The glycoprotein B gene and its syn3 locus of herpes simplex virus type 1 are involved in the synthesis of virus-associated growth factor (HSGF-1).

A putative growth factor (HSGF-1) associated with herpes simplex virus type 1 (HSV-1), which is similar to PRGF associated with pseudorabies virus, and/or HSGF-2 associated with HSV-2, was described. Experiments with four syncytial (syn) and four nonsyncytial (syn+) HSV-1 strains showed that the ability of this virus to produce HSGF-1 in infected cells is associated with the syn+ phenotype. Double infection of cells with syn+ and syn strain resulted either in enhancement or complete inhibition of HSGF-1 production, depending on the chosen pair of syn+ and syn strains. The studies with the recombinants between the syn+ strain KOS and syn strain ANGpath in the gene for glycoprotein B (gB) and syn3 locus revealed that the gB gene and its syn3 locus play a role in the HSGF-1 synthesis.