Bovine herpesvirus 1 requires glycoprotein H for infectivity and direct spreading and glycoproteins gH(W450) and gB for glycoprotein D-independent cell-to-cell spread

By analogy with glycoprotein H (gH) of herpes simplex virus type 1 (HSV-1) and pseudorabies virus (PRV), gH may also be essential for penetration and cell-to-cell spread of bovine herpesvirus 1 (BHV-1). This was verified with a gH-negative BHV-1 mutant (gH(-)BHV-1), which replicated normally on gH-e xpressing cells but was unable to form plaques and infectious progeny on no n-complementing cells. The block in entry could be overcome by polyethylene glycol-induced membrane fusion, demonstrating that gH is not essential for egress. Propagation of gH(-)BHV-1 on cell lines expressing wild-type gH or gH(W450), which complements the function of BHV-1 go for cell-to-cell spre ad, indicated that gH(W450) is more efficient than wild-type gH in mediatin g direct spread of BHV-1. This was supported by the plaque sizes induced by rescued gH-BHV-1 that expressed wild-type gH and gH(W450). infection of ce ll lines expressing gH of BHV-1, HSV-1 and PRV with gH(-) BHV-1, HSV-1 and PRV mutants demonstrated that heterologous gH molecules could not complemen t gH function in penetration or cell-to-cell spread.