Ultrastructural studies of the envelopment and release of guinea pig herpes-like virus in cultured cells

The process of envelopment and release of guinea pig herpes-like virus was examined in both infected guinea pig kidney and thymus tissue culture cells by electron microscopy. The majority of the nucleocapsids were enveloped by budding into nuclear vacuoles; some were enveloped by budding from the inner nuclear membrane. Budding into cytoplasmic vacuoles was also seen. Many enveloped virus particles inside the nuclear vacuoles were pear shaped with a tail-like structure. Approximately 23% of pear-shaped virus particles were seen in the infected thymus fibroblastic cells, but only 6% were found in the infected epithelial cells. The envelopes of all nuclear enveloped virus particles appeared as smooth membranes, while the majority of particles exhibiting fuzzy and thick dense envelopes were seen in the cytoplasm or extracellular space. The average diameter of the cytoplasmic or extracellular enveloped virus particles was approximately 167 nm, and the average diameter of the nuclear enveloped virus particles was about 146 nm.Data also showed that mature nuclear virus particles were first released into perinuclear cisterna and then traveled through cytoplasmic channels to the extracellular space.