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suMMARY An ELISA method was developed for the measurement of toxoplasma IgG antibodies in human serum using antigen-coated polystyrene beads as a solid phase and anti human IgG-horse radish peroxidase conjugate as an enzymatic tracer. In order to assess ELISA sensitivity and specificity, a between methods comparison was made using 'conventional' serological tests as reference (dye-test, crossover-linked immunoassay, passive haemagglutination, indirect immunofluorescence). From an analysis of the group classifications obtained some considerations emerged: the ELISA specificity looks comparable with that of the 'reference' tests, as no sample classified as negative by all these tests was ELISA-positive, and vice versa; ELISA appears to correlate better with haemagglutination and immunofluorescence, on the basis of the respective class frequencies; in particular, the number of positives, which is much lower for the dye-test and crossover-linked immunoassay, suggests that a higher sensitivity is reached in the former cases.None of the several tests mostly used for the serodiagnosis of toxoplasmosis appears fully adequate for mass-screening purposes as far as analytical reliability, experimental ease, and promptness of response are concerned. As a matter of fact some of them need special equipment not widely available, and others cannot be used as single tests owing to the incompleteness of the information obtainable and the poor correlation with the clinical situation.Recently, the enzyme-linked immunosorbent assay (ELISA) has been proposed as a promising serological test for infective and infestive diseases. '-5 Also in our laboratories attempts were made to evaluate the actual potential of ELISA in the diagnosis of toxoplasma infections. In particular, this study was aimed at defining the specificity and sensitivity of an ELISA method we have recently developed through a comparison with other serological tests assumed as references, such as the dyetest, crossover-linked immunoassay, indirect haemagglutination, and indirect immunofluorescence.

SUMMARYUsing murine monoclonal antibodies (MAbs) to rubella virus haemagglutinin, five epitopes were identified in competitive ELISA binding assays: A, B, D and E by haemagglutination-inhibiting (HI) MAbs with no neutralizing (Nt) activity, and C by a MAb with neither activity. However, when HI and Nt activities were determined in the presence of anti-mouse immunoglobulins, epitopes A, B and D were defined by both HI and Nt MAbs, whereas epitopes C and E were identified by HI MAbs without Nt activity. A synergistic Nt activity, in the absence of anti-mouse immunoglobulins, was displayed by mixtures of antibodies of different epitope groups. Analysis of mixtures of MAb pairs each belonging to a different epitope class, showed that synergistic Nt activity was elicited primarily by the group A epitope, secondarily by groups B and D and only minimally by groups C and E.

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A capture enzyme-linked immunosorbent assay (ELISA) for detection of virus-specific immunoglobulin M (IgM) antibody was developed which used a panel of labeled monoclonal antibodies to rubella virus hemagglutinin. The rapidity of the test system was increased by using, after 1-h incubation of the test serum, a second 1-h incubation of the serum with a mixture of viral antigen and labeled monoclonal antibody. The new assay was tested for specificity on 371 human sera from people without any recent contact with rubella virus;