Human cytomegalovirus (HCMV) infection of endothelial cells resulted in increased adhesion of the cells to peripheral blood leukocytes. It was demonstrated by flow cytometry that increased adhesiveness parallels the increased expression of cell surface adhesion molecules (ELAM-1, ICAM-1, VCAM-1). The increased adhesion of PMN and T-lymphocytes was due to upregulation in the expression of ELAM-1 and ICAM-1. The upregulation of VCAM-1 resulted in the increased adhesiveness of monocytes and T-lymphocytes to HCMV-infected HUVEC. The increased adhesiveness to leukocytes was caused by HCMV replication since endothelial cells exposed to HCMV-free supernatants and UV-inactivated HCMV did not show any increase in adhesiveness to any of the leukocytes tested.

Human cytomegalovirus (HCMV) is a source of major complications in immunosuppressed individuals, and endothelial involvement in HCMV infection is well documented. Traditionally laboratory strains of HCMV have been used in experimental investigations in vitro; however the continuous propagation of these strains in fibroblasts have attenuated the virus making it unsuitable for infecting other cell systems such as endothelial cells. In this study a recent clinical isolate of HCMV was propagated through several passages in endothelial cells and was used to investigate the effect of HCMV infection of human umbilical vein endothelial cells (HUVEC) on IL-1 production and cell proliferation. Infection of HUVEC with the clinical isolate of HCMV (at multiplicity of infection 5:1) suppressed the production of IL-1 alpha (82%) and IL-1 beta (99%) at 5 h post infection; the levels returned to that of the control within 24h post infection. Ultraviolet inactivated (but not heat killed) virus produced similar suppression confirming that a thermolabile viral structural protein or intact virion were responsible for this suppression. Infection of HUVEC with the clinical isolate increased the number of these cells and the rate of their proliferation. An increase of infected HUVEC number under quiescent growth conditions continued as the infection progressed (6-10 days post infection), exhibiting, at 3 days post infection, 5 times the number of uninfected HUVEC (control) which did not tolerate the quiescent culture conditions for more than 4 days. Live virus is responsible for this increase because UV-inactivated virus did not maintain the proliferation of HUVEC. These studies suggest that while infection of HUVEC with a recent clinical isolate of HCMV suppressed the production of IL-1 at early hours after infection, it increased the proliferation of these cells at later stages of infection.

Human cytomegalovirus infection of human umbilical vein endothelial cells reduces the ability of these cells to bind to fibronectin, collagen type IV and laminin. This suppression requires active virus, since UV-inactivated virus did not alter the binding ability of these cells to adhere to fibronectin, collagen type IV, and laminin. In an attempt to elucidate the molecular mechanism of this altered interaction, the surface expression of alpha 5 beta 1, alpha 2 beta 1, alpha 3 beta 1, and alpha 6 beta 1 integrins on cytomegalovirus-infected endothelial cells was examined using attachment inhibition assay and flow cytometric analysis. The results presented here show that infection with human cytomegalovirus selectively alters the expression of integrin on human endothelial cells, with the ability to induce downregulation of alpha 5 beta 1 and alpha 2 beta 1 (p = 0.001) and p = 0.03, respectively), while significantly upregulating alpha 6 beta 1 (p = 0.03), and marginally upregulating alpha 3 beta 1 (p = 0.05).

The effect of human cytomegalovirus (CMV) infection on lipopolysaccharide (LPS)-stimulated and unstimulated monocytes from seronegative donors was studied by using the laboratory-adapted strain AD169 and a recent clinical isolate. LPS-stimulated and unstimulated monocytes infected with the isolate showed expression of immediate-early CMV antigens and were significantly more suppressive for lymphocyte proliferation than were strain AD169-infected monocytes, which rarely expressed detectable viral protein. Human CMV infection of LPS-stimulated and unstimulated monocytes resulted in abrogation of interleukin-1 activity, with the effect being marked in LPS-stimulated monocytes infected with the clinical isolate of CMV. Addition of interleukin-1 to infected, stimulated monocytes completely restored lymphoproliferative responses to phytohemagglutinin, whereas addition of this leukokine to infected, unstimulated cells could not restore this response.

The effect of mycoplasma-free human cytomegalovirus (HCMV) on the production and biologic activity of interleukin-1 (IL-1) from peripheral blood monocytes was examined. The use of biologic thymocyte assays revealed a time-dependent decrease in the IL-1 activity of both HCMV-challenged and control monocytes after initiation of culture. A decrease in the amount of IL-1 beta secreted as measured by ELISA was also detected. The amount of IL-1 beta secreted by HCMV-challenged cells was always greater than that produced by control cultures at similar times. Despite containing higher levels of IL-1 beta, supernatants from challenged cells were markedly less effective in supporting thymocyte proliferation. It is proposed that this is due to the concomitant production of an inhibitor of IL-1 activity from HCMV-challenged monocyte cultures.