Detection of measles IgM antibodies by enzyme-linked immunosorbent assay (ELISA)

Comparison of the MEASLESTAT M test kit with the sucrose density gradient centrifugation-hemagglutination inhibition method for detection of measles virus-specific immunoglobulin M

A new commercial kit, MEASLESTAT M (Whittaker Bioproducts, Inc.), was compared with the sucrose density gradient centrifugation-hemagglutination inhibition method for the detection of measles virus-specific immunoglobulin M. Overall agreement between the two procedures was 97.1% for 104 single and paired serum samples tested. The sensitivity and specificity of MEASLESTAT M were 98.4 and 95.2%, respectively.

Specific immunoglobulin M enzyme-linked immunosorbent assay for confirming the diagnosis of measles

An enzyme-linked immunosorbent assay (ELISA) was evaluated for the detection of measles virus-specific immunoglobulin M (IgM) (MIgM). The ELISA was standardized by deriving a seronegative range of values from sera which should not contain MIgM (24 cord sera, 59 sera from immune health care workers, and 47 sera from infants before the administration of measles vaccine). These values were separable from those obtained from individuals convalescing from measles. Twenty sera containing rheumatoid factor were MIgM seronegative. Of 30 acute-phase sera from suspected measles cases, 26 contained MIgM; those that were seronegative were obtained on day 0, 0, 2, or 9. All 25 convalescent-phase samples contained MIgM. Of the 25 paired samples, 22 were IgG positive at the first sampling; 3 of the 22 did not show a rise in IgG titer. The MIgM ELISA can be used for confirming suspected measles cases, often requiring only a single serum specimen.

Assay of measles virus IgM and IgG class antibodies by use of peroxidase-labelled viral antigens

Purified measles virions, nucleocapsid protein and crude lysate of measles infected cells were labelled with horseradish peroxidase, and used for the detection of IgM and IgG antibodies to measles virus by direct enzyme immunoassay. The assays consisted of three layers: anti-human IgM or IgG immunoglobulins on solid-phase, test serum specimen and enzyme labelled viral antigen. For the expression of the results, a standard curve was included in each test and the O.D. values were changed to arbitrary antibody units. Specificity and sensitivity of the assays were compared with indirect EIAs. The specificity studies included a collection of serum specimens containing either rheumatoid factor, antinuclear antibodies or IgM antibody specific for other viruses. The assays proved both reliable and simple to perform and sensitivity was slightly higher than that for indirect EIAs. However, specificity was dependent on the purity of the viral antigens. When crude infected cell lysate antigen was used, some nonspecific results were obtained, particularly with serum specimens containing antinuclear antibodies. When virion or nucleocapsid protein were used, no nonspecific reactions were obtained.

Comparison of nonspecific reactivity in indirect and reverse immunoassays for measles and mumps immunoglobulin M antibodies

Serum specimens collected from patients convalescing from acute measles or mumps infections, other viral infections, or rheumatoid arthritis and from blood donors were tested in indirect and reverse assays for measles and mumps immunoglobulin M (IgM) antibodies. All the samples from patients convalescing from acute mumps and measles infections gave positive IgM results in both tests. However, 6% of sera from patients recovering from other viral infections, 68.4% of sera from patients with rheumatoid arthritis, and 5.6% of sera from normal blood donors gave false-positive results by the indirect measles IgM enzyme immunoassay (EIA). By the indirect mumps IgM EIA, 9% of sera from other viral infections, 70.1% of sera from patients with rheumatoid arthritis, and 5.6% of sera from normal blood donors gave false-positive reactions. The reverse test system for measles IgM gave false-positive results in 1.5% of sera from the group with other viral infections, and the reverse mumps EIA gave false-positive results in 0.9% of the patients. Other sera groups did not react in either measles or mumps reverse IgM assays. The results indicated that although nonspecific reactions are frequent in indirect IgM tests for viral antibodies, such reactions are rarely encountered when reverse IgM EIA tests are employed.

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.