Infection of endothelial cells with an endothelial cell-tropic clinical isolate of cytomegalovirus (CMV), C1FE, induced enhanced production of the neutrophil chemoattractant C-X-C chemokines interleukin-8 and GROalpha. Infected endothelial cell supernatants induced neutrophil chemotaxis in a transendothelial migration assay. Neutrophils acquired the CMV structural protein pp65 following either coculture with infected endothelial cells or transmigration through infected endothelium. The lack of CMV p72 expression in the neutrophils indicated that viral replication had not occurred in these cells. Of importance, neutrophils acquired infectious CMV during transmigration across infected endothelium and were subsequently able to transmit infectious virus to fibroblasts. Thus, CMV-infected endothelial cells can recruit neutrophils by the secretion of C-X-C chemokines and can transmit the virus to them by direct cell-to-cell contact and during neutrophil transendothelial migration, suggesting that the neutrophil-endothelial cell interaction plays an important role in virus dissemination in vivo.

Herpes simplex virus (HSV) infects dendritic cells (DC

Virus‐induced alterations in the cellular expression of chemokines may be important in directing the migration of specific leucocyte subsets to sites of infection, thereby playing a pivotal role in viral pathogenesis. We show here that cytomegalovirus (CMV) infection of human fibroblasts resulted in significantly increased expression of the C‐X‐C or α‐chemokine interleukin‐8 (IL‐8), at both the mRNA and protein levels. Increased IL‐8 production was seen following infection with the high passage laboratory CMV strains AD169, Towne, or Davis, as well as the low passage clinical CMV isolates Toledo or C1F. The increase in IL‐8 production had functional consequences, as demonstrated by the ability of supernatants from CMV‐infected fibroblasts to significantly enhance neutrophil transendothelial migration. The latter was independent of alterations in adhesion molecule expression on the endothelial cells, and was abrogated by neutralizing antibodies specific for IL‐8. Direct infection of endothelium with the endothelial cell‐tropic CMV strain C1FE, also resulted in enhanced neutrophil transendothelial migration. Neutrophils play an important role in the dissemination of CMV throughout the body, and thus CMV‐induced neutrophil recruitment would be expected to enhance CMV dissemination. Increased production of chemokines in response to CMV infection could also disrupt the fine balance between a beneficial and a destructive immune response, thereby potentially contributing to pathology.

The highly fibroblast-passaged AD169, Towne, and Davis strains of cytomegalovirus (CMV) were found to have a restricted capacity to infect endothelial cells in vitro. Although such replication could be increased by a combination of low speed centrifugation and sodium butyrate treatment, the extracellular virus produced was infectious for fibroblasts but not for endothelial cells. In contrast, the low passage Toledo strain, and a low passage fibroblast-grown clinical isolate of CMV, C1F, could be continually passaged in endothelial cells, giving the strains C1FE and Toledo.E. Whilst, using the conditions described above, initial infection of endothelial cells with AD169 or C1F resulted in similar titres of extracellular virus as assayed on fibroblasts, only the virus from the C1F strain was infectious for endothelial cells. Passage of C1F in fibroblasts decreased its ability to infect endothelial cells, whilst retaining equal ability to infect fibroblasts. Although endothelial-cell-passaged cell-free C1FE virus was endothelial cell-tropic, it was still much more infectious for fibroblasts than for endothelial cells. It is concluded that the C1F and Toledo strains, but not the AD169, Towne, or Davis strains, contained endothelial cell tropic variants, which could be lost on passage through fibroblasts, but retained on passage through endothelial cells. Furthermore, virus in an ex vivo source of CMV, a blood specimen, was found to be more tropic for fibroblasts than for endothelial cells, suggesting that in vivo CMV exists as quasi strains with different cell tropism, some of which might be lost in vitro by passage in an inappropriate cell type.

The expression of a trypsin-sensitive receptor for the Fc portion of IgG (Fc gammaR) was demonstrated by flow cytometry on the surface of human umbilical vein endothelial cells and fibroblasts infected with human cytomegalovirus (CMV). Double-labeling experiments showed strong expression of the CMV Fc gammaR in a perinuclear region of infected cells but not in bystander uninfected cells. The CMV Fc gammaR did not react with a panel of murine monoclonal antibodies directed against the known human IgG Fc receptors, Fc gammaRI, Fc gammaRII, and Fc gammaRIII. The cytoplasmic form but not the cell surface form of CMV Fc gammaR bound murine IgG3 moderately and murine IgG1 more weakly, while both forms bound rabbit IgG almost as strongly as human IgG. The function of CMV Fc gammaR is unclear, but it may allow CMV to evade host antibody responses. However, the binding of immune complexes to infected endothelium might also contribute to immunopathology.