CONCERNING EGRESS OF HERPES SIMPLEX VIRUS FROMINFECTED CELLS - ELECTRON AND LIGHT MICROSCOPE OBSERVATIONS

Electron microscopic studies of the cytoplasm of HEp-2 cells productively infected with herpes simplex virus revealed a network of branched tubules 65 nm in diameter. The membranes limiting the tubules were continuous at one end with the outer lamellae of the nuclear membrane and at the other end with the cytoplasmic membrane. At 8 hours after infection enveloped nucleocapsids appeared at the junction of the tubules with the nucleus; tubules were filled with enveloped nucleocapsids 16 hours after infection. Branched fibrils were seen in infected cells with phase optics; they stained with conjugated human convalescent antibody in immunofluorescence tests. The ducts as seen by the electron microscope and fibrils as seen by light microscopy were absent from uninfected cells and from DK cells abortively infected with the same virus. Cross sections of the tubules appear as vacuoles; the finding of vacuoles" containing virus led in the past to the erroneous conclusion that they serve to transport enveloped virus to the extracellular fluid by "reverse phagocytosis." It is suggested that the tubules function as a third compartment of the cell to (1) prevent the uncoating of the virus in the cytoplasm and (2) furnish a pathway for egress from the site of envelopment to the extracellular fluid. © 1969."