The detection of cytomegalovirus (CMV)-specific IgM using peroxidase labelled antigen: comparison with an indirect enzyme-linked immunoassay

Abstract

Three hundred and forty-seven serum samples were obtained from 54 renal transplant patients, seven patients who had heterophil antibody negative mononucleosis, 23 with non-specific febrile illnesses, 10 patients who were positive for anti-nuclear antibody and who had systemic lupus erythematosus (SLE), 58 patients with other diseases of non-viral aetiology and 195 healthy individuals. These were examined for the presence of cytomegalovirus-specific IgM antibody by an IgM capture assay utilizing CMV-peroxidase labelled antigen and a commercially available indirect enzyme immunoassay (Enzygnost, Behring). The former assay detected 22 CMV-IgM positive specimens whereas the latter assay detected only 16 of these 22 (73%) samples following rheumatoid factor (RF) removal. The CMV-binding activity detected in five of the sera which gave discordant results was shown to be located in the IgM fractions by the capture assay following sucrose density gradient fraction. Thus there was no indication of false positive reactions in the IgM capture assay. In addition, the presence of anti-nuclear antibodies did not interfere with the enzyme immunoassay investigated. These results, therefore, suggest that the CMV-IgM capture assay utilizing enzyme-labelled CMV antigen is a sensitive and specific procedure which should have important applications in the diagnosis of CMV infections with distinct advantages over the indirect immunoassay.