MUTATIONS IN THE CYTOPLASMIC TAIL OF HERPES-SIMPLEX VIRUS GLYCOPROTEIN-H SUPPRESS CELL-FUSION BY A SYNCYTIAL STRAIN

We have developed a complementation assay, using transiently transfect ed COS cells, to facilitate a molecular analysis of the herpes simplex virus type 1 glycoprotein gH. When infected by a gH-null syncytial vi rus, COS cells expressing,wild-type gH generate infectious progeny vir ions and form a syncytium with neighboring cells. By deletion and poin t mutagenesis, we have found particular residues in the gH cytoplasmic tail to be essential for generation of a syncytium but apparently dis pensable for production of infectious virions. This study emphasizes t he different requirements for cell-cell and cell-envelope fusion and d emonstrates that changes in the non-syn locus UL22-gH can reverse the syncytial phenotype.