Critical residues in the CC' ridge of the human nectin1 receptor V domain enable herpes simplex virus entry into the cell and act synergistically with the downstream region.

The site on nectin1 receptor required for herpes simplex virus (HSV) entry into the cell was previously mapped to the 64-94 region, encompassing the predicted CC'C" region of the immunoglobulin V domain. Within it lies a minimal HSV entry site (residues 77-94). Here we transferred the 65-76 region (C strand and CC' loop) and portions, or single amino acids, thereof to nectin2, a homolog nonfunctional for wt HSV-1 entry. Replacement of the seven- or of three-amino-acid-long stretches from nectin1 to nectin2 (amino acids 69-75, 69-71, or 72-75) transferred wt HSV-1 and BHV-1 entry activity and enhanced HSV-2, PrV, and HSV-HSV(U21) entry to levels observed with nectin1. Thus, the CC' ridge is sufficient to mediate wt HSV entry at a reduced level and responsible for the wide virus range of the receptor. Altogether the HSV entry site appears to be composed of contiguous synergistic regions, 64-76 and 77-94, each independently capable of mediating virus entry at reduced efficiency.