Studies on the Morphogenesis of Murine Cytomegalovirus

Abstract

Two modes of assembly of murine cytomegalovirus (MCMV) were observed in cultured mouse embryo fïbroblasts, generating two morphologically different types of viral particles: monocapsid virions and multicapsid virions. The assembly of nucleocapsids appeared to be the same for both types of morphogenesis. Three successive stages of intranuclear capsid formation could be distinguished: capsids with electron-lucent cores, coreless capsids, and capsids with dense cores. Some of the capsids were enveloped at the inner nuclear membrane to form monocapsid virions, which were first detectable in the perinuclear cisterna. Other capsids left the nucleus via nuclear pores and usually entered cytoplasmic capsid aggregates that received an envelope by budding into extended cytoplasmic vacuoles, thereby forming multicapsid virions. Since the formation of multicapsid virions is not restricted to cell culture conditions and also occurs in vivo in immunosuppressed mice, multicapsid virions may play a role in the pathogenesis of cytomegalovirus infection.

Replication of a herpes-like virus in larvae of the flat oyster Tiostrea chilensis at ambient temperatures

“…In turn, LCC appeared to develop into empty capsids. This interpretation is supported by the observations of Weiland et al (1986) that electron-lucent capsids in murine cytomegalovirus (CMV) infection develop to empty (1967( ), 4Jacob (1968, 'Nii et al (1968), 'Stackpole & Mizell (1968), 'Schwartz & Roizman (1969a), astackpole (1969, 'Cook & Stevens (1970) (1997), "This study. "resent in Crassostrea virginica (Farley et al 1972) capsids.…”

Site-restricted persistent cytomegalovirus infection after selective long-term depletion of CD4+ T lymphocytes.

“…In this cell type, MCMV replicates with a morphogenesis distinct from that seen for other cell types (6,9,29,30), and it can be speculated that viral antigen processing and presentation may thus also differ.…”

“…It was known before that in immunocompetent mice MCMV replicates without tissue damage in glandular epithelial cells of salivary gland tissue (29), whereas in -y-irradiated, immunodepleted mice, infection ofconnective tissue fibroblasts was also observed (F. Weiland, unpublished observations) . As it has been described for embryo fibroblasts in vitro (30) and for interstitial lung fibroblasts (6), as well as for adrenal cortical parenchymal cells (9) in vivo, the morphogenesis of MCMV in salivary gland fibroblasts is characterized by the formation ofmulticapsid virions . During persistent infection in CD4 subset-deficient mice, infected fibroblasts and tissue lesions were not observed.…”

Late phase inhibition of murine cytomegalovirus replication by synergistic action of interferon-gamma and tumour necrosis factor

“…Therefore, MCMV morphogenesis was analysed by electron microscopy 24 and 48 h after infection. In the absence of cytokine treatment nucleocapsids, predominantly those with an electron-lucent core, arise in the nuclei of MCMV-infected cells together with morphological changes in nuclear structures (Weiland et al, 1986) (Fig. 5a and c).…”

“…Remarkably, the latter form predominates in cytokine-treated cells. The enzymatic degradation of the inner shell of the capsid probably represents a step prior to the take-up of the electrondense core material (Weiland et al, 1986). If this order of events is correct, the function responsible for this inner shell degradation might represent a target for the cytokine effect, and this results in the accumulation of these otherwise transient forms.…”