No abstract

Seventy-seven clones of hybridomas selected for reactivity by immunofluorescence with human cytomegalovirus (CMV)-infected cells were produced by fusing mouse myeloma cells with the spleen cells of mice immunized with CMV strain AD169. The clones were classified into seven groups on the basis of the electrophoretic properties of the polypeptides immune precipitated from extracts of CMV-infected cells. Studies on the three groups of monoclonal antibodies directed against CMV surface membrane antigens showed the following. Clones in each group were differentiated by immunoglobulin subclass, neutralizing activity, and reactivity with the antigenic domains of proteins exposed on the surface membranes of intact CMV-infected cells. Monoclonal antibodies in each group precipitated one slowly migrating protein and multiple faster migrating forms which shared antigenic determinants. The first group of monoclonal antibodies precipitated four glycosylated polypeptides with apparent molecular weights of 130,000, 110,000, 100,000, and 60,000. Monoclonal antibody CH51 of this group neutralized infectious virus but failed to react with antigenic domains on the surfaces of infected cells. The second group of monoclonal antibodies precipitated four polypeptides with apparent molecular weights of approximately 66,000, 55,000, 50,000, and 46,000. Monoclonal antibodies CH65 and CH134 in this group had neutralizing activity and reacted with antigenic domains of proteins exposed on the surface of CMV-infected cells. The third group of monoclonal antibodies precipitated four polypeptides with apparent molecular weights of 49,000, 48,000, 34,000, and 25,000. Serological analysis of 15 naturally occurring CMV strains with a panel of monoclonal antibodies to surface membrane proteins showed that the antigenic determinants reactive with the antibodies tested were conserved in all of the strains. Monoclonal antibodies to surface membrane proteins on CMV-infected cells may prove to be valuable reagents for identification of virus isolates.

There was 100% agreement between enzyme immunoassay (EIA) (Abbott Laboratories), Western blot, and indirect immunofluorescence (IF) when these three methods were used to measure antibody to the acquired immune deficiency syndrome (AIDS) virus in sera from 142 high-risk individuals, indicating that IF was a sensitive alternative method for detecting antibody to this agent. Thirty-two (64%) of 50 EIA-positive plasma specimens from a blood bank and 6 (21%) of 28 EIA-positive sera from alternative testing sites were negative by IF. In addition, two EIA-negative sera from the latter group were positive by IF. Western blotting agreed with IF on those 40 specimens which gave discrepant results by EIA and IF. The IF method was determined to be equal to Western blotting in sensitivity and specificity for detection of AIDS antibody, and it was found to be useful for confirming positive EIA results, especially in specimens from individuals in low-risk groups.

Serodiagnosis of cytomegalovirus (CMV) infection by complement fixation tests depends on showing a fourfold rise in antibody titer from acuteto convalescent-phase sera. Freeze-thaw and glycine-extracted, infected cell culture antigens used for these tests give markedly different titers in reactions with the same sera. In this study, we characterized the CMV-infected cell polypeptides contained in freeze-thaw and glycine-extracted antigens and identified the proteins precipitated by 23 pairs of human acute and convalescent sera. Our results were as follows. First, freeze-thaw and glycine-extracted antigens prepared from infected cells radiolabeled with [35S]methionine and subjected to electrophoresis in sodium dodecyl sulfate-polyacrylamide gels yielded similar patterns, and the bulk of the label was contained in late structural proteins and glycoproteins. Glycine-extracted preparations contained a greater proportion of soluble 66,000and 50,000-molecular-weight proteins than did freeze-thaw antigens. Second, convalescent sera precipitated proteins migrating with apparent molecular weights of 150,and 25,000. Of these the 130,000-, 110,000-, 96,000-, 66,000-, 50,000-, and 25,000-molecular-weight proteins comigrated with glucosamine-labeled polypeptides. Both immunoglobulin G and M antibodies in human sera precipitated these proteins from CMV-infected cell preparations. Implications of the results for serodiagnosis of CMV infections are discussed.