THE ECTODOMAIN OF A NOVEL MEMBER OF THE IMMUNOGLOBULIN SUBFAMILY RELATED TO THE POLIOVIRUS RECEPTOR HAS THE ATTRIBUTES OF A BONA-FIDE RECEPTOR FOR HERPES-SIMPLEX VIRUS TYPE-1 AND TYPE-2 IN HUMAN-CELLS

We report on the functional cloning of a hitherto unknown member of th e immunoglobulin (Ig) superfamily selected for its ability to confer s usceptibility to herpes simplex virus (HSV) infection on a highly resi stant cell line (J1. 1-2 cells), derived by exposure of BHKtk- cells t o a recombinant HSV-1 expressing tumor necrosis factor alpha (TNF-alph a). The sequence of herpesvirus Ig-like receptor (HIgR) predicts a tra nsmembrane protein with an ectodomain consisting of three cysteine-bra cketed domains, one V-like and two C-like. HIgR shares its ectodomain with and appears to be an alternative splice variant of the previously described protein PRR-1 (poliovirus receptor-related protein). Both H IgR and PRR-1 conferred on J1.1-2 cells susceptibility to HSV-1, HSV-2 , and bovine herpesvirus 1. The viral ligand of HIgR and PRR-1 is glyc oprotein D, a constituent of the virion envelope long known to mediate viral entry into cells through interaction with cellular receptor mol ecules. Recently, PRR-1, renamed HveC (herpesvirus entry mediator C), and the related PRR-5 renamed HveB, were reported to mediate the entry of HSV-1, HSV-2, and bovine herpesvirus 1, and the homologous poliovi rus receptor was reported to mediate the entry of pseudorabies virus ( R. J. Geraghty, C. Krummenacher, G. H. Cohen, R. J. Eisenberg, and P. G. Spear, Science 280:1618-1620, 1998; M. S. Warner, R. J. Geraghty, W .M. Martinez, R. I. Montgomery, J. C. Whitbeck, R. Xu, R. J. Eisenberg , G. H. Cohen, and P. G. Spear, Virology 246:179-189, 1998). Here we f urther show that HIgR or PRR-1 proteins detected by using a monoclonal antibody to PRR-1 are widely distributed among human cell lines susce ptible to HSV infection and commonly used for HSV studies. The monoclo nal antibody neutralized virion infectivity in cells transfected with HIgR or PRR-1 cDNA, as well as in the human cell lines, indicating a d irect interaction of virions with the receptor molecule, and prelimina rily mapping this function to the ectodomain of HIgR and PRR-1. Northe rn blot analysis showed that HIgR or PRR-1 mRNAs were expressed in hum an tissues, with the highest expression being detected in nervous syst em samples. HIgR adds a novel member to the cluster of Ig superfamily members able to mediate the entry of alphaherpesviruses into cells. Th e wide distribution of HIgR or PRR-1 proteins among human cell lines s usceptible to HSV infection, coupled with the neutralizing activity of the antibody in the same cells, provides direct demonstration of the actual use of this cluster of molecules as HSV-1 and HSV-2 entry recep tors in human cell lines. The high level of expression in samples from nervous system makes the use of these proteins in human tissues very likely. This cluster of molecules may therefore be considered to const itute bona fide receptors for HSV-1 and HSV-2.