An ultrastructural investigation of cytomegalovirus replication in murine hepatocytes.

The morphological characteristics of murine cytomegalovirus replication in murine hepatocytes were investigated by electron microscopy and structural evidence of an unusual mode of virus maturation was detected. Nucleocapsids form in the nucleus; those with electron-dense cores bud into the perinuclear cisternae and acquire an outer envelope from the inner membrane of the nuclear envelope. Viral envelopes fuse with the outer membrane of the nuclear envelope releasing nucleocapsids in the paranuclear zone where they aggregate and form cytoplasmic inclusions. These inclusions are invariably surrounded by lamellae and vesicles of the Golgi complex into which nucleocapsids again bud. Virions, now covered with a new membrane envelope, are transported within secondary lysosomes and released by emiocytosis into the extracellular space.