Detection of antibodies to Campylobacter in humans using enzyme-linked immunosorbent assays: a review of the literature

Campylobacteriosis is the most common cause of bacterial foodborne illness in the European Union and the United States. Infection with Campylobacter spp. is frequently associated with different sequelae including neuropathies and reactive arthritis. Diagnosis is mainly by bacterial culturing which is time consuming, expensive, and not well suited for diagnosing sequelae or identifying infections from stool samples with nonviable bacteria. Serologic assays, in particular ELISAs, are well suited for this purpose, but, at present, there is no international consensus on antibody assays for human campylobacteriosis. In an extensive literature review, 19 studies validating such assays were identified of which 13 were more than 10 years old. We conclude that the best validated of these assays are developed and used in-house for research purposes rather than for routine diagnostics. Considering the burden of disease and potential long-term severity of Campylobacter infections, developing a standardized, commercially available antibody assay could be of great benefit for diagnostic and surveillance purposes worldwide.     

Comparison of two anti-hepatitis C virus enzyme-linked immunosorbent assays

BACKGROUND: Third-generation anti-hepatitis C virus (HCV) enzyme-linked immunosorbent assays (ELISA) are now implemented in most laboratories in Europe, but have not yet been fully implemented in the United States. STUDY DESIGN AND METHODS: Two ELISAs (Ortho 3.0 and Ortho 2.0, Ortho Diagnostics, Raritan, NJ) were compared by tests on various serum panels: A) blood donor samples (n = 530) that tested positive in first- or second-generation anti-HCV ELISA; B) samples from persons with chronic non-A, non-B hepatitis (n = 185); C) samples from multiply transfused patients (n = 79); D) samples from patients on hemodialysis (n = 473); and E) samples from Dutch random blood donors (n = 2153). RESULTS: In panels A, B, and C, 247 (100%) of 247 polymerase chain reaction (PCR)-positive and 278 (100%) of 278 second-generation recombinant immunoblot assay (RIBA-2)-positive specimens were detected by Ortho 2.0 and 3.0 (sensitivity, 100%). In the sera of panel D, used to represent a group of patients with a high risk for HCV, no additional positives were found by Ortho 3.0. In panel E, of 2153 blood donor samples, 2 (0.1%) were positive in Ortho 2.0 and 8 (0.4%) in Ortho 3.0. Two samples that were positive in both Ortho 2.0 and 3.0 were also positive in RIBA-2; one was positive on PCR. From the 6 remaining Ortho 3.0-positive (Ortho 2.0-negative) samples, 1 was positive in RIBA-2 (isolated anti-c100) and 3 were positive in third- generation RIBA (1/3 isolated anti-c100, 2/3 isolated NS5). All 6 samples were PCR negative. In first-time donors, no difference in specificity was found. CONCLUSION: The sensitivity and specificity of the Ortho 3.0 ELISA are comparable to those of the Ortho 2.0 ELISA.     

Evaluation of enzyme-linked immunosorbent assays for detecting circulating antibodies to Candida albicans

Published studies indicate that Candida albicans antibody assays utilizing cytoplasmic antigens offer greater utility for identifying cases of systemic candidiasis when compared with assays utilizing cell wall components. We assessed the performance characteristics of a commercially available system that utilizes cytoplasmic antigens to measure C. albicans IgG, IgM, and IgA (Candida Detect ELISA reagents). Intra-assay variation was < or =5%, inter-assay variation was < or =10%, and good linearity was observed for all the three antibody isotypes. Results for specimens stored under various conditions were comparable to those obtained initially. Inter-laboratory reproducibility was excellent; qualitative concordance was > or =93% for all the three isotypes, with slopes and R(2) values approaching 1.0 in linear regression analyses. Seroprevalence in persons without apparent systemic candidiasis was evaluated using three different serum panels; seroprevalence rates ranged from 24 to 32% for IgG, 2-14% for IgM, and 15-36% for IgA. Seroprevalence rates in a panel of sera containing antibodies to other fungi were similar to rates observed in panels from individuals without systemic candidiasis. These findings demonstrate the acceptable performance of assay systems employing Candida Detect ELISA reagents.     

Measurement of urinary retinol-binding protein by enzyme-linked immunosorbent assay, and its application to detection of tubular proteinuria

An enzyme-linked immunosorbent assay (ELISA) for urinary retinol-binding protein (RBP) has been developed and compared with urinary beta 2-microglobulin for the detection of tubular proteinuria. The assay has a working range of 10 to 250 micrograms of RBP per liter of urine. The within-assay CV was 3.2-7.1%, the between-assay CV 12.5%. A control population of 118 male subjects gave a geometric mean urinary RBP concentration of 7.7 micrograms per millimole of creatinine and a 95th centile of 22 micrograms per millimole of creatinine. Comparison of urinary RBP and beta 2-microglobulin concentrations in 80 control subjects and 117 subjects exposed to cadmium fumes gave correlations of r = 0.59 and 0.91, respectively. Of the 117 subjects exposed to cadmium fumes, 103 gave both RBP and beta 2-microglobulin concentrations on the same side of the upper 95th centile values of 22 and 38 micrograms per millimole of creatinine for RBP and beta 2-microglobulin respectively (Chi-square analysis p less than 0.001), demonstrating that RBP and beta 2-microglobulin detect tubular proteinuria with equal sensitivity and specificity. ELISA and an established latex immunoassay gave well-correlated results.     

An enzyme-linked immunosorbent assay for measurement of protein S

Protein S is an important component of the haemostatic balance mechanism, and deficiency of this protein predisposes to thrombotic risk. We describe an inexpensive and reliable enzyme-linked immunosorbent assay for measurement of protein S, which is suitable for use in routine hospital laboratories.     

Evaluation of seven different enzyme-linked immunosorbent assays for serodiagnosis of Staphylococcus aureus bacteremia

OBJECTIVE: Serologic assays for Staphylococcus aureus antibodies were evaluated regarding their ability to differentiate between uncomplicated and complicated S. aureus bacteremia, between S. aureus and non-S. aureus bacteremia, and between S. aureus and non-S. aureus endocarditis. METHODS: Enzyme-linked immunosorbent assays (ELISAs) were performed to measure Ig G antibodies against seven S. aureus antigens (peptidoglycan, teichoic acid, S. aureus ultrasonicate, whole S. aureus cells, alpha-toxin, lipase and capsular polysaccharide) in 129 patients with S. aureus bacteremia (including 51 with endocarditis), 78 patients with non-S. aureus bacteremia (including 27 with endocarditis) and 100 febrile non-bacteremic controls. RESULTS: Whole-cell ELISA was the most sensitive assay. The specificity of all assays was low. Two different combinations of ELISAs for whole cells, teichoic acid,alpha-toxin, lipase and capsular polysaccharide did distinguish between S. aureus and non-S. aureus endocarditis, but not between uncomplicated and complicated S. aureus bacteremia.     

Effect of switching from first- to second-generation enzyme-linked immunosorbent assays on screening for human immunodeficiency virus antibody

When a commercial antiglobulin or competitive enzyme-linked immunosorbent assay (ELISA) was used for initial human immunodeficiency virus (HIV) antibody screening, switching from a first-generation test (antigen prepared from HIV-infected human cells) to a second-generation test (antigen prepared by recombinant DNA technology) reduced but did not abolish false-positive reactivity. This conclusion applied if specimens were obtained either from a low (attenders at a voluntary walk-in clinic) or very-low prevalence population (attenders at an in-vitro fertilisation unit). Even when the specimen was reactive in second-generation screening ELISAs of both antiglobulin or competitive format, confirmatory testing was still essential. Same-day reporting of HIV antibody test results should therefore only be done circumspectly.     

The detection by enzyme-linked immunosorbent assays of non-complement- fixing HLA antibodies in transfusion medicine

BACKGROUND: Noncomplement-fixing white cell antibodies have been demonstrated by the use of immunofluorescence flow cytometry against intact lymphocytes. However, such antibodies may be either HLA-specific or directed against other white cell antigens. Commercial enzyme-linked immunosorbent assay (ELISA) kits, using solubilized HLA molecules as targets, enable such HLA-specific antibodies to be detected in patients who are refractory to platelet transfusion, patients experiencing febrile transfusion reactions, and patients whose sera give nonspecific hemagglutination in indirect antiglobulin tests. STUDY DESIGN AND METHODS: Sera from all three groups of patients, previously screened for cytotoxic antibodies by using complement-dependent lymphocytotoxicity, were re-investigated with commercial ELISA kits for HLA antibody screening and identification using the manufacturers' recommended test methods. RESULTS: Non-complement fixing HLA antibodies were detected by ELISA in many sera that were lymphocytotoxicity test- negative; that is, 14 (17.5%) of 80 from refractory patients, 8 (23.5%) of 34 from those with febrile reactions, and 11 (22.4%) of 49 from those with nonspecific hemagglutination in the direct antiglobulin test. However, not all cytotoxic white cell antibodies were detectable by ELISA: only 19 (82.6%) of 23, 19 (67.8%) of 28, and 11 (73.6%) of 49, respectively in the three groups. Similarly, only 143 (79.4%) of 181 cytotoxic sera with clear-cut HLA-A or -B locus specificities were detectable by ELISA. CONCLUSION: ELISAs detect some but not all clinically significant HLA antibodies, irrespective of their ability to fix complement in vitro.     

Screening and characterization of specific anti-lipopolysaccharide antibodies in Belgian blood donors by enzyme-linked immunosorbent assays

The goal of this project was to find and collect high concentrations of endotoxin-specific antibodies for therapeutic IgG- or IgM-enriched preparations. Various enzyme-linked immunosorbent assays (ELISAs) were developed to perform longitudinal studies of the serological response to a large panel of smooth and rough purified lipopolysaccharide (LPS) extracts in a population of healthy blood donors. To accomplish this, 1612 human serum samples from volunteer blood donors collected by seven different blood banks in Belgium were screened and specific IgM and IgG activities were measured. Approximately 17% of the donors had anti-LPS concentrations higher than 40 mg L⁻¹. Of these, 10.9% had anti-smooth LPS antibodies, 3.7% had anti-rough LPS antibodies and 2.8% were found to be positive towards both types of LPS. The mean anti-LPS antibody concentration was 8 mg L⁻¹ for rough LPS and 14 mg L⁻¹ for smooth LPS. Age- and sex-related distributions of the activities indicated that the greatest prevalence of high anti-LPS concentration was in women aged 40–49 years and in men older than 60 years. Differential absorption experiments showed that the pooled serum of selected blood donors contained a mixture of specific and cross-reacting antibodies. We detected predominantly anti-LPS activities due to the IgG₁ and IgG₂ subclasses. The range of specificities to different LPS was increased by the pooling of selected sera. It was concluded that pools of naturally occurring specific anti-LPS immunoglobulin antibodies may be obtained in Belgium by screening blood donors using ELISAs that we have developed.     

Comparison of Western blot,counterimmunoelectrophoresis, complement fixation and enzyme-linked immunosorbent assay for the diagnosis of Campylobacter infection

Four different techniques, counterimmunoelectrophoresis (CIE), complement fixation test (CFT), enzyme-linked immunosorbent assay (ELISA) and Western blotting (WB) have been evaluated and compared for the serological diagnosis of infections by Campylobacter jejuni/coli (CJC). All tests were performed on serum samples from 103 culture postive enteritic patients and 93 healthy blood donors. The sensitivities of the CIE, CFT, ELISA and WB were 56.3%, 71.8%, 50% and 83%, while the specificity of these four tests was 92.5%, 90.1%, 85% and 60% respectively. The poor specificity of the WB test was considered either a potential consequence of its greater sensitivity, detecting antibodies from previous infection in healthy donors, or due to antigenic crossreactivity with other organisms. Attempts were made to develop a more specific antigen for WB using fusion-proteins of Escherichia coli β-galactosidase and a selected part of the campylobacter flagellin. However because of extensive crossreactions with the β-galactosidase part of this fusion-protein this strategy was unsuccessful. Taking into account time, cost, ease of test performance, and value of the test we would recommend the CFT, together with culture, in diagnosing Campylobacter infections.     

Studies to assess the biological relevance of anti-Tamm-Horsfall protein antibodies detected by direct-binding enzyme-linked immunosorbent assay

1. A role has been suggested for anti-Tamm-Horsfall protein (THP) antibodies in renal disease based on the results of immunoassays of pathological sera. The putative autoantibodies have not been isolated from such sera nor have definitive inhibition studies of their binding been carried out. We have carried out such studies using rabbit anti-THP antibodies as control reagents. 2. Urinary THP prepared by salt precipitation was used to prepare four immunoabsorbent columns by covalent coupling to CNBr-activated Sepharose 4B. After washing with a variety of dissociating agents to remove any non-covalently bound subunit THP, each column was incubated with normal and immune rabbit serum. Fractions washed and eluted from columns were tested for anti-THP antibodies by enzyme-linked immunosorbent assay (ELISA) and THP antigen by radioimmunoassay, and showed NH4SCN (3 mol/l) and guanidine hydrochloride (GuHCl) (6 mol/l) equivalent and sodium dodecyl sulphate (20 g/l) to be inferior in their capacity to produce immunoabsorbent THP capable of isolating specific antibodies from immune rabbit serum. 3. The column treated with GuHCl (6 mol/l) was used further in attempts to isolate putative anti-THP antibodies from five patients, who had a history of urinary tract infections and whose sera showed strong binding by ELISA. 4. Results from direct and inhibition ELISA experiments on fractions collected after washing and elution with all sera suggested that the putative human anti-THP antibodies were of very low affinity and/or directed against non-subunit THP. 5. The pathological relevance of human anti-THP antibodies measured by ELISA remains to be established.     

Evaluation of two fully automated novel enzyme-linked immunosorbent assays for the determination of human adiponectin in serum

BACKGROUND: In contrast to RIA, recently available ELISAs provide the potential for fully automated analysis of adiponectin. To date, studies reporting on the diagnostic characteristics of ELISAs and investigating on the relationship between ELISA- and RIA-based methods are rare. METHODS: Thus, we established and evaluated a fully automated platform (BEP 2000; Dade-Behring, Switzerland) for determination of adiponectin levels in serum by two different ELISA methods (competitive human adiponectin ELISA; high sensitivity human adiponectin sandwich ELISA; both Biovendor, Czech Republic). Further, as a reference method, we also employed a human adiponectin RIA (Linco Research, USA). Samples from 150 patients routinely presenting to our cardiology unit were tested. RESULTS: ELISA measurements could be accomplished in less than 3 h, measurement of RIA had a duration of 24 h. The ELISAs were evaluated for precision, analytical sensitivity and specificity, linearity on dilution and spiking recovery. In the investigated patients, type 2 diabetes, higher age and male gender were significantly associated with lower serum adiponectin concentrations. Correlations between the ELISA methods and the RIA were strong (competitive ELISA, r=0.82; sandwich ELISA, r=0.92; both p<0.001). However, Deming regression and Bland-Altman analysis indicated lack of agreement of the 3 methods preventing direct comparison of results. The equations of the regression lines are: Competitive ELISA=1.48 x RIA-0.88; High sensitivity sandwich ELISA=0.77 x RIA+1.01. CONCLUSIONS: Fully automated measurement of adiponectin by ELISA is feasible and substantially more rapid than RIA. The investigated ELISA test systems seem to exhibit analytical characteristics allowing for clinical application. In addition, there is a strong correlation between the ELISA methods and RIA. These findings might promote a more widespread use of adiponectin measurements in clinical research.     

Development of 2 alternative enzyme-linked immunosorbent assays for routine screening of glutamic acid decarboxylase autoantibodies

BACKGROUND: Antibodies to GAD65 (GADA) are considered highly predictive humoral markers of the type 1 diabetes mellitus and also of the insulin requirement in adult-onset patients presumptively classified as type 2 diabetics or LADA. METHODS: We present 2 methods for GADA assessment. The first one (fluid phase, ELISA Protocol A) is carried out in a 2-step procedure in which serum GADA are first allowed to react with a fixed dose of GAD65-biotin in solution and the residual free antigen is later assayed by a conventional ELISA. In the second test (solid phase, ELISA Protocol B) GADA are measured in an ELISA that depends on the ability of divalent autoantibodies to form a bridge between immobilized TrxGAD65 and liquid-phase biotinylated TrxGAD65. RESULTS: All normal control samples scored negative in both variants of ELISA and RBA, hence specificity was 100% for all methods; the relative sensitivity of ELISA Protocol A respect of the RBA was 94% and that of ELISA Protocol B was 76%. CONCLUSIONS: Although ELISA Protocol A exhibited a better performance in terms of relative sensitivity than ELISA Protocol B, the simplicity of execution and the intended use of the assay must also be taken in consideration for the final choice.     

Epitope characterization of acetaminophen bound to protein and nonprotein sulfhydryl groups by an enzyme-linked immunosorbent assay

The oxidation of acetaminophen to N-acetyl-p-benzoquinone imine and its subsequent binding to protein sulfhydryl groups may be important in the observed toxicity of acetaminophen. An avidin biotin-amplified competitive enzyme-linked immunosorbent assay has been developed which utilizes solid phase acetaminophen bound to metallothionein and antiserum obtained from rabbits that were immunized with 3-(N-acetyl-L-cystein-S-yl)acetaminophen covalently bound to keyhole-limpet hemocyanin. Over 25 synthetic analogs of acetaminophen conjugates and structurally similar compounds have been ranked relative to their ability to compete in the avidin biotin-amplified enzyme-linked immunosorbent assay. The most effective inhibitor was 3-(N-acetyl-L-cystein-S-yl)acetaminophen, which had an observed 50% inhibitory concentration of 120 fmol/well. Approximately 6200-fold higher concentrations of unbound acetaminophen and 5.2 x 10(6)-fold higher concentrations of N-acetyl-L-cysteine were required for comparable inhibition. It was demonstrated with acetaminophen analogs that the hydroxyl group and the N-acetyl moiety of acetaminophen were important in epitope recognition. A 5000-fold decrease in detection was observed when the analog did not contain the hydroxyl group or when the N-acetyl moiety was replaced with a hydroxyl substituent. Recognition by antibody was also dependent upon the stereochemistry of the analogs. The 50% inhibitory concentration for 3-(L-cystein-S-yl)acetaminophen was 2300 fmol/well, whereas a 25-fold higher concentration of 3-(D-cystein-S-yl)acetaminophen was required for 50% inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)     

夹心酶联免疫吸附试验检测人表皮生长因子的方法建立及其应用研究

目的:建立临床适用的表皮生长因子(epidermalgrowthfactor,EGF)酶联免疫检测方法,探讨EGF在临床常见肿瘤患者血清中的含量变化规律。方法:采用EGF单抗包被酶标板,兔抗EGF多抗为二抗,以辣根过氧化物酶标记的羊抗兔IgG作为酶标抗体建立夹心法ELISA检测临床常见肿瘤患者及健康体检人群的血清EGF含量。结果:建立的EGF酶联免疫吸附法最小检测限达15.6ng/L,批内精密度为8.7%,批间精密度为11.6%,平均回收率为94.7%,符合临床检测要求。血清EGF含量在31名正常人为(1.305±0.382)ng/mL,24名乳腺癌病人术前值为(0.729±0.347)ng/mL,术后为(0.711±0.332)ng/mL,17名结直肠癌病人术前为(0.678±0.311)ng/mL,术后为(0.658±0.298)ng/mL,19名胃癌病人术前为(0.598±0.224)ng/mL,术后为(0.614±0.257)ng/mL。各肿瘤组患者血清EGF水平较健康对照组明显降低(P<0.01)。结论:建立了适用于临床检测的EGF酶联免疫检测方法,肿瘤患者血清中EGF含量较健康对照组明显下降,该检...     

间接酶联免疫法测定抗Jo-1抗体及其临床应用

目的利用基因工程表达的组氨酰转移核糖核酸合成酶自身抗原Jo-1蛋白,建立ELISA法,初步用于检测多发性肌炎/皮肌炎(PM/DM)中的抗Jo-1抗体。方法用表达蛋白建立间接ELISA,摸索反应时间、抗原包被浓度、样本稀释浓度及抗抗体工作浓度等工作条件,进一步检测方法的重复性及稳定性。用建立的方法,检测40例健康体检者、30例系统性红斑狼疮(SLE)、30例类风湿关节炎(RA)、20例干燥综合征(SS)、90例多发性肌炎/皮肌炎(PM/DM)患者血清中抗Jo-1抗体。结果成功建立间接ELISA法,并确立了一系列反应条件。临床检测结果显示,PM/DM患者抗Jo-1抗体的阳性率为25.6%,而非PM/DM患者均为阴性。PM/DM组Jo-1抗体阳性率与疾病对照组及健康对照组比较,差异均有统计学意义(均P<0.01)。结论本研究成功应用基因工程表达的Jo-1蛋白建立了间接ELISA法,检测抗Jo-1抗体,与国外报道的结果基本相当,与常用免疫印迹法对比检测的结果一致。     

Serodiagnosis of recently acquired Toxoplasma gondii infection in pregnant women using enzyme-linked immunosorbent assays with a recombinant dense granule GRA6 protein

Indirect immunoglobulin G (IgG) and IgM enzyme-linked immunosorbent assays (ELISAs) with a recombinant GRA6 protein of Toxoplasma gondii were developed and evaluated for accurate diagnosis of recently acquired infection in pregnant women. According to the results from Toxoplasma serodiagnostic tests, women were classified into 3 groups representing acute (group I), chronic (group II), or no Toxoplasma infection (group III). To discriminate group I from group II sera, the GRA6–IgG-ELISA reached sensitivity and specificity of 87.5% and 94.1%, respectively. Although 22 (91.7%) of 24 group I sera were positive by the GRA6–IgM-ELISA, only 1 (2.9%) of 34 group II sera scored positive. The GRA6–IgM-ELISA displayed a meaningful correlation with Vidas Toxo IgM and exhibited higher specificity (97.1%) than Euroimmun IgM ELISA (88.2%) (Euroimmun, Lübeck, Germany) for detection of recent infection. These results demonstrate that IgG and IgM ELISA with rGRA6 are useful to identify and discriminate recent from past Toxoplasma infection in pregnant women.     

Antimicrobial susceptibility of Campylobacter jejuni and Campylobacter fetus subsp. fetus to eight cephalosporins with special reference to species differentiation.

Agar dilution antimicrobial susceptibility testing showed that Campylobacter jejuni was significantly more resistant than Campylobacter fetus subsp. fetus (intestinalis) to cephalosporin C, cephaloridine, cephalothin, cefazolin, and cefamandole. No species differences in susceptibility were noted with cephalexin, cefotaxime, and cefoxitin. Rapid species differentiation on the basis of an antibiogram could be achieved with the disk diffusion method. C jejuni failed to produce a zone of inhibition around a 30-microgram cephalothin disk but produced a significant zone around a 30-microgram nalidixic acid disk. C. fetus subsp. fetus (intestinalis) produced exactly the reverse pattern.