Herpes Simplex Virus Glycoproteins H/L Bind to Cells Independently of αVβ3 Integrin and Inhibit Virus Entry, and Their Constitutive Expression Restricts Infection

Abstract

ABSTRACT Herpes simplex virus (HSV) fusion with cells requires the gD, gB, and gH/gL glycoprotein quartet. gD serves as a receptor binding glycoprotein. gB and gH/gL execute fusion in an as-yet-unclear manner. To better understand the role of gH/gL in HSV entry, we produced a soluble version of gH/gL carrying a One-STrEP tag (gH t.st /gL). Previous findings implicated integrins as possible ligands to gH/gL (C. Parry et al., J. Gen. Virol. 86:7-10, 2005). We report that (i) gH t.st /gL bound a number of cells in a dose-dependent manner at concentrations similar to those required for the binding of soluble gB or gD. (ii) gH t.st /gL inhibited HSV entry at the same concentrations required for binding. It also inhibited cell-cell fusion in transfected cells. (iii) The absence of β3 integrin did not prevent the binding of gH t.st /gL to CHO cells and infection inhibition. Conversely, integrin-negative K562 cells did not acquire the ability to bind gH t.st /gL when hyperexpressing αVβ3 integrin. (iv) Constitutive expression of wild-type gH/gL (wt-gH/gL) restricted infection in all of the cell lines tested, a behavior typical of glycoproteins which bind cellular receptors. The extent of restriction broadly paralleled the efficiency of gH/gL transfection. RGD motif mutant gH/gL could not be differentiated from wt-gH with respect to restriction of infection. Cumulatively, the present results provide several lines of evidence that HSV gH/gL interacts with a cell surface cognate protein(s), that this protein is not necessarily an αVβ3 integrin, and that this interaction is required for the process of virus entry/fusion.