Comparison of different antigen preparations in an evaluation of the immune response to Campylobacter pylori

Characterizing antigenic determinants in Helicobacter pylori CagA capable of detecting serum antibodies in children

Helicobacter pylori can persistently colonize the mucosa of the human stomach, resulting in gastric disorders. Endoscopic biopsy for rapid urease test and histopathologic examination are considered as the most accurate diagnostic methods for H. pylori infection. Serological methods are recommended for children because of invasiveness of the diagnosis mentioned above. Here, the cytotoxin-associated gene A protein (Cag A), as an immunodominant antigen, was subdivided to determine which regions harbor antigenicity for humans. CagA was divided into 17 overlapping fragments of ∼400 bp, which were used for the analysis of antigenic determinants. The partial proteins were subjected to immunoblot analysis using pooled serum samples from children with gastric symptoms. A partial recombinant CagA protein containing epitope regions (683-749 amino acids), which were identified in this study, was produced and used for the detection of anti-CagA antibodies and further investigated its serodiagnostic value for determination of H. pylori infection in children. The serum IgG reactivities from children with gastric symptoms were significantly three times more than that of serum samples from children with non-gastric symptoms (P < 0.005). Moreover, the serum IgG reactivities from children showing strong urease activity of gastric biopsies were significantly higher than those with moderate and weak urease activities (P < 0.05). Hence, the partial CagA is a candidate antigen for diagnosis of H. pylori infection.

A review of serological tests to assist diagnosis of reactive arthritis: critical appraisal on methodologies

On a population-based level, the incidence of reactive arthritis (ReA) is 0.6–27/100,000. The definition of ReA varies and its pathogenesis is not yet clear. Attempts in basic immunology to suggest hypotheses for proliferation of forbidden B cell clones, molecular mimicry, and involvement of cross-reactive antibodies are helpful but not sufficient. Importantly, for the clinical diagnosis of the preceding infection, serology is widely used. Unfortunately, the accuracy of associations between serologic findings and clinical conclusions is plagued by poor standardization of methods. So far, few attempts have been done to examine the pitfalls of different approaches. Here, we review several serologic techniques, their performance and limitations. We will focus on serology for Yersinia, Campylobacter, Salmonella, Shigella, and Chlamydia trachomatis because these bacteria have a longer history of being associated with ReA. We also address controversies regarding the role of serology for some other bacteria linked to autoimmune disorders.

Diagnosis and genotyping of Helicobacter pylori by polymerase chain reaction of bacterial DNA from gastric juice

BACKGROUND

Efficient and accurate detection of Helicobacter pylori infection as well as identification of virulence-associated alleles are important for the treatment of gastroduodenal diseases caused by this gastric pathogen. The present study was performed to test the efficiency of gastric juice polymerase chain reaction (PCR) method for the rapid detection of H. pylori infection and to determine the bacterial genotypes without the need for culture, which is often not feasible especially in developing countries.

METHODS

DNA was extracted from gastric juice samples collected from 45 subjects and was used to amplify urease B gene (ureB) for H. pylori. Results obtained from this method were further confirmed by rapid urease test (RUT), histology and culture. Genotypes of the infected strains predicted from gastric juice PCR were compared to the genotype data obtained from the isolated strains.

RESULTS

Among 45 cases, 32 were positive by RUT, 37 by histological examination, 25 by gastric juice PCR method, while culture yielded positive results for 19 samples. Except for one case, all the 19 culture-positive strains gave the same genotype with the gastric juice PCR result. It was found that the gastric juice PCR is more efficient for detection of multiple-strain infection as compared to genotype data obtained from strains isolated as pooled culture.

CONCLUSIONS

This moderately sensitive technique could be employed with good efficiency, particularly in cases where it is difficult to obtain biopsy. Moreover, with this method bacterial genotype could be obtained.

Western blotting is useful in the salivary diagnosis of Helicobacter pylori infection

BACKGROUND

The salivary diagnosis of Helicobacter pylori infection offers attractive possibilities for the epidemiological study of infection in children. Salivary enzyme linked immunosorbent assay (ELISA) is less reliable then serum ELISA, owing to variable transudation of immunoglobulin. In addition, children are more difficult to study because of lower specific serum antibody concentrations to H pylori. The performance of salivary western blotting in comparison with serum western blotting and serum ELISA was investigated in school children.

SUBJECTS AND METHODS

Paired serum and saliva specimens were obtained from 669 [corrected] school children aged 9-11 in 10 British towns. All saliva and serum specimens were first analysed by ELISA; subsequently, western blotting of both specimens was performed on 31 and 34 specimens, respectively, to establish the criteria for positivity for western blotting. The remaining 121 specimens were then tested blindly and saliva was compared with the serum.

RESULTS

The sensitivity and specificity of salivary ELISA in the 669 [corrected] specimens was 32 of 50 (64%) and 530 of 619 (86%) [corrected], respectively, when compared with serum ELISA. The western blotting validation was performed on 28 subjects with positive serum and positive salivary ELISA, 28 saliva positives with negative serum, 16 saliva negatives with positive serum, and 50 doubly negative subjects. Compared with serum western blots, the sensitivity and specificity of salivary western blots was 38 of 47 (81%) and 68 of 75 (91%), respectively. Using serum ELISA as the gold standard, the sensitivity and specificity were 32 of 44 (73%) and 72 of 78 (92%), respectively, the specificity being significantly higher than salivary ELISA (p < 0.001).

CONCLUSION

Salivary western blotting for IgG is useful in the diagnosis of H pylori infection and is superior to ELISA. It also permits the identification of pathogenic strains.

Utilization of proteinase K-treated cells as lipopolysaccharide antigens for the serodiagnosis of Helicobacter pylori infections

We have evaluated the use of proteinase K (PK)-treated cells isolated from Helicobacter pylori as lipopolysaccharide (LPS) antigens in an immunoblot assay and an enzyme-linked immunosorbent assay (ELISA) for the serodiagnosis of H. pylori infection. The sera from patients with chronic gastritis, gastric ulcer, duodenal ulcer or gastric cancer, and from healthy adults with or without H. pylori infection were assayed with three commercial serodiagnostic kits (HM-CAP, Helico-G, and G.A.P. II) and novel methods relying on the use of PK-treated cells. The PK-treated cells used in these assays were selected on the basis of their possibility to possess a common epitope in the O-polysaccharides of H. pylori, which is known to be highly immunogenic in humans. Of the sera from these patients, 71-94% were positive with the commercial kits, 97% with immunoblot assay, and 90% with ELISA. On the other hand, of the healthy adults infected with H. pylori, 72-97% were positive with the commercial kits, 86% with immunoblot assay, and 72% with ELISA. PK-treated cells that did not contain the common epitope were unsuitable as an antigen for immunoblot assay or ELISA. Furthermore, the reactivity of these sera reacted specifically with H. pylori PK-treated cells but not with LPSs from other gram-negative bacteria, such as Campylobacter, Proteus, Bordetella, and Salmonella. These results demonstrate that the serological assays relying on the use of H. pylori PK-treated cells possessing a highly antigenic epitope are potentially useful as a serodiagnostic test for H. pylori infection.

Antibodies against Helicobacter pylori in feces and saliva before and after eradication therapy

OBJECTIVE: To determine specific antibody levels against Helicobacter pylori antigens in stool and saliva specimens from H. pylori-infected subjects and seronegative controls. METHODS: Antibody levels against a total membrane preparation (MP) and purified flagellin from H. pylori were measured by enzyme-linked immunosorbent assays (ELISAs) in fecal extracts (FEs) and sera from 21 H. pylori-infected and 17 non-infected adult Swedish volunteers; specific antibody levels in saliva (IgG and IgA titers) were also measured in the majority of them. Follow-up specimens after successful eradication of H. pylori were collected after 5--7 weeks (all specimens) and 5 months (FEs and sera). RESULTS: Geometric mean specific IgA antibody levels, adjusted to total IgA concentration, in FEs were significantly higher (p<0.05) in the H. pylori-infected than in the control group against MPs (p<0.05) and flagelin (p<0.05). The total IgA concentrations in FEs from infected and seronegative controls were comparable and the IgA was mainly of the secretory type. Saliva specimens from H. pylori-infected subjects had higher ELISA IgA than IgG titers against MP. Anti-MP antibodies of both isotypes were higher in the infected than in the non-infected group (p<0.05 for both isotypes). The total IgA levels were also significantly (p<0.05) higher in saliva from the H. pylori-infected subjects than in saliva from the controls (geometric mean 292 mg/L and 173 mg/L, respectively). Eradication therapy resulted in a more rapid decline in antibody levels in FEs than in corresponding sera or saliva specimens. CONCLUSIONS: Specific antibodies against H. pylori MP were detected in FEs as well as in saliva from most of the infected volunteers, the mean antibody levels being significantly higher in specimens from the H. pylori-infected subjects than from seronegative controls. The results suggest that analyses of antibody levels in FEs may be used for follow-up of patients early (5--7 weeks) after onset of successful eradication therapy.

An analysis of seven different methods to diagnose Helicobacter pylori infections

BACKGROUND

It has been debated which diagnostic test should be preferred for the diagnosis of Helicobacter pylori in patients with gastroduodenal diseases.

METHODS

The H. pylori infection was diagnosed prospectively in 97 untreated patients. H. pylori was diagnosed by means of tests based on five different principles: 1) culture, 2) microscopy (HLO), 3) urease activity (urea breath test (UBT) and urease test on biopsy specimens (CLO test)), 4) DNA detection (polymerase chain reaction (PCR)), and 5) IgG antibody detection (enzyme-linked immunosorbent assay (EIA) and Western blotting (WB)).

RESULTS

This study showed that two positive tests out of five tests, based on different principles, were most reliable for predicting the H. pylori infection. Most tests had specificities and predictive values for a negative result greater than 90%. The most important difference between the tests was the sensitivity and the predictive value for a positive result (PPV). WB, HLO, UBT, and PCR had sensitivities and PPV greater than 75%.

CONCLUSIONS

The non-invasive tests UBT and WB are reliable, both alone and in combination, and they are recommended for the pre-endoscopic diagnosis of H. pylori. WB is recommended as a confirmative test for antibody detection by EIA. When patients have an upper endoscopy, we recommend taking biopsy specimens for culture and histology because of the additional information obtained about susceptibility, virulence determinants, and morphology, including the degree of inflammation.

Immunoblot assay for serodiagnosis of Helicobacter pylori infections

An immunoblot assay for the serological diagnosis of Helicobacter pylori infection was evaluated. Serum samples from patients whose gastric biopsy specimens were known to be positive or negative for H. pylori on culture were used to establish interpretive criteria for the immunoblot assay. A panel of sera from patients with diseases other than H. pylori infection and sera from healthy blood donors were included to validate these criteria. All sera were initially assessed in an enzyme immunoassay (Ge-EIA), based on acid glycine-extracted cell surface proteins of H. pylori NCTC 11637. The same antigen extract was used in the immunoblot assay. In addition, the Ge-EIA and the immunoblot assay were compared with a commercially available EIA (Seradyn, Color Vue Pylori). Bands of 110/120 kDa and/or two of five low-molecular-mass proteins (26, 29, 30, 31, and 33 kDa, in any combination) showed a strong correlation with the H. pylori culture-positive patients (97.5%) compared to the correlation obtained with the EIA results (Ge-EIA, 87.5%; Seradyn EIA, 92.5%), and the antibody responses to these proteins were considered specific reactions. In 37 of 40 serum samples from culture-negative patients and also in sera from patients with other disorders, a moderate antibody reactivity to the medium-size proteins (43 to 66 kDa) was observed, and these were considered not valuable for a specific immunoblot assay. Among sera from culture-positive patients, 39 of 40 serum samples were defined to be immunoblot positive, and from among sera from culture-negative patients, 3 of 40 serum samples were defined to be immunoblot positive. The use of sera from patients with negative cultures for H. pylori as negative controls may decrease the sensitivity due to sampling error and false-negative culture results. Immunoblot assay-positive results were detected among 10% of sera from patients with other diseases, whereas they were detected among 42.5% of sera by the Ge-EIA and 47.5% of sera by the Seradyn-EIA. The higher number of EIA-positive sera in this group reflects a possible cross-reactivity (false-positive EIA result). Of the blood donors, representing asymptomatic but possibly colonized subjects, 24% were immunoblot positive. In conclusion, our data indicate that immunoblotting is more sensitive as well as more specific than EIA. Moreover, it permits detection of antibody responses to specific antigens, e.g., the cytotoxin-associated CagA protein, which may have pathological implications.

The role of serology in the diagnosis of Helicobacter pylori infection in children

The aim of this study was to evaluate the diagnostic accuracy of serologic tests and to verify whether specific IgG antibody can be used in the diagnosis of Helicobacter pylori infection in children without endoscopy. Serologic and endoscopic examinations were performed in 310 children (1 month-15 years) with gastrointestinal symptoms. Serologic outcomes were compared with the results of rapid urease test, histologic examination, and culture. The prevalence of H. pylori infection was 21.0% and the seropositivity of H. pylori was 24.2% in these symptomatic children. Serologic examination for diagnosis of H. pylori showed a sensitivity of 94.9% and a specificity of 92.4%, diagnostic reliability equal to the rapid urease test and histologic examination in children. The serum IgG test is a useful tool for the diagnosis of H. pylori infection, especially in children.

Helicobacter pylori antibodies in sera of children suffering from chronic abdominal pain

107 pediatric patients aged 9 to 18 with persistent gastric complaints were examined serologically and bacteriologically for Helicobacter pylori. Helicobacter was identified in 48 (45%) of individuals. 51 (48%) of children were found to be seropositive when H. pylori antibodies were detected by the ELISA; 56 (52%) when the passive haemagglutination test was used, and 41 (38%) in the latex agglutination test. 25% of culture-negative patients were found to be seropositive. The percentage of raised H. pylori antibody titres in the control (healthy subjects) varied from 20 to 27%, depending on the method applied.

Immunological activity of lipopolysaccharide of Helicobacter pylori on human peripheral mononuclear blood cells in comparison to lipopolysaccharides of other intestinal bacteria

Lipopolysaccharide of Helicobacter pylori was tested for its mitogenicity and for its ability to stimulate cytokine release in human peripheral blood mononuclear cells (PBMC) of healthy and H. pylori-infected blood donors. Mitogenicity in PBMC induced by H. pylori LPS was similar to that induced by Campylobacter jejuni lipopolysaccharide, but lower than that induced by Escherichia coli lipopolysaccharide in the H. pylori negative blood donor group. Furthermore, H. pylori LPS was able to induce tumour necrosis factor (TNF) interleukin 1 (IL-1) and interleukin 6 (IL-6) secretion of PBMC. Compared with the ability of C. jejuni and E. coli lipopolysaccharides to stimulate cytokine release, H. pylori lipopolysaccharide induced a significantly lower TNF and IL-1 secretion of PBMC than the other tested bacterial lipopolysaccharides. Similar amounts of IL-6 release were obtained by stimulation of PBMC with H. pylori and C. jejuni lipopolysaccharides, whereas a higher IL-6 release was measured by stimulation with E. coli lipopolysaccharide. The results of this study suggest that H. pylori lipopolysaccharide has a lower immunological activity than lipopolysaccharides of other intestinal bacteria. This is probably due to its unusual acylation and phosphorylation pattern of lipid A.

Serological detection of Helicobacter pylori by a flow microsphere immunofluorescence assay

A flow cytometric immunofluorescence assay (FMIA) for the detection of immunoglobulin G antibodies to Helicobacter pylori was developed. A multicomponent antigen was prepared and used to coat carboxylated polystyrene microspheres for reaction with patient sera followed by fluorescein isothiocyanate-labelled goat anti-human immunoglobulin G. The reacted microspheres were collected with a flow cytometer, and fluorescence was quantitated relative to the cutoff value provided by pooled sera from patients in whom H. pylori could not be demonstrated by culture or histology. Serum samples from 28 H. pylori-positive patients and 27 H. pylori-negative patients were tested by FMIA. Additionally, an in-house enzyme-linked immunosorbent assay (ELISA) employing the same antigen preparation and a commercially available ELISA were used to assay the patient population. Both the FMIA and in-house ELISA were 100% sensitive and 89% specific with positive and negative predictive values of 90 and 100% and no equivocal results. The commercial ELISA was 96% sensitive and 89% specific with positive and negative predictive values of 90 and 96% and five equivocal results. FMIA provides a rapid, inexpensive, and easily performed means for serodiagnosis of H. pylori.

Effect of antimicrobial therapy on the specific serological response to Helicobacter pylori infection

The systemic immune response to Helicobacter pylori was studied in 247 infected adult patients before antimicrobial therapy and at different intervals following therapy. Endoscopy with simultaneous collection of biopsies was performed in all patients immediately before treatment, 4 to 6 weeks after the end of therapy and 6 to 12 months later. A 14C-urea breath test was performed 3 to 6 months after the end of treatment. Biopsy specimens were cultured and examined histologically using Giemsa stain. Sera were tested for Helicobacter pylori IgG antibodies with a commercial enzyme immunoassay using species-specific antigens. Overall, Helicobacter pylori was eradicated in 120 patients while the other 127 remained infected with the organism. The follow-up period ranged from 4 weeks to 33 months (mean 10.2 months). Pretreatment IgG levels did not differ significantly between the two groups of patients. Six weeks after the end of treatment a slight but definite decrease in the IgG antibody levels was seen irrespective of treatment success. In the 127 patients who remained Helicobacter pylori-positive, the level of IgG antibodies remained stable or increased with time. A continuous fall in antibody levels was observed following bacterial eradication in the other 120 patients, but the difference in antibody levels between treatment responders and nonresponders became significant only more than six months after the end of treatment (p = 0.001). Serological testing may be useful for monitoring the outcome of long-term treatment of Helicobacter pylori infection and obviate the need for endoscopy.

Serodiagnosis of Helicobacter pylori infections with an enzyme immunoassay using the chromatographically purified 120 kilodalton protein

A membrane-associated 120 kDa protein of Helicobacter pylori with known species-specificity was isolated and used in an enzyme immunoassay (EIA) for the detection of Helicobacter pylori-specific IgG antibodies in patient sera. The EIA was compared with two other methods used for serodiagnosis of Helicobacter pylori infections: an EIA using sonicated whole Helicobacter pylori cell antigen and Western immunoblot. In a prospective study 127 unselected patients (76 patients with antrum gastritis, 51 patients without gastritis) who underwent gastroscopy were studied histologically and serologically. The EIA using the purified 120 kDa protein had the highest specificity (92%) compared with the EIA using a whole cell sonicate of a single Helicobacter pylori strain as antigen (60.7%) and the immunoblot (90.2%). The sensitivity was 96%, 100% and 92%, respectively. Sera of three control patients reacted strongly in all three methods, indicating possible Helicobacter pylori infection with negative histological findings. The EIA using the 120 kDa protein as antigen was shown to be a specific and sensitive technique for the serodiagnosis of Helicobacter pylori infections.

Serodiagnosis of Helicobacter pylori infections by detection of immunoglobulin G antibodies using an immunoblot technique and enzyme immunoassay

A transferable solid phase enzyme immunoassay (TSP-EIA) and an immunoblot technique were evaluated for the detection of IgG antibodies against Helicobacter pylori. Using the biopsy urease test as reference method, the sensitivity and specificity of the EIA were 96% and 100%, respectively. Immunoblot analysis was carried out by testing sera from patients with a positive urease test who suffered from type B gastritis, gastric and duodenal ulcers, and a negative control group. The immunoblotted Helicobacter pylori proteins showed reproducible immunoreactive bands at molecular weights of 130, 93, 75 and 67 kDa. The molecular weight protein fractions of Helicobacter pylori of 180 kDa and higher were found to be of minor immunological significance. Proteins of less than 60 kDa exhibited wide serum-specific variations in reactivity after immunostaining. No correlation between specific immunoblot patterns and clinical signs induced by Helicobacter pylori infection was observed.

Immunoglobulin G antibodies to Helicobacter pylori in patients with dyspeptic symptoms investigated by the western immunoblot technique

Helicobacter pylori is a gram-negative, curved, rod-shaped bacterium known to cause gastritis and to be an important factor in the pathogenesis of peptic ulcers. Serological testing has recently been proposed as an aid in diagnosis of H. pylori infections. In this study, we used the Western immunoblot technique to evaluate the possibility of using one or more of the antigens from H. pylori for this purpose. Thirteen major bands and about 30 minor bands could be identified by Western blotting when sera from 53 consecutive dyspeptic patients, 27 healthy children, and 25 blood donors were evaluated. Antibodies against most of the major bands were found significantly more frequently in patients with H. pylori infections than in patients without such infections. However, antibodies against a single polypeptide were not produced by all patients with H. pylori infection. Polypeptides with molecular masses of 120, 50, and between 19 and 36 kDa seem to be the most specific polypeptides for the diagnosis of H. pylori infections. This study showed only minor differences in antigenic composition between different clinical isolates of H. pylori, and serological cross-reactions with other bacteria were limited. Major serological cross-reactions were found only with Campylobacter jejuni and with bacterial lipopolysaccharide. However, one band at 60 kDa reacted with antiserum to the Legionella micdadei common antigen, which may indicate a cross-reaction with common antigen from several other bacteria. This study demonstrates that a number of bands may be useful as antigens in serological tests after isolation and purification.

Serodiagnosis of Helicobacter pylori-associated gastritis with a monoclonal antibody competitive enzyme-linked immunosorbent assay

Forty-nine monoclonal antibodies against Helicobacter pylori were screened to investigate their capacity to be used in enzyme-linked immunosorbent assay (ELISA) competitive systems for the serodiagnosis of Helicobacter pylori infection. On the basis of the inhibition pattern showed by the sera of five infected patients, the antibodies were subdivided into five groups. The immunoblotting analysis showed that the antibodies recognized a total of nine different antigenic determinants. In a study of the reaction of the antibodies with 12 isolates of H. pylori a total of 9 antigenic profiles were identified. Two monoclonal antibodies, HpN44 and HpN45, which recognized a 64-kD protein, were inhibited by all 5 positive sera. Antibody HpN45 was labeled with horseradish peroxidase, and the competitive ELISA was compared with an ordinary indirect ELISA in a study of 102 patients undergoing gastroscopy. Seventy-three patients proved to be infected by H. pylori according to urease or histologic tests. The sensitivity and specificity were 90.4% and 89.6%, respectively, for the indirect ELISA and 100% and 89.6% for the HpN45 competitive assay. The three patients who were 'false seropositive' with both serologic tests had atrophic gastritis. The high diagnostic performance and simplicity of the HpN45 monoclonal competitive ELISA make it suitable for routine serodiagnosis of H. pylori infection.

Diagnostic value of decreasing IgG, IgA, and IgM antibody titres after eradication of Helicobacter pylori

Titres of antibody to Helicobacter pylori are known to fall with eradication of bacteria. To find out what degree of fall would reliably indicate eradication, 144 patients with Helicobacter pylori infection were given antimicrobial therapy for 2 weeks and then followed up at 6 weeks, 6 months, and 12 months with serological tests, bacterial cultures, and histological studies of gastric specimens. 6 weeks after treatment IgG titres had fallen by 20-30% irrespective of the success of bacterial eradication. In the 121 bacteria-negative patients the decrease continued. 6 and 12 months after treatment the titre was 50% or less of pretreatment value in 97% of these patients. In the 23 patients who remained infected, the initial drop of IgG titres, if any, was followed by unchanged or slightly rising titres. IgA and IgM titres, initially raised in 64% and 4% of the patients, respectively, showed similar trends. The high sensitivity (97%) of the IgG antibody tests and a consistent fall within 6 months after eradication of H pylori infection made IgG the most useful immunoglobulin class for follow-up of antimicrobial therapy in individual patients. IgA antibodies were valuable in the 2% patients who had raised titres in this immunoglobulin class only. The few patients (5.5%) who had raised IgM titres also had high IgG titres. Serological tests thus are a cheap and reliable means of monitoring success of eradication of H pylori.

Cell surface proteins of Helicobacter pylori as antigens in an ELISA and a comparison with three commercial ELISA

Cell surface proteins of Helicobacter pylori were solubilized by extraction with acidic glycine buffer, N-octyl-glucoside, lithium chloride, and distilled water, and by sonication. The preparations were evaluated as antigens in ELISA to detect serum IgG responses in patients and healthy subjects. SDS-PAGE analyses of the preparations from a type strain (NCTC 11637) and of acidic glycine extracts of 4 clinical isolates showed multiple protein bands. The sera were classified as HP+ve and HP-ve by culture of biopsy and immunoblotting. Sera were considered positive for H. pylori if they detected the specific 120kD antigen or 4-5 other bands. 49 sera were HP+ve; the 51 HP-ve sera did not react in immunoblotting. 35/44 sera (80%) that reacted with the 120kD antigen demonstrated high titers in ELISA with all antigen preparations, and the remaining 9(20%) sera gave discordant results. 4/5 HP+ve sera that did not react with the 120kD antigen, demonstrated high ELISA titers with all 5 antigen preparations. Glycine extracts of 3 isolates did not exhibit the 120kD protein, but were equally sensitive in ELISA. The role of 120kD antigen in our ELISA was not clear. Immunoblotting demonstrated that the 5 antigen preparations share similar antigenic components. All preparations were similarly high in sensitivity and specificity, indicating that surface antigens could be satisfactorily used in our ELISA. Our ELISA using the glycine extract was compared with commercial H. pylori ELISAs developed by Bio-Rad Laboratories, USA (GAP ELISA), Roche, Switzerland (EIA 2G), and Whittaker Bioproducts, USA (Pyloristat).(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated risk of Helicobacter pylori infection in submarine crews

In a prospective study designed to elucidate the route of transmission of Helicobacter pylori, the seroprevalence and incidence of Helicobacter pylori infection was determined in the following branches of the armed forces presumed to be at increased risk of acquiring transmissible diseases by the fecal-oral or oral-oral route: German submarine crews (n = 64, mean age 26.2 years) and regular officers of the French infantry (n = 51, mean age 26.5 years) who had served for a minimum of three years. The submarine crews were compared with air force staff (n = 74, mean age 23.7 years), and the French officers with French infantry recruits (n = 135, mean age 20.5 years) who started their service at the beginning of the study. The frequency of IgG and IgA antibody responses to the 120, 88, 86 and 82 kDa proteins was determined by the immunoblot method. The frequency of a positive antibody response was strongly dependent on age (p less than 0.001). When results were controlled for age by the logistic regression analysis, the submarine crews revealed significantly increased frequencies of the IgG and IgA responses compared to air force staff. The antibody responses of French officers and recruits were not significantly different. It is concluded that submarine crews serving during their missions in an overcrowded space with extremely limited sanitary facilities must be considered a high-risk group for Helicobacter pylori infection. These results strongly suggest person-to-person transmission of Helicobacter pylori, by either the oral-oral or the fecal-oral route.

Evaluation of a commercial latex test for serological diagnosis of Helicobacter pylori infection in treated and untreated patients

The value of a commercially available latex test (Pyloriset) for the diagnosis of Helicobacter pylori infection by demonstration of specific antibodies was compared with that of direct diagnostic methods such as culture, biopsy-urease test and microscopy of fuchsin-stained smears. The sera were from 136 patients who prior to this study either had or had not been treated for Helicobacter pylori-infection simultaneously with amoxicillin (3 x 750 mg/day) and metronidazole (3 x 500 mg/day) for 12 days. On average, the sensitivity of the test was 90%. The specificity with sera from untreated patients was 75.9%; with sera from treated patients specificity was 22.2%, 28% and 20% 1, 3 and 6 months respectively after start of treatment. Only as late as one year after the onset of chemotherapy did the specificity return to 67%. Because of its low specificity this test does not offer any advantage over other tests in the detection of Helicobacter pylori-infection or in monitoring the chemotherapeutic success.

Helicobacter pylori infection and the risk of gastric carcinoma

BACKGROUND

Infection with Helicobacter pylori has been linked with chronic atrophic gastritis, an inflammatory precursor of gastric adenocarcinoma. In a nested case-control study, we explored whether H. pylori infection increases the risk of gastric carcinoma.

METHODS

From a cohort of 128,992 persons followed since the mid-1960s at a health maintenance organization, 186 patients with gastric carcinoma were selected as case patients and were matched according to age, sex, and race with 186 control subjects without gastric carcinoma. Stored serum samples collected during the 1960s were tested for IgG antibodies to H. pylori by enzyme-linked immunosorbent assay. Data on cigarette use, blood group, ulcer disease, and gastric surgery were obtained from questionnaires administered at enrollment. Tissue sections and pathology reports were reviewed to confirm the histologic results.

RESULTS

The mean time between serum collection and the diagnosis of gastric carcinoma was 14.2 years. Of the 109 patients with confirmed gastric adenocarcinoma (excluding tumors of the gastroesophageal junction), 84 percent had been infected previously with H. pylori, as compared with 61 percent of the matched control subjects (odds ratio, 3.6; 95 percent confidence interval, 1.8 to 7.3). Tumors of the gastroesophageal junction were not linked to H. pylori infection, nor were tumors in the gastric cardia. H. pylori was a particularly strong risk factor for stomach cancer in women (odds ratio, 18) and blacks (odds ratio, 9). A history of gastric surgery was independently associated with the development of cancer (odds ratio, 17; P = 0.03), but a history of peptic ulcer disease was negatively associated with subsequent gastric carcinoma (odds ratio, 0.2; P = 0.02). Neither blood group nor smoking history affected risk.

CONCLUSIONS

Infection with H. pylori is associated with an increased risk of gastric adenocarcinoma and may be a cofactor in the pathogenesis of this malignant condition.

Helicobacter pylori infection induces antibodies cross-reacting with human gastric mucosa

The authors' previous observation that many of the monoclonal antibodies against Helicobacter pylori cross-react with the cells of the human gastric mucosa prompted them to investigate the possibility that gastric self-antigens cross-reacting with H. pylori could be involved in the immune response against this organism. It was found that three antibodies against H. pylori, CB-4, CB-10, and CB-14, that cross-react with the human gastric mucosa also intensely cross-reacted with murine gastric epithelial cells. A strong reaction against autologous mucosa was also evident in the sera of mice immunized with H. pylori but not with other bacteria. A serological study performed in a group of 82 patients undergoing gastroscopy showed that the presence of seropositivity against H. pylori was strongly correlated with the presence of autoantibodies against human antral gastric mucosa. This activity was neutralized after absorption of the sera with H. pylori but not with other gram-negative bacteria. The antibodies in the mouse and in the human did not react with other segments of the gastrointestinal tract or with most of the other organs. Mice bearing hybridomas secreting a cross-reacting antibody (CB-4) had histopathologic abnormalities in their stomachs. These lesions were absent in the stomachs of mice bearing hybridomas secreting a non-cross-reacting antibody (CB-26). It was concluded that H. pylori infection can stimulate antibodies cross-reacting with gastric autoantigens and that this immunologic mechanism may represent a pathogenic link between H. pylori and gastritis.

Evaluation of an immunofluorescence assay for specific detection of immunoglobulin G antibodies directed against Helicobacter pylori, and antigenic cross-reactivity between H. pylori and Campylobacter jejuni

An immunofluorescence assay (IFA) for the detection of immunoglobulin G antibodies directed against Helicobacter pylori was evaluated by comparing 20 serum specimens from patients with a positive urease test on biopsy material and 20 serum specimens from patients with a negative test and with defined clinical symptoms. The resulting anti-H. pylori titers were classified as follows: negative, less than or equal to 64; borderline, 128; and positive, greater than or equal to 256. By using these criteria, the IFA was subsequently tested, using 100 serum specimens from patients with gastric complaints. Overall, the titers were 71% positive, 10% borderline, and 19% negative. Depending on the patients' biopsy urease test results, the sensitivity and specificity of the assay were calculated to be 96%. Furthermore, these sera were classified into three subgroups on the basis of clinical manifestations: gastritis with 74% positive and 10% borderline titers, duodenal ulcer with 84% positive and 4% borderline titers, and gastric ulcer with 52% positive and 16% borderline titers. A serologic follow-up study was carried out with three patients with gastric ulcers who had been treated with colloidal bismuth subcitrate for 4 weeks and erythromycin for the final 2 weeks. The results indicate that a significant decrease in titer could be expected within 9 to 12 months after successful therapy, as determined by repeated negative CLO tests. Absorption experiments demonstrated that possible cross-reactivity between H. pylori and C. jejuni did not influence serodiagnosis.

Usefulness of a new serological test (Bio-Rad) to diagnose Helicobacter pylori-associated gastritis

A semiquantitative serological test (G.A.P. test; Bio-Rad) to diagnose Helicobacter (Campylobacter) pylori-associated gastritis has recently become commercially available. This test was evaluated with sera from 72 dyspeptic patients with known H. pylori status. When the instructions provided by the manufacturer were applied strictly, the sensitivity of the test was only 32.7%. With a slight modification of the instructions, the performance characteristics were still unsatisfactory (specificity, 43.5%). When a new cutoff value was determined by a receiver operating curve, the quality of the test (positive predictive value, 95.6%; negative predictive value, 77.8%) was slightly lower than that of a noncommercial enzyme-linked immunosorbent assay (positive predictive value, 95.7%; negative predictive value, 84.0%). It is concluded that the Bio-Rad G.A.P. test has low diagnostic yield, and it is stressed that commercial tests should be evaluated extensively before being applied in daily practice.

Antigenicity of fractions of Helicobacter pylori prepared by fast protein liquid chromatography and urease captured by monoclonal antibodies

The antigenicity of Helicobacter pylori protein fractions separated by fast protein liquid chromatography size exclusion was investigated by EIA with sera from patients of well defined Helicobacter pylori status. The antigenic material of Helicobacter pylori was confined to fractions 8 and 14 to 21. Urease containing fractions (14/15) and flagella containing fractions (17/18) were identified. Fraction 8 non-specifically bound human immunoglobulin as demonstrated by the binding of Helicobacter pylori negative sera. The remaining fractions 14 to 21 when used individually as EIA antigens were 91-100% specific, however fractions 16 to 19 showed a reduced sensitivity (78%) compared with the acid extract (95%). The urease fractions were 91% sensitive. Purified urease antigen captured by antiurease monoclonal antibodies was 83% sensitive and 93.3% specific.

Comparison of ELISA antigen preparations alone or in combination for serodiagnosing Helicobacter pylori infections

The immunoglobulin G antibody response to Helicobacter pylori was assessed in 78 patients with non-ulcer dyspepsia using five different antigen preparations. All patients were endoscoped and biopsied. The H pylori state was determined histologically on at least two endoscopic biopsy specimens using a modified Giemsa stain. The ultracentrifuged cell sonicate, acid glycine extract, and 120 kilodalton protein antigens were specific in diagnosing infection (95-98%), but had only moderate sensitivity (70-84%). By mixing either of the two complex antigens with the 120 kilodalton protein, the sensitivity of the test was increased to 97% without affecting the high specificity. The combination of ultracentrifuged sonicate or acid glycine extract with the 120 kilodalton protein therefore seems to be superior to the individual antigen preparations and is particularly suitable for the serodiagnosis of H pylori infection.

Frequency of occurrence and characterization of catalase negative Campylobacter isolated from human feces in Vienna

Of a total of 124 Campylobacter (C.) strains isolated 1988 from fecal specimens, 4 (3.2%) were catalase-negative. Two strains were catalase-negative variants of C. jejuni. The other two were identified as C. upsaliensis on the basis of their biochemical properties and of the results of DNA-DNA hybridization with biotinylated probes from C. upsaliensis and C. jejuni. Both had been isolated from patients after their return from Asia (India and Thailand, respectively). In one case, a significant decrease of the antibody titre was observed within 12 months when the patient strain was used as an antigen. Since this patient had been suffering from diarrhoea during her stay and since with the exception of amoebic cysts, no other intestinal pathogen was isolated, C. upsaliensis is thought to have been the reason for the diarrhoeal episode.

Detection of antibodies to Helicobacter pylori cell surface antigens

Serum IgG antibodies of Helicobacter pylori were detected in single-dilution ELISA using glycine extracted material. Among 148 endoscopy patients 59% displayed antibodies; as expected, a higher occurrence (90%) was found in patients with positive gastric culture for H. pylori than in culture negative patients (37%). Among 68 blood donors the frequency of H. pylori antibodies was 28%. In 73 children less than 15 years of age examined for unrelated disorders the occurrence was 4%. By immunoblotting using the same extract, 3 prominent bands, 29K, 54K and 60K and several weak bands were identified. These were formed by 57%, 92%, and 65%, respectively, of the ELISA positive patient sera. Comparing culture positive and negative patients, the 3 bands occurred more often among the culture positive subjects though between 18 and 61% of the sera from culture negative patients gave either of the bands. When comparing the glycine extracts of 4 different H. pylori strains with separate haemagglutinating patterns no differences in the position of the major bands emerged. By absorption experiments no immunological cross-reactivity with components of Escherichia coli, Klebsiella pneumoniae, Campylobacter jejuni or C. fetus was found. Thus, the glycine extract seemed specific for the detection of antibodies to H. pylori.

Campylobacter pylori and gastroduodenal disease

Campylobacter pylori is a newly described, spiral-shaped, gram-negative bacillus that is oxidase positive, catalase positive, and urease positive and grows slowly in culture. Although observed in human tissue at the beginning of the century, it was not cultured until 1982. Because there are significant morphological and genetic differences between this organism and other species of Campylobacter, it will probably be reclassified in a new genus. Current information indicates that the organism primarily resides in the stomach tissue of humans and nonhuman primates and may occasionally spread to the esophagus or other parts of the alimentary tract under appropriate conditions. Significant evidence has accumulated in the last several years to show that it causes gastritis, and there is mounting evidence that it may participate in the development of duodenal ulcers. It may also be associated with gastric ulcers and nonulcer dyspepsia. It can be detected in patients by culture of biopsy specimens or histological staining of biopsy tissue. Indirect evidence for the presence of the organism can be obtained by detection of urease in a tissue biopsy specimen, by urea breath tests, or by detection of specific antibody. It may not be necessary to implement these procedures for routine use, however, until the role of the organism can be defined better. Ultimately, the discovery of this organism may lead to radical changes in the diagnosis and treatment of gastric disease.

Seroepidemiology of Campylobacter pylori infection in various populations

Campylobacter pylori infection has been recognized as being strongly associated with chronic gastritis and duodenal ulceration, but the prevalence of C. pylori infection in a normal population is not known. A serological survey was conducted in four countries with different geographical and socioeconomic status, in a randomly chosen population as representative as possible, by using an enzyme-linked immunosorbent assay (ELISA) with a sonic extract of two strains as the antigen. The test had a specificity of 94% when 600 ELISA units was used as the threshold. In France, few children were infected before the age of 10 years. The prevalence then increased gradually to 36.7% in the sixth decade of life. This increasing prevalence of infection with age was also observed in Algeria, Vietnam, and the Ivory Coast but at a higher rate (80 to 90%). In Vietnam, as in France, few children were infected, whereas in Africa, C. pylori infection occurred earlier. The prevalence of infection did not differ with sex for a particular age group; it also did not differ with respect to gastric symptoms, smoking and drinking habits, or urban or rural residence when these potential risk factors were studied. The epidemiological data available on peptic ulcer disease in developing countries compared with developed countries led to the speculation that infection with C. pylori is not a sufficient condition to develop this disease.