Essential role of Helicobacter pylori γ‐glutamyltranspeptidase for the colonization of the gastric mucosa of mice

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Infection with the gastric bacterial pathogen Helicobacter pylori is typically contracted in early childhood and often persists for decades. The immunomodulatory properties of H. pylori that allow it to colonize humans persistently are believed to also account for H. pylori's protective effects against allergic and chronic inflammatory diseases. H. pylori infection efficiently reprograms dendritic cells (DCs) toward a tolerogenic phenotype and induces regulatory T cells (Tregs) with highly suppressive activity in models of allergen-induced asthma. We show here that two H. pylori virulence determinants, the γ-glutamyl transpeptidase GGT and the vacuolating cytotoxin VacA, contribute critically and nonredundantly to H. pylori's tolerizing effects on murine DCs in vitro and in vivo. The tolerancepromoting effects of both factors are independent of their described suppressive activity on T cells. Isogenic H. pylori mutants lacking either GGT or VacA are incapable of preventing LPS-induced DC maturation and fail to drive DC tolerization as assessed by induction of Treg properties in cocultured naive T cells. The Δggt and ΔvacA mutants colonize mice at significantly reduced levels, induce stronger T-helper 1 (Th1) and T-helper 17 (Th17) responses, and/or trigger more severe gastric pathology. Both factors promote the efficient induction of Tregs in vivo, and VacA is required to prevent allergen-induced asthma. The defects of the Δggt mutant in vitro and in vivo are phenocopied by pharmacological inhibition of the transpeptidase activity of GGT in all readouts. In conclusion, our results reveal the molecular players and mechanistic basis for H. pyloriinduced immunomodulation, promoting persistent infection and conferring protection against allergic asthma.bacterial virulence factors | hygiene hypothesis | persistent bacterial infection | human microbiota | persistence strategies T he bacterial pathogen Helicobacter pylori persistently colonizes the gastric mucosa of humans. It is typically acquired in early childhood (1) and, in the absence of antibiotic therapy, may persist for the entire lifespan of the host (2, 3). The extraordinary ability of H. pylori to resist a vigorous adaptive immune response driven in large part by T-helper 1 (Th1) and/or T-helper 17 (Th17)-polarized effector T cells (4, 5) has been attributed to its perfect adaptation to-and manipulation of-the human innate and adaptive immune systems (6). H. pylori has colonized its human host for at least 60,000 y (7) and during this long period of coevolution has evolved elaborate ways to systemically manipulate adaptive immune responses and to promote its persistence through the preferential induction of regulatory T-cell (Treg) over T-effector cell responses. Treg-predominant responses are characteristic of heavily colonized but asymptomatic carriers (4) and of children with particularly mild forms of Helicobacter-associated gastritis (8). Several recent functional studies using experimentally infected animals have implicated Tregs and dendritic cells (...

Section: Discussionmentioning

confidence: 99%

Section: Efficient Gastric Colonization By H Pylori and Tolerogenicmentioning

confidence: 98%

Helicobacter pylori γ-glutamyl transpeptidase and vacuolating cytotoxin promote gastric persistence and immune tolerance

Oertli

Noben

Engler

et al. 2013

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190

“…The pres-ence of H. pylori bacteria was determined by a biopsy urease test (25) performed on half of each stomach and by quantitative culturing of the remaining gastric tissues. Viable counts of H. pylori were estimated by serial dilutions of the homogenized tissues in peptone broth and plating in parallel on 2.0% agar standard selective plates (26) and selective plates supplemented with kanamycin.…”

Section: Methodsmentioning

confidence: 99%

Pathogen DNA as target for host-generated oxidative stress: Role for repair of bacterial DNA damage in Helicobacter pylori colonization

O’Rourke

Chevalier

Pinto

et al. 2003

Self Cite

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110

Helicobacter pylori elicits an oxidative stress during host colonization. This oxidative stress is known to cause lesions in the host DNA. Here we addressed the question as to whether the pathogen DNA is subject to lethal or mutational damage by the host-generated oxidative response. H. pylori Hpnth mutants unable to repair oxidized pyrimidines from the bacterial DNA were generated. H. pylori strains lacking a functional endonuclease III (HpNth) showed elevated spontaneous and induced mutation rates and were more sensitive than the parental strain to killing by exposure to oxidative agents or activated macrophages. Although under laboratory conditions the Hpnth mutant strain grows as well as the wild-type strain, in a mouse infection the stomach bacterial load gradually decreases while the population in the wild-type strain remains stable, showing that endonuclease III deficiency reduces the colonization capacity of the pathogen. In coinfection experiments with a wild-type strain, Hpnth cells are eradicated 15 days postinfection (p.i.) even when inoculated in a 1:9 wild-type:mutant strain ratio, revealing mutagenic lesions that are counterselected under competition conditions. These results show that the host effectively induces lethal and premutagenic oxidative DNA adducts on the H. pylori genome. The possible consequences of these DNA lesions on the adaptability of H. pylori strains to new hosts are discussed.

“…Additionally, GGT is a virulence factor associated with the colonization of the gastric mucosa by Helicobacter pylori, the pathogen responsible for gastritis and ulcer and gastric cancer (10,11).…”

mentioning

confidence: 99%

Crystal structures of γ-glutamyltranspeptidase from Escherichia coli , a key enzyme in glutathione metabolism, and its reaction intermediate

Okada

Suzuki

Wada

et al. 2006

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␥-Glutamyltranspeptidase (GGT) is a heterodimic enzyme that is generated from the precursor protein through posttranslational processing and catalyzes the hydrolysis of ␥-glutamyl bonds in ␥-glutamyl compounds such as glutathione and͞or the transfer of the ␥-glutamyl group to other amino acids and peptides. We have determined the crystal structure of GGT from Escherichia coli K-12 at 1.95 Å resolution. GGT has a stacked ␣␤␤␣ fold comprising the large and small subunits, similar to the folds seen in members of the N-terminal nucleophile hydrolase superfamily. The active site Thr-391, the N-terminal residue of the small subunit, is located in the groove, from which the pocket for ␥-glutamyl moiety binding follows. We have further determined the structure of the ␥-glutamyl