Herpesvirus entry: An update

The entry of herpesviruses into cells depends upon interactions of several viral glycoproteins with multiple cell surface receptors. Also, each herpesvirus may have evolved multiple pathways for entry into different cell types, as is evident for HSV and EBV. The broad host range of HSV is consistent with its use of cell surface heparan sulfate as a binding receptor and both 3-O-sulfated heparan sulfate and multiple conserved and widely expressed proteins as entry receptors. The more limited host range of EBV (at least in the case of its B-cell target) is also consistent with its use of binding and entry receptors that are found together on very few cell types, chief of which are B cells. Much remains to be learned about the actual requirements for entry of these viruses into the target cell types that are critical for disease and about the mechanisms of virus-induced membrane fusion.