Glycoprotein gIII deletion mutants of pseudorabies virus are impaired in virus entry

gIII is one of the major structural glycoproteins of pseudorabies virus (PrV). Though nonessential for replication in cell culture, it plays a prominent role in virus adsorption and virus release from infected cells. In this study the effect of inactivation of gIII on virus uptake into cells was investigated using isogenic PrV glycoprotein mutants. Kinetic analyses demonstrated that deletion of the gIII gene severely impaired entry of PrV into cells, whereas inactivation of the genes coding for nonessential glycoproteins gI, gp63, or gX had no influence on the rate of virus penetration. Loss of gIII is therefore associated with a reduced rate of virus penetration indicating a gIII-independent way of virus entry which is significantly slower than the gIII-dependent penetration process.