China
Africa
Explore chapters and articles related to this topic
Helicobacter pylori infection
Published in Phillip D. Smith, Richard S. Blumberg, Thomas T. MacDonald, Principles of Mucosal Immunology, 2020
Diane Bimczok, Anne Müller, Phillip D. Smith
The H. pylori cytotoxin-associated gene (cag) pathogenicity island is an important determinant of disease severity. A 40 kb segment of H. pylori DNA, the cag pathogenicity island encodes more than 25 proteins, including Cag3, CagM, and CagH, that form a type IV secretion system (T4SS), which mediates the translocation of CagA into host epithelial cells. Notably, recent studies show that iron depletion enhances the assembly and function of the cag T4SS and the severity of H. pylori-induced premalignant lesions in humans, consistent with epidemiological evidence that links iron deficiency and accelerated H. pylori-induced carcinogenesis.
Endoscopic screening for upper gastrointestinal malignancy
Published in David Westaby, Martin Lombard, Therapeutic Gastrointestinal Endoscopy A problem-oriented approach, 2019
The particular subtype of H. pylori infection is becoming important. Subjects infected who have CagA antibodies were 5.8-fold more likely to develop gastric cancer, whereas those without CagA antibodies had an odds ratio of 2.2. The function of this immunodominant CagA protein is unknown. The CagA gene is the marker for a 40-kb pathogenicity island of H. pylori. The most important strain has been characterized further as being CagAvacAS1a positive. These bacteria increase proliferation and also decrease apoptosis. However, those patients infected with CagA strains may be protected against the complications of gastro-oesophageal reflux disease, Barrett’s oesophagus, dysplasia and carcinoma.
Helicobacter
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
CagPAI contains various bacterial toxins. CagA is injected into gastric surface epithelial cells through the bacterial type IV secretion system and is tyrosine-phosphorylated with Src and Abl100 at variable EPIYA (Glu-Pro-Ile-Tyr-Ala) motif repeats region, which shows structural diversity between East Asian and Western countries.101 The East-Asian CagA binds more strongly to SHP2 and induces morphological change, called hummingbird phenotype, than does Western CagA.102H. pylori found in the former possesses EPIYA-A, B, and D motifs, which may contribute in geographical difference for gastric carcinogenesis. Phosphorylated CagA then activates SHP-2 phosphatase, which dephosphorylates FAK kinase resulting in impairment of epithelial cell adhesion and morphology.103 Wild-type CagA transgenic mice confirmed the oncogenicity of this bacterial protein with development of gastrointestinal epithelial hyperplasia and adenocarcinomas as well as hematopoietic malignancies, whereas phosphorylation-resistant CagA did not.104
Immunostimulatory membrane proteins potentiate H. pylori-induced carcinogenesis by enabling CagA translocation
Published in Gut Microbes, 2021
Matthew G. Varga, Cecily R. Wood, Julia Butt, Mackenzie E. Ryan, Wei-Cheng You, Kaifeng Pan, Tim Waterboer, Meira Epplein, Carrie L. Shaffer
CagA translocation into AGS cells was performed as described previously.18 Briefly, AGS cells were infected at an MOI of 100 in triplicate in for 6 h prior to at least three washes in 1X PBS to remove non-adherent bacteria. AGS cells were lysed in buffer containing 1% NP-40 with cOmplete™ mini EDTA-free protease inhibitor (Roche) and PhosSTOP phosphatase inhibitor (Roche). The soluble fraction was separated on a 7.5% gel (Bio-Rad) for immunoblot analysis probed by an anti-phosphotryosine antibody (α-PY99, Santa Cruz). Membranes were subsequently probed for total CagA (α-CagA, Santa Cruz), β-tubulin (Invitrogen), and H. pylori outer membrane protein (α-OMP, Santa Cruz). CagA translocation assays were performed at least four times per strain, and the ratio of translocated CagA (pY-CagA) to total CagA was determined by densitometry analysis for each strain in biological replicate experiments using ImageJ as previously described.18
Dietary Intake of Nutrients Involved in One-Carbon Metabolism and Risk of Gastric Cancer: A Prospective Study
Published in Nutrition and Cancer, 2019
Pierre-Antoine Dugué, Julie K. Bassett, Maree T. Brinkman, Melissa C. Southey, Jihoon E. Joo, Ee Ming Wong, Roger L. Milne, Dallas R. English, Graham G. Giles, Alex Boussioutas, Hazel Mitchell, Allison M. Hodge
A commercially available immunoblotting kit (Helicoblot 2.1; Genelabs Diagnostics, Singapore) which has 96% sensitivity and 93% specificity for the detection of H. pylori infection was used to assess the H. pylori status of cases and controls in plasma collected at baseline (27). The use of immunoblotting allows determination of the CagA status of the infecting strain. The criteria for H. pylori-seropositivity, based on the manufacturer’s instructions, are (i) the presence of the 116 kDa band (CagA), with one or more of the following bands: 89 kDa (VacA), 37 kDa, 35 kDa, 30 kDa (UreA) and 19.5 kDa together, or with the current infection marker; (ii) the presence of any one band at 89, 37 or 35 kDa, with or without the current infection marker; and (iii) the presence of both the 30 and 19.5 kDa bands, with or without the current infection marker.
Helicobacter pylori infection & immune thrombocytopenic purpura in children and adolescents: A randomized controlled trial
Published in Platelets, 2015
Helena Shino Hanai Brito, Josefina Aparecida Pellegrini Braga, Sandra Regina Loggetto, Rodrigo Strehl Machado, Celso Francisco Hernandes Granato, Elisabete Kawakami
The mechanisms of the association between H. pylori and ITP remain unclear. It has been postulated that antibodies to H. pylori components such as CagA cross-react with PLT surface antigens, such as PLT associated immunoglobulin G [29], suggesting that there is a molecular similarity between these proteins. In our study, almost all H. pylori infected patients had a positive CagA strain, as other authors have reported [18, 22], thus we could not determine the relationship between exposure to a CagA strain and PLT response. Also, PLT autoantibodies might be produced by autoreactive clonal B cells that are induced by chronic immunologic stimulus by H. pylori [30]. Increased P-selectin (PLT-activating factor) expression [31], some HLA class 2 alleles associated with a higher probability of PLT response [32], changes in inhibitory Fcγ factor [33], and association of some genotypes of inflammatory cytokine TNF-β with PLT recovery [34] have also been described.