Identification of shared antigenic determinants of different polypeptides from Davis and Towne cytomegalovirus strains with monoclonal antibodies

Six colonies producing antibodies were obtained by fusing mouse myeloma SP2-O cells with spleen cells from mice immunized with cytomegalovirus Davis strain. Among 88 surviving clones, 29 produced antibodies detectable by immunofluorescence on infected MRC5 cells and 2 others produced neutralizing antibodies against a homologous virus. Supernatants from these 31 positive clones and 4 others which were negative in immunofluorescence or neutralization were tested for their capacity to bind polypeptides from labelled Davis-infected cell extracts. Only 8 were found to be positive: five clones (A8, E3, F2, F8 and F20) precipitated 76 K, 60 K and 54 K bands; three others (A4, B9 and C24) precipitated 76 K and 54 K only. Surprisingly, these 8 monoclonal antibodies recognized a unique polypeptide 67 K of Towne-infected MRC5 cells. No correlation was found between (1) the pattern of fluorescence on MRC5 cells infected with Davis strain, (2) the neutralizing activity, and (3) the polypeptides recognized by the monoclonal antibodies.