we analyzed H. pylori genetic adaptation in the Mongolian gerbil model. This model is of particular interest because H. pylori-infected gerbils develop a high level of gastric inflammation and often develop gastric adenocarcinoma or gastric ulceration. We analyzed the whole genome sequences of H. pylori strains cultured from experimentally infected gerbils, in comparison to the genome sequence of the input strain. The mean annualized single nucleotide polymorphism (SNP) rate per site was 1.5e-5, which is similar to the rates detected previously in H. pylori-infected humans. Many of the mutations occurred within or upstream of genes associated with iron-related functions (fur, tonB1, fecA2, fecA3, and frpB3) or encoding outer membrane proteins (alpA, oipA, fecA2, fecA3, frpB3 and cagY). Most of the SNPs within coding regions (86%) were non-synonymous mutations. Several deletion or insertion mutations led to disruption of open reading frames, suggesting that the corresponding gene products are not required or are deleterious during chronic H. pylori colonization of the gerbil stomach. Five variants (three SNPs and two deletions) were detected in isolates from multiple animals, which suggests that these mutations conferred a selective advantage. One of the mutations (FurR88H) detected in isolates from multiple animals was previously shown to confer increased resistance to oxidative stress, and we now show that this SNP also confers a survival advantage when H. pylori is co-cultured with neutrophils. Collectively, these analyses allow the identification of mutations that are positively selected during H. pylori colonization of the gerbil model.

14.
Infect Immun ; 86(5)2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29531133

RESUMO

Helicobacter pylori, a Gram-negative bacterium, is a well-known risk factor for gastric cancer. H. pylori vacuolating cytotoxin A (VacA) is a secreted pore-forming toxin that induces a wide range of cellular responses. Like many other bacterial toxins, VacA has been hypothesized to utilize lipid rafts to gain entry into host cells. Here, we used giant plasma membrane vesicles (GPMVs) as a model system to understand the preferential partitioning of VacA into lipid rafts. We show that a wild-type (WT) toxin predominantly associates with the raft phase. Acid activation of VacA enhances binding of the toxin to GPMVs but is not required for raft partitioning. VacA mutant proteins with alterations at the amino terminus (resulting in impaired membrane channel formation) and a nonoligomerizing VacA mutant protein retain the ability to preferentially associate with lipid rafts. Consistent with these results, the isolated VacA p55 domain was capable of binding to lipid rafts. We conclude that the affinity of VacA for rafts is independent of its capacity to oligomerize or form membrane channels.


Assuntos
Proteínas de Bactérias/metabolismo , Toxinas Bacterianas/metabolismo , Helicobacter pylori/metabolismo , Helicobacter pylori/patogenicidade , Microdomínios da Membrana/metabolismo , Neoplasias Gástricas/patologia , Vacúolos/metabolismo , Interações Hospedeiro-Patógeno
15.
Gut ; 67(10): 1793-1804, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-28924022

RESUMO

OBJECTIVE: Helicobacter pylori is the strongest risk factor for gastric cancer; however, the majority of infected individuals do not develop disease. Pathological outcomes are mediated by complex interactions among bacterial, host and environmental constituents, and two dietary factors linked with gastric cancer risk are iron deficiency and high salt. We hypothesised that prolonged adaptation of H. pylori to in vivo carcinogenic microenvironments results in genetic modification important for disease. DESIGN: Whole genome sequencing of genetically related H. pylori strains that differ in virulence and targeted H. pylori sequencing following prolonged exposure of bacteria to in vitro carcinogenic conditions were performed. RESULTS: A total of 180 unique single nucleotide polymorphisms (SNPs) were identified among the collective genomes when compared with a reference H. pylori genome. Importantly, common SNPs were identified in isolates harvested from iron-depleted and high salt carcinogenic microenvironments, including an SNP within fur (FurR88H). To investigate the direct role of low iron and/or high salt, H. pylori was continuously cultured in vitro under low iron or high salt conditions to assess fur genetic variation. Exposure to low iron or high salt selected for the FurR88H variant after only 5 days. To extend these results, fur was sequenced in 339 clinical H. pylori strains. Among the isolates examined, 17% (40/232) of strains isolated from patients with premalignant lesions harboured the FurR88H variant, compared with only 6% (6/107) of strains from patients with non-atrophic gastritis alone (p=0.0034). CONCLUSION: These results indicate that specific genetic variation arises within H. pylori strains during in vivo adaptation to conditions conducive for gastric carcinogenesis.


Assuntos
Carcinogênese , Infecções por Helicobacter , Helicobacter pylori , Neoplasias Gástricas , Proteínas de Bactérias/genética , Infecções por Helicobacter/patologia , Infecções por Helicobacter/fisiopatologia , Helicobacter pylori/genética , Helicobacter pylori/patogenicidade , Humanos , Técnicas In Vitro/métodos , Polimorfismo de Nucleotídeo Único/fisiologia , Neoplasias Gástricas/microbiologia , Neoplasias Gástricas/patologia , Neoplasias Gástricas/fisiopatologia
16.
Infect Immun ; 86(3)2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29229727

RESUMO

Helicobacter pylori infection and high dietary salt intake are risk factors for the development of gastric adenocarcinoma. One possible mechanism by which a high-salt diet could influence gastric cancer risk is by modulating H. pylori gene expression. In this study, we utilized transcriptome sequencing (RNA-seq) methodology to compare the transcriptional profiles of H. pylori grown in media containing different concentrations of sodium chloride. We identified 118 differentially expressed genes (65 upregulated and 53 downregulated in response to high-salt conditions), including multiple members of 14 operons. Twenty-nine of the differentially expressed genes encode proteins previously shown to undergo salt-responsive changes in abundance, based on proteomic analyses. Real-time reverse transcription (RT)-PCR analyses validated differential expression of multiple genes encoding outer membrane proteins, including adhesins (SabA and HopQ) and proteins involved in iron acquisition (FecA2 and FecA3). Transcript levels of sabA, hopA, and hopQ are increased under high-salt conditions, whereas transcript levels of fecA2 and fecA3 are decreased under high-salt conditions. Transcription of sabA, hopA, hopQ, and fecA3 is derepressed in an arsS mutant strain, but salt-responsive transcription of these genes is not mediated by the ArsRS two-component system, and the CrdRS and FlgRS two-component systems do not have any detectable effects on transcription of these genes. In summary, these data provide a comprehensive view of H. pylori transcriptional alterations that occur in response to high-salt environmental conditions.


Assuntos
Proteínas da Membrana Bacteriana Externa/genética , Helicobacter pylori/genética , Helicobacter pylori/metabolismo , Cloreto de Sódio/metabolismo , Transcrição Genética , Proteínas da Membrana Bacteriana Externa/metabolismo , Regulação Bacteriana da Expressão Gênica , Infecções por Helicobacter/microbiologia , Humanos , Óperon , Regulação para Cima
17.
PLoS One ; 12(11): e0188804, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29186206

RESUMO

Helicobacter pylori is a genetically diverse bacterial species that colonizes the stomach in about half of the human population. Most persons colonized by H. pylori remain asymptomatic, but the presence of this organism is a risk factor for gastric cancer. Multiple populations and subpopulations of H. pylori with distinct geographic distributions are recognized. Genetic differences among these populations might be a factor underlying geographic variation in gastric cancer incidence. Relatively little is known about the genomic features of African H. pylori strains compared to other populations of strains. In this study, we first analyzed the genomes of H. pylori strains from seven globally distributed populations or subpopulations and identified encoded proteins that exhibited the highest levels of sequence divergence. These included secreted proteins, an LPS glycosyltransferase, fucosyltransferases, proteins involved in molybdopterin biosynthesis, and Clp protease adaptor (ClpS). Among proteins encoded by the cag pathogenicity island, CagA and CagQ exhibited the highest levels of sequence diversity. We then identified proteins in strains of Western African origin (classified as hspWAfrica by MLST analysis) with sequences that were highly divergent compared to those in other populations of strains. These included ATP-dependent Clp protease, ClpS, and proteins of unknown function. Three of the divergent proteins sequences identified in West African strains were characterized by distinct insertions or deletions up to 8 amino acids in length. These polymorphisms in rapidly evolving proteins represent robust genetic signatures for H. pylori strains of West African origin.


Assuntos
Helicobacter pylori/genética , África Ocidental , Sequência de Aminoácidos , Proteínas de Bactérias/química , Genes Bacterianos , Homologia de Sequência de Aminoácidos
18.
Toxins (Basel) ; 9(10)2017 10 12.
Artigo em Inglês | MEDLINE | ID: mdl-29023421

RESUMO

Helicobacter pylori VacA is a channel-forming toxin unrelated to other known bacterial toxins. Most H. pylori strains contain a vacA gene, but there is marked variation among strains in VacA toxin activity. This variation is attributable to strain-specific variations in VacA amino acid sequences, as well as variations in the levels of VacA transcription and secretion. In this review, we discuss epidemiologic studies showing an association between specific vacA allelic types and gastric cancer, as well as studies that have used animal models to investigate VacA activities relevant to gastric cancer. We also discuss the mechanisms by which VacA-induced cellular alterations may contribute to the pathogenesis of gastric cancer.


Assuntos
Proteínas de Bactérias , Helicobacter pylori , Neoplasias Gástricas/microbiologia , Alelos , Animais , Proteínas de Bactérias/genética , Modelos Animais de Doenças , Helicobacter pylori/genética , Helicobacter pylori/fisiologia , Humanos , Fatores de Risco , Estômago/microbiologia , Estômago/patologia , Neoplasias Gástricas/epidemiologia , Neoplasias Gástricas/patologia , Virulência
19.
Oxid Med Cell Longev ; 2017: 1320241, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28744336

RESUMO

Switching of cellular energy production from oxidative phosphorylation (OXPHOS) by mitochondria to aerobic glycolysis occurs in many types of tumors. However, the significance of this switching for the development of gastric carcinoma and what connection it may have to Helicobacter pylori infection of the gut, a primary cause of gastric cancer, are poorly understood. Therefore, we investigated the expression of OXPHOS complexes in two types of human gastric carcinomas ("intestinal" and "diffuse"), bacterial gastritis with and without metaplasia, and chemically induced gastritis by using immunohistochemistry. Furthermore, we analyzed the effect of HP infection on several key mitochondrial proteins. Complex I expression was significantly reduced in intestinal type (but not diffuse) gastric carcinomas compared to adjacent control tissue, and the reduction was independent of HP infection. Significantly, higher complex I and complex II expression was present in large tumors. Furthermore, higher complex II and complex III protein levels were also obvious in grade 3 versus grade 2. No differences of OXPHOS complexes and markers of mitochondrial biogenesis were found between bacterially caused and chemically induced gastritis. Thus, intestinal gastric carcinomas, but not precancerous stages, are frequently characterized by loss of complex I, and this pathophysiology occurs independently of HP infection.


Assuntos
Complexo I de Transporte de Elétrons/biossíntese , Gastrite/enzimologia , Regulação Enzimológica da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Infecções por Helicobacter/enzimologia , Helicobacter pylori , Proteínas de Neoplasias/biossíntese , Fosforilação Oxidativa , Neoplasias Gástricas/enzimologia , Feminino , Gastrite/patologia , Infecções por Helicobacter/patologia , Humanos , Masculino , Neoplasias Gástricas/patologia
20.
ACS Appl Mater Interfaces ; 9(32): 26719-26730, 2017 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-28696672

RESUMO

Acinetobacter baumannii is a Gram-negative bacterium of increasing concern due to its virulence and persistence in combat and healthcare environments. The incidence of both community-acquired and nosocomial A. baumannii infections is on the rise in foreign and domestic healthcare facilities. Treatment options are limited due to the acquisition of multidrug resistance to the few effective antibiotics. Currently, the most effective pharmaceutically based treatment for multidrug-resistant A. baumannii infections is the antibiotic colistin (polymyxin E). To minimize side effects associated with administration of colistin or other toxic antimicrobial agents, we propose the development of a nanotechnology-mediated treatment strategy. In this design-based effort, colistin-functionalized multilayered, inorganic, magnetoplasmonic nanoconstructs were fabricated to bind to the surface of A. baumannii. This result, for the first time, demonstrates a robust, pharmaceutical-based motif for high affinity, composite nanoparticulates targeting the A. baumannii surface. The antibiotic-activated nanomaterials demonstrated cytocompatibility with human cells and no acute bacterial toxicity at nanoparticle to bacterial concentrations <10 000:1. The magnetomotive characteristics of the nanomaterial enabled magnetic extraction of the bacteria. In a macroscale environment, maximal separation efficiencies exceeding 38% were achieved. This result demonstrates the potential for implementation of this technology into micro- or mesofluidic-based separation environments to enhance extraction efficiencies. The future development of such a mesofluidic-based, nanotechnology-mediated platform is potentially suitable for adjuvant therapies to assist in the treatment of sepsis.


Assuntos
Acinetobacter baumannii , Infecções por Acinetobacter , Antibacterianos , Colistina , Farmacorresistência Bacteriana Múltipla , Compostos Férricos , Humanos , Testes de Sensibilidade Microbiana
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