INFLUENCE OF THE HOST-CELL ON THE ASSOCIATION OF ICP4 AND ICP0 WITH HERPES-SIMPLEX VIRUS TYPE-1

ICP4 and ICP0 are two immediate-early proteins of herpes simplex virus type 1 associated with the transcriptional activation of viral genes within infected cells. Previous studies in our laboratory have shown t hat approximately 100-200 molecules each of ICP4 and ICP0 are associat ed with the tegument region of virions purified from Vero and HEp-2 ce lls (F. Yao and R. J. Courtney, 1989, J. Virol. 63, 3338-3344 and 1999 , J. Virol. 66, 2709-2716). However, other studies have shown that ICP 4 molecules are primarily associated with non-capsid-containing light (L) particles obtained from BHK-21 cells and purified by 5-15% continu ous Ficoll gradients (J. McLauchlan and F. J. Rixon, 1992, J. Gen. Vir ol. 73, 269-276). To reconcile these findings with regard to the assoc iation of immediate-early protein with virions obtained from different cell lines, our studies have focused on determining if the host cell type influences the amounts of ICP4 and ICP0 associated with the capsi d-containing heavy (H) virus particles (purified virions) compared to the amounts associated with L particles. Virus particles were purified from three different cell lines, Vero, HEp-2, and BHK-21 cells. The H and L virus particles were resolved on 5-15% Ficoll gradients. The re sults presented indicate that although ICP4 and ICP0 are readily detec table in H particles obtained from Vero and HEp-2 cells, minimal amoun ts of ICP4 and ICP0 are associated with H particles obtained from BHK- 21 cells. The data suggest that the host cell may influence the relati ve amounts of ICP4 and ICP0 associated with the tegument region of vir us particles. Finally, physical particle counts of the H and L particl es also suggest that the host cell influences the relative number of L particles produced within the cell. (C) 1995 Academic Press, Inc.