Use of monoclonal antibodies to human immunoglobulin M in "capture" assays for measles and rubella immunoglobulin M

Evaluation of hemagglutinin protein-specific immunoglobulin M for diagnosis of measles by an enzyme-linked immunosorbent assay based on recombinant protein produced in a high-efficiency mammalian expression system

Recombinant hemagglutinin (H) of the measles virus (MV) expressed in a mammalian high-expression system based on the Semliki Forest virus replicon was used in an enzyme-linked immunosorbent assay (ELISA) for the detection of specific immunoglobulin M (IgM) and IgG in patients with acute-phase measles. One hundred twelve serum specimens from 70 patients with measles were analyzed. Case definition was based on a commercial IgM ELISA that utilizes MV-infected cells (MV-ELISA) (Enzygnost; Behring Diagnostics); the clinical criteria of the Centers for Disease Control and Prevention (Atlanta, Ga.); and/or the increase in hemagglutinin test titers, neutralization test titers, and levels of MV-specific IgG whenever paired sera were available. The initial time courses of the IgM signal after the onset of rash are similar in the H- and MV-ELISAs. On days 0 to 19, both ELISAs detected IgM in 67 of 68 (98.5%) sera. Average maximal levels of IgM seem to persist, however, about 10 days longer in the MV-ELISA (up to day 25) than in the H-ELISA (day 15). From days 20 to 29 and 30 to 59, the H-ELISA detected only 64.3 (9 of 14) and 19.2% (5 of 26), respectively, of sera that were IgM positive by MV-ELISA. At least up to day 30, the performance of the H-ELISA seemed to be similar to that reported for commercial ELISAs based on whole MV. Our results demonstrate that MV H-specific IgM can be used to diagnose most measles cases from a single serum specimen collected within 19 days after the onset of rash and that the recombinant protein used in this study is suitable for this purpose.

Automated microparticle enzyme immunoassays for IgG and IgM antibodies to Toxoplasma gondii

Fully automated microparticle enzyme immunoassays (MEIA) for the IMx immunoassay analyser were developed to detect IgG and IgM antibodies to Toxoplasma gondii. The IgG MEIA results are expressed in International Units (IU) of IgG antibody interpolated from a six point calibration curve covering the range from 0 to 300 IU/ml. Reproducible results were obtained from a calibration curve stored in the instrument for at least one month. The qualitative IgM MEIA expresses results as an index using a single calibrator included in each run. The Toxo IgG MEIA and Toxo IgM MEIA were in 98% and 97% agreement, respectively, with the reference assays used. Twenty four sera can be completely processed in about 35 minutes.

Development of automated immunoassays for immune status screening and serodiagnosis of rubella virus infection

The fully automated IMx immunoassay analyzer was used to develop a system for the detection of IgG and IgM antibodies to rubella virus for immune status screening and diagnosis of primary infections. Reagents and assay protocol software were developed using rubella virus sensitized microparticles as the solid phase to capture specific antibodies from serum samples. Anti-human IgG or IgM antibody coupled to alkaline phosphatase enzyme followed by methylumbelliferyl phosphate substrate was used to detect the presence or absence of antibodies specific to the antigens on the solid phase. To evaluate the efficacy of the IMx rubella IgG assay, immune status screening was performed with a clinical patient population of 501 sera. When compared to an IgG specific enzyme immunoassay and passive hemagglutination assay the agreement was greater than 99%. The IMx rubella IgM assay was utilized to determine the presence of rubella specific IgM antibodies in 462 sera. These results were compared to IgM specific enzyme immunoassay results and also demonstrated greater than 99% agreement. Seroconversion following rubella vaccination of susceptible individuals was demonstrated by IgG and IgM antibody responses as early as two weeks postvaccination. In addition to automation, the IMx system offers rapid assay times and calibration curve storage without sacrificing clinical efficacy.

Comparison of an antibody-capture IgM enzyme-linked immunosorbent assay with IgM-indirect immunofluorescence for the diagnosis of acute Sindbis and West Nile infections

The development and evaluation of an antibody-capture ELISA for the detection of IgM antibodies to Sindbis (SIN) and West Nile (WN) viruses are described. Comparison of the ELISA results with those obtained by indirect immunofluorescence (IIF) antibody tests using both fluorescein and biotinylated anti-human IgM conjugates, showed that the former technique was both more sensitive and specific than the IIF methods. There were no false positives by the ELISA whereas with the IgM-IIF assays a high percentage of false positives were obtained. These were due to rheumatoid factor and also to an interfering factor which was not detected by the RF latex agglutination test. Absorption of the sera with anti-IgG was necessary to eliminate this interference in the IgM-IIF tests.

Selection and performance of monoclonal and polyclonal antibodies in an IgM antibody capture enzyme immunoassay for rubella

Monoclonal anti-human IgM and anti-rubella antibodies were prepared and tested in an IgM capture enzyme immunoassay (MACEIA) for rubella-specific IgM and compared with polyclonal reagents. Assay sensitivity was increased with monoclonal antibodies resulting in the improved discrimination of adult sera with low levels of specific IgM. Despite high IgM binding, interference by IgM anti-Ig was not a major problem. The use of monoclonal antibodies allowed assay simplification by the simultaneous rather than sequential addition of antigen and conjugate. Although comparable results were obtained with 33 test samples in the sequential and simultaneous MACEIA, the specificity and sensitivity of this modification requires further evaluation.

An assessment of available rapid immunologic diagnostic methods

A critical evaluation of immunologic methods for diagnosis is presented. The issues of antibody versus antigen detection are addressed. Reverse capture immunoglobulin M detection is described as a potentially useful method. Agglutination procedures currently in use for antigen detection are summarized. Comparative evaluations of commercially available products are presented. The final issue discussed is that of enzyme immunoassay versus fluorescent antibody microscopy. Using Chlamydia detection as an example, advantages and disadvantages of each technology are assessed.

Comparison of enzyme-linked immunosorbent assay with enzyme-linked fluorescence assay with automated readers for detection of rubella virus antibody and herpes simplex virus

The enzyme-linked immunosorbent assay (ELISA) was compared with the enzyme-linked fluorescence assay (ELFA) for the detection of rubella antibody and herpes simplex virus antigen. Test parameters, specimens, antigen or antibody, and conjugates for the two types of assays were identical except that p-nitrophenyl phosphate was used as the substrate for the ELISA and 4-methylumbelliferyl phosphate was used as the substrate for ELFA. Automated readers were used for both assays. Antibody titers and sensitivity of antigen detection were quite similar for ELISA and ELFA. ELFA for rubella antibody, however, could be conducted with less antigen or shorter substrate incubation time (5 min for ELFA versus 30 min for ELISA). For herpes simplex virus antigen detection, ELFA could also be read after a shorter substrate incubation time (15 min for ELFA versus 30 min for ELISA). Clear polystyrene microtiter plates routinely used for ELISA could be used for ELFA, but clear polyvinyl chloride plates had high background fluorescence. Black polystyrene and polyvinyl chloride plates gave lower background fluorescence than did clear plates. ELFA is of particular value as a substitute for ELISAs in which long substrate incubations are required or antigens of only low titer are available.