Detection of IgM antibodies to measles virus by enzyme-immunoassay.

A method of solid-phase enzyme-immunoassay (EIA) with horseradish-peroxidase-conjugated anti-mu-globulin was used to determine IgM antibodies to measles virus in human sera. Antigens prepared from measles-infected and noninfected Vero cells passively adsorbed to polystyrene cuvettes were both important for the tests, because sera from many patients convalescing from viral infections and sera from rheumatoid arthritis patients were able to bind to control antigen. Sera from measles patients, patients with other viral infections, rheumatoid arthritis (RA) patients, and from blood donors were tested in a dilution of 1:200. Almost all of the acute-phase measles sera (37/38) were positive. The first measles-IgM-negative specimen was found 9 weeks after the onset of rash. Seven percent (15/213) of patients with other viral infections gave positive results in these IgM tests. False-positive reactions were also found in 33 of 51 (65%) sera from RA patients. This nonspecific binding could be abolished by absorptions with latex-IgG particles. This treatment did not have any effect on specific IgM. The IgM-EIA test developed for measles virus antibodies, which requires only a single serum specimen, appears to be a useful diagnostic method for routine virus laboratories.