Reactivity to p52 and CM2 recombinant proteins in primary human cytomegalovirus infection with a microparticle agglutination assay

Multiplex bead array assays: performance evaluation and comparison of sensitivity to ELISA

The measurement of soluble cytokines and other analytes in serum and plasma is becoming increasingly important in the study and management of many diseases. As a result, there is a growing demand for rapid, precise, and cost-effective measurement of such analytes in both clinical and research laboratories. Multiplex bead array assays provide quantitative measurement of large numbers of analytes using an automated 96-well plate format. Enzyme-linked immunosorbent assay (ELISAs) have long been the standard for quantitative analysis of cytokines and other biomarkers, but are not well suited for high throughput multiplex analyses. However, prior to replacement of ELISA assays with multiplex bead array assays, there is a need to know how comparable these two methods are for quantitative analyses. A number of published studies have compared these two methods and it is apparent that certain elements of these assays, such as the clones of monoclonal antibodies used for detection and reporting, are pivotal in obtaining similar results from both assays. By careful consideration of these variables, it should be possible to utilize multiplex bead array assays in lieu of ELISAs for studies requiring high throughput analysis of numerous analytes.

Human cytomegalovirus infection: diagnostic potential of recombinant antigens for cytomegalovirus antibody detection

Recombinant antigen-based enzyme immunoassays (EIAs) for the detection of human cytomegalovirus (HCMV) specific antibody are believed to yield a higher sensitivity and specificity than virus lysate EIAs. The aim of the present study was to evaluate the accuracy of newly established HCMV assays (Copalis CMV Multiplex, Sorin; Cobas Core CMV IgG and IgM EIAs, Roche Diagnostics; Anti-HCMV recombinant IgG, gB-IgG, IgM and IgA, Biotest; and ETI-CYTOK-G PLUS and M reverse PLUS, Sorin) based on recombinant antigens and/or virus lysate for laboratory diagnosis of HCMV infection. For the assessment of sensitivity, follow-up samples from patients suffering from active HCMV infection were tested. Testing a large number of potentially interfering samples challenged the specificity of the assays. There was no statistically significant difference in the performance of HCMV IgG assays. The results were more heterogeneous for the detection of serological markers of active infection (HCMV IgM, HCMV IgA and anti-CM2). The sensitivities of the different assays ranged between 40.5 and 71.4%. A variable number (17.8-1.7%) of false-positive results were obtained among potentially interfering serum samples. Two of the recombinant antigen based assays showed a high degree of interference with EBV VCA-IgM-positive sera. The best performance was achieved with ETI-CYTOK-M reverse PLUS since it combined the highest sensitivity with specificity. Commercially available assays based on recombinant antigens showed, overall, a poorer performance than the virus lysate EIA.

Cross-reactivity of Epstein-Barr virus-specific immunoglobulin M antibodies with cytomegalovirus antigens containing glycine homopolymers

Timely and reliable detection of acute primary human cytomegalovirus (HCMV) infection is important in prenatal screening programs and for differential diagnosis of infectious mononucleosis-like disease. Enzyme-linked immunosorbent assays (ELISAs) based on HCMV proteins enable the sensitive detection of immunoglobulin M (IgM) antibodies during primary infection. However, concerns have been raised about possible cross-reactivities of the HCMV antigens used for the design of such ELISAs with IgM antibodies induced by Epstein-Barr Virus (EBV). In this study we investigated whether IgM antibodies generated during acute EBV infection reacted with recombinant HCMV antigens. Serum samples from patients with primary EBV infection frequently scored positive when tested in different HCMV IgM ELISAs, irrespective of whether conventional or recombinant antigens were used for the design of the HCMV IgM assays. Such cross-reactive IgM antibodies were found to be directed against short glycine-rich motifs contained within the nonstructural HCMV proteins pUL44 and pUL57. Further analyses revealed that these glycine-rich motifs were major antigenic domains for IgM antibodies induced during HCMV infection. Their deletion from recombinant proteins abrogated reactivity with IgM synthesized during HCMV infection. EBV-induced IgM antibodies that reacted with HCMV antigens showed similar kinetics of reactivity in HCMV- or EBV-specific assays in the course of primary EBV infection, indicating that the two populations of antibodies were highly overlapping. The results demonstrate that primary EBV infection leads to the induction of IgM antibodies that specifically bind to widely used diagnostic antigens of HCMV. This has to be considered in the interpretation of HCMV-specific IgM assays.