Detection of antibodies in schistosomiasis by enzyme-linked immunosorbent assay (ELISA)

Gelatin particle indirect agglutination test for serodiagnosis of schistosomiasis: comparative study with enzyme-linked immunosorbent assay

A new serological test, the gelatin particle agglutination test (GPAT), was used for the serodiagnosis of schistosomiasis mansoni. This technique showed the sensitivity (90.6%) and specificity (97.8%) close to those of enzyme-linked immunosorbent assay. The GPAT can be easily and rapidly performed without specialized equipment, by using lyophilized antigen-coated gelatin particles. The test also seems to be useful for mass screening of Schistosoma infection in field conditions.

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

The application of a new serological method, time-resolved fluoroimmunoassay (TRFIA), is described for the diagnosis of urinary schistosomiasis. A chelate of lanthanides (europium) with a long fluorescent life-time is used as label. The intensity of fluorescence is measured after a delay selected to eliminate almost completely the background fluorescence, which decays rapidly. TRFIA was compared with an established method, enzyme linked immunosorbent assay (ELISA). Using sera from proven cases of Schistosoma haematobium infection, 98.1% of the samples were positive by TRFIA and 86.5% by ELISA. Sera from patients infected with helminths other than schistosomes produced only 1.5% of false positives with TRFIA, compared with 12.3% by ELISA. TRFIA is more sensitive and specific than ELISA.

The epidemiology of schistosomiasis in the later stages of a control programme based on chemotherapy: the Basrah study. 2. The serological profile and the validity of the ELISA in seroepidemiological studies

An epidemiological study of Schistosoma haematobium infection in Al-maadan locality, considered to be the main remaining endemic focus in Basrah, southern Iraq was carried out. The association between the serological profile of the population, measured by the enzyme linked immunosorbent assay (ELISA), and various factors including current infection by urine examination, water contact pattern, past history of, and treatment for, schistosomiasis, and cercarial dermatitis was investigated. Further study of the serological data by the relative operating characteristic (ROC) analysis to assess the validity of the ELISA in detecting schistosomal infection, showed that current infection, past history of infection, age, cercarial dermatitis and category of household were significantly associated with the serological profile of the population. The analysis allowed quantification of the effects of past history of infection and cercarial dermatitis on the validity of the ELISA in detecting schistosomiasis.

Molecular identity of a major antigen of Schistosoma mansoni which cross-reacts with Trichinella spiralis and Fasciola hepatica

A glycoprotein cross-reactive among Schistosoma mansoni, Trichinella spiralis and Fasciola hepatica was identified and characterized by use of monoclonal antibodies prepared against S. mansoni glycoproteins. Four monoclonal antibodies recognized the same antigen which was one of the major S. mansoni glycoproteins precipitated by sera of hosts infected with either S. mansoni or T. spiralis. This antigen was expressed in S. mansoni cercariae, adult male and female worms, and eggs, and in S. haematobium but not in S. japonicum. Radio-immunoprecipitation and partial proteolytic digest mapping showed that the monoclonal antibodies each recognized a unique epitope. These epitopes were heat labile, sensitive to chaotropic agents, but resistant to reduction and alkylation or digestion with glycosidases, indicating that the recognition sites were amino acids and not carbohydrates. Epitopes recognized by the four monoclonal antibodies were expressed in F. hepatica, whereas only two were expressed in T. spiralis. Analysis by immunofluorescence microscopy showed that the antigen was expressed in S. mansoni in the parenchymal tissue and on the surface of the dorsal tubercles; in mature F. hepatica in the parenchymal tissue, vitelline glands and eggs; in immature F. hepatica only in the parenchymal tissue and in larval T. spiralis in the hypodermis.

An evaluation of the ELISA for schistosomiasis in a hospital population

In order to evaluate the ELISA for schistosomiasis under the conditions of clinical practice, 1576 hospital patients were tested using a crude soluble Schistosoma mansoni egg antigen. Test sensitivity in detection of S. mansoni was found to be 96.2% and in S. haematobium 92.3%. The predictive value of positive results was high, reaching 88% at antibody levels three or more times the screening level. The test was considered by clinicians to be valuable for diagnosis and patient management, though it did not distinguish active from recently treated infections. Of 37 apparently false positive schistosome ELISA results only seven could be attributed to other helminth infections. Another nine patients had hepatitis. It is suggested that the antigens and antibodies of the two diseases are mutually cross-reactive, since reports have suggested a high increase of HBsAg patients with schistosomiasis.

Schistosoma mansoni, S. haematobium, and S. japonicum: identification of genus- and species-specific antigenic egg glycoproteins

Immunoreactive egg glycoproteins of Schistosoma mansoni, S. haematobium, and S. japonicum which are genus- and species-specific, or react with sera of patients infected with other parasites, have been identified. Egg proteins were labeled with Iodine-125, and the concanavalin A-binding glycoproteins were immunoprecipitated with sera of patients infected with one of four species of Schistosoma or Trichinella spiralis, Taenia solium, Echinococcus granulosus, Entamoeba histolytica, or Wuchereria bancrofti. These immunoprecipitates were analyzed by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Despite the strikingly different patterns of glycoproteins of the African species, the antibody immune responses of patients infected with S. mansoni and S. haematobium were found to be so similar that differentiation could not be established. In contrast, sera of patients infected with S. japonicum, S. mekongi, or parasites not of the genus Schistosoma, immunoprecipitated fewer of the major S. mansoni or S. haematobium glycoproteins. Likewise, antibody immune responses of patients infected with the Oriental schistosomes (S. japonicum and S. mekongi) could not be differentiated. Only a few quantitative differences were noted between our S. mansoni egg glycoprotein extract and a standardized soluble egg antigen extract. This study provides an explanation for the extensive cross-reactivity observed in diagnostic assays which utilize various fractions of schistosomal egg extracts as the antigen.

Erythroadsorption and enzyme-linked immunoassays (EAIA and ELISA) for specific circulating antibodies and antigens in schistosomiasis

We developed a method of immunologic titration by erythroadsorption in order to assay anti-Schistosoma mansoni soluble cercarial antigen IgM antibodies and anti-S. mansoni soluble worm and egg antigen IgG antibodies. This method was compared to the ELISA technique. Results obtained using the two techniques were similar, although the erythroadsorption technique was less sensitive for identifying IgM during the acute phase of the disease. Both assay systems revealed a correlation between the level of circulating soluble antigens contained in the eggs and the number of eggs found in the stools of this particular group of patients.

Schistosoma mansoni, S. haematobium, and S. japonicum: identification of genus-, species-, and gender-specific antigenic worm glycoproteins

Immunoreactive glycoproteins of Schistosoma mansoni, S. haematobium, and S. japonicum adult worms which are genus-, species-, and gender-specific, or react with sera of patients infected with other parasites, have been identified. Schistosomes were metabolically labeled with [35S]methionine and the concanavalin-A binding glycoproteins that were immunoprecipitated with sera of patients infected with one of three species of Schistosoma or Trichinella spiralis, Taenia solium, Echinococcus granulosus, Entamoeba histolytica, or Wuchereria bancrofti were analyzed by one- and two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The S. mansoni glycoproteins that were immunoprecipitated by sera of patients infected with S. mansoni were indistinguishable from those precipitated by sera of patients infected with S. haematobium. Analogous results were obtained by use of S. haematobium glycoproteins as the radiolabeled antigen. In contrast, sera of patients infected with S. japonicum or parasites not of the genus Schistosoma immunoprecipitated fewer than half of the major S. mansoni or S. haematobium glycoproteins. Likewise, several S. japonicum glycoproteins were cross-reactive, while others exhibited genus, species, and gender specificity.

Evaluation of enzyme linked immunosorbent assay (ELISA) as a diagnostic tool for schistosomiasis

The sensitivity and specificity of the ELISA were assessed in the diagnosis of schistosomiasis in two groups of school children, one attending a rural school where schistosomiasis is highly prevalent, the other attending a school in an urban locality where schistosomiasis is absent. The results showed that the ELISA had a sensitivity of 92.2% and 100% in Schistosoma mansoni and mixed infection, respectively. The specificity of the test increased from 92.1% to 98% when a fourth stool examination was done in cases giving false positive results. ELISA positively was significantly increased with the increase in egg count till it reached 100% in cases with 160 eggs per gram stools.

Separation and comparative immunoassay (DASS, ELISA) with antigens from adult Schistosoma mansoni

Antigenic fractions were prepared from adult Schistosoma mansoni by homogenization and solubilization in phosphate buffer, and subsequent separation on Ultrogel AcA-44. The fractions were tested for antigenicity in two immunodiagnostic techniques, the defined antigen substrate spheres (DASS) system, and the enzyme-linked immunosorbent assay (ELISA), using serum from schistosomiasis patients. The results obtained in the two tests correspond to each other. Sera from 25 patients with proven schistosomiasis were tested with ELISA, using the antigen fractions. For all sera tested, the titres obtained, were dependent on the antigen fraction used. However, areas of high antigenicity were different for different sera. Antigens with molecular weight lower than 60,000, gave negative results for about 30% of the sera but those with molecular weight higher than 60,000 gave positive results for all sera. For about 60% of the sera, the sensitivity of ELISA increased when antigens of increasing molecular weight were used. Cross reactions with two other helminth infections occurred mainly with high molecular weight antigens.

A comparison between a new serological method, thin layer immunoassay (TIA), and the enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies in schistosomiasis

A comparison has been made of a new serological method, thin layer immunoassay (TIA), and an established method, enzyme-linked immunosorbent assay (ELISA), in the detection and quantification of antibodies in schistosomiasis. Using sera from known S. haematobium and S. mansoni cases, the performance of the two tests was almost identical; 95.6% positive for TIA and 96.4% by ELISA. TIA however produced a small number of false positives with sera from other helminth infections whereas ELISA gave none. There was excellent correlation between the tests in the quantification of anti-S. haematobium antibodies, both in human cases and in infected baboons. TIA has the advantage of being extremely simple to perform, but has the disadvantage of requiring a higher concentration of antigens.

Enzyme immunoassays with special reference to ELISA techniques

In this review outlines are given on various types of enzyme immunoassay. The applications to such enzyme immunoassays, especially ELISA, are dealth with in detail. It is concluded that these techniques have high sensitivity and will be suitable in due course as routine laboratory tests.

The use of ELIEDA (enzyme-linked-immuno-electro-diffusion-assay)) in the study of humoral antibodies in human schistosomiasis

In order to improve the sensitivity of immuno-electrodiffusion (IED) we have developed a technique of treating the precipitated immune complexes with enzyme-labelled antibodies. This technique we term ELIEDA (Enzyme-Linked-Immuno-Electro-Diffusion-Assay). The enzyme-labelled antibodies can be made monospecific for each class of immunoglobulins found in patients with schistosomiasis and which precipitate with schistosome antigens. We believe that this sensitive technique will prove valuable in studying the sequential development of antibodies in human and experimental schistosomiasis.

A comparison of isotopic and enzyme-immunoassays for tropical parasitic diseases

A comparison is made of enzyme-immunoassay and radio-immunoassay for the detection of antibody in Chagas's disease, sleeping sickness, malaria, schistosomiasis ans invasive amoebiasis. Both assays were sensitive and reproductible and gave comparable results.