HUMORAL IMMUNE-RESPONSE TO FUNCTIONAL REGIONS OF HUMAN CYTOMEGALOVIRUS GLYCOPROTEIN-B

Sera from patients with primary human cytomegalovirus (HCMV) infection s, both acute and convalescent phase, and from HCMV-seropositive healt hy subjects were analyzed to determine whether the sera would recogniz e antigenic domains on HCMV glycoprotein B (gB) that function in virio n infectivity and spread of virus from cell to cell. The intact gB mol ecule, amino-terminal derivatives of different lengths, and internal d eletion derivatives were expressed in eukaryotic cells and reacted by immunofluorescence with the sera. All convalescent-phase sera and most sera from healthy seropositive individuals reacted with full-length g B and with an amino-terminal derivative containing 687 amino acids (aa ), gB-(1-687); approximately half of the sera recognized an amino-term inal derivative of 447 aa, gB-(1-447), and one-third reacted with the shortest deletion derivative of 258 aa, gB-(1-258). Of the acute-phase sera, 77% recognized intact gB and gB-(1-687), 32% recognized gB-(1-4 47), and 14% recognized gB-(1-258). Deletion of aa 548 to 618 dramatic ally reduced the percentage of reactive sera, whereas deletion of aa 4 11 to 447 had a minor impact on reactivity of sera. To investigate the epitope specificity of human antibodies to gB, we carried out competi tion experiments between human sera with neutralizing activity and sel ected monoclonal antibodies (mAbs) to conformational epitopes on gB. W e found that antibodies in human sera preclude syncytium formation in UB15-11 glioblastoma cells constitutively expressing gB and compete wi th certain murine mAbs that block virus entry into cells and transmiss ion of infection from cell to cell. Our results show that HCMV-immune human sera contain antibodies to functional regions on gB, and the abu ndance of these antibodies in convalescent-phase sera suggests that th ey may play a central role in limiting dissemination of virus in the h ost. (C) 1997 Wiley-Liss, Inc.