Ultrastructural Development of Guinea Pig Cytomegalovirus in Cultured Guinea Pig Embryo Cells

Abstract

SUMMARYThe ultrastructural development of guinea pig cytomegalovirus (GPCMV) in guinea pig embryo cells was studied using electron microscopy. Tubular structures were found in nuclei of virus infected cells, followed by the appearance of intranuclear inclusions containing virus nucleocapsids. While some nucleocapsids were enveloped at the inner nuclear membrane, others were released into the cytoplasm where they were associated with, or within, dense matrix which was subsequently enveloped by cytoplasmic membranes to form enveloped dense virions. Dense bodies without virus capsids were formed in the cytoplasm and enveloped in a similar manner. An involvement of the nuclear pores in the release of unenveloped virus capsids from the nucleus to the cytoplasm was postulated. Evidence that the enveloped dense virions and dense bodies shared common envelope antigen(s) was obtained by immunoelectron microscopy. The similarities and differences in the ultrastructuraI development of GPCMV and other cytomegaloviruses are discussed.

Ultrastructural Localization of Cytomegalovirus DNA Synthesis in Infected Guinea-pig Cells

“…The tubular structures stained with uranyl acetate could not be destained by EDTA treatment while all DNA-containing structures were destained by EDTA (C. K. Y. Fong, unpublished data). Furthermore, this finding is in agreement with the previously published report that the synthesis of the tubular structures was not inhibited by the presence of a DNA inhibitor (Fong et al, 1979); it appears that the tubular structures are probably protein in nature.…”

“…The time sequence of GPCMV replication in relationship to virus morphogenesis in cultured GPE cells was reported previously (Fong et al, 1979). The correlation between the development of morphological structures present in virus-induced inclusions with virus DNA * Nearly confluent monolayer GPE cells were infected with GPCMV at 5 TCIDs0/cell.…”

“…followed by dehydration in graded ethanol and embedding in Epon as described previously (Fong et al, 1979). The procedures for autoradiography used in this study were partially modified from the procedures described by Kopriwa (1973) and Granboulan (1967).…”

“…The inclusion body consists of virus nucleocapsids, proteinaceous tubular structures, amorphous matrices with moderate electron density, and occasionally, electron-dense fibrils (Middelkamp et al, 1967;Fong et al, 1979). The chemical nature of the amorphous matrices and fibrils has not been identified.…”

On the Intracellular Transport and the Nuclear Association of Human Cytomegalovirus Structural Proteins

“…Like other herpesviruses, HCMV replicates its DNA and forms its capsid within the nucleus of the host cell, and becomes enveloped in the process of budding (Kanich & Craighead, 1972;Fong et al, 1979). In contrast to herpes simplex virus (HSV), HCMV is less cytocidal and has a much longer growth cycle (Smith & De Harven, 1973).…”