Use of chimeric nectin-1 (HveC)-related receptors to demonstrate that ability to bind alphaherpesvirus gD is not necessarily sufficient for viral entry

Human nectin-1 (HveC, Prr1), a member of the immunoglobulin superfamily and a receptor for the entry of herpes simplex viruses 1 and 2 (HSV-1, HSV-2), pseudorabies virus (PRV), and bovine herpesvirus 1 (BHV-1), binds to viral go. For HSV-1, HSV-2, and PRV, the go-binding region of nectin-1 has been localized to the N-terminal V-like domain. To determine whether the two C-l ike domains of nectin-1 influenced go binding and entry activity, genes enc oding chimeric proteins were constructed. Portions of nectin-1 were replace d with homologous regions from nectin-2 (HveB, Prr2), a related protein wit h ability to mediate the entry of PRV, HSV-2, and Rid mutants of HSV-1, but not HSV-1 or BHV-1. Also, one or more domains of nectin-1 were fused to th e two membrane-proximal Ig domains of CD4, a protein with no herpesvirus en try or go-binding activity. The chimeric proteins were expressed in Chinese hamster ovary cells, which normally lack alphaherpesvirus entry receptors, and detected on the cell surface by one or more anti-nectin-1 monoclonal a ntibodies. One chimeric protein (nectin-1 amino acids 1-124 fused to CD4) f ailed to bind to soluble forms of HSV-1, HSV-2, PRV, and BHV-1 go and, as e xpected, also failed to mediate entry of the viruses from which these gDs w ere derived. The other chimeric receptors bound all forms of go. Some media ted the entry of all the viruses tested but others mediated entry of some b ut not all the viruses. We conclude that binding of go to the nectin-1 V do main is not sufficient for entry activity, that there are structural requir ements for entry activity independent of go binding, and that these require ments are different for the several alphaherpesviruses that can use nectin- 1 as a receptor. (C) 2001 Academic Press.