Ultrastructural localization of glycoproteins in rabbit fibroblasts altered by Herpes simplex virus type 1 infection

The periodic acid-thiocarbohydrazide (SO2)--OsO4 method was used to examine the distribution of glycoproteins in rabbit fibroblast cells infected with Herpes simplex virus type 1. In non-infected cells, a low level of staining was seen over the plasma membrane and the membranes of the Golgi apparatus. At 17 hr post-infection, the intensity of reaction was increased to include not only a relatively heavy staining of the plasma membrane, including the numerous microvilli characteristic of infected cells, and of the newly proliferated Golgi membranes, but also the envelopes of intracytoplasmic and extracellular virions. A very faint but only occasional staining also was associated with the virus-induced reduplications of the inner nuclear membrane and the envelopes of associated enveloping nucleocapsids. We suggest that such differences in the intensity of staining may be related either to the amount of glycoproteins or to the sequential maturation of the viral glycoproteins. We also observed that the structurally modified portions of the Golgi membranes at the position where intracytoplasmic naked nucleocapsids bud into the Golgi cisternae usually exhibit a more intense reaction for glycoproteins than do the adjacent portions of the Golgi membranes. This supports the evidence for an envelopment of nucleocapsids in the cytoplasm, but it does not indicate whether this event obligatorily follows or only occasionally takes the place of the envelopment of nucleocapsids at the inner nuclear membrane. In either event, the envelopes of all mature virions exhibit a prominent reaction to glycoproteins.