A POPULATION SCREENING-TEST FOR ANTIBODY TO MEASLES-VIRUS

Abstract

In areas where sporadic cases of measles continue to occur in spite of vaccination programs, the availability of a simple screening test for determination of seropositivity to measles virus is desirable. A sensitive radioimmunoassay (RIA) screening test (ST) for the detection of IgG antibody to measles virus, based on a solid phase RIA, is described. The assays were performed on polyvinyl microtiter plates for which the RIAST requires only 5 .mu.l of serum/subject. Antigen consisted of a sonicated extract of measles virus-infected [African green monkey kidney] Vero cells. Rabbit anti-human IgG specific for the Fc-segment of human IgG, labeled with 125I, was used to detect human IgG bound to viral antigen. The basic RIA method was characterized by carrying out full titrations on the sera of 53 healthy adults, 10 children and 13 patients with measles-associated illness. These sera were also tested by the hemagglutination inhibition (HI) technique; most of the measles sera were also tested by complement fixation. RIAST results (expressed as binding ratios) obtained for 52 healthy adults are compared with their RIA serum titers. Of the 200 sera of patients of various ages tested by the RIAST, 63 borderline sera were also tested by HI. The RIAST which does not require serum treatment other than inactivation, proved to be more sensitive than HI as an indicator of seropositivity. Implications of the results and practical applications of the screening test are discussed.