Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:6.3.4.6 (urease)
7,490 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Salmonella typhi Ty800, deleted for the Salmonella phoP/phoQ virulence regulon has been shown to be a safe and immunogenic single dose oral typhoid fever vaccine in volunteers. This promising vaccine strain was modified to constitutively express a heterologous protein of Gram negative bacterial origin, Helicobacter pylori urease subunits A and B, yielding S. typhi strain Ty1033. Seven volunteers received single oral doses of > or = 10(10) colony forming units of Ty1033; an eighth volunteer received two doses 3 months apart. Side effects were similar to those observed previously in volunteers who received the unmodified vector Ty800. All volunteers had strong mucosal immune responses to vaccination as measured by increases in IgA-secreting cells in peripheral blood directed against S. typhi antigens. Seven of eight volunteers had convincing seroconversion as measured by increases in serum IgG directed against S. typhi flagella and lipopolysaccharide antigens by ELISA. No volunteer had detectable mucosal or humoral immune responses to the urease antigen after immunization with single doses of Ty1033. A subset of three volunteers received an oral booster vaccination consisting of recombinant purified H. pylori urease A/B and E. coli heat labile toxin adjuvant 15 days after immunization with Ty1033. None of three had detectable humoral or mucosal immune responses to urease. Expression of a stable immunogenic protein in an appropriately attenuated S. typhi vector did not engender detectable mucosal or systemic antibody responses; additional work will be needed to define variables important for immunogenicity of heterologous antigens carried by live S. typhi vectors in humans.
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PMID:Safety and immunogenicity of phoP/phoQ-deleted Salmonella typhi expressing Helicobacter pylori urease in adult volunteers. 1051 34

Age-specific prevalence of IgA and IgG antibodies in 714 subjects without gastrointestinal complaints aged 6 months to 90 yr was measured by an enzyme linked immunoassay using an acid-glycine extract of H. pylori as the antigen. The urease test and histology were used for the diagnosis of H. pylori infection in 83 subjects with a clinical diagnosis of dyspepsia, and these results were compared with measurement of IgG, IgA and IgM antibodies. The age specific prevalence of IgG and IgA antibodies respectively was 57 and 43 per cent for subjects aged 6 months to 4 yr and showed an increase with age to a maximum of 90 per cent for IgG in subjects > 60 yr of age and to 87 per cent for IgA in subjects between 51 and 60 yr. In symptomatic patients, there was a high degree of correlation between severity of H. pylori infection on histopathological examination and IgG (P < 0.02) levels. The use of IgG and IgA estimation could have identified H. pylori infection without endoscopy in 50 of the 83 patients. Serology for IgG and IgA antibodies against H. pylori may play a major role in decreasing the need for endoscopy, but cut-off values must be determined for each assay based on the prevalence of antibodies in the population.
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PMID:Use of serology, the urease test & histology in diagnosis of Helicobacter pylori infection in symptomatic & asymptomatic Indians. 1061 9

The discovery of the gastric pathogen Helicobacter pylori has created a need for accurate methods to study immune responses locally in the human stomach. Therefore, we have developed a quick and easy method for extraction of antibodies from gastric biopsies using saponin and compared this method with the more laborious analysis of antibody-secreting cells (ASCs) from gastric biopsies. We have also analyzed the antibody content in gastric aspirates, saliva and plasma. There was a strong correlation between the total IgA levels in the biopsy extracts and the frequencies of IgA-secreting cells. In addition, the IgA and IgG levels against a H. pylori whole membrane preparation and purified urease in the biopsy extracts correlated well with the frequencies of specific IgA and IgG secreting cells. However, the antibody levels in gastric aspirates, saliva and plasma specimens did not correlate with the frequencies of corresponding ASC in the gastric biopsies. Thus, the saponin extraction method is suitable for monitoring local antibody responses in the stomach, while analyses of gastric aspirates, saliva or plasma are not appropriate for this purpose.
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PMID:Development of a new method for the determination of immune responses in the human stomach. 1066 69

Immunization with urease can protect mice from challenge with Helicobacter pylori, though results vary depending on the particular vaccine, challenge strain, and method of evaluation. Unlike mice, rhesus monkeys are naturally colonized with H. pylori and so may provide a better estimate of vaccine efficacy in humans. The purpose of this study was to examine the effectiveness of H. pylori urease as a vaccine in specific-pathogen (H. pylori)-free rhesus monkeys. Monkeys raised from birth and documented to be free of H. pylori were vaccinated with orogastric (n = 4) or intramuscular (n = 5) urease. Two control monkeys were sham vaccinated. All monkeys were challenged with a rhesus monkey-derived strain of H. pylori, and the effects of vaccination were evaluated by use of quantitative cultures of gastric tissue, histology, and measurement of serum immunoglobulin G (IgG) and salivary IgA. Despite a humoral immune response, all monkeys were infected after H. pylori challenge, and there were no differences in the density of colonization. Immunization with urease therefore does not fully protect against challenge with H. pylori. An effective vaccine to prevent H. pylori infection will require different or more likely additional antigens, as well as improvements in the stimulation of the host immune response.
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PMID:Immunization with recombinant Helicobacter pylori urease in specific-pathogen-free rhesus monkeys (Macaca mulatta). 1076 44

The heat-labile toxin (LT) of Escherichia coli is a potent mucosal adjuvant that has been used to induce protective immunity against Helicobacter felis and Helicobacter pylori infection in mice. We studied whether recombinant LT or its B subunit (LTB) has adjuvant activity in mice when delivered with H. pylori urease antigen via the parenteral route. Mice were immunized subcutaneously or intradermally with urease plus LT, recombinant LTB, or a combination of LT and LTB prior to intragastric challenge with H. pylori. Control mice were immunized orally with urease plus LT, a regimen shown previously to protect against H. pylori gastric infection. Parenteral immunization using either LT or LTB as adjuvant protected mice against H. pylori challenge as effectively as oral immunization and enhanced urease-specific immunoglobulin G (IgG) responses in serum as effectively as aluminum hydroxide adjuvant. LT and LTB had adjuvant activity at subtoxic doses and induced more consistent antibody responses than those observed with oral immunization. A mixture of a low dose of LT and a high dose of LTB stimulated the highest levels of protection and specific IgG in serum. Urease-specific IgG1 and IgG2a antibody subclass responses were stimulated by all immunization regimens tested, but relative levels were dependent on the adjuvant used. Compared to parenteral immunization with urease alone, LT preferentially enhanced IgG1, while LTB or the LT-LTB mixture preferentially enhanced IgG2a. Parenteral immunization using LT or LTB as adjuvant also induced IgA to urease in the saliva of some mice. These results show that LT and LTB stimulate qualitatively different humoral immune responses to urease but are both effective parenteral adjuvants for immunization of mice against H. pylori infection.
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PMID:Parenteral adjuvant activities of Escherichia coli heat-labile toxin and its B subunit for immunization of mice against gastric Helicobacter pylori infection. 1076 72

Escherichia coli heat-labile enterotoxin (LT), which causes a characteristic diarrhea in humans and animals, is a strong mucosal immunogen and has powerful mucosal adjuvant activity towards coadministered unrelated antigens. Here we report the different mucosal adjuvanticity of nontoxic LT derivatives, LTS63Y and LTdelta110/112, generated by immunizing through two different mucosal routes. Intragastric (IG) immunization with Helicobacter pylori urease alone resulted in poor systemic IgG and IgA responses and no detectable local secretory IgA, but IG co-immunization with urease and LTdelta110/112 induced high titers of urease-specific local secretory IgA and systemic IgG and IgA, comparable to those induced by wild-type LT. LTS63Y showed far lower adjuvant activity towards urease than LTdelta110/112 in IG immunization, but was more active than LTdelta110/112 in inducing immune responses to urease by intranasal (IN) immunization. LTdelta110/112 predominantly enhanced the induction of urease-specific IgG1 levels following IG immunization, whereas LTS63Y induced high levels of IgG1, IgG2a and IgG2b following IN immunization. In addition, quantitative H. pylori culture of stomach tissue following challenge with H. pylori demonstrated a 90-95% reduction (p < 0.0002) in bacterial burden in mice immunized intranasally with urease using either mutant LT as an adjuvant. These results indicate that the mechanism(s) underlying the adjuvant activities of mutant LTs towards coadmnistered H. pylori urease may differ between the IN and IG mucosal immunization routes.
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PMID:The mucosal adjuvanticity of two nontoxic mutants of Escherichia coli heat-labile enterotoxin varies with immunization routes. 1092 18

This paper reviews current diagnostic techniques for Helicobacter pylori infection and critically questions their value under different diagnostic circumstances. As long as we do not have general treatment recommendations for H. pylori infection, endoscopy is still the basis for primary diagnosis because it assesses therapy indications. In addition, histology characterizes the gastroduodenal lesions observed and may reveal malignant diseases. New rapid urease tests from the biopsies are inexpensive, simple, and quick giving results reliably within 1 h. Culturing H. pylori from gastric samples after therapy failure and testing the strains for antimicrobial susceptibility is becoming increasingly important with higher prevalence of drug resistances. Nonendoscopic tests are more convenient to the patient. Serological tests inexpensively detect circulating IgG or IgA antibodies. However, inspite of the cost attractiveness, serology might be problematic in indicating present H. pylori infection. The tests of choice for noninvasive monitoring therapy success or failure are the 13C-urea breath test and the faecal antigen immunoassay. Both tests are also of value for first diagnosis in children when endoscopy is not indicated. In the future, serological detection of virulence factors and polymerase chain reaction with molecular fingerprinting might help to identify H. pylori strains with high pathogenicity or antibiotic resistance.
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PMID:Detection of Helicobacter pylori infection: when to perform which test? 1132 20

Serological testing to diagnose Helicobacter pylori infection in children is still controversial, although commonly used in clinical practice. We compared the immunoglobulin G (IgG) and IgA results of two commercially available enzyme immunoassays (EIAs) (Pyloriset IgG and IgA and Enzygnost II IgG and IgA) for 175 children with abdominal symptoms divided into three age groups (0 to < or =6 years, n = 47; >6 to < or =12 years, n = 77; >12 years, n = 51). A child was considered H. pylori infected if at least two of three tests (histology, rapid urease test, 13C-urea breath test) or culture were positive and noninfected if all results were concordantly negative. Of 175 children, 93 (53%) were H. pylori negative and 82 were H. pylori positive. With the recommended cutoff values, the overall specificity was excellent for all four EIAs (95.7 to 97.8%) regardless of age. Sensitivity varied markedly between tests and was 92.7, 70.7, 47.5, and 24.4% for Enzygnost II IgG, Pyloriset IgG, Enzygnost II IgA, and Pyloriset IgA, respectively. Sensitivity was low in the youngest age group (25 to 33.3%), except for Enzygnost II IgG (91.6%). Receiver-operating curve analyses revealed that lower cutoff values would improve the accuracy of all of the tests except Enzygnost II IgG. Measurement of specific IgA, in addition to IgG, antibodies hardly improved the sensitivity. The specificity of commercial serological tests is high in children when the cutoff values obtained from adults are used. In contrast, sensitivity is variable, with a strong age dependence in some, but not all, tests. We speculate that young children may have a different immune response to H. pylori, with preferable responses to certain antigens, as well as lower titers than adults. The Pyloriset test may fail to recognize these specific antibodies.
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PMID:Evaluation of two commercial enzyme immunoassays, testing immunoglobulin G (IgG) and IgA responses, for diagnosis of Helicobacter pylori infection in children. 1157 78

The diagnostic accuracy of serological tests for Helicobacter pylori was studied in 145 consecutive outpatients aged 45 years or less referred for gastroscopy. Helicobacter pylori infection can be detected by serological tests, including rapid whole-blood tests. The low prevalence of the disease in young people may have a negative effect on the positive predictive value of a test. In this study, the presence of Helicobacter pylori was assessed by a biopsy urease test and histological examination, and by several serological tests: a rapid whole-blood test on fingerstick blood, a latex agglutination serum test, a commercial enzyme immunoassay (EIA) test, and an in-house EIA for detection of antibodies of both the IgG and IgA classes. Helicobacter pylori infection was diagnosed with invasive tests in 21 (14.5%) patients. The sensitivity, specificity, and positive and negative predictive values of the EIA-based tests, compared to histological examination, were 100%, 96-97%, 81-84%, and 100%, respectively. The positive predictive value of the latex agglutination test was 78%, whereas it was only 47% for the whole-blood rapid test used. Although the results of the whole-blood rapid test were unsatisfactory, the quantitative EIA-based tests could reliably detect Helicobacter pylori among young patients, in whom the prevalence of the infection is low.
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PMID:Serologic diagnosis of Helicobacter pylori infection in outpatients aged 45 years or less. 1168 34

Mucosal IgA and IgG are involved in the immune defense against Helicobacter pylori in infected patients. In contrast to IgG, IgA is transported into the gastric lumen and is responsible for the first-line defense. Therefore antigens recognized by mucosal IgA are possible candidates for vaccination. This study compared the IgA and IgG immune response to H. pylori in the gastric mucosa and that in the serum of 21 patients with H. pylori gastritis by the immunoblotting technique. In particular, mucosal IgA immune response against the urease antigen of H. pylori was studied in detail, as vaccination with this antigen was not curative in men. The results show that mucosal IgA was not represented by serum IgA and IgG, and that the H. pylori specific mucosal IgA and IgG immune responses differ in antigen-recognition pattern. This disparity may reflect the different transport ways and functions of these two immunoglobulin isotypes. Furthermore, mucosal IgA specific for urease was found inconsistently in patients with H. pylori gastritis. As vaccination antigens should induce an appropriate mucosal IgA immune response against H. pylori, our findings may have important implications for the selection of antigens for vaccination against H. pylori.
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PMID:Disparity between mucosal and serum IgA and IgG in Helicobacter pylori infection. 1218 3


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