Helicobacter pylori infection and gastric carcinoma among Japanese Americans in Hawaii

Is Helicobacter pylori a causal agent in gastric carcinoma?

The aim of this study is to clarify the relationship between Helicobacter pylori (H. pylori) infection and gastric carcinoma. 94 patients with gastric carcinoma and 111 patients with chronic gastritis were involved in this study. They were classified into 3 age groups: Group A (40 years and under), Group B (41-59), Group C (60 years and over). Serum samples were tested for H. pylori IgG antibodies by ELISA and for pepsinogen (PG) by RIA. The ratio of PG I/PG II was used as a marker for atrophic gastritis. Results were as follows. In the incidence of H. pylori antibodies, there was no significant differences between gastric carcinoma and chronic gastritis in any of the groups. In the quantity of H. pylori antibodies, there was no significant difference between gastric carcinoma and chronic gastritis in any of the groups. The ratio of PG I/PG II was significantly decreased in H. pylori positive cases when compared to H. pylori negative cases in each group with chronic gastritis and group A and B with gastric carcinoma. The ratio of PG I/PG II in gastric carcinoma was significantly lower than that of chronic gastritis. As conclusion, from the point of view of the prevalence of H. pylori, it is suggested that H. pylori is not a direct causal agent in the pathogenesis of gastric carcinoma.

Immunisation against gastric infection with Helicobacter species: first step in the prophylaxis of gastric cancer?

The discovery of the gastric bacterium, Helicobacter pylori and the demonstration of its role in the pathogenesis of gastroduodenal disease, has been one of the major microbiological advances in the last decade. Recent demonstration of long term infection with this bacterium as a risk factor in gastric carcinoma suggests that intervention in a disease of major morbidity and mortality is possible. Using a model of Helicobacter infection in mice it has been shown that oral immunisation with a sonicate of Helicobacter felis plus the adjuvant cholera toxin results in protection against an oral challenge with large numbers of viable bacteria. The success of the immunising regimen has been shown to correlate with the development of local immunity. Formulation of equivalent safe vaccines of H. pylori will make possible the immunisation of children in countries such as China, Japan and Columbia and so prevent the establishment of long term inflammation and thus significantly reduce the incidence of gastric cancer in those societies. This animal model is proposed as a major tool in the development of effective oral immunisation.

Long term infection of the gastric mucosa with Helicobacter species does induce atrophic gastritis in an animal model of Helicobacter pylori infection

Gastric atrophy is a precursor lesion in the development of gastric cancer. It has been proposed that atrophy is part of a natural progression of inflammatory changes that result from long term infection with the bacterium Helicobacter pylori. The aim of this study was to test this hypothesis using an animal model of human Helicobacter infection. Conventional mice were infected with either a cat isolate of Helicobacter felis or a human isolate of "Gastrospirillum hominis". All infected mice showed a slowly progressive chronic gastritis with increasing numbers of infiltrating mononuclear cells and polymorphonuclear leucocytes. After a year and a half, the inflammatory reaction was so severe that atrophic changes were seen in both the antral and fundic mucosa. Control animals initially showed no inflammatory changes however as the animals aged, the gastric mucosa of some animals became infected with a bacterium Helicobacter muridarum that normally inhabits the small and large bowel of the rodent. The presence of this bacterium was also associated with gastritis and atrophic changes. This is the first report of experimentally induced atrophic changes induced by a gastric bacterium and opens the way for important experiments that will help better understand the induction of gastric cancer.

Bacterial ureases: structure, regulation of expression and role in pathogenesis

The nickel metalloenzyme urease catalyses the hydrolysis of urea to ammonia and carbamate, and thus generates the preferred nitrogen source of many organisms. When produced by bacterial pathogens in either the urinary tract or the gastroduodenal region, urease acts as a virulence factor. At both sites of infection urease is known to enhance the survival of the infecting bacteria. Ammonia resulting from the action of urease is believed to increase the pH of the environment to one more favourable for growth, and to injure the surrounding epithelial cells. In addition, in the urinary tract urease activity can result in the formation of urinary calculi. Bacterial urease gene clusters contain from seven to nine genes depending upon the species. These genes encode the urease structural subunits and accessory polypeptides involved in the biosynthesis of the nickel metallocentre. So far, three distinct mechanisms of urease gene expression have been described for ureolytic bacteria. Some species constitutively produce urease; some species produce urease only if urea is present in the growth medium; and some species produce urease only during nitrogen-limiting growth conditions. For either the urea-inducible genes or the nitrogen-regulated genes transcription appears to be positively regulated. In the nitrogen-regulated systems, urease gene expression requires Nac (nitrogen assimilation control), a member of the LysR family of transcriptional activators. Urea dependent expression of urease requires UreR (urease regulator), a member of the AraC family of transcriptional activators. An evolutionary tree for urease genes of eight bacterial species is proposed.

Identification and characterization of Helicobacter pylori phospholipase C activity

We analyzed 11 H. pylori isolates from humans using the artificial chromogenic substrate paranitrophenylphosphorylcholine to detect phospholipase C (PLC) activity. The range of PLC in sonicates was 8.8-92.3 (Mean 56.9 +/- 6.5) nmol of substrate hydrolysed min-1 mg-1 protein; the amount of activity was not associated with urease or cytotoxin levels. Addition of sorbitol or glycerol enhanced PLC activity of H. pylori sonicate and purified PLC from C. perfringens (PLC1) but not purified PLC from B. cereus (PLC3). H. pylori sonicates had little acid phosphatase and no detectable alkaline phosphatase activity, and H. pylori PLC showed markedly different biochemical characteristics from either phosphatase. In total, these studies indicate that activity measured in H. pylori sonicate by PLC assay is due to PLC and not phosphatase activity. The temperature optimum for PLC activity of H. pylori sonicate was 56 degrees C and for PLC 1 was 65 degrees C. For H. pylori PLC and PLC1, optimal activity occurred at pH 8. Despite multiple similarities between H. pylori PLC and PLC1, known PLC inhibitors show different interactions with each enzyme. Although PLC activity is present in many subcellular constituents of H. pylori, including culture supernatants and water extracts, highest specific activity is associated with a membrane-enriched fraction.

Therapeutics used to alleviate peptic ulcers inhibit H. pylori receptor binding in vitro

Treatment with bismuth-containing remedies has been long associated with the alleviation of minor gastric ailments. Bismuth salts have a potent antimicrobial activity, and are part of the current standard regime used to treat Helicobacter pylori infection. H. pylori is considered to be the major etiological factor in the development of peptic ulcer disease. Earlier efficacious treatments for peptic ulcer included the oral administration of Tween detergents. We have found that these agents have an inhibitory effect on H. pylori adhesion to the lipid species phosphatidylethanolamine (PE) and gangliotetraosylceramide (Gg4) shown previously to be receptors for H. pylori binding in vitro. H. pylori binding to PE and Gg4 was inhibited after a thirty minute preincubation with different bismuth compounds: bismuth subsalicylate > bismuth subgallate > bismuth carbonate > colloidal bismuth subcitrate > tripotassium dicitrato bismuthate. No inhibitory effect on H. pylori binding was observed when bismuth salts were added directly into the binding assay. No changes in bacterial morphology and motility were observed after the thirty minute incubation. Pretreatment with Tween detergents also inhibited H. pylori receptor binding by up to 80% at concentrations as low as 0.0001%. These results suggest that inhibition of H. pylori/host cell adhesion might play a role in efficacious treatment for this infection.

Humoral immune response against Helicobacter pylori as determined by immunoblot

An immunoblot method has been evaluated to diagnose Helicobacter pylori infection serologically by comparing 69 serum specimens from patients with a positive Gram stain and/or culture result and a positive urease test on biopsy material, as well as 51 serum specimens from patients with at least 4 negative urease tests, and negative microscopy and culture results. Sensitivity and specificity was found to be 100%. Recognition of the cross-reacting flagellin (66 kDa), flagellar sheath protein (51 kDa), and a 14 kDa protein are not a criterion for a current H. pylori infection. On the other hand, any combination of at least two of the 180, 120, 90, 75, 67, 29.5 and 19 kDa bands were diagnostic of infection. Three H. pylori strains, which were compared with both gel electrophoretic analyses and immunoblot reactivity, exhibited in part strong qualitative and quantitative differences that particularly affect the 120 kDa pathogenic factor, the large urease subunit and other proteins especially in the molecular mass range from 50 to 67 kDa. IgG immunoblot patterns showed that the choice of H. pylori strain, as well as a reproducible and standardizable antigen preparation, is of great importance for the reliability of serodiagnostic tests. The immunoblot method was found to be a valuable tool for the semi-quantitative confirmation of results achieved with other serological methods as well as optimization and quality control of the antigens used for serodiagnostic purposes.

Stimulatory effects of Helicobacter pylori on human peripheral blood mononuclear cells of H. pylori infected patients and healthy blood donors

The ability of 23 different strains of Helicobacter pylori to induce proliferative response of human peripheral blood mononuclear cells (PBMC) was investigated. All tested strains stimulated the DNA synthesis of PBMC from both healthy and H. pylori infected blood donors, but with lower stimulation of PBMC of infected donors. Using different bacterial antigen preparations, such as crude membranes, cytoplasmic proteins, and urease, a significantly lower induction of the proliferative response of PBMC from H. pylori infected than from healthy blood donors could also be demonstrated. In contrast to this result the reaction to phytohemagglutinin and purified protein derivative of tuberculin was similar in both groups. The stimulation pathway was interleukin 2 (IL-2) dependent as proved by inhibition of the proliferative response with an alpha-IL-2-receptor antibody. Using an antibody against HLA-DR the lymphoproliferation could also be blocked showing the importance of the major histocompatibility class II (MHCII) complex. Only coincubation of T cells with monocytes plus antigen or with antigen-preincubated monocytes led to a proliferative response showing the necessity of antigen-presenting cells. At least a part of the lymphoproliferative response is MHCII restricted as could be shown with H. pylori specific T-cell lines. These results and the kinetics of the proliferative response with a maximum at day 7 suggest that the proliferative response of human PBMC was mainly induced by antigens than by a mitogen.

Seroconversion for Helicobacter pylori

The prevalence of Helicobacter pylori antibodies increases with age, but it is unknown whether this is due to a constant rate of infection in different age groups, or whether most infection occurs in childhood. Follow-up data on infection rates and the course of infection in an untreated population are scarce. We measured H pylori IgG antibody concentrations in patients who were seen at our endoscopy unit between 1979 and 1983. 115 of 164 eligible patients (70%) participated in the study. H pylori IgG antibody concentrations were measured in two serum samples taken with a mean interval of 11.5 years. 56 patients tested positive at the first visit. During follow-up, 2 patients became infected (annual infection rate 0.30%, 95% Cl 0.04-1.08%). Evidence of infection disappeared in 6 patients: after gastric surgery in 3 and due to an unknown cause in the remaining 3 patients. A non-significant decrease of infection was shown in different age cohorts during follow-up. Antibody concentrations did not increase with age. These results strongly support the concept of dominant infection rates in childhood. Elimination of infection may occur in a few patients without eradication therapy.

Social and geographical risk factors in Helicobacter pylori infection

A correlation between childhood crowding and the later development of gastric cancer has been demonstrated by Barker and colleagues, who proposed that the relationship was the consequence of infection by an organism such as Helicobacter pylori. In order to test this hypothesis the presence of IgG antibodies to H. pylori in sera from blood donors in North Wales has been investigated. During donation sessions, donors answered questions relating to social conditions and domicile in childhood (at age 10 years) and adult life (the preceding 2 years). A stepwise logistic regression analysis of the data demonstrated significant independent relationships between seropositivity and the following factors: sharing a bed in childhood, housing density, locality of birth, adult social class and age.

Characteristics of Helicobacter pylori alcohol dehydrogenase

BACKGROUND

Helicobacter pylori shows alcohol dehydrogenase activity, which in the presence of ethanol leads to in vitro production of acetaldehyde, a toxic and highly reactive substance. The present study was undertaken to further define H. pylori-related ethanol and acetaldehyde metabolism by characterizing H. pylori alcohol dehydrogenase and by determining whether the organism possesses aldehyde dehydrogenase.

METHODS

Cytosolic alcohol and aldehyde dehydrogenase activities were determined spectrophotometrically. Acetaldehyde produced by cytosol during incubation with ethanol was measured by head space gas chromatography. Isoenzyme pattern was studied using isoelectric focusing.

RESULTS

Significant alcohol dehydrogenase activity was observed at a neutral pH known to occur in gastric mucus. The Km for ethanol oxidation was approximately 100 mmol/L for the two strains tested. Acetaldehyde was formed already from a low ethanol concentration known to prevail in the stomach endogenously. Isoelectric focusing of the enzyme showed activity bands with pI at 7.1-7.3, a pattern different from that of gastric mucosal alcohol dehydrogenase. 4-methylpyrazole inhibited enzyme activity in a competitive manner and suppressed the growth of the organism during culture. Neither Helicobacter strain studied showed aldehyde dehydrogenase activity and can thus not remove acetaldehyde by that pathway.

CONCLUSIONS

Acetaldehyde production by H. pylori from exogenous or endogenous ethanol may be a pathogenetic mechanism behind mucosal injury associated with the organism.

The time trend and age-period-cohort effects on incidence of adenocarcinoma of the stomach in Connecticut from 1955-1989

BACKGROUND

Adenocarcinoma of the gastric cardia has been be increasing in Connecticut, and the risk factors responsible for the increasing incidence are unknown. This study examined the incidence pattern of adenocarcinoma of the gastric cardia and distal stomach in Connecticut during the past decades and identified components of birth cohort, period, and age as determinants of the observed time trends by regression modeling.

METHODS

This study was based on all histologically confirmed incident cases of gastric adenocarcinoma reported to the Connecticut Tumor Registry between 1955 and 1989. Stomach cancers were grouped into cancers of the gastric cardia, distal stomach, or unknown/unspecified subsite. Age-adjusted incidence rates were calculated by the direct method standardized to the 1970 United States population. A regression model was used to identify birth cohort, period, and age as determinants of the observed time trends.

RESULTS

The results indicated that the incidence rate of adenocarcinoma of the cardia is increasing, particularly in white males, whereas adenocarcinoma of the distal stomach is now decreasing in both sexes in Connecticut. Regression modeling suggests that the increase of adenocarcinoma of the cardia may be explained partly by a birth cohort phenomenon.

CONCLUSION

There is little information regarding the risk factors that might be responsible for the observed increasing trend for adenocarcinoma of the cardia, although smoking, alcohol intake, retinol intake, and hiatal hernia have been associated with an increased risk of adenocarcinoma of the cardia or gastric cancer. Considering the different epidemiologic features of adenocarcinoma of the cardia and distal stomach, future analytic studies should separate cancer of the gastric cardia and cancer of the distal stomach in searching for etiologic factors.

Cloning, expression and sequencing of Helicobacter felis urease genes

Urease genes from Helicobacter felis were cloned and expressed in Escherichia coli cells. A genomic bank of Sau3A-digested H. felis chromosomal DNA was created using a cosmid vector. Cosmid clones were screened for urease activity following subculture on a nitrogen-limiting medium. Subcloning of DNA from an urease-positive cosmid clone led to the construction of pILL205 (9.5 kb) which conferred a urease activity of 1.2 +/- 0.5 mumole urea min-1 mg-1 bacterial protein to E. coli HB101 bacteria grown on a nitrogen-limiting medium. Random mutagenesis using a MiniTn3-Km transposable element permitted the identification of three DNA regions on pILL205 which were necessary for the expression of an urease-positive phenotype in E. coli clones. To localize the putative structural genes of H. felis on pILL205, extracts of clones harbouring the mutated copies of the plasmid were analysed by Western blotting with anti-H. felis rabbit serum. One mutant clone did not synthesize the putative UreB subunit of H. felis urease and it was postulated that the transposable element had disrupted the corresponding structural gene. By sequencing the DNA region adjacent to the transposon insertion site two open reading frames, designated ureA and ureB, were identified. The polypeptides encoded by these genes had calculated molecular masses of 26,074 and 61,663 Da, respectively, and shared 73.5% and 88.2% identity with the corresponding gene products of Helicobacter pylori urease.

Helicobacter pylori, dietary factors, and atrophic gastritis in five Japanese populations with different gastric cancer mortality

In a cross-sectional study of 634 men aged 40 to 49 years, randomly selected from five areas of Japan with different rates of gastric cancer mortality, 121 men of 624 evaluated were diagnosed as having atrophic gastritis through serum pepsinogen I < 70 ng/ml and the pepsinogen I (PGI)/pepsinogen II (PGII) ratio < 3.0. We examined the relation of Helicobacter pylori (H. pylori) antibodies and dietary factors, including plasma level of antioxidant micronutrients, to the presence of atrophic gastritis. Presence of H. pylori IgG antibodies was associated with increased risk of atrophic gastritis (odds ratio [OR] = 1.9, 95 percent confidence interval [CI] = 1.1-3.3). As the level of plasma beta-carotene increased, we found a steady decrease in the risk of atrophic gastritis (OR for second quartile = 0.7, third quartile = 0.6, fourth quartile = 0.4, with CI = 0.2-0.8). Frequent intake of yellow vegetables also was associated with lower risk, while frequent intake of soybean products was related to increased risk. Although H. pylori antibodies, beta-carotene level, and intake of soybean products were all significant in the multivariate analysis, these factors did not explain the differences in atrophic gastritis prevalence among the five regions. The analysis of these risk factors in relation to each pepsinogen marker showed that although both H. pylori infection and low plasma beta-carotene were associated with the decreased level of serum PGI/II ratio, the former was derived from the increase of PGII, which is common in early stage of atrophic gastritis, and the latter from the decrease of PGI, which is specific to severe atrophic gastritis.(ABSTRACT TRUNCATED AT 250 WORDS)

Mortality and incidence of cancer among sewage workers: a retrospective cohort study

To study the incidence of and mortality from cancer among sewage workers a retrospective analysis was performed on a cohort of 656 men employed for at least one year at any one of 17 Swedish sewage plants during the years 1965-86. Assessment of exposure was done by classification of work tasks. Lower than expected total mortality (standardised mortality ratio (SMR) = 0.75, 95% confidence interval (95% CI) 0.58-0.97) and cardiovascular mortality (SMR = 0.61, 95% CI 0.39-0.91) was found. This was interpreted as a result of the healthy worker effect. For all cancers combined the mortality (SMR = 1.08, 95% CI 0.68-1.67) and morbidity (SMR = 1.02, 95% CI 0.72-1.38) were comparable with those of the general population. There were increased incidences for brain tumours (SMR = 2.19, 95% CI 0.45-6.39), gastric cancers (SMR = 2.73, 95% CI, 1.00-5.94), and renal cancers (SMR = 1.68, 95% CI = 0.35-4.90). For lung cancer the risk was reduced (SMR = 0.70, 95% CI 0.15-2.05). Allowance for a latency period of 10 years from the start of exposure did not change the pattern. Logistic modelling was used to search for exposure-response relations. In a logistic model with the confounder age forced in, renal cancer had a significant positive relation with a weighted sum of employment times, where the weights describe the classification of exposure. No exposure-response relations were found for brain tumors or gastric cancers. The increased risks are based on small numbers of cases. A future follow up will add more conclusive power to the study. Specific exposures need to be identified to allow for a better dose-response analysis.

Contact of lymphocytes with Helicobacter pylori augments natural killer cell activity and induces production of gamma interferon

We studied the capacity of glutaraldehyde-fixed Helicobacter pylori to stimulate natural killer (NK) cell activity. Bacteria were incubated overnight with peripheral blood lymphocytes enriched for large granular lymphocytes (LGL), the mediators of non-major histocompatibility complex-restricted cellular cytotoxicity. Then, the cytolytic activity of LGL was tested against various tumor target cells. We observed that efficient cytolytic activity was generated against resistant and nonresistant tumor target cell lines. Nine local clinical isolates of H. pylori and the reference strain NCTC 11637 were tested, and they all were equally effective in inducing NK cell activity. However, flagellin antigen, glycine extract, urease, and lipopolysaccharide prepared from H. pylori NCTC 11637 all failed to induce significant NK cell activity. The supernatants which were collected after coincubation of bacteria with LGL contained a factor(s) which could activate resting LGL into efficient cytolytic activity. The supernatants were also analyzed for interferon (IFN) activity. We observed that high titers of IFN were produced and that IFN activity was neutralized with anti-gamma interferon (IFN-gamma) antiserum, but not with anti-IFN-alpha antiserum. Thus, contact of lymphocytes with H. pylori leads to efficient stimulation of NK cell activity and the production of IFN-gamma.

Helicobacter pylori infection and chronic atrophic gastritis among Japanese blood donors: a cross-sectional study

To evaluate an association between Helicobacter pylori (H. pylori) infection and chronic atrophic gastritis (CAG), an established precursor of gastric cancer, we performed a cross-sectional study using IgG antibody against H. pylori and pepsinogens of blood donors in four prefectures in Japan. Although a geographic correlation between the age-adjusted prevalence rates for H. pylori infection and those for CAG was not seen, the age-adjusted odds ratios (OR) of H. pylori infection for CAG were high in each area (around five for men and from four to 12.6 for women). The association between them weakened with advancing age; the ORs in the youngest age group (16-29 yrs) and in the oldest age group (50-64 yrs) were 12.5 and 2.8 for men, and 11.5 and 5.2 for women, respectively. These findings suggest that H. pylori infection is strongly associated with CAG, while there are some other factors interacting in the development of CAG. A prospective cohort study in which CAG and H. pylori infection are taken into account will be necessary to assess the risks of gastric cancer.

Cloning and genetic characterization of the Helicobacter pylori and Helicobacter mustelae flaB flagellin genes and construction of H. pylori flaA- and flaB-negative mutants by electroporation-mediated allelic exchange

Helicobacter pylori is one of the most common human pathogens. It causes chronic gastritis and is involved in the pathogenesis of gastroduodenal ulcer disease and possibly gastric carcinoma. Helicobacter mustelae is a bacterium closely related to H. pylori that causes gastritis and ulcer disease in ferrets and is therefore considered an important animal model of gastric Helicobacter infections. Motility, even in a viscous environment, is conferred to the bacteria by several sheathed flagella and is regarded as one of their principal virulence factors. The flagellar filament of H. pylori consists of two different flagellin species expressed in different amounts. The gene (flaA) encoding the major flagellin has recently been cloned and sequenced. Here we report the cloning and sequencing of two highly homologous new flagellin genes from H. pylori 85P and H. mustelae NCTC 12032. The nucleotide sequence of the H. pylori gene proved that it encoded the second flagellin molecule found in H. pylori flagellar filaments. The genes were named flaB. The H. mustelae and H. pylori flaB genes both coded for proteins with 514 amino acids and molecular masses of 54.0 and 53.9 kDa, respectively. The proteins shared 81.7% identical amino acids. The degree of conservation between H. pylori FlaB and the H. pylori FlaA major flagellin was much lower (58%). Both flaB genes were preceded by sigma 54-like promoter sequences. Mapping of the transcription start site for the H. pylori flaB gene by a primer extension experiment confirmed the functional activity of the sigma 54 promoter. To evaluate the importance of both genes for motility, flaA- and flaB-disrupted mutants of H. pylori N6 were constructed by electroporation-mediated allelic exchange and characterized by Western blot (immunoblot) analysis and motility testing. Both mutations selectively abolished the expression of the targeted gene without affecting the synthesis of the other flagellin molecule. Whereas flaA mutants were completely nonmotile, flaB mutants retained motility.

Diagnosis of Helicobacter pylori infection by using pyloriset EIA-G and EIA-A for detection of serum immunoglobulin G (IgG) and IgA antibodies

We evaluated the performance of new enzyme immunoassay (EIA) kits (Pyloriset; Orion Corporation, Orion Diagnostica, Espoo, Finland) for the detection of immunoglobulin G (IgG) and IgA antibodies to Helicobacter pylori in serum. Serum samples from 195 patients with upper abdominal complaints were collected. Biopsy specimens of the gastric mucosae were taken for histological analysis and bacterial culture. The sensitivity, specificity, and positive and negative predictive values, and efficacy of the Pyloriset EIA-G in detecting IgG antibodies to H. pylori were 92, 84, 88, 90, and 89%, respectively, when compared with those of the reference methods used. The corresponding data for detection of IgA antibodies were 80, 89, 89, 79, and 84%, respectively. The overall prevalence of defined H. pylori positivity was 54%. Moreover, the antibody tests showed a very good correlation with the biopsy findings. IgG antibodies were found in 93% of sera from patients with documented gastritis and H. pylori positivity, whereas only 4% of the sera from patients with documented gastritis and H. pylori-negative patients was positive. The results obtained for IgA antibodies were 81 and 6%, respectively. We conclude that the Pyloriset EIA-G, the test for IgG antibodies, is a good and reliable test for the detection of antibodies to H. pylori and as an indication of H. pylori infection. The determination of IgA antibodies may be used as a test that complements the IgG antibody assay.

Local and systemic immune responses in murine Helicobacter felis active chronic gastritis

Helicobacter felis inoculated per os into germfree mice and their conventional non-germfree counterparts caused a persistent chronic gastritis of approximately 1 year in duration. Mononuclear leukocytes were the predominant inflammatory cell throughout the study, although polymorphonuclear cell infiltrates were detected as well. Immunohistochemical analyses of gastric mucosa from H. felis-infected mice revealed the presence of mucosal B220+ cells coalescing into lymphoid follicles surrounded by aggregates of Thy-1.2+ T cells; CD4+, CD5+, and alpha beta T cells predominated in organized gastric mucosal and submucosal lymphoid tissue, and CD11b+ cells occurred frequently in the mucosa. Follicular B cells comprised immunoglobulin M+ (IgM+) and IgA+ cells. Numerous IgA-producing B cells were present in the gastric glands, the lamina propria, and gastric epithelium. Infected animals developed anti-H. felis serum IgM antibody responses up to 8 weeks postinfection and significant levels of IgG anti-H. felis antibody in serum, which remained elevated throughout the 50-week course of the study.

Helicobacter mustelae and Helicobacter pylori bind to common lipid receptors in vitro

Helicobacter pylori is a recently recognized human pathogen causing chronic-active gastritis in association with duodenal ulcers and gastric cancer. Helicobacter mustelae is a closely related bacterium with similar biochemical and morphologic characteristics. H. mustelae infection of antral and fundic mucosa in adult ferrets causes chronic gastritis. An essential virulence property of both Helicobacter species is bacterial adhesion to mucosal surfaces. The aim of this study was to determine whether H. mustelae binds to the same lipids shown previously to be receptors for H. pylori adhesion in vitro. By using thin-layer chromatography overlay and a receptor-based enzyme-linked immunosorbent assay, H. mustelae was found to bind the same receptor lipids as H. pylori, namely, phosphatidylethanolamine and gangliotetraosylceramide. In addition, both H. pylori and H. mustelae bound to a deacylplasmalogen phosphatidylethanolamine. In contrast to H. pylori, H. mustelae binding to receptors was unaffected by motility or viability. Murine monoclonal and bovine polyclonal antibodies against exoenzyme S, and exoenzyme S itself (from Pseudomonas aeruginosa), inhibited binding of H. mustelae to phosphatidylethanolamine and gangliotetraosylceramide. These findings show that H. mustelae binds in vitro to the same lipid receptors as H. pylori and suggest that the adhesion of H. mustelae to such species is mediated by preformed, surface-exposed adhesins which include an exoenzyme S-like protein.

Receptor affinity purification of a lipid-binding adhesin from Helicobacter pylori

Our previous work has shown that Helicobacter pylori specifically recognizes gangliotetraosylceramide, gangliotriaosylceramide, and phosphatidylethanolamine in vitro. This binding specificity is shared by exoenzyme S from Pseudomonas aeruginosa, and monoclonal antibodies against this adhesin prevent the attachment of H. pylori to its lipid receptors. We now report the use of a novel, versatile affinity matrix to purify a 63-kDa exoenzyme S-like adhesin from H. pylori which is responsible for the lipid-binding specificity of this organism.

An international association between Helicobacter pylori infection and gastric cancer. The EUROGAST Study Group

Gastric infection with Helicobacter pylori seems to be a risk factor for gastric cancer. We have conducted a multicentre epidemiological study to investigate this relation further. Our study was designed to look at the relation between the prevalence of H pylori infection and gastric cancer rates in 17 populations from 13 countries, chosen to reflect the global range of gastric cancer incidence. In each centre, about 50 males and 50 females in each of the two age groups 25-34 years and 55-64 years were selected at random from the local population and provided blood samples. Serum samples were assayed for the presence of IgG antibodies to H pylori in a single laboratory. Prevalence rates of H pylori seropositivity were related to local gastric cancer incidence and mortality rates using linear regression. There was a statistically significant relation between the prevalence of seropositivity and cumulative rates (0-74 years) for both gastric cancer incidence and mortality with regression coefficients of 2.68 (p = 0.001) and 1.79 (p = 0.002), respectively. Our findings are consistent with an approximately six-fold increased risk of gastric cancer in populations with 100% H pylori infection compared with populations that have no infection.

Aflagellated mutants of Helicobacter pylori generated by genetic transformation of naturally competent strains using transposon shuttle mutagenesis

Three out of 10 Helicobacter pylori clinical isolates were found to be naturally competent for genetic transformation to streptomycin resistance by chromosomal DNA extracted from a spontaneous streptomycin-resistant H. pylori mutant. The frequency of transformation varied between 5 x 10(-4) and 4 x 10(-6), depending on the H. pylori isolate used. Transposon shuttle mutagenesis based on this natural competence was established using the flagellin gene flaA as the target. The cloned flaA gene was interrupted by insertion of TnMax1, a mini-Tn1721 transposon carrying a modified chloramphenicol-acetyltransferase gene, the catGC cassette. Natural transformation of competent H. pylori strains with plasmid constructs harbouring a catGC-inactivated flaA gene resulted in chloramphenicol-resistant transformants at an average frequency of 4 x 10(-5). Southern hybridization experiments confirmed the replacement of the chromosomal H. pylori flaA gene by the cat-inactivated cloned gene copy via homologous recombination resulting in allelic exchange. Phenotypic characterization of the mutants demonstrated the absence of flagella under the electron microscope and the loss of bacterial motility. Immunoblots of cell lysates of the H. pylori mutants with an antiserum raised against the C-terminal portion of recombinant H. pylori major flagellin (FlaA) confirmed the absence of the 54 kDa FlaA protein. This efficient transposon shuttle mutagenesis procedure for H. pylori based on natural competence opens up new possibilities for the genetic assessment of putative H. pylori virulence determinants.

Cloning and expression of a high-molecular-mass major antigen of Helicobacter pylori: evidence of linkage to cytotoxin production

A high-molecular-mass (120- to 128-kDa) Helicobacter pylori antigen has been associated with peptic ulcer disease. We created a bank of 40,000 random chromosomal fragments of H. pylori 84-183 by using lambda ZapII. Screening of this bank in Escherichia coli XL1-Blue with absorbed serum from an H. pylori-infected person permitted the isolation and purification of a clone with a 3.5-kb insert. Subcloning of this insert (pMC3) permitted the expression of a recombinant H. pylori protein that had a mass of approximately 96 kDa and that was recognized by the human serum. Sera that were obtained from H. pylori-infected persons and that recognized the native 120- to 128-kDa H. pylori antigen recognized the recombinant 96-kDa pMC3 protein to a significantly greater extent than did sera that did not recognize the native H. pylori antigen. All 19 H. pylori isolates producing the 120- to 128-kDa antigen hybridized with pMC3; none of 13 nonproducers did so (P < 0.001). Because all 15 isolates producing the vacuolating cytotoxin hybridized with pMC3, we called the gene cagA (cytotoxin-associated gene). Sequence analysis of pMC3 identified an open reading frame of 859 amino acids, without a termination codon. Parallel screening of a lambda gt11 library with human serum revealed positive plaques with identical 0.6-kb inserts and sequences matching the sequence of the downstream region of pMC3. To clone the full-length gene, we used the 0.6-kb fragment as a probe and isolated a clone with a 2.7-kb insert from the lambda ZapII genomic library. Nucleotide sequencing of this insert (pYB 2) revealed a 785-bp sequence that overlapped the downstream region of pMC3. Translation of the complete nucleotide sequence of cagA revealed an open reading frame of 1,181 amino acids yielding a protein of 131,517 daltons. There was no significant homology with any previously reported protein sequence. These findings indicate the cloning and characterization of a high-molecular-mass H. pylori antigen potentially associated with virulence and with cytotoxin production.

Helicobacter pylori serology in patients with gastric carcinoma

Helicobacter pylori-associated gastritis has been put forward as a distinct risk factor for gastric cancer. Furthermore, among H. pylori-positive individuals a correlation between a high serum level of H. pylori antibodies and the risk of gastric cancer has been found in two different studies. Other studies have challenged this hypothesis. We therefore studied the presence and level of H. pylori serum antibodies, using an enzyme-linked immunosorbent assay technique in 116 gastric cancer patients (65 men; mean age, 67 years; range, 23-92 years) and 116 controls matched for age and sex. Patients and controls were selected on referral for gastroscopy. The prevalence of infection in gastric cancer patients was 77% (89 of 116) and in controls 79% (92 of 116). This difference is not statistically significant, nor is the prevalence of infection in cases and controls of different age cohorts significantly different. High levels of serum antibodies were found in 46% (53 of 116) of gastric cancer patients and 40% (46 of 116) of controls. Comparison of the prevalence of high serum levels of antibodies for the total population and for the different age cohorts did not show significant differences either. We conclude that the comparison of actual H. pylori infection in a cross-sectional study of gastric cancer patients and controls does not enable relative risk calculation in the study of the role of H. pylori infection in gastric carcinogenesis. Prospective studies showing diminishment of the risk for gastric cancer after eradication of H. pylori are required.

Evaluation of QuickVue, a rapid enzyme immunoassay test for the detection of serum antibodies to Helicobacter pylori

QuickVue is an enzyme immunoassay test for qualitative detection of serum immunoglobulin-G antibodies to Helicobacter pylori. We evaluated its ability to predict infection by H. pylori in 100 adult and 49 pediatric patients referred for gastric endoscopy. A patient was defined as infected with H. pylori if either culture or histology was positive. Of the 100 adult patients, 64 had H. pylori infection and QuickVue correctly identified 59 of the 64. Of 36 H. pylori-negative patients, 20 were correctly identified as negative by the test. In this sample of patients, QuickVue had a sensitivity of 92% and a specificity of 56%. In the 49 pediatric patients, QuickVue correctly identified nine of 11 infected cases and 34 of 38 noninfected patients. In this group, the sensitivity was 82% and the specificity was 89%. Overall the test had a sensitivity of 91% and a specificity of 73%. The positive predictive value was 77% and the negative predictive value was 89%.

Helicobacter pylori and gastric cancer

This review focuses on the similarities between the epidemiology of gastric cancer and the epidemiology of Helicobacter pylori. Their demographic patterns and the results of studies regarding familial and environmental risk factors are described. The association of gastric cancer and H. pylori infection with both gastric ulcer and chronic atrophic gastritis is also characterized and the possibility that a H. pylori infection could lead to gastric cancer is discussed.

Effects of ATPase inhibitors on the response of HeLa cells to Helicobacter pylori vacuolating toxin

Approximately 50% of Helicobacter pylori strains produce a toxin in vitro that induces vacuolation of eukaryotic cells. To determine whether ion transport pathways are important in the formation of toxin-induced vacuoles, HeLa cells were incubated with H. pylori toxin in the presence of nine different inhibitors of ion-transporting ATPases. Oligomycin, an inhibitor of predominantly F1F0-type ATPases, had no effect on toxin activity. Inhibitors of predominantly V-type ATPases, exemplified by bafilomycin A1, inhibited the formation of vacuoles in response to the H. pylori toxin and reversed the vacuolation induced by the toxin. In contrast, at concentrations of > or = 100 nM, ouabain and digoxin, inhibitors of the Na(+)-K+ ATPase, potentiated the activity of H. pylori toxin. The inhibitory effects of bafilomycin A1 could not be overcome by the potentiating effects of ouabain. These data suggest that intact activity of the vacuolar ATPase of eukaryotic cells is a critical requirement in the pathogenesis of cell vacuolation induced by H. pylori toxin and that vacuole formation by this toxin is associated with altered cation transport within eukaryotic cells.

Use of autoradiography to assess viability of Helicobacter pylori in water

Autoradiographic methods have been developed to detect metabolic activity of viable but nonculturable cells of Helicobacter pylori in water. Four strains of H. pylori were studied by using microcosms containing suspensions of 72-h cultures in water. The suspensions of aged, nonculturable cells of H. pylori were incubated with [3H]thymidine for 24 to 72 h, after which the cell suspensions were exposed to Kodak NTB2 emulsion for 3 to 28 days. Each sample was processed with three separate controls to rule out false-positive reactions. The organism remains viable and culturable under these conditions for up to 48 h and, in some cases, 20 to 30 days, depending on physical conditions of the environment. We found that temperature was a significant (P < or equal to 0.01) environmental factor associated with the viability of H. pylori cells in water. Autoradiographs of tritium-labeled cells of H. pylori revealed aggregations of silver grains associated with uptake by H. pylori of radiolabelled substrate. Findings based on the autoradiographic approach give strong evidence supporting the hypothesis that there is a waterborne route of infection for H. pylori. The possibility that H. pylori may persist in water in a metabolically active stage but not actively growing and dividing is intriguing and relevant to public health concerns.

An in vitro adherence assay reveals that Helicobacter pylori exhibits cell lineage-specific tropism in the human gastric epithelium

Helicobacter pylori is a microaerophilic bacterium found in the stomach of asymptomatic humans as well as patients with acid peptic disease and gastric adenocarcinoma. We have developed an in situ adherence assay to examine the cell lineage-specific nature of binding of this organism and to characterize the nature of cell surface receptors that recognize its adhesin. Fluorescein isothiocyanate-labeled H. pylori strains were bound to surface mucous cells present in the pit region of human and rat gastric units but not to mucous neck, parietal, or chief cell lineages present in the glandular domains of these units. Binding was abolished by proteinase K treatment of tissue sections and by pretreatment of the bacteria with bovine submaxillary gland mucin, a rich source of fucosylated and sialylated carbohydrates. Several lines of evidence suggest that binding to surface mucous cells is not dependent upon terminal nonsubstituted alpha 2,3- and alpha 2,6-linked sialic acids in the adhesin receptor: (i) binding was not inhibited by incubating H. pylori strains with sialylated glycoconjugates such as fetuin and free sialyllactose; (ii) immunohistochemical stainings using the sialic acid-specific Sambucus nigra and Maackia amurensis lectins and the cholera toxin B subunit did not detect any sialylated glycoconjugates in these epithelial cells; and (iii) binding was not sensitive to metaperiodate under conditions that selectively cleaved carbons 8 and 9 of terminal nonmodified sialic acids. A role for fucosylated epitopes in the glycoprotein(s) that mediate binding of H. pylori to surface mucous cells was suggested by the facts that this lineage coexpresses the adhesin receptor and major fucosylated histo-blood group antigens, that monoclonal antibodies specific for histo-blood group antigens H, B, and Leb block binding, and that the lectin Ulex europaeus type 1 agglutinin, which is specific for alpha-L-fucose, also bound to the same cells that bound the bacteria. Furthermore, human colostrum secretory IgA inhibited adhesion in a metaperiodate- and alpha-L-fucosidase-sensitive but neuraminidase-independent fashion. The in situ adherence assay should be useful in further characterizing the H. pylori adhesin and its receptor and for identifying therapeutically useful compounds that inhibit strain-specific and cell lineage-specific binding of this human pathogen.

Paracrystalline inclusions of a novel ferritin containing nonheme iron, produced by the human gastric pathogen Helicobacter pylori: evidence for a third class of ferritins

An abundant 19.3-kDa Helicobacter pylori protein has been cloned, and the sequence is homologous with a ferritin-like protein produced by Escherichia coli K-12. Homologies are also present with a number of eucaryotic ferritins, as well as with the heme group-containing bacterioferritins. All amino acids involved in chelation of inorganic iron by ferritins from humans and other higher species are conserved in the H. pylori protein. Consistent with the structural data indicating an iron-binding function, E. coli overexpressing the H. pylori ferritin-like protein accumulates almost 10 times more nonheme iron than vector controls, and the iron-binding activity copurifies with the 19.3-kDa protein. Immunoelectron microscopy of H. pylori, as well as of E. coli overexpressing the H. pylori gene, demonstrates that the gene product has a cytoplasmic location where it forms paracrystalline inclusions. On the basis of these structural and functional data, we propose that the H. pylori gene product (termed Pfr) forms the basis for a second class of bacterial ferritins designed to store nonheme iron.

Helicobacter pylori may be transmitted through gastrofiberscope even after manual Hyamine washing

Endoscopy is an effective diagnostic technique for gastric cancer, which is believed to be associated with Helicobacter pylori. Manual Hyamine washing is a widely used fiberscope cleaning method. Urease B gene of Helicobacter pylori was detected in 50% of the wash-out samples from the biopsy-suction channel of a fiberscope after manual Hyamine washing by nested polymerase chain reaction, and bacterial culture revealed viable Helicobacter pylori in 19%. However, Helicobacter pylori was not detected by either of the above methods in the biopsy-suction channel of the fiberscope after mechanical washing. These findings indicate that manual Hyamine washing of fiberscopes is insufficient to prevent iatrogenic Helicobacter pylori transmission, and that mechanical washing after manual Hyamine washing is essential.

Role of Helicobacter pylori in the pathogenesis of gastritis, peptic ulcer and gastric cancer

Helicobacter pylori is the major causal factor in chronic gastritis. Its acquisition leads to a chronic, usually lifelong, inflammation of the gastric mucosa, which may gradually progress to atrophy (with intestinal metaplasia) in a significant proportion of infected individuals. This progression is probably multifactorial, being influenced by genetic or environmental factors in addition to H. pylori infection. The pathogenesis of peptic ulcer and gastric cancer is closely associated with H. pylori gastritis and its subsequent atrophic sequelae (atrophic gastritis). H. pylori-induced gastritis is an important risk factor in the multifactorial aetiology of these diseases. It causes a cascade of reactions that damage the gastric mucosa and epithelium in various ways. The specific mechanisms involved are largely unknown. Some are probably bacterium-related reactions, which are influenced by various virulence factors, and others are consequences of the mucosal inflammation and atrophy. The risk of peptic ulcer and gastric cancer in patients with H. pylori gastritis can be summarized as follows: i) the risk of both peptic ulcer and gastric cancer is low in individuals with a normal stomach; ii) the risk of peptic ulcer is approximately ten times higher and the risk of gastric cancer approximately twice as high in patients with non-atrophic H. pylori-positive gastritis as in those with a normal stomach; iii) these risks are further increased (twofold to threefold) when there is antral atrophy; whereas iv) in the presence of corpus atrophy the risk of gastric cancer remains high, but that of peptic ulcer decreases gradually to zero with increasing severity of corpus atrophy.

Cigarette smoking and Helicobacter pylori infection

The direct urease test was used in 462 patients with normal upper digestive tracts, 108 with duodenal ulcers and 43 with gastric ulcers who attended for upper digestive endoscopy in a prospective study. There was a strong association between Helicobacter pylori infection and current cigarette smoking in patients with normal endoscopy (49.6% vs 35.5%, P < 0.01). The associations of peptic ulcer both with H. pylori infection and cigarette smoking were also confirmed. The excess of peptic ulcer disease in cigarette smokers may be explained by their increased susceptibility to H. pylori infection.

Pathology of the gastric antrum and body associated with Helicobacter pylori infection in non-ulcerous patients: is the bacterium a promoter of intestinal metaplasia?

A series of 115 consecutive, non-ulcerous, dyspeptic patients were examined for Helicobacter pylori (H. pylori) colonization in the gastric antral and/or body mucosa using Giemsa staining. Findings were correlated with the presence and degree of activity of superficial gastritis, deep gastritis, atrophic gastritis and with the presence of intestinal metaplasia. The prevalence of H. pylori positivity was 61.7%. In 59 of the 71 positive patients (83%), H. pylori was detected in the antrum or in both the antral and oxyntic mucosa. In the remaining 12 positive patients, H. pylori was detected only in the oxyntic mucosa nad in all these cases, the antrum showed intestinal metaplasia associated with atrophic gastritis (25%). In both antral and oxyntic mucosa, the activity of the gastritis was significantly correlated with H. pylori colonization. Linear logistic regression analysis showed that in patients with intestinal metaplasia the presence of H. pylori infection was significant in predicting the presence of more extensive intestinal metaplasia after adjusting for age. The prevalence of intestinal metaplasia types II and III was 65.5% in the H. pylori positive and 25% in the H. pylori negative patients. The antral mucosa is thought to be the elective site for H. pylori related histological lesions. At a later stage, H. pylori can be detected only in the oxyntic area while the antral mucosa shows extensive metaplastic or atrophic lesions. We would suggest that H. pylori plays a promotional role in the morphogenesis of intestinal metaplasia.

Pepsinogens in health and disease

Pepsinogens, precursors of pepsins (potent and abundant digestive enzymes that are the primary products of the gastric chief cells), are members of the family of aspartic proteases. Because of the heterogeneity of pepsinogens, several classifications have appeared in the literature. I describe the recommended classification and nomenclature of the aspartic proteases and discuss their genetics, biochemistry (structure, activation of zymogens, mechanism of proteolytic activity and inhibitors), and physiology. The focus will be on the zymogens of pepsin, the so-called pepsinogens. The measurement of these enzymes in serum is a reliable noninvasive biochemical method for evaluating peptic secretion and obtaining information on the gastric mucosal status. A detailed review of the methods for the measurement of pepsinogens in serum, urine, and gastric mucosa is also provided. Data on pepsinogen levels in healthy subjects are discussed with respect to sex, age, smoking habit, and the presence of a circadian rhythm. The value of pepsinogen measurements in peptic ulcer to determine ulcer outcome and recurrence, in gastric cancer, and in Helicobacter pylori infection is reviewed. Finally, the effects of drugs on peptic secretion are discussed. In light of these data, the measurement of aspartic proteases, and in particular that of pepsinogen A and C, may be regarded as an effective biochemical approach to the evaluation and monitoring of patients with upper gastrointestinal diseases.

The Helicobacter pylori 19.6-kilodalton protein is an iron-containing protein resembling ferritin

The gastric pathogen Helicobacter pylori has been shown to produce a 19.6-kDa protein with apparent binding activity for erythrocytes, human buccal epithelial cells, and laminin. In this report we demonstrate that it is an iron-binding protein, resembling ferritin both structurally and biochemically. Also, because its binding activity for laminin, erythrocytes, and buccal cells was abolished by low concentrations of Tween 20, binding is likely nonspecific.

Purification and characterization of the urease enzymes of Helicobacter species from humans and animals

The urease enzymes of Helicobacter pylori, H. mustelae, H. felis, and H. nemestrinae have been purified to homogeneity by affinity chromatography and characterized. The native urease enzymes of the four organisms were found to be almost identical, with a pI of 6.1 and molecular masses of 480 to 500 kDa, as determined by electrophoretic mobility in nondenaturing polyacrylamide gels. Transmission electron microscopy of the native urease showed it to be a molecule approximately 13 nm in diameter, with hexagonal symmetry. Denaturation studies indicated that each urease enzyme molecule was composed of two nonidentical subunits with molecular masses of approximately 64 and 30 kDa. The subunits were present in a 1:1 ratio, suggesting a hexameric stoichiometry for the native molecule. The predicted molecular mass of H. pylori urease, based on subunit molecular weight and stoichiometry, is 568 kDa. N-terminal amino acid sequencing of the enzyme subunits from the four species revealed high levels of homology. The large subunits (UreB) were found to be 92 to 100% homologous, and the small subunits (UreA) were 75 to 95% homologous over the first 12 to 20 residues. The high degree of homology suggests a common ancestral origin and an important role for the urease enzymes of these organisms.

Construction of a Helicobacter pylori genome map and demonstration of diversity at the genome level

Genomic DNA from 30 strains of Helicobacter pylori was subjected to pulsed-field gel electrophoresis (PFGE) after digestion with NotI and NruI. The genome sizes of the strains ranged from 1.6 to 1.73 Mb, with an average size of 1.67 Mb. By using NotI and NruI, a circular map of H. pylori UA802 (1.7 Mb) which contained three copies of 16S and 23S rRNA genes was constructed. An unusual feature of the H. pylori genome was the separate location of at least two copies of 16S and 23S rRNA genes. Almost all strains had different PFGE patterns after NotI and NruI digestion, suggesting that the H. pylori genome possesses a considerable degree of genetic variability. However, three strains from different sites (the fundus, antrum, and body of the stomach) within the same patient gave identical PFGE patterns. The genomic pattern of individual isolates remained constant during multiple subcultures in vitro. The reason for the genetic diversity observed among H. pylori strains remains to be explained.