Comparison of murine and human nectin1 binding to herpes simplex virus glycoprotein D (gD) reveals a weak interaction of murine nectin1 to gD and a gD-dependent pathway of entry

The murine nectin1 alpha (mNectin1 alpha), a homolog of human nectin1 alpha (hNectin1 alpha, or PRR1, HveC), mediates the entry of herpes simplex viru s (HSV) into cells. Previously, we reported that the binding of hNectin1 to HSV glycoprotein D (gD) was readily detectable, whereas the binding of mNe ctin1 to go was not detectable, thus raising the question whether mNectin1 mediates a gD-dependent or a go-independent pathway of entry. Here we repor t comparative binding studies of murine- and human-nectin1 alpha to virions and to go. The assays consistently showed either a very weak binding or no detectable binding of murine nectin1 alpha to go. They included (i) bindin g of soluble mNectin1-Fc or hNectin1-Fc to virions and competition of the b inding by soluble gD(Delta 290-299t) and by monoclonal antibodies to SD; (i i) pull-down experiments of wt go from lysates of infected cells: and (iii) ELISA binding of soluble gD(Delta 290-299t) to cells expressing mNectin1 o r hNectin1. in contrast to the binding studies, the entry studies readily s howed that entry mediated by mNectin1 was dependent on go. Thus, a gDnull ( gD-/-) mutant virus was unable to enter mNectin1-expressing cells, and entr y of wild-type virus was inhibited by antibodies to go or soluble go at sim ilar concentrations. We infer that go represents a weak ligand in the inter action between mNectin1 and virions, whereas it represents a strong and the major ligand for hNectin1. Yet go is required in HSV-1 entry mediated by m Nectin1 alpha. We conclude that a high-affinity binding of the receptor to go is not a requirement in the go-dependent pathway of HSV entry to cells. (C) 2001 Academic Press.