A new serological technique, time-resolved fluoroimmunoassay (TRFIA), for the immunological diagnosis of urinary schistosomiasis

Establishment of Galectin-3 Time-resolved Fluoroimmunoassay and its Application in Idiopathic Membranous Nephropathy

The aim of this study was to establish a time-resolved fluorescent immunoassay (TRFIA) for the detection of serum Galectin-3 (Gal-3) and apply this method to evaluate the clinical significance of serum Gal-3 in predicting Idiopathic Membranous Nephropathy (IMN) progression. The Gal-3-TRFIA was established using the double antibody sandwich method, with the capture antibodies coated on a 96-well microplate and the detection antibodies chelated with Europium (III) (Eu³⁺). Serum Gal-3 was detected in 81 patients with IMN and 123 healthy controls to further evaluate the value of the Gal-3 in staging of IMN. The sensitivity of the Gal-3-TRFIA assay was 0.85 ng/mL, and the detection range was 0.85-1000 ng/mL. The Gal-3 intra-batch and inter-batch coefficients of variation were 3.45% and 5.12%, respectively. The correlation coefficient (R) between the Gal-3-TRFIA assay and commercially available enzyme-linked immunosorbent assay kits was 0.83. The serum Gal-3 concentration was higher in patients with IMN (65.57 ± 55.90 ng/mL) compared to healthy controls (16.29 ± 9.91 ng/mL, P < 0.0001). In this study, a wide detection range Gal-3-TRFIA assay was developed using lanthanide (Eu³⁺) chelates for the detection of Gal-3 concentrations in serum. Gal-3 concentration is elevated in patients with IMN.

Serological approaches for the diagnosis of schistosomiasis - A review

Schistosomiasis is a common disease in endemic areas of Sub-Saharan Africa, South America and Asia. It is rare in Europe, mainly imported from endemic countries due to travelling or human migration. Available methods for the diagnosis of schistosomiasis comprise microscopic, molecular and serological approaches, with the latter detecting antigens or antibodies associated with Schistosoma spp. infection. The serological approach is a valuable screening tool in low-endemicity settings and for travel medicine, though the interpretation of any diagnostic results requires knowledge of test characteristics and a patient's history. Specific antibody detection by most currently used assays is only possible in a relatively late stage of infection and does not allow for the differentiation of acute from previous infections for therapeutic control or the discrimination between persisting infection and re-infection. Throughout the last decades, new target antigens have been identified, and assays with improved performance and suitability for use in the field have been developed. For numerous assays, large-scale studies are still required to reliably characterise assay characteristics alone and in association with other available methods for the diagnosis of schistosomiasis. Apart from S. mansoni, S. haematobium and S. japonicum, for which most available tests were developed, other species of Schistosoma that occur less frequently need to be taken into account. This narrative review describes and critically discusses the results of published studies on the evaluation of serological assays that detect antibodies against different Schistosoma species of humans. It provides insights into the diagnostic performance and an overview of available assays and their suitability for large-scale use or individual diagnosis, and thus sets the scene for serological diagnosis of schistosomiasis and the interpretation of results.

Development of a time-resolved fluorescence immunoassay for Epstein-Barr virus nuclear antigen 1-immunoglobulin A in human serum

Enzyme-linked immunosorbent assay (ELISAs) specific for Epstein-Barr virus nuclear antigen 1 (EBNA1)-immunoglobulin A (IgA) are most commonly used in the clinical diagnosis of EBV infection. But they have a low sensitivity and the enzyme-labeled antibodies are unstable. In this study, a novel immunoassay based on an indirect time-resolved fluoroimmunoassay (TRFIA) was developed. Microtiter plates were coated with recombinant EBNA1. We used Eu(3) (+)-labeled anti-human IgA as probe. The precision, sensitivity, specificity, and stability were evaluated, and comparison with traditional and commercially available ELISAs was also made. The cut-off value for our TRFIA was 2.7. Intra- and inter-assay coefficients of variation for the TRFIA were 1.56-4.99% and 3.92-6.95%, respectively; whereas those for the ELISA were 4.54-8.16% and 7.07-10.52%, respectively. Sensitivity was obviously better than traditional ELISA when diluted positive samples serially. Additionally, stability, specificity test and comparison of sensitivity and specificity between the TRFIA and commercial ELISAs all proved satisfactory. In conclusion, the results demonstrated that EBNA1 IgA TRFIA was a sensitive immunoassay and had potential value in large-scale screening of human serum samples in developing countries.

Fast measurement of serum amyloid A in different specimens from swine by using a new one-step time-resolved fluorescent immunoassay

The objective of the present study was to develop a one-step, fast, competitive time-resolved fluorescent immunoassay to determine porcine serum amyloid A (SAA) by using species-specific reagents. The assay consisted of an all-in-one format involving only 55 min of incubation that was adapted and validated for use in 3 different specimens: serum, saliva, and meat juice. The method had overall within- and between-run coefficients of variation under 8% and 12%, respectively, and coefficients of determination higher than 0.93 for linearity under dilution analysis for all specimens. The limits of detection were 0.32 mg/l, 0.28 mg/l, and 1.74 mg/l for serum, saliva, and meat juice measurements, respectively. Upper and lower limits of quantification were determined for each sample type and resulted in wide assay ranges that allowed a precise SAA measurement in all the fluids investigated. Statistically significant differences (P = 0.0004 for serum and P < 0.0001 for the saliva and meat juice samples) in SAA levels were found when healthy (n = 20) and diseased (n = 20) pigs were compared. The obtained results indicate that this fast, sensitive, and robust assay for SAA measurement could be of use to determine health and welfare status in swine by employing alternative samples to serum.

The expressions and clinical significances of tissue and serum galectin-3 in pancreatic carcinoma

PURPOSE

Galectin-3, a member of the beta-galactoside-binding protein family, is involved in many biological processes, including cell proliferation, regulating cell cycle, angiogenesis, tumorigenesis, metastasis, etc. The aim of this study is to elucidate the relationship between galectin-3 and clinicopathological variables and to evaluate the clinical significance of serum galectin-3 in the diagnosis of pancreas carcinoma.

METHODS

Galectin-3 expression in 78 pairs of pancreatic carcinoma tissues and the adjacent nontumorous tissues was tested by immunohistochemistry. The relationship between galectin-3 expression and clinical variables was analyzed. A sensitive method of time-resolved fluorescence immunological assay (TRFIA) for the detection of galectin-3 was established, and serum galectin-3 in cases with different pancreatic diseases was measured by TRFIA and ELISA. Further we compared the sensitivity and specificity of determining galectin-3, carcinoembryonic antigen (CEA) and carbohydrate antigen199 (CA199) for diagnosis of pancreatic carcinoma and assessed the complementary diagnostic value of galectin-3, CEA and CA199 for pancreatic carcinoma.

RESULTS

Immunohistochemistry showed that galectin-3 expression was significantly higher in the human pancreatic carcinoma tissues than in the adjacent nontumorous tissues. The expression levels were correlated with the differentiation degree with the higher expression in poor differentiation tissues. Serum galectin-3 detected by both TRFIA and ELISA was much higher in patients with pancreatic carcinoma than in other groups. Serum galectin-3 was not correlated with CEA and CA199. Combined determination of these three markers has the complementary diagnostic value for human pancreatic carcinoma and may increase the diagnostic sensitivity to 97.5%.

CONCLUSIONS

Galectin-3 is overexpressed in pancreatic carcinoma tissues, and it is correlated with the tumor differentiation. Serum galectin-3 is higher in cases with pancreatic carcinoma than in benign pancreatic diseases and healthy persons. Combined determination of serum galectin-3, CEA and CA199 may improve the diagnostic power for pancreatic carcinoma.

Determination of anti-Cryptosporidium coproantibodies by time-resolved immunofluorometric assay

The role of the mucosal immune response against Cryptosporidium has been suggested by studies on the therapeutic effects of hyperimmune colostrum. In order to study the intestinal response to this infection, we have developed a sandwich-type time-resolved immunofluorometric assay for the determination of anti-Cryptosporidium coproantibodies. This assay has the inherent sensitivity of an immunoassay without the problems due to background responses from other biological compounds, and is thus suitable for faecal samples. The intra-assay coefficients of variation (5.1%, 4.6%, and 5.8% for immunoglobulins (Ig) A, M and G respectively), inter-assay coefficients of variation (9.4%; 10.5% and 12.2% for IgA, IgM and IgG, respectively) and specificity (100% for all 3 isotypes) were all satisfactory. Using this assay to study 12 patients with the acquired immune deficiency syndrome (AIDS) who were infected with cryptosporidiosis, we found a marked elevation of anti-Cryptosporidium IgA and IgM coproantibody titres relative to 18 healthy control values, but no correlation with the gravity of the infection in terms of oocyst shedding. These results suggest that a non-protective mucosal immune response develops to Cryptosporidium in AIDS patients.

The serological diagnosis of human hydatid disease by time-resolved fluoroimmunoassay

The use of a new immunoassay, time-resolved fluoroimmunoassay (TR-FIA), in the diagnosis of human hydatid disease has been evaluated. This technique, which is based on the labelling of antibodies with europium (Eu), was compared with a well-established method, the enzyme linked immunosorbent assay (ELISA). Of 102 patients with hydatid disease, 97 (95.1%) were positive according to TR-FIA and 83 (81.4%) according to ELISA. The rate of non-specificity for other parasitic infections (n = 206) was 8.7% for TR-FIA and 17.5% for ELISA. It is concluded that TR-FIA is more sensitive and more specific than ELISA in the diagnosis of human hydatid disease.

Time-resolved immunofluorometric assay (TR-IFMA) for the detection of the schistosome circulating anodic antigen

We report the development of a time-resolved immunofluorometric assay (TR-IFMA) for the quantitative determination of the schistosome circulating anodic antigen (CAA). A mouse monoclonal antibody (line 120-1B10-A), recognizing a repetitive epitope on CAA, was used as both antigen-capture antibody and as Europium-labelled antigen-detecting antibody. The lower detection limit of the assay was 20 pg of trichloroacetic acid soluble fraction of adult worm antigen (AWA-TCA) per ml, with a nearly linear measuring range from 20 pg to 130 ng AWA-TCA per ml. The TR-IFMA was compared with an enzyme-linked immunosorbent assay (ELISA), in which the same monoclonal antibody was used as antigen-capture antibody and as alkaline phosphatase-conjugated antibody. The lower detection limit of the TR-IFMA was tenfold lower than that of the ELISA, while the linear range of the TR-IFMA exceeded that of the ELISA one hundred-fold. Serum samples of 80 Burundese individuals infected with Schistosoma mansoni (egg counts ranging from 4 to 2583 eggs per gram of faeces) were tested in both assays. Antigen concentrations in serum of individuals infected with S. mansoni ranged from 0-500 ng AWA-TCA per ml. The correlation between antigen levels measured by TR-IFMA and ELISA was good: Spearman's p = 0.92. Whereas in the ELISA the samples had to be titrated, the wide linear range of the TR-IFMA allowed the assay to be performed at a single serum dilution, at which an exact estimation of the antigen concentration was possible.