Characterization of human cytomegalovirus glycoprotein induced fusion

Human cytomegalovirus (CMV) dissemination is dependent on the functions of structural glycoproteins at multiple stages of the viral lifecycle. These proteins mediate the initial attachment and fusion events that occur between the viral envelope and the host cell plasma membrane, as well as virion-independent cell-cell spread of the infection. This dissertation focuses on identification and characterization of the glycoproteins required to mediate membrane fusion. CMV encodes a tripartite complex consisting of glycoprotein H (gH), gL, and gO that is thought to be important for membrane fusion. Previous investigations have not shown that coexpression of the genes encoding gH, gL, and gO was sufficient to reconstitute this complex in the absence of other viral protein synthesis. As such, Chapter 2 focuses on gH/gL/gO complex formation and reconstitution of this complex in two mammalian cell culture systems. The complexity of the CMV envelope has hindered efforts to conclusively identify the minimum number of viral proteins required for virus entry. In addition, very few reagents existed to fully characterize the functions of these proteins in the absence of other viral proteins. Accordingly, Chapter 3 describes the development of several new reagents and assays to characterize the functions of CMV glycoproteins. During the course of this study, the proteins required to mediate cell-cell fusion of several herpesviruses have been identified. The emerging paradigm evokes a multi-component fusion machine consisting of multiple viral and cellular factors. Chapter 4 describes the identification and characterization of a fusogenic glycoprotein complex of CMV, the gH/gL heterodimer. The information presented herein suggests that all herpesviruses employ a conserved mechanism revolving around the functions of gH/gL to induce membrane fusion.