Efficient Human Cytomegalovirus Replication Research Articles

Inhibition of cyclooxygenase 2 blocks human cytomegalovirus replication.

Cyclooxygenase 2 (COX-2) mRNA, protein, and activity are transiently induced after infection of human fibroblasts with human cytomegalovirus. Prostaglandin E(2), the product of COX-2 activity, is transiently increased by a factor of >50 in cultures of virus-infected fibroblasts. Both specific (BMS-279652, 279654, and 279655) and nonspecific (indomethacin) COX-2 inhibitors can abrogate the virus-mediated induction of prostaglandin E(2) accumulation. Levels of COX-2 inhibitors that completely block the induction of COX-2 activity, but do not compromise cell viability, reduce the yield of human cytomegalovirus in human fibroblasts by a factor of >100. Importantly, the yield of infectious virus can be substantially restored by the addition of prostaglandin E(2) together with the inhibitory drug. This finding argues that elevated levels of prostaglandin E(2) are required for efficient replication of human cytomegalovirus in fibroblasts. COX-2 inhibitors block the accumulation of immediate-early 2 mRNA and protein, but have little effect on the levels of immediate-early 1 mRNA and protein. Viral DNA replication and the accumulation of some, but not all, early and late mRNAs are substantially blocked by COX-2 inhibitors. Elevated levels of prostaglandin E(2) apparently facilitate the production of immediate-early 2 protein. The failure to produce normal levels of this critical viral regulatory protein in the presence of COX-2 inhibitors might block normal progression beyond the immediate-early phase of human cytomegalovirus infection.

Receptor-Initiated Activation of Cells and Their Oncogenes by Herpes-Family Viruses

The interaction of human cytomegalovirus (HCMV) with the cell membrane has been shown to initiate a cascade of physiologic and biochemical responses that result in the transcriptional activation of specific cellular proto-oncogenes. The cell-activation responses initiated by the virus membrane interaction appear to be important for efficient HCMV replication, as pharmacologic inhibition of cell activation responses significantly reduces the expression of immediate early viral genes and the production of infectious progeny virus. Cellular receptor proteins for other viruses have been shown to be molecules with physiologic activities. Binding of virus to these receptors may trigger the cell to initiate changes that are important for efficient viral replication. These viruses may also trigger inappropriate physiologic responses in the absence of viral replication, thereby causing more covert manifestations of viral pathology.

Human cytomegalovirus productively infects primary differentiated macrophages.

Monocytes are one of the predominant cell types in the peripheral blood that are infected by human cytomegalovirus (HCMV). Although virus can be detected in these cells in vivo, HCMV replication in cultured monocytes has been unsuccessful. In this study, we demonstrate efficient HCMV replication in cultured monocytes. HCMV permissiveness in these cells was dependent on nonadherent cell-induced stimulation of the monocyte, with subsequent morphological differentiation into macrophages. Approximately 40% of the cells infected by virus were detected by immunofluorescent staining with both immediate-early and late antibodies. In addition, viral plaque assays demonstrated significant productive infection of macrophages. These observations are consistent with the suggestion that the monocyte/macrophage serves as a source of viral amplification and dissemination.

Cytomegalovirus replicates efficiently in human kidney mesangial cells.

Human cytomegalovirus (HCMV) is a major renal pathogen in congenitally infected infants and renal allograft recipients. We postulated that a specific renal cell type was involved in HCMV infection and reactivation. Human fetal kidney cortex cell cultures were assayed for their ability to support HCMV infection. Infectious center assays indicated that the low level of viral replication observed by virus yield assay occurred from a fraction of the cells in the mixed cultures. Virus-specific immunofluorescence and in situ hybridization documented the presence of HCMV-specific protein and nucleic acid, respectively, in a morphologically distinct cell type. These cells were purified, were identified as kidney mesangial cells, and were observed to support efficient HCMV replication. Our research identifies mesangial cells as a renal cell type that supports HCMV replication and provides evidence to implicate these cells in the pathogenesis of HCMV-induced renal disease.