OBSERVATIONS ON THE MODE OF RELEASE OF HERPES VIRUS FROM INFECTED HELA CELLS

Abstract

The development of a well adapted strain of herpes virus has been studied in HeLa cells using thin sectioning techniques for electron microscopy. Particular attention was directed to events in the cytoplasm and certain new features were observed. Profuse immature particles with a nucleoid and single limiting membrane were present in the nuclei of infected cells, often in crystalline array; morphologically indistinguishable immature particles were also found very frequently in the cytoplasm. Cells with such particles were intact and well preserved, and contained smooth vacuoles apparently derived from the Golgi component of the endoplasmic reticulum. The cytoplasmic particles escaped from the cells by bulging out as buds through the cell membrane or through that of the cytoplasmic vacuoles until they were attached only by a pedicle and then became free. During this process the particles were gradually enclosed by the membrane through which they passed and carried a coat of it with them as they matured. After permanganate fixation the triple-layered structure of the cell membrane and vacuolar membranes was evident and was identical with that of the outer coat of the mature virus. These findings are discussed both in relation to different types of virus structure and to function in the endoplasmic reticulum and cell membrane.Early morphological studies on herpes simplex infection using thin sectioning methods for electron microscopy (1-3) gave results which agreed on two important points. Firstly, the virus formed in the nucleus of infected cells, and appeared there as a particle having a single membrane around a dense nucleoid; and secondly, the mature extracellular virus was larger, and apparently possessed two membranes. However, the maturation process and mode of release of the agent remained obscure.The maturing particle was at first believed to acquire its second coat in the cytoplasm (1), but forms with this coat were subsequently observed within nuclei (2, 3), in groups close to the nuclear envelope, and surrounded by a membrane derived perhaps from the latter by invagination (3). More recently, elaborate infoldings and reduplications of the nuclear envelope have been found in infected cells (4, 5) and these are, at present, thought to provide a means for the virus to pass out of the intact nucleus (4), possibly by budding (5), and to be the source both of the second membrane of the agent and of the sacs known to surround it in the cytoplasm (4, 5).In the course of an investigation into the structure and composition of mature extracellular herpes virus (6), immature particles were frequently seen lying free in the cytoplasm of undamaged, morphologically intact, infected HeLa cells. This unusual finding did not seem to fit in with current views on the developmental cycle of the agent (4, 5) and it was therefore considered 589 on

The Pseudorabies Virus VP1/2 Tegument Protein Is Required for Intracellular Capsid Transport

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Glycoproteins Specified by Herpes Simplex Viruses

“…Alternatively, on the basis of electron microscopic studies with another herpesvirus, it has been proposed that egress is a process involving fusion of perinuclear virus with the outer lamella of the nuclear envelope and reenvelopment of the resulting cytoplasmic nucleocapsid at a cytoplasmic membrane (Stackpole, 1969). Electron micrographs have been presented as evidence that envelopment of HSV nucleocapsids can occur at cytoplasmic membranes (Epstein, 1962;Siminoff and Menefee, 1966).…”

Herpes Simplex Virus Type 2 Glycoprotein Biogenesis: Effect of Monensin on Glycoprotein Maturation, Intracellular Transport and Virus Infectivity

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