GLYCOPROTEIN-D OF HERPES-SIMPLEX VIRUS (HSV) BINDS DIRECTLY TO HVEM, A MEMBER OF THE TUMOR-NECROSIS-FACTOR RECEPTOR SUPERFAMILY AND A MEDIATOR OF HSV ENTRY

Glycoprotein D (gD) is a structural component of the herpes simplex vi rus (HSV) envelope which is essential for virus entry into host cells. Chinese hamster ovary (CHO-K1) cells are one of the few cell types wh ich are nonpermissive for the entry of many HSV strains. However, when these cells are transformed with the gene for the herpesvirus entry m ediator (HVEM), the resulting cells, CHO-HVEM12, are permissive for ma ny HSV strains, such as HSV-1(KOS), By virtue of its four cysteine-ric h pseudorepeats, HVEM is a member of the tumor necrosis factor recepto r superfamily of proteins. Recombinant forms of gD and HVEM, gD-1(306t ) and HVEM(200t), respectively, were used to demonstrate a specific ph ysical interaction between these two proteins. This interaction was de pendent on native gD conformation but independent of its N-linked olig osaccharides, as expected from previous structure-function studies. Re combinant forms of gD derived from HSV-1(KOS)rid1 and HSV-1(ANG) did n ot bind to HVEM(200t), explaining the inability of these viruses to in fect CHO-HVEM12 cells. A variant gD protein, gD-1(Delta 290-299t), sho wed enhanced binding to HVEM(200t) relative to the binding of gD-1(306 t), Competition studies showed that gD-1(Delta 290-299t) and gD-1(306t ) bound to the same region of HVEM(200t), suggesting that the differen ces in binding to HVEM are due to differences in affinity. These diffe rences were also reflected in the ability of gD-1(Delta 290-299t) but not gD-1(306t) to block HSV type I infection of CHO-HVEM12 cells. By g el filtration chromatography, the complex between gD-1(Delta 290-299t) and HVEM(200t) had a molecular mass of 113 kDa and a molar ratio of 1 :2. We conclude that HVEM interacts directly with gD, suggesting that HVEM is a receptor for virion gD and that the interaction between thes e proteins is a step in HSV entry into HVEM-expressing cells.