Direct enzyme immunoassay for detection of specific IgG antibody to rubella virus by use of labelled antigen.

A new solid phase enzyme immunoassay (EIA) for detection of rubella-specific immunoglobulin G (IgG) antibody was developed. The test uses polystyrene microtiter strips coated with rabbit anti-human IgG immunoglobulins as the solid phase and an enzyme-labelled semipurified rubella antigen as indicator. The direct EIA was compared with hemagglutination inhibition (HI), single radial hemolysis (SRH), radioimmunoassay (RIA) and time-resolved fluoroimmunoassay (TR-FIA) using 52 serum specimens from patients with remote rubella infection. The overall agreement of direct EIA with HI was 96.1%, with SRH and RIA 98.1% and with TR-FIA 100%. The linear regression coefficient varied from 0.77 to 0.91, the best being obtained with direct EIA and SRH. The direct EIA was also suitable for diagnosis of acute infections, as a significant increase in antibody levels was detected in all paired specimens tested from patients with acute rubella infection. The sensitivity and were comparable to those of the assays employed. An advantage of the present assay is that the same method and same labelled antigen can be used to test for different classes of antibody using simply a solid phase with capture antibodies of different chain specificity.