Herpes simplex virus (HSV) and other alpha-herpesviruses possess the amazing innate ability to spread very rapidly from infected cells to neighboring cells, especially in biologically important epithelial and neuronal tissues. This process of cell-to-cell spread involves specialized virus machinery that: i) directs virus particles to junctions formed between cells and ii) allows the virus to cross cell junctions and enter neighboring cells. HSV glycoprotein gE/gl plays an important role in both these facets of virus cell-to-cell spread but, significantly, does not play a role in entry of extracellular virus particles at the apical surfaces of epithelial cells. As such gE/gl is an important molecular handle to study herpesvirus cell-to-cell spread. The cytoplasmic domain of gE/gl affects sorting of the glycoprotein to trans-Golgi network (TGN) of cells and plays an important role in virus envelopment into cytosolic membranes. The TGN is the major site of basolateral/apical sorting in polarized cells and gE/gl promotes sorting of nascent virions specifically to basolateral surfaces of cells and cell junctions. Moreover, we have two new pieces of evidence that the extracellular domain of gE/gl binds to components of cell junctions, cellular receptors, and that this promotes infection of adjacent cells. First, mutations in the extracellular domain of gE significantly diminish cell-to-cell spread. Second, expression of gE/gl in cells, in trans, interferes with cell-to cell spread. The ? aims of the research proposed here are to: i) better understand the intracellular traffic of gE/gl and how this determines sorting of nascent virions to cell junctions, ii) to characterize the contribution of gE/gl and other HSV glycoproteins in cytoplasmic envelopment of nucleocapsids, iii) to characterize the extracellular domains of gE/gl in mediating movement of viruses across cell junctions and into adjacent cells, and iv) to examine the effects of gE/gl mutations on HSV spread in the cornea. These studies will help elucidate this poorly understood process of herpesvirus cell-to-cell spread, and will also expand our knowledge of how a herpesvirus moves through mucosal epithelium and within the nervous system. ? ?
