BACKGROUND & AIMS: vacA encodes the vacuolating cytotoxin of Helicobacter pylori and exhibits marked variation in signal sequence and midgene coding regions. The implications for gastroduodenal pathology are unknown. The aim of this study was to define the association of vacA genotype with gastric inflammation and injury, in vitro cytotoxin activity, and peptic ulceration. METHODS: Sixty-one consecutive dyspeptic patients underwent endoscopy and gastric biopsy. The biopsy specimens were processed for H. pylori culture, and 52 specimens were also processed for histology. H. pylori vacA was typed by polymerase chain reaction and colony hybridization. Cytotoxin activity was assessed by a HeLa cell vacuolation assay. RESULTS: vacA signal sequence type s1a strains were associated with greater antral mucosal neutrophil and lymphocyte infiltration than s1b or s2 strains (P > 0.05). vacA midregion type m1 strains were associated with greater gastric epithelial damage than m2 strains (P > 0.05). Both midregion and signal sequence were associated with cytotoxin activity in vitro. Duodenal ulcer disease occurred in 89% of 18 patients with s1a strains vs. 29% of 14 with s1b strains (P > 0.01), 20% of 10 with s2 strains (P > 0.001), and 16% of 19 uninfected patients (P > 0.001). CONCLUSIONS: H. pylori strains of vacA signal sequence type s1a are associated with enhanced gastric inflammation and duodenal ulceration. vacA s2 strains are associated with less inflammation and lower ulcer prevalence. (Gastroenterology 1997 Jan;112(1):92-9)
Helicobacter pylori is remarkable for its genetic variation; yet, little is known about its genetic changes during early stages of human infection, as the bacteria adapt to their new environment. We analyzed genome and methylome variations in a fully virulent strain of H pylori during experimental infection.
We performed a randomized Phase I/II, observer-blind, placebo-controlled study of 12 healthy, H pylori–negative adults in Germany from October 2008 through March 2010. The volunteers were given a prophylactic vaccine candidate (n = 7) or placebo (n = 5) and then challenged with H pylori strain BCM-300. Biopsy samples were collected and H pylori were isolated. Genomes of the challenge strain and 12 reisolates, obtained 12 weeks after (or in 1 case, 62 weeks after) infection were sequenced by single-molecule, real-time technology, which, in parallel, permitted determination of genome-wide methylation patterns for all strains. Functional effects of genetic changes observed in H pylori strains during human infection were assessed by measuring release of interleukin 8 from AGS cells (to detect cag pathogenicity island function), neutral red uptake (to detect vacuolating cytotoxin activity), and adhesion assays.
The observed mutation rate was in agreement with rates previously determined from patients with chronic H pylori infections, without evidence of a mutation burst. A loss of cag pathogenicity island function was observed in 3 reisolates. In addition, 3 reisolates from the vaccine group acquired mutations in the vacuolating cytotoxin gene vacA, resulting in loss of vacuolization activity. We observed interstrain variation in methylomes due to phase variation in genes encoding methyltransferases.
We analyzed adaptation of a fully virulent strain of H pylori to 12 different volunteers to obtain a robust estimate of the frequency of genetic and epigenetic changes in the absence of interstrain recombination. Our findings indicate that the large amount of genetic variation in H pylori poses a challenge to vaccine development. ClinicalTrials.gov no: NCT00736476.
Helicobacter pylori, a gram-negative bacterium, is the causative agent of gastric disorders and gastric cancer in the human stomach. Vacuolating cytotoxin A (VacA) is among the multi-effect protein toxins released by H. pylori that enables its persistence in the human stomach.
To evaluate the effect of anti-VacA egg yolk immunoglobulin (anti-VacA IgY) on H. pylori infection, a highly specific anti-VacA IgY was produced from egg yolks of hens immunized with a mixture of two purified recombinant VacAs. Female C57BL/6 mice were supplemented anti-VacA IgY daily with drinking water for 2 weeks before and 4 weeks after H. pylori ATCC 43504 inoculation. Anti-VacA IgY recognized both native and denatured structures of VacA by enzyme-linked immunosorbent assay and immunoblotting analyses, respectively.
Oral administration of anti-VacA IgYs significantly (p < .05) reduced the serum levels of anti-H. pylori antibodies compared to those in the H. pylori-infected, untreated group. The reduction in the immune response was accompanied by a significant (p < .05) decrease in eosinophilic infiltration of the stomach in anti-VacA IgY treated group compared to other groups. Concomitantly, H. pylori–induced histological changes and H. pylori antigen-positivity in gastric tissues were decreased significantly (p < .05) in anti-VacA IgY treated group similar to the control group.
Oral administration of anti-VacA IgY is correlated with a protective effect against H. pylori colonization and induced histological changes in gastric tissues. Our experimental study has proved that it is expected to be a new drug candidate of Hp infection by further study.