Production and characterization of monoclonal antibodies specific for a glycosylated polypeptide of human cytomegalovirus

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Abstract
Nine hybrid cell lines producing antibodies specific for cytomegalovirus (CMV) antigen were obtained after fusion of P3/X63-Ag8 myeloma cells with spleen cells from BALB/c mice immunized with CMV complement-fixing antigen. By the immunoblot technique, five of nine antibodies (4D11, 7B4, 7D2, 8E3, and 8E10) were identified as being reactive to a CMV glycosylated polypeptide with molecular weight of 66,000 (GP66). Four other antibodies (1B8, 8E9, 4D2, and 7E2) appeared to be reactive with CMV antigen(s) only if the antigen was not denatured by sodium dodecyl sulfate. These remain unassigned until further studies are done. With the enzyme-linked immunosorbent assay (ELISA), competitive bindings were performed with a constant amount of horseradish peroxidase-conjugated antibody and various concentrations of unconjugated homologous and heterologous antibodies on CMV antigen-coated ELISA wells, and the antigenic determinant specific for each antibody was determined. The nine antibodies could be classified into six different groups, each group reacting with a different epitope or a different region with two or more antigenic determinants which are so close to each other that they cause binding inhibition. They are groups A (4D11), B (7B4, 8E10), C (7D2), D (4D2, 7E2, 8E9), E (8E3), and F (1B8). The extent of competition among antibodies within each group was the same. By using the two antibodies that reacted with different epitopes on GP66, a double-antibody sandwich ELISA method was developed. The method was sensitive enough to detect as little as 50% of the antigen present in one infected cell or 0.000245 U of CMV complement-fixing antigen per test well. Other strains of CMV (David, Kerr, Espilat, C-87, and five clinical isolates) gave positive results, whereas herpes simplex virus types 1 and 2, varicella-zoster virus and Epstein-Barr virus nuclear antigen preparations did not. By the indirect immunofluorescence assay, antibodies 4D11 and 8E3 were able to detect GP66 in the nucleus of CMV-infected F-5000 human embryonic fibroblasts as early as 2 h postinfection and were superior in this respect to the remaining seven antibodies tested. By the double-antibody sandwich ELISA, the presence of GP66 in CMV-infected cells was detected as early as 2 h postinfection.