HSV Entry and Spread

This chapter deals with assays commonly used to follow herpes simplex virus type 1 (HSV-1) entry into and spread between cells in tissue culture These are complex processes, known to involve several of the 20 or more HSV-encoded membrane proteins (see refs. 1 and 2 for recent reviews). HSV entry is mediated by a number of proteins on the surface of the virus particle. Recognition of and binding to target cells are known to involve at least three glycoproteins-gB, gC, and gD. gC mediates the initial interaction with cells, recognizing heparan sulfate proteoglycans on the cell surface. gB also interacts with heparan sulfate proteoglycans, and can substitute for gC in gC negative viruses. This initial, heparin-sensitive attachment to cells is relatively weak, and is followed by a more stable attachment to cells, apparently mediated by gD. Following attachment, the virus particle fuses with the cell membrane to mediate entry. Fusion is known to require gB and gH/gL, and possibly also gD, but their precise functions are uncertain. The roles of other virus-encoded membrane proteins in entry are unclear, but it is possible that different proteins may be required for entry into different cell types.