Several human and animal alphaherpesviruses can enter cells via human herpesvirus entry mediator C (HveC), a receptor for viral glycoprotein D (gD). In previous studies with cells expressing unknown entry mediators, cellular expression of alphaherpesvirus gD was shown to inhibit entry of the homologous virus and sometimes also of heterologous alphaherpesviruses. To investigate the mechanism of gD-mediated interference and the basis for cross-interference among alphaherpesviruses, HveC was expressed in cells as the sole entry mediator, in the presence or absence of one of the gDs encoded by herpes simplex virus type 1, pseudorabies virus, or bovine herpesvirus type 1. Cells expressing HveC alone were highly susceptible to entry of all three viruses, whereas cells coexpressing HveC and any one of the gDs were at least partially resistant to infection by each virus. Coexpression of gD with HveC did not cause reduced levels of cell-surface HveC but the HveC had reduced ability to bind to exogenous gD. Coimmunoprecipitation experiments revealed that HveC was complexed with gD in lysates of cells expressing both. Thus, cellular expression of gD can interfere with alphaherpesvirus entry by blocking ligand-binding sites of the gD receptor(s) used for entry and cross-interference can occur because different forms of alphaherpesvirus gD can compete for shared entry receptors. (C) 2000 Academic Press.
Bibliographical noteFunding Information:
We thank B. Lum, J. Esko, K. Knight, T. Mettenleiter, L. Bello, R. Johnston, G. Cohen, R. Eisenberg, G. Keil, and V. Gerdts for reagents; C. Waltenbaugh, R. Caldwell, B. Fife, and W. Karpus for advice about experimental procedures; N. Susmarski and M. L. Parish for technical assistance. This work was supported by a grant from the National Institute of Allergy and Infectious Diseases (RO1 AI 36293). R. J. Ger-aghty was supported by National Research Service Award F32 AI09471.