Role of ELISA in H. pylori detection and its correlation with urease test

Helicobacter pylori is one of the most common chronic bacterial infection in humans linked to acid peptic diseases, gastric carcinomas and lymphomas. The bacilli produces large amounts of urease and this property has formed the basis of detection of H. pylori by the Christensen's urease test. Where endoscopy is not clinically indicated, serology may be used to establish the diagnosis. This study was undertaken to diagnose H. pylori with the help of Christensen's urease test on endoscopic biopsy specimens & correlated with the detection in Sera, of IgG antibodies against H. pylori, by ELISA technique. The study was conducted on 100 patients suffering from acid peptic disorders out of which 40 (40%) tested positive for H. pylori both by urease and serology. Christensen's urease and ELISA were found to have sensitivities of 85.7% & 90.9% and specificities of 96% and 87.5% respectively. Christensen's urease was taken as a standard method of diagnosis and its correlation with ELISA worked out to (+1) which meant there was a strong positive association between both the tests. Hence either test could be used for primary diagnosis of H. pylori instead of histopathological study and/or culture of H. pylori.     

幽门螺杆菌尿素酶B单克隆抗体的制备、鉴定及应用

目的：制备幽门螺杆菌（Hp）尿素酶B（ureB）单克隆抗体并鉴定。 方法： 以Hp重组纯化蛋白ureB为抗原，运用杂交瘤技术制备ureB单克隆抗体，用间接ELISA法检测抗体免疫学活性，用双抗夹心的IRMA法检测不同单抗是否识别相同的表位，并用于检测Hp感染。 结果： 获得两株识别不同表位的ureB单抗杂交瘤细胞，可测得Hp 感染的相关抗原。 结论： 抗ureB单抗可特异性与Hp结合，可用于建立幽门螺杆菌现症感染的检测方法。     

人幽门螺杆菌尿素酶抗体诊断试剂盒的研制

幽门螺杆菌 (Ｈｅｌｉｃｏｂａｃｔｅｒｐｙｌｏｒｉ,Ｈ .ｐｙｌｏｒｉ)为慢性胃炎、消化性胃溃疡的致病菌 ,并且与胃癌的发生密切相关 ,世界卫生组织 (ＷＨＯ)将其列为一级致癌因子 ,早期诊断Ｈ .ｐｙｌｏｒｉ感染并对其治疗和预后的观察具有重要意义。目前 ,临床上用于诊断Ｈ .ｐｙｌｏｒｉ感染的方法主要有胃镜下组织活检、细菌培养、13 Ｃ呼气试验等 ,前者需活检组织 ,病人痛苦大 ,且阳性率低 ,后者需特殊性设备 ,不易推广 ,细菌培养则阳性检出率低 ,而血清学诊断具有灵敏、快速、准确、简便、费用低等优点 ,易在临床上广泛使用。但是 ,…     

Comparison of four stains and a urease test for rapid detection ofHelicobacter pylori in gastric biopsies

Gastric biopsies were obtained from 125 subjects to compare detection ofHelicobacter pylori by culture, a rapid urease test and histopathologic examination using haematoxylin-eosin, Gram, Giemsa, Warthin-Starry silver and acridine orange stains.Helicobacter pylori was isolated from 39 specimens. Acridine orange and Giemsa were the most sensitive stains, detecting 85 % and 79 % of positive specimens respectively. All stains showed high specificity (97–100 %). The sensitivity and specificity of the rapid urease test was 62 % and 100 % respectively. These stains or the rapid urease test may be useful for rapid detection ofHelicobacter pylori in gastric biopsies.     

幽门螺旋杆菌感染检测：快速尿酶法（RUT）和银染法（W-S）的比较

目的：快速尿酶法(rapid urease test,RUT)是一种快速、简便的幽门螺旋杆菌(Helicobacter pylori, Hp)检测方法,将其与病理诊断中传统的银染法(W-S)进行比较,通过对比二者的阳性率,以传统银染法(W-S)的阳性率为基准,判断快速尿酶法(RUT)是否能在临床诊断中发挥更好的作用,使Hp感染患者能够得到及时的确诊和治疗。方法：选取2012年8月至2013年8月期间,未使用过抗生素、质子泵抑制剂、H2受体阻滞剂等可能影响Hp检测结果药物的患者164例,同步完成快速尿酶法(RUT)和银染法(W-S)检测,对比快速尿酶法(RUT)和银染法(W-S)的阳性率。结果：快速尿酶法(RUT)的阳性率(35.37%)略高于银染法(W-S)的阳性率(32.32%)。结论：快速尿酶法(RUT)操作便捷,但容易受到诸多不稳定因素的影响,更适合Hp感染的初筛。银染法(W-S)操作相对复杂,但病理诊断结果具有更高的准确性,更适合作为Hp感染最终的确诊手段。     

Culture ofHelicobacter pylori from gastric biopsies transported in biopsy urease test tubes

Gastric biopsy specimens of 57 consecutively observed dyspeptic patients were studied for the presence ofHelicobacter pylori by histological examination, biopsy urease test (BUT) and culture. For culture, biopsy samples were transported in both Stuart media and BUT tubes. All 15 isolates could be cultured from both Stuart and BUT tubes. Thus, if the main reason for culture ofHelicobacter pylori is for antimicrobial susceptibility testing, only positive BUT tubes need to be submitted. This would reduce both the expense and the number of biopsies needed.     

Histology compared with chemical testing for urease for rapid detection of Helicobacter pylori in gastric biopsy specimens.

Gastric biopsy specimens from 283 patients with ulcer and non-ulcer dyspepsia attending five gastroenterology clinics in the northern region of the United Arab Emirates (UAE) were tested by the agar gel test (n = 115) or the ultra-rapid endoscopy room test (n = 168) for the presence of Helicobacter pylori urease. Results were compared with a histological technique using the Romanowsky type (Diff-3) stain for detecting H pylori in both antral and body type gastric mucosa. A sensitivity of 94% and specificity of 100% using the agar gel test compared with 87% sensitivity and 99.3% specificity for the ultra-rapid endoscopy room test. Grading of H pylori in gastric biopsy specimens showed that the higher the histological grade, the more likely that the urease test would be positive. Both forms of urease tests have high specificity for detecting H pylori in gastric biopsy specimens, although the urea agar test has a higher sensitivity than the ultra-rapid test. Low numbers of H pylori in gastric biopsy specimens are the most important determinant of a false negative urease test.     

Monoclonal antibodies against the native urease of Helicobacter pylori: synergistic inhibition of urease activity by monoclonal antibody combinations.

Monoclonal antibodies (MAbs) against the native urease of Helicobacter pylori NCTC 11637 were found to clearly inhibit the urease activity. Interestingly, synergistic inhibition by two MAbs recognizing different subunits was also observed. Ten MAbs were produced and classified as two isotypes of the immunoglobulin G (IgG) subclass, IgG1, and IgG2a. Western blot (immunoblot) analysis using sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that five MAbs recognized the large subunit and the other five recognized the small subunit of the urease. Among the MAbs, L2 and S2, which recognized the large and the small subunits, respectively, were also able to inhibit the urease activity of clinical isolates from H. pylori-infected patients. The combination of L2 and S2 led to augmented synergistic inhibition. L2, but not S2, could also inhibit the urease activity from Helicobacter mustelae; enzyme-linked immunosorbent assay and Western blot analysis showed that L2 cross-reacted with this urease. These results suggested that the epitope recognized by L2 had a structure common to both Helicobacter species and may be involved in the active site of the urease. In contrast to the MAbs, a polyclonal antibody in sera from mice immunized with H. pylori urease did not have the ability to inhibit H. pylori urease activity. However, the polyclonal antibody retained the ability to abolish the inhibitory action of these MAbs. Moreover, other MAbs which could not inhibit H. pylori urease activity also abolished the inhibitory action.     

抗重组幽门螺杆菌VacA单克隆抗体的制备

目的 制备抗重组幽门螺杆菌致细胞空泡毒素抗原(VacA)的单克隆抗体(mAb).方法 用基因工程菌pQr30-v-DH5α大最表达重组蛋白VaeA,经Ni2+-NTA树脂纯化后,Western blot鉴定抗原性,免疫家兔后ELISA法检测血清VacA抗体鉴定其免疫原性.用重组vacA免疫Balb/c小鼠.取免疫鼠脾细胞与骨髓瘤SP2/O细胞融合,HAT选择性培养和间接EIJSA进行筛选,并检测所分泌抗体的效价和分析Ig类别.结果 获得4株能稳定分泌VacA mAb的杂交瘤细胞,能分泌IgG2b、lgM和IgG1 3类抗体,轻链均为k型.其中,IgG1 mAb经Western blot鉴定能与重组VacA发牛特异性反应.结论 应用纯化的重组VacA,成功获得了能稳定分泌幽门螺杆菌VacA单克隆抗体的杂交瘤细胞,并制备了单克隆抗体.为进一步研制检测VacA的试剂盒及探讨VacA的致病机制奠定了基础.     

A catalytic antibody heavy chain HpU-2 degrading its epitope peptide and H. pylori urease

The HpU-2 monoclonal antibody (mAb) raised against Helicobacter pylori urease mainly recognized the alpha-subunit of the urease. On the other hand, the heavy chain of HpU-2 mAb (HpU-2-H) isolated from the parent mAb recognized both the alpha- and beta-subunit, in which the beta-subunit was recognized more strongly than the beta-subunit. HpU-2-H cleaved a peptide, SVELIDIGGNRRIFGFNALVD, which is the epitope sequence recognized by HpU-2 mAb, showing a double-phase reaction profile at 25 degrees C in a phosphate buffer. After an induction time of 24h, the cleavage of the peptide was initiated by HpU-2-H at a high rate and it was completed at 80 h of incubation. By mass spectroscopy, two main fragmented peptides, SVELIDIGGNRR and SVELIDIGGNRRIFG, were identified. In addition, many small peptide fragments were produced by successive cleavage of the fragmented peptides. Cleavage tests for H. pylori urease by HpU-2-H revealed that the beta-subunit of the urease was cleaved first and completely decomposed at 20 h of incubation. Cleavage of the alpha-subunit started after the complete decomposition of the beta-subunit. These cleavage results were in good agreement with the immunological features of HpU-2-H. The irrelevant proteins, BSA and HSA, were hardly cleaved by HpU-2-H.     

Optimization of a medium for the rapid urease test for detection of Campylobacter pylori in gastric antral biopsies.

We developed a buffered azide-free urea medium which is sensitive, specific, and nontoxic for rapid detection of Campylobacter pylori in gastric biopsies. Detection of urease produced by the organism provides the basis for the test. The substrate is urea in monobasic sodium phosphate buffer, and phenol red provides indication of the pH change that results from urease activity. A rapid change from yellow to red occurs in the presence of C. pylori, even at low concentrations of the organism. A slower color change occurs with higher concentrations of other urease producers, such as Yersinia enterocolitica and Proteus mirabilis. Experience with 51 patients with our medium showed excellent results in detection of C. pylori in gastric mucosal biopsies. In clinical research and practice, a rapid bedside test will be helpful for rapid diagnosis of C. pylori-positive patients.     

A capture antibody ELISA for detection of antibodies against bovine enterovirus

A capture antibody ELISA was developed for detecting antibodies against bovine enterovirus. Chicken IgG F(ab')2 fragments against strain J2129 captured virus effectively. The captured virus was used to detect specific antibodies against the virus in bovine sera. The specificity of the ELISA is high. The factors affecting the specificity are discussed. The assay is more sensitive and economic than traditional serum neutralisation.     

Comparison of five ELISA assays for IgG antibody against coxsackievirus B1

Enterovirus type and group specificities of five different IgG ELISA methods were compared, using neutralization titration tests as an indicator of the presence or absence of antibodies to coxsackie B (CB) viruses. One of the ELISA assays was a "standard" IgG assay, where the solid phase was coated directly with the purified virus, followed by incubations with human serum, biotinylated anti-human-IgG, streptavidin-peroxidase, and the substrate/chromogen. In a modified standard assay, blocking of common epitopes was attempted by incubating the CB1 virus antigen on the solid phase with a rabbit antiserum to CB5 before the human serum was added. In another modification the serum dilution buffer contained heat-denatured heterologous enteroviruses in an attempt to consume human antibodies reacting with common epitopes. In one assay the purified CB1 virus was captured by purified horse anti-CB1 IgG on the solid phase, before incubation with human serum. In the last of the five assays the serum specimen was incubated with CB1 virus (in the liquid phase) before the virus or virus-antibody complex was captured with purified horse anti-CB1-IgG. Reactions against common antigens dominated in the first three assays. The antigen-capture assay appeared to be at least predominantly type specific. Our data indicate that the liquid-phase assay may be type specific, but more studies are needed. The method of virus purification was critical for the type specificity of the antigen-capture and liquid-phase assays.     

A practical single sample dry latex agglutination test for Helicobacter pylori antibody detection.

Assessment of a single serum sample for Helicobacter pylori antibodies is frequently requested in routine diagnostic laboratories. Current enzyme linked immunosorbent assay (ELISA) kits are not ideal for testing small numbers of serum samples and some have low sensitivities, specificities or large grey zones. A panel of 90 serum samples from patients who had presented for routine upper endoscopy was used to compare three kits for the detection of H pylori antibodies: (1) Pyloriset Dry, total antibody latex agglutination, Orion Diagnostica, Espoo, Finland; (2) Pyloriset enzyme immunoassay (EIA), IgG ELISA, Orion; and (3) Hel-p, IgG ELISA, Amrad, Kew, Victoria, Australia. Diagnosis of H pylori positivity was made if culture results and either rapid urease test or histopathology were positive. The sensitivity, specificity, positive, and negative predictive value for each test was as follows: Orion: latex 93.3%, 95.6%, 95.5%, 93.3%, respectively; Orion: EIA-G 84.4%, 97.8%, 97.4%, 84.4%, respectively; and Amrad: EIA-G 100%, 88.9%, 90%, 100%, respectively. The latex test performed better than the EIAs with respect to sensitivity and specificity.     

New plate medium for growth and detection of urease activity of Helicobacter pylori.

A new medium for detection of urease activity and isolation of Helicobacter pylori is proposed. This medium, containing Columbia Agar Base, was supplemented with IsoVitaleX, hemin, urea, and phenol red (nonselective medium [NSM]). Both bacterial growth and color change were evaluated and compared with growth in the same medium supplemented with cefsulodin, vancomycin, polymyxin B sulfate, and amphotericin B (selective medium [SM]). Twenty-five recent clinical isolates and antral biopsy specimens from 33 patients who underwent endoscopy were examined. The isolates showed a rapid color change and good growth at 5 days of incubation with NSM and SM. H. pylori-positive biopsies revealed a color change within 36 h, and bacterial growth was better appreciated in NSM, but with more contaminating flora than in SM.     

Comparison of sensitivities of ELISA and radioimmunoassay for detection of class-specific antibody in mouse serum

The limits of detection of IgG1 antibody in a standard mouse antiserum by a single antiglobulin enzyme-linked immunosorbent assay (ELISA) and 2 amplified systems, a double antiglobulin ELISA and a double antiglobulin radioimmunoassay (RIA), were compared in microtitration plates with the same antigen preparation and antisera. Compared with the single antiglobulin ELISA, both amplified assays demonstrated a 64-fold increase in sensitivity for the detection of antibody at high dilutions of standard antiserum. It is concluded that the amplified ELISA offers a safer assay than the amplified RIA and of equal sensitivity for comparable consumption of antisera.     

Indirect ELISA for the detection of a specific antibody response against Mycoplasma gallisepticum

An indirect enzyme-linked immunosorbent assay (ELISA) was developed for determining Mycoplasma gallisepticum antibodies in chicken sera. The M. gallisepticum antigen was detergent extracted and incorporated into ISCOMs. Sediment of broth medium treated with sarcosyl was used as control antigen. Sera were tested before and after absorption with broth medium components and ELJSA titres are expressed as optical density (OD) at 492 nm. Sera from experimentally or naturally infected chickens, those vaccinated with Salsbury Mg bacterin or both vaccinated and experimentally infected were compared with sera from M. gallisepticum free or SPF chickens. A high OD was observed when unabsorbed sera (even from SPF chickens) were tested with control antigen. The non-specific binding of M. gallisepticum negative sera could be removed by absorbing the sera with broth media components before the ELISA was performed. In contrast, ELISA titres obtained with sera from M. gallisepticum positive birds did not decrease significantly after absorption, except in the vaccinated and experimentally infected group. When the OD obtained with control antigen was subtracted from that obtained with ISCOM antigen, the mean value for M. gallisepticum free chickens was 0.083. Higher values were obtained with absorbed sera from experimentally or naturally infected (0.248-0.526), vaccinated (0.506), or vaccinated and infected (0.276-0.930) birds. The use of the ISCOM antigen presentation system in the indirect ELISA, combined with absorption of sera with broth components was demonstrated to be a useful diagnostic assay for M. gallisepticum antibodies.     

Evaluation of a monoclonal antibody for detection ofHelicobacter pylori in a direct immunofluorescence test

A monoclonal antibody was developed for detection ofHelicobacter pylori in gastric tissue sections in a direct immunofluorescence test. On a comparison of the immunofluorescence test with standard methods for detection ofHelicobacter pylori, i.e. culture, the urease activity test and histological examination of tissue sections, using 158 biopsy specimens, 30 specimens were positive in all methods and 64 negative. In the remaining cases comparison was not possible because either immunofluorescence (29 specimens) or the standard methods (16 specimens) gave ambiguous results. The direct immunofluorescence test may have potential as an alternative to standard methods, but further testing in a defined patient population is necessary.     

Micro-indirect hemagglutination test for detection of antibody against transmissible gastroenteritis virus of pigs.

A micro-indirect hemagglutination (IHA) test was developed for detecting antibody against transmissible gastroenteritis (TGE) virus of pigs. TGE virus propagated in swine kidney cell cultures was highly purified and concentrated by the combination of ammonium sulfate precipitation, treatment with fluorocarbon, and sucrose density gradient centrifugation. Tanned sheep erythrocytes were sensitized with purified virus for use in the IHA test. The results of testing 104 serum samples collected from pigs in the field indicated that the IHA antibody titers were approximately five times higher than those obtained by a serum neutralization test and that there was good correlation between the antibody titers determined by the two tests. High IHA antibody titers developed in pigs experimentally exposed to virulent TGE virus. Sensitized sheep erythrocytes were stable under long-term storage at 4 degrees C (at least for 50 days). The conclusions made are that the IHA test described is more sensitive than the serum neutralization test for the detection of TGE antibody and may be of value for serodiagnosis of TGE.