THE EFFECT OF HERPES-SIMPLEX VIRUS TYPE-1 L-PARTICLES ON VIRUS ENTRY,REPLICATION, AND THE INFECTIVITY OF NAKED HERPESVIRUS DNA

Herpes simplex virus type 1(HSV-1) L-particles are known to be compose d mainly of envelope and tegument proteins, to lack the nucleocapsid, and to be noninfectious. Thus L-particles represent interesting vaccin e candidates. L-particles at >1000/cell interfered with HSV-1 virion a dsorption and penetration. While L-particles did not affect HSV-1 grow th kinetics in resting or nonresting BHK cultures infected with purifi ed virions, treatment with L-particles before, or after, transfection with HSV-1 DNA resulted in a progressive increase in plaque numbers (f ive- to sixfold at 1000 L-particles/cell). Transfection assays using H SV-1 ts mutant DNA (ts1201) revealed that enhancement was due to induc tion of otherwise nonreplicating genomes. The enhancement obtained wit h L-particles produced by WT HSV-1 or by mutants that are either delet ed, or defective, in certain gene products was compared. Most importan t were the Vmw110 (ICPO) and Vmw65 (alpha-TIF) proteins, but VP11/12, VP13/14, and vhs also have a role. The L-particle-associated Vmw175 (I CP 4) protein did not appear be involved. The effect of homologous and heterologous combinations of pseudorabies virus, equineherpesvirus-1, and HSV-1 DNA's and L-particles was investigated in transfection assa ys. The L-particles of each virus, to varying extent, enhanced the pla quing efficiency of their own DNA but were also effective in heterolog ous combinations. (C) 1997 Academic Press.