Replication of human cytomegalovirus in endothelial cells

Relationship of human cytomegalovirus-infected endothelial cells and circulating leukocytes in the pathogenesis of disseminated human cytomegalovirus infection: A narrative review

Among the leucocyte subpopulations circulating in peripheral blood of immune-compromised patients with disseminated Human cytomegalovirus (HCMV) infection, polymorphonuclear leuckocytes (PMNL) and M/M may carry infectious virus. While only in PMNL early HCMV replicative events do occur, monocytes are susceptible to complete virus replication when they enter human organs, where as macrophages become a site of active complete virus replication. In vivo leucocytes and endothelial cells interact continuously, as suggested by several in vitro experimental findings showing the bidirectional HCMV transmission from leucocytes to and from endothelial cells with the critical aid of adhesion molecules. Recently, the neutralising antibody response in sera from subjects with primary HCMV infection was reported to be much higher and earlier than in human embryonic lung fibroblasts (HELF) cells when measured in endothelial cells and epithelial cells, where virus entry is mediated mostly by the pentamer complex gH/gL/pUL128/pUL130/pUL131, whereas it was much lower and delayed when determined in HELF, where virus entry is mediated mostly by the trimer complex gH/gL/gO. Thus, these results suggested that products of UL128L were the molecules primary responsible for the differential neutralising antibody response. This conclusion was confirmed by a series of polyclonal and monoclonal antibodies directed to the components of pUL128L. Very recently, based on two sets of experiments including inhibition and immunoblotting assays, the pentamer complex/trimer complex ratio has been finally identified as the main factor of the neutralising antibody response. This ratio may change with the virus suspension producer and target cell system as well as number of cell culture passages.

Subviral Dense Bodies of Human Cytomegalovirus Induce an Antiviral Type I Interferon Response

(1) Background: Cells infected with the human cytomegalovirus (HCMV) produce subviral particles, termed dense bodies (DBs), both in-vitro and in-vivo. They are released from cells, comparable to infectious virions, and are enclosed by a membrane that resembles the viral envelope and mediates the entry into cells. To date, little is known about how the DB uptake influences the gene expression in target cells. The purpose of this study was to investigate the impact of DBs on cells, in the absence of a viral infection. (2) Methods: Mass spectrometry, immunoblot analyses, siRNA knockdown, and a CRISPR-CAS9 knockout, were used to investigate the changes in cellular gene expression following a DB exposure; (3) Results: A number of interferon-regulated genes (IRGs) were upregulated after the fibroblasts and endothelial cells were exposed to DBs. This upregulation was dependent on the DB entry and mediated by the type I interferon signaling through the JAK-STAT pathway. The induction of IRGs was mediated by the sensing of the DB-introduced DNA by the pattern recognition receptor cGAS. (4) Conclusions: The induction of a strong type I IFN response by DBs is a unique feature of the HCMV infection. The release of DBs may serve as a danger signal and concomitantly contribute to the induction of a strong, antiviral immune response.

Cytomegalovirus infection is associated with an increase in aortic stiffness in older men which may be mediated in part by CD4 memory T-cells

Human Cytomegalovirus (CMV) infection is associated with atherosclerosis, higher cardiovascular disease (CVD) risk, and an increase in memory T-cells (T_mem). T-cells have also been implicated in CVD, independently of CMV infection. To better understand the CMV-associated CVD risk, we examined the association between CMV (IgG) serostatus and central aortic (carotid-to-femoral) pulse wave velocity (cfPWV), an early, independent predictor of CVD. We also investigated if such an association might be reflected by the distribution of T_mem and/or other T-cell subsets.

Methods: Healthy older volunteers (60-93 years) underwent routine clinical and laboratory evaluation, including assessment of cfPWV in eligible participants. Flow-cytometry was used to assess proportions of memory T-cells, CD28^null T-cells, and CMV-specific T-cells. The following associations were examined; CMV serostatus/cfPWV, CMV serostatus/proportion of T_mem, proportion of T_mem/cfPWV, CD28^null T-cells/cfPWV, and CMV-specific T-cells/cfPWV. Linear regression models were used to adjust for age, sex, socioeconomic status, smoking, waist-to-hip ratio, cholesterol, and blood pressure as required.

Results: Statistically significant positive associations were found (P-values for the fully adjusted models are given); CMV serostatus/cfPWV in men (P ≤ 0.01) but not in women, CMV serostatus/proportions of CD4 T_mem in men (P ≤ 0.05) but not in women; proportions of CD4 T_mem/cfPWV among CMV seropositive (CMV+) people (P ≤ 0.05) but not CMV seronegative (CMV-) people.

Conclusion: CMV infection increases the CVD risk of older men by increasing cfPWV. This may be mediated in part by increased proportions of CD4 T_mem, higher numbers of which are found in CMV+ older people and more so among men than women. Given the high prevalence of CMV worldwide, our findings point to a significant global health issue. Novel strategies to mitigate the increased CVD risk associated with CMV may be required.

Expansions of Cytotoxic CD4+CD28- T Cells Drive Excess Cardiovascular Mortality in Rheumatoid Arthritis and Other Chronic Inflammatory Conditions and Are Triggered by CMV Infection

A large proportion of cardiovascular (CV) pathology results from immune-mediated damage, including systemic inflammation and cellular proliferation, which cause a narrowing of the blood vessels. Expansions of cytotoxic CD4⁺ T cells characterized by loss of CD28 (“CD4⁺CD28⁻ T cells” or “CD4⁺CD28^null cells”) are closely associated with cardiovascular disease (CVD), in particular coronary artery damage. Direct involvement of these cells in damaging the vasculature has been demonstrated repeatedly. Moreover, CD4⁺CD28⁻ T cells are significantly increased in rheumatoid arthritis (RA) and other autoimmune conditions. It is striking that expansions of this subset beyond 1–2% occur exclusively in CMV-infected people. CMV infection itself is known to increase the severity of autoimmune diseases, in particular RA and has also been linked to increased vascular pathology. A review of the recent literature on immunological changes in CVD, RA, and CMV infection provides strong evidence that expansions of cytotoxic CD4⁺CD28⁻ T cells in RA and other chronic inflammatory conditions are limited to CMV-infected patients and driven by CMV infection. They are likely to be responsible for the excess CV mortality observed in these situations. The CD4⁺CD28⁻ phenotype convincingly links CMV infection to CV mortality based on a direct cellular-pathological mechanism rather than epidemiological association.

Cytomegalovirus-induced immunopathology and its clinical consequences

Human cytomegalovirus (CMV) is a ubiquitous DNA virus that causes severe disease in patients with immature or impaired immune systems. During active infection, CMV modulates host immunity, and CMV-infected patients often develop signs of immune dysfunction, such as immunosuppression and autoimmune phenomena. Furthermore, active viral infection has been observed in several autoimmune diseases, and case reports have linked primary CMV infection and the onset of autoimmune disorders. In addition, CMV infection promotes allograft rejection and graft-versus-host disease in solid organ and bone marrow transplant recipients, respectively, further implicating CMV in the genesis and maintenance of immunopathological phenomena. The mechanisms by which CMV could induce inhibition of host defense, inflammation, and autoimmunity are discussed, as is the treatment of virus-induced immunopathology with antivirals.

Cytomegalo virus as a possible risk factor for neonatal gastrointestinal surgical conditions

The present work aims to evaluate the possible causal relationship between CMV infection and gastrointestinal surgical conditions in the neonates. 33 neonate operated on because of gastrointestinal surgical conditions in Assiut University Children Hospital. Detection of CMV IgG and IgM from both mother and newborn was done. Surgical specimen was taken for pathologic examination. Positive serological tests (CMV IgM) were found only in four neonates (3 males and one female). Maternal CMV IgM were positive only in two cases. All surgical specimens showed characteristic CMV nuclear inclusion bodies.

Human cytomegalovirus tropism for endothelial/epithelial cells: scientific background and clinical implications

Human cytomegalovirus (HCMV) has been routinely isolated from and propagated in vitro in human embryonic lung fibroblast (HELF) cell cultures, while in vivo it is known to infect predominantly endothelial and epithelial cells. In recent years, genetic determinants of the HCMV tropism for endothelial/epithelial cells were identified in the UL131A/UL130/UL128 locus of HCMV genome of wild-type strains. UL131A-UL128 gene products form a complex with glycoprotein H (gH) and L (gL) resulting in a gH/gL/UL131A-UL128 complex that is required for HCMV entry into endothelial/epithelial cells. In contrast, virus entry into fibroblasts has its genetic determinants in the complex gH/gL/gO (or gH/gL). During primary HCMV infection, the neutralising antibody response measured in endothelial cells (EC) is potent, occurs very early and is directed mostly against combinations of two or three gene products of the UL131A-128 locus. On the contrary, neutralising antibodies measured in fibroblasts appear late, are relatively weak in potency and are directed against gH and gB. The T-cell immune response to UL131A-UL128 gene products remains to be investigated. Recently, a role has been proposed for neutralising antibody in conferring prevention/protection against HCMV infection/disease in pregnant women with primary HCMV infection. However, the level of cooperation between humoral immunity and the well-established T-cell protection remains to be defined.

Review Article: Anemia post—lung transplantation: mechanisms and approach to diagnosis

Anemia is a common complication in post-lung transplant recipients. Although its mechanism is often multifactorial, clinicians should investigate an eventual underlying explanation to provide the best care. Among the reasons for anemia in lung transplant recipients, blood loss should be thought within the first few days after surgery. Later on, immune-mediated mechanisms, microangiopathic hemolytic anemia and reduction in red blood cell production mediated by viruses, drugs and infiltrative disorders prevail. This article reviews the mechanisms of anemia in post—lung transplant patients and provides an algorithm towards its approach.

Cytomegalovirus-infected human endothelial cells can stimulate allogeneic CD4+ memory T cells by releasing antigenic exosomes

Human CMV infection is controlled by T cell-mediated immunity and in immunosuppressed transplant patients it is associated with acute allograft rejection as well as chronic allograft vasculopathy. CMV infects endothelial cells (EC) and it is thought that CMV-specific host immune responses to infected allograft EC contribute to rejection. In vitro, CD4(+) T cells from CMV-positive donors (but not CMV-negative donors) are readily activated by CMV-infected allogeneic EC, although it is unclear how allogeneic CMV-infected EC activate self-class II MHC-restricted memory CD4(+) T cells. In this study, we confirm that purified CD4(+) T cells from CMV(+) donors are activated by allogeneic CMV-infected EC, but find that the response is dependent upon copurified APC expressing class II MHC that are autologous to the T cells. The transfer of CMV Ags from infected EC to APC can be mediated by EC-derived exosome-like particles. These results provide a mechanism by which CMV can exacerbate allograft rejection and suggest a novel function of EC-derived exosomes that could contribute in a more general manner to immune surveillance.

Cytomegalovirus cell tropism

The human cytomegalovirus (HCMV) can infect a remarkably broad cell range within its host, including parenchymal cells and connective tissue cells of virtually any organ and various hematopoietic cell types. Epithelial cells, endothelial cells, fibroblasts and smooth muscle cells are the predominant targets for virus replication. The pathogenesis of acute HCMV infections is greatly influenced by this broad target cell range. Infection of epithelial cells presumably contributes to inter-host transmission. Infection of endothelial cells and hematopoietic cells facilitates systemic spread within the host. Infection of ubiquitous cell types such as fibroblasts and smooth muscle cells provides the platform for efficient proliferation of the virus. The tropism for endothelial cells, macrophages and dendritic cells varies greatly among different HCMV strains, mostly dependent on alterations within the UL128-131 gene locus. In line with the classification of the respective proteins as structural components of the viral envelope, interstrain differences concerning the infectivity in endothelial cells and macrophages are regulated on the level of viral entry.

Human cytomegalovirus virion protein complex required for epithelial and endothelial cell tropism

Human cytomegalovirus replicates in many different cell types, including epithelial cells, endothelial cells, and fibroblasts. However, laboratory strains of the virus, many of which were developed as attenuated vaccine candidates by serial passage in fibroblasts, have lost the ability to infect epithelial and endothelial cells. Their growth is restricted primarily to fibroblasts, due to mutations in the UL131-UL128 locus. We now demonstrate that two products of this locus, pUL130 and pUL128, form a complex with gH and gL, but not gO. The AD169 laboratory strain, which lacks a functional UL131 protein, produces virions containing only the gH-gL-gO complex. An epithelial and endothelial cell tropic AD169 variant in which the UL131 ORF has been repaired, termed BADrUL131, produces virions that carry both gH-gL-gO and gH-gL-pUL128-pUL130 complexes. Antibodies against pUL130 and pUL128 block infection of epithelial and endothelial cells by BADrUL131 and the fusion-inducing factor X clinical human cytomegalovirus isolate but do not affect the efficiency with which fibroblasts are infected.

Human cytomegalovirus UL131 open reading frame is required for epithelial cell tropism

Epithelial cells are one of the prominent cell types infected by human cytomegalovirus (HCMV) within its host. However, many cultured epithelial cells, such as ARPE-19 retinal pigmented epithelial cells, are poorly infected by laboratory-adapted strains in cell culture, and little is known about the viral factors that determine HCMV epithelial cell tropism. In this report, we demonstrate that the UL131 open reading frame (ORF), and likely the entire UL131-128 locus, is required for efficient infection of epithelial cells. Repair of the mutated UL131 gene in the AD169 laboratory strain of HCMV restored its ability to infect both epithelial and endothelial cells while compromising its ability to replicate in fibroblasts. ARPE-19 epithelial cells support replication of the repaired AD169 virus as well as clinical isolates of HCMV. Productive infection of cultured epithelial cells, endothelial cells, and fibroblasts with the repaired AD169 virus leads to extensive membrane fusion and syncytium formation, suggesting that the virus may spread through cell-cell fusion.

The mechanisms by which infectious agents may contribute to atherosclerosis and its clinical manifestations

Three infectious agents have recently gained considerable interest as potential pathogens in atherosclerosis and in its clinical manifestations: herpes simplex virus, cytomegalovirus, and Chlamydia pneumoniae. Chronic and often asymptomatic infections with these agents occur widely in the general population. These pathogens may affect atherosclerosis either directly or indirectly. Direct effects on vascular wall cells might include cell lysis, transformation, lipid accumulation, proinflammatory changes, and augmentation of procoagulant activity. Indirect systemic effects may involve induction of acute-phase proteins, establishment of a prothrombotic state, hemodynamic stress caused by tachycardia, increased cardiac output, or a regional inflammatory activation in response to systemic endotoxemia and cytokinemia. The effects of microbial infection, usually in combination with other risk factors (for example, smoking, hyperlipidemia, family history), might promote atherogenesis and eventually trigger acute coronary events.

Cytomegalovirus ischemic colitis: a near-fatal presentation of HIV infection

Cytomegalovirus infection occurs in immunocompromised patients. We present a 45-year-old male with no prior medical history who presented to the hospital with weight loss and non-bloody diarrhea. During hospitalization, he developed severe hematochezia and hypotension. Colonoscopy revealed dusky, friable mucosa. The patient arrested and was resuscitated. Specimen from emergent colectomy showed ischemic changes secondary to cytomegalovirus infection of endothelium and small-vessel thrombosis. An HIV test was subsequently positive with CD4 count of 2 per microliter. The patient was treated with antiretroviral therapy and ganciclovir. He survived postoperative infections and was eventually discharged. In summary, this case of near-fatal cytomegalovirus colitis represents an unusual presentation of undiagnosed HIV infection. Cytomegalovirus infection should be included in the differential diagnosis of immunocompromised patients with gastrointestinal symptoms. Hematochezia may be from intestinal ulceration or severe ischemic damage. Antiretroviral therapy and ganciclovir or foscarnet should be initiated promptly. Surgery is indicated in life-threatening hemorrhage or obvious bowel necrosis.

Thrombotic microangiopathy and cytomegalovirus in liver transplant recipients: a case-based review

BACKGROUND

Thrombotic microangiopathy (TMA) is a rare but potentially lethal complication encountered in solid organ and bone marrow transplant recipients, requiring rapid recognition, diagnosis, and initiation of therapy. Several potential causes have been identified in this setting, including viral infections and medications.

METHODS

We report a case of TMA in a liver transplant recipient with active cytomegalovirus (CMV) gastritis. A 41-year-old female presented 3 months after liver transplantation with a 5-week history of nausea, vomiting, anorexia, and diarrhea. CMV serology was donor seropositive and recipient seronegative (D+/R-). The immunosuppressive regimen consisted of tacrolimus, mycophenolate mofetil, and prednisone. Evaluation revealed CMV viremia with a high viral load and intravenous ganciclovir was started. A decline in hemoglobin and platelets with an increase in lactate dehydrogenase (LDH) warranted hematologic evaluation, which revealed findings consistent with microangiopathic hemolytic anemia. Ganciclovir and tacrolimus were discontinued. Intravenous immunoglobulin was administered and daily plasmapheresis was initiated. As the patient's blood counts and LDH started to improve, ganciclovir was cautiously reinstituted. The patient's gastrointestinal symptoms gradually resolved and her blood counts continued to improve with prolonged plasmapheresis (a total of 23 plasmapheresis sessions). Tacrolimus and possibly CMV infection were suspected to be the cause for her TMA, and cyclosporine was substituted.

CONCLUSIONS

TMA is an important entity in the differential diagnosis of acute hemolytic anemia in liver transplant recipients. Many cases seem to be medication-induced. However, in treatment-resistant or relapsing cases, a possibility of concomitant CMV infection should be considered.

Proteolytic processing of human cytomegalovirus glycoprotein B is dispensable for viral growth in culture

Glycoprotein B (gB) of human cytomegalovirus (HCMV), which is considered essential for the viral life cycle, is proteolytically processed during maturation. Since gB homologues of several other herpesviruses remain uncleaved, the relevance of this property of HCMV gB for viral infectivity is unclear. Here we report on the construction of a viral mutant in which the recognition site of gB for the cellular endoprotease furin was destroyed. Because mutagenesis of essential proteins may result in a lethal phenotype, a replication-deficient HCMV gB-null genome encoding enhanced green fluorescent protein was constructed, and complementation by mutant gBs was initially evaluated in transient-cotransfection assays. Cotransfection of plasmids expressing authentic gB or gB with a mutated cleavage site (gB-DeltaFur) led to the formation of green fluorescent miniplaques which were considered to result from one cycle of phenotypic complementation of the gB-null genome. To verify these results, two recombinant HCMV genomes were constructed: HCMV-BAC-DeltaMhdI, with a deletion of hydrophobic domain 1 of gB that appeared to be essential for viral growth in the cotransfection experiments, and HCMV-BACDeltaFur, in which the gB cleavage site was mutated by amino acid substitution. Consistent with the results of the cotransfection assays, only the DeltaFur mutant replicated in human fibroblasts, showing growth kinetics comparable to that of wild-type virus. gB in mutant-infected cells was uncleaved, whereas glycosylation and transport to the cell surface were not impaired. Extracellular mutant virus contained exclusively uncleaved gB, indicating that proteolytic processing of gB is dispensable for viral replication in cell culture.

Thrombosis associated with cytomegalovirus infection in patients with ANCA-positive vasculitis

Three cases of venous thrombosis with pulmonary embolism in two patients associated with underlying antineutrophil cytoplasmic autoantibody (ANCA)-positive vasculitis and reactivated cytomegalovirus (CMV) infection are described. In vitro studies previously have shown that infection of endothelium with CMV increases the release of procoagulant factors and stimulates the expression of adhesion molecules. Because the endothelial cell plays a pivotal role in maintaining the equilibrium between procoagulant and anticoagulant states, injury by ANCA-positive vasculitis and additional infection with CMV may ignite a local thrombosis easily. Although venous thrombosis is uncommon in CMV infection (eg, in the immunosuppressed state after organ transplantation), the combination of vasculitis and reactivated CMV infection may have contributed to injury of the vessel wall with subsequent development of thrombosis. A better awareness of this association could improve morbidity and may lead to prevention of potentially life-threatening pulmonary embolism. Patients with ANCA-positive vasculitis and CMV infection may profit from prophylactic anticoagulant therapy with heparin or low-molecular-weight heparin.

Replication of wild-type and mutant human cytomegalovirus in life-extended human diploid fibroblasts

A cDNA encoding the catalytic subunit of human telomerase was used to generate life-extended derivatives of primary human diploid fibroblasts. The life-extended cells supported efficient human cytomegalovirus (HCMV) replication. A subclone of the life-extended cells was generated containing the HCMV UL82 gene and used to isolate and propagate a virus that exhibited a profound growth defect after infection at a low input multiplicity.

An association between cytomegalovirus infection and chronic rejection after liver transplantation

BACKGROUND

Previous studies suggest a link between cytomegalovirus (CMV) infection and chronic rejection. Since these studies, more sophisticated diagnostic methods with high sensitivity and specificity for CMV have been developed and effective therapy/prophylaxis for CMV is now available. We sought CMV prospectively by polymerase chain reaction of serum and urine and by conventional methods in a group of 33 patients undergoing 57 transplants during 1993 or 1994, selected from a larger series. There were 13 grafts lost to chronic rejection. The remaining 44 grafts that did not develop chronic rejection served as controls and comprised 15 successful primary grafts, 15 second transplants, 8 third transplants, and 6 primary grafts that were lost for reasons other than chronic rejection.

RESULTS

The combination donor CMV antibody negative with recipient antibody positive and the duration of CMV infection >30 days were associated with an increased relative risk of chronic rejection. In contrast, the presence of CMV infection alone, symptomatic CMV infection, the detection of CMV by PCR of serum or urine, and the peak/cumulative viral load were not predictive. CMV infection occurred earlier in those undergoing a second transplant for chronic rejection than for those undergoing a second transplant for other reasons. In addition, a human leukocyte antigen B mismatch was associated with prolonged CMV infection.

CONCLUSION

These data are consistent with the hypothesis that prolonged subclinical cytomegalovirus infection is associated with an increased risk of chronic rejection.

Coronary artery disease after heart transplantation and its relation to cytomegalovirus

The most common cause of death and retransplantation after heart transplantation is a rapidly progressive, obliterative vascular disease involving the coronary arteries, termed cardiac allograft vasculopathy (CAV). Most believe that this is a form of chronic rejection. Several clinical series have suggested an association between cytomegalovirus and CAV. Rat cytomegalovirus enhances the development of CAV in rat heterotopic heart or aortic transplantation models. The mechanism(s) by which cytomegalovirus might have an impact on the severity of chronic rejection include the augmentation of vascular growth factors, the alteration in the alloimmune response directly or the alteration of cytokines and cell adhesion molecules, enhancing cellular and humoral interactions. We previously reported that the infection of smooth muscle cells by cytomegalovirus resulted in the alteration of major histocompatibility complex class I molecules on the smooth muscle cell surface. In a subsequent report we demonstrated that a sublethal inoculum of cytomegalovirus produced no cytopathology in smooth muscle cells yet had the same viral burden as fibroblasts, which demonstrated cytopathology. The identical effects on major histocompatibility complex class I were observed in smooth muscle cells, and cytokine gene transcription was altered, favoring a proinflammatory milieu. These and most in vitro studies are carried out with the use of traditional laboratory strains of cytomegalovirus. We have subsequently demonstrated major genotypic differences between laboratory and clinical strains of cytomegalovirus that are associated in differences in biological activity in vitro. These include differences in tropism for vascular cells, differences in cell surface antigen expression, and differences in mesenchymal growth factor gene expression. All of these may have important implications with regard to associating cytomegalovirus with CAV.

Vasculitis-induced membranous fat necrosis

Membranous fat necrosis (MFN) a distinct degenerative process of adipose tissue, is characterised by the presence of membranocystic lesions (MCLs) superimposed on a background of typical traumatic-type fat necrosis. MCLs are cysts, of varying size and shape, that are lined by an eosinophilic, crenulated membrane, having the staining properties of ceroid. Although MFN has been documented in varying systemic adipose tissue sites and in tumours, the pathogenesis of this pathological curiosity is unknown. To date, an ischemic basis for MFN has been the most proximate, and atherosclerosis and venous insufficiency, due to large and medium vessel disease, have been the most popular underlying clinical disorders. Although systemic vasculitis has been quoted as the underlying ischemic disorder in some patients, vasculitis has not been commented on nor demonstrated in tissue sections in association with MFN. In,reporting vasculitis-induced MFN, we document the occurrence of MFN in association with uncommon causes of vasculitis, namely: 1) Granulomatous vasculitis in a post-herpetic zosteriform scar; 2) Cytomegalovirus-induced vasculitis in the clinical setting of systemic lupus erythematosus; and 3) Lymphocytic vasculitis in a tetanus toxoid immunization site reaction.

Two clinical isolates and the Toledo strain of cytomegalovirus contain endothelial cell tropic variants that are not present in the AD169, Towne, or Davis strains

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.

Nuclear import as a barrier to infection of human umbilical vein endothelial cells by human cytomegalovirus strain AD169

Human embryonal fibroblasts (HEF) are fully permissive for infection by human cytomegalovirus (HCMV) strain AD169, whereas human umbilical vein endothelial cells (HUVEC) seem to form an almost complete barrier to infection with this virus. To investigate this difference in permissiveness, HCMV infection of both cell types was studied using in situ hybridisation (ISH) as well as immunocytochemistry to detect viral DNA and viral proteins. At 2 h post-infection (p.i.), viral DNA was detected dispersed throughout the cytoplasm in both HEF and HUVEC, indicating that HCMV enters all cells of both cell types. At 4 h p.i., the viral DNA was found in the nucleus in HEF, and at the same time expression of immediate early (IE) antigen was found. In contrast, in HUVEC the expression of the IE proteins occurred in a limited number of cells at 8 h p.i., while in most HUVEC an accumulation of viral DNA around the nuclei was observed at this time point. In HUVEC, the nuclear localisation of viral DNA was detected 16 h p.i. in a minority of cells, indicating that transport of HCMV DNA into the nucleus is considerably slower in HUVEC than in HEF. Furthermore, the number of HUVEC containing HCMV DNA decreased about six-fold between 8 and 48 h p.i., indicating that HCMV DNA is either transported into the nucleus or eliminated. Apparently, the lower permissiveness of HUVEC for the HCMV strain AD169 relative to HEF is due to inefficient transport of HCMV DNA into the nuclei of infected HUVEC.

Cytolytic activity against allogeneic human endothelia: resistance of cytomegalovirus-infected cells and virally activated lysis of uninfected cells

BACKGROUND

Cytomegalovirus (CMV) has been implicated as an exacerbating agent in the development of transplant vascular sclerosis; however, specific etiologic mechanisms remain unresolved. Based upon our previous observations that CMV-infected endothelial cells (ECs) stimulate proliferation and cytokine production by allogeneic T cells, we now test the hypothesis that CMV-driven cytolytic activity may contribute to graft endothelial injury.

METHODS

Limiting dilutions of CMV-seropositive or -seronegative donor-derived T cells were stimulated with CMV-infected or uninfected allogeneic ECs in the presence of interleukin-2. T-cell proliferation was monitored by assay of [3H]thymidine incorporation and stimulated T cells were tested for lytic activity against CMV-infected or uninfected radiolabeled EC targets by 51Cr release assay. Natural killer (NK) cell activity was examined by incubating freshly isolated peripheral blood mononuclear cells with 51Cr-labeled targets, followed by assay of radiolabel release.

RESULTS

CMV-infected ECs were resistant to T cell- and NK-mediated cytolysis regardless of donor serostatus, nature of stimulation, or level of T-cell proliferation. In contrast, although uninfected ECs were unharmed by NK cells, these targets experienced significant lysis by T cells stimulated with either uninfected or CMV-infected ECs.

CONCLUSIONS

These results implicate CMV-infected graft endothelium as a persistent source of infectious virus, a chronic stimulus for potentially destructive host inflammatory activity, and a potential trigger for the generation of lytic injury to uninfected bystander endothelia, suggesting multiple mechanisms by which this virus might perturb equilibrium at the graft/host interface.

Human cytomegalovirus inhibits major histocompatibility complex class II expression by disruption of the Jak/Stat pathway

Human cytomegalovirus (HCMV) is a ubiquitous herpesvirus that is able to persist for decades in its host. HCMV has evolved protean countermeasures for anti-HCMV cellular immunity that facilitate establishment of persistence. Recently it has been shown that HCMV inhibits interferon gamma (IFN-gamma)-stimulated MHC class II expression, but the mechanism for this effect is unknown. IFN-gamma signal transduction (Jak/Stat pathway) and class II transactivator (CIITA) are required components for IFN-gamma-stimulated MHC class II expression. In this study, we demonstrate that both a clinical isolate and a laboratory strain of HCMV inhibit inducible MHC class II expression at the cell surface and at RNA level in human endothelial cells and fibroblasts. Moreover, reverse transcriptase polymerase chain reaction and Northern blot analyses demonstrate that neither CIITA nor interferon regulatory factor 1 are upregulated in infected cells. Electrophoretic mobility shift assays reveal a defect in IFN-gamma signal transduction, which was shown by immunoprecipitation to be associated with a striking decrease in Janus kinase 1 (Jak1) levels. Proteasome inhibitor studies with carboxybenzyl-leucyl-leucyl-leucine vinyl sulfone suggest an HCMV-associated enhancement of Jak1 protein degradation. This is the first report of a mechanism for the HCMV-mediated disruption of inducible MHC class II expression and a direct virus-associated alteration in Janus kinase levels. These findings are yet another example of the diverse mechanisms by which HCMV avoids immunosurveillance and establishes persistence.

Herpesvirus in atherosclerosis and thrombosis: etiologic agents or ubiquitous bystanders?

The role of herpesvirus infections in the pathogenesis of vascular diseases remains an enigma. Although there is abundant circumstantial evidence of a role for herpesviruses in atherosclerosis and related processes, a cause-and-effect relationship has yet to be definitively established. This article will review the pathological, molecular, and biochemical evidence supporting the hypothesis that herpesviruses are involved in the development of atherosclerosis, restenosis after coronary angioplasty, accelerated atherosclerosis in recipients of heart transplants, and the induction of a prothrombotic phenotype in vascular endothelial cells.

Endothelial cells from diverse tissues exhibit differences in growth and morphology

An increased recognition of the role of endothelial cells in disease and the development of methods for endothelial cell culture has led to an upsurge in in vitro studies of endothelial cell function. However, the cells most often used for these studies do not reflect the in vivo heterogeneity of endothelial cells. To assess intrinsic differences between large and small vessel endothelial cells from different tissues, primary cultures of endothelial cells from capillaries (brain, lung, and adipose tissue) and a large vessel (aorta) of sheep were isolated, purified by fluorescence-activated cell sorting of acetylated low density lipoprotein (DiI-Ac-LDL) labeled cells, and characterized by phase contrast and ultrastructural morphology, expression of von Willebrand factor, and lack of expression of cytokeratin, smooth muscle actin, and glial fibrillary acidic protein (GFAP). Although all endothelial cells were cultured in the same media, only the brain microvascular endothelial cells demonstrated tight junctions by electron microscopy. Only the large vessel (aortic) endothelial cells contained Weibel-Palade bodies. Expression of von Willebrand factor decreased with passage of cells, but uptake of DiI-Ac-LDL was consistently positive regardless of culture conditions or passage number. These studies demonstrate that the unique ultrastructural characteristics of microvascular and macrovascular endothelial cells are intrinsic to the cells themselves and are not determined by differential culture conditions. This system allows the study of pathologic processes that affect endothelial cells of certain target organs selectively and should more accurately represent the response of tissue-specific endothelial cells in inflammatory processes.

Activation of protein kinase C enhances the infection of endothelial cells by human cytomegalovirus

The infection of cultured endothelial cells with human cytomegalovirus (HCMV) is generally limited to less than 10% of the cells in contrast to HCMV infection of fibroblasts, where essentially all cells can be infected. It is known that HCMV infection influences a number of signal transduction pathways of infected cells. We therefore questioned whether, conversely, the infectivity of human umbilical vein endothelial cells could be influenced by the deliberate activation of these pathways. When endothelial cells were treated prior to infection with phorbol myristoyl acetate, an activator of protein kinase C, the number of HCMV-positive cells increased two to three times. On the other hand, pretreatment of the cells with RO 31-8220, a specific protein kinase C inhibitor, or with staurosporine, a general protein kinase inhibitor, resulted in a decreased infection level and in abolishment of the PMA-induced effect. Pretreatment with the protein phosphatase inhibitor, okadaic acid, caused a slight increase in infectivity, whereas pretreatment with the protein tyrosine kinase inhibitor, genistein, was without effect. Furthermore, neither forskolin and ilomedine, compounds known to activate the endothelial adenylate cyclase, nor the calcium ionophore A23187 were able to influence HCMV infectivity. It is concluded that: (a) the HCMV infection level of unstimulated endothelial cells is influenced by the basal level of protein kinase C; and (b) stimulation of protein kinase C prior to infection results in an increase of infection by HCMV.

Patients with diabetes mellitus and atherosclerosis; a role for cytomegalovirus?

Diabetic patients are known to have an impaired immune response to viral antigens and a high incidence of atherosclerosis. This study was initiated to evaluate the association between cytomegalovirus infection and atherosclerosis in patients with diabetes mellitus. Patients with diabetes mellitus type 1 and 2 (> 5 years) with (group A) and without (group B) clinical signs of atherosclerosis were included. Cytomegalovirus cultures were obtained, serum was screened for CMV-antibodies and CMV-IgG and CMV-IgM titers were determined. Cytomegalovirus antibodies were detected more often in diabetic patients with atherosclerosis compared to patients without atherosclerosis (70.7 vs. 45.2%, P = 0.018. In female patients the prevalence of CMV-antibodies was 89.5 vs. 40.0% (P = 0.0037). CMV IgG titers were twice as high in group A compared to group B. Cytomegalovirus was cultured from four urine samples and two throat swabs in group B and in one urine and one throat swab in group A. The prevalence of cytomegalovirus antibodies was higher in diabetic patients with atherosclerosis compared to diabetic patients without atherosclerosis. This difference was most striking in the female population. CMV-IgG titers were twice as high in the atherosclerosis group. These data suggest that cytomegalovirus may play a role in the development of clinical atherosclerosis in patients with diabetes mellitus.

Comparison of the infectivity of the laboratory strain AD169 and a clinical isolate of human cytomegalovirus to human smooth muscle cells

The results displayed by human cytomegalovirus (HCMV) IE/E antigen expression and virus release into the supernatant at various times post infection with a clinical isolate (C3/p5) and AD169 laboratory strain of HCMV, illustrated differences in the biology of these viruses on the various cell lines. While AD169 strain was shown to infect fibroblasts efficiently, it showed a low infectivity profile to smooth muscle cells, whereas C3/p5 displayed comparable infectivity characteristics on both cell lines. Neither virus demonstrated propensity for infecting endothelial cells, although passaging of the C3/p5 for additional 11 passages in endothelial cells provided virus capable of infecting endothelial cells efficiently. These results show that HCMV is capable of infecting smooth muscle cells which could be of relevance to the proposed role of HCMV in atherogenesis and provides further evidence on the adaptation of AD169 to fibroblasts.

A dual role for endothelial cells in cytomegalovirus infection? A study of cytomegalovirus infection in a series of rat endothelial cell lines

Several clinical findings point to the involvement of microvascular endothelial cells in cytomegalovirus-related pathology. In this study the interactions of cytomegalovirus (CMV) with microvascular endothelial cells was investigated in an in vitro rat model. A series of rat endothelial cell lines, considered representative for the heterogeneity of heart microvascular endothelium in vivo, were infected with rat CMV (RCMV). The course of infection and production of infectious virus were examined using immunofluorescence staining and plaque titration assays, and was compared with infection of fully permissive rat fibroblasts. These endothelial cell lines displayed differences in susceptibility to CMV infection. Two endothelial cell lines (RHEC 50 and 191) were practically non-permissive, while four endothelial cell lines (RHEC 3, 10, 11 and 116) were partly permissive for CMV infection. In contrast to CMV infection in fibroblasts, only limited infection of the permissive endothelial cell lines was observed without spreading of CMV infection through the monolayer, although infectious virus was produced. Detachment of infected endothelial cells and recovery of the monolayer with time was observed. The detached endothelial cells were able to transmit CMV infection to fibroblast monolayers, but not to endothelial monolayers. Our in vitro results demonstrate differences in permissiveness for RCMV between the series of rat endothelial cell lines, which is suggestive for endothelial heterogeneity to CMV infection in vivo. Our findings indicate that endothelial cells are relatively resistant to CMV infection and that, upon infection, the endothelial monolayer may dispose of the virus via detachment of the infected cells. This points to a dual role for the endothelium in CMV infection in vivo: a barrier for CMV infection (by the endothelial monolayer) on the one hand and spreading of CMV infection (by detached infected cells) on the other hand.

Cytomegalovirus infection-enhanced chronic kidney allograft rejection is linked with intercellular adhesion molecule-1 expression

In human kidney allografts, association of acute rejection and glomerulopathy with cytomegalovirus (CMV) infection has been demonstrated. To investigate the effect of CMV infection on the development of experimental chronic kidney allograft rejection, heterotopic kidney allografts from DA (Ag-B4, RT1a1) rat donors to WF (Ag-B2, RT1u) rat recipients were used. The animals received cyclosporine A (CsA) 5 mg/kg/day s.c. either for 1 or 12 weeks. Two groups of recipients were infected with 10(5) plaque-forming units of rat CMV (RCMV) and two other groups were left noninfected and used as controls. The grafts were removed 12 weeks after transplantation for histology and immunohistochemistry. RCMV infection significantly enhanced the development of chronic kidney allograft rejection in rats on continuous CsA the intensity of interstitial inflammation (P < 0.025), particularly the degree of pyroninophilic cells in the inflammatory infiltrate (P < 0.025), the glomerular mesangial matrix increase (P < 0.05) and capillary basement membrane thickening (P < 0.01), the extent of endothelial cell swelling (P < 0.025) and intimal proliferation (P < 0.025) in the graft vasculature, and the extent of tubular epithelial atrophy (P < 0.025). Chronic allograft damage index (CADI) was significantly increased to 4.3 +/- 0.8 in RCMV-infected allografts, compared to 0.8 +/- 0.4 in noninfected (P < 0.02). In addition, RCMV infection significantly increased the number of acute rejection episodes (serum creatinine > 200 mumol/liter, P < 0.05) and almost doubled the end-stage serum creatinine. RCMV infection significantly increased ICAM-1 expression on the vascular endothelium (P < 0.05) and tubular epithelial cells (P < 0.01), and was linked with enhanced interstitial, glomerular, and tubular inflammation. In 80% of allografts on continuous CsA, RCMV antigens could be observed in sporadic inflammatory cells one week after infection and in tubular epithelial cells at 12 weeks. In heavily inflamed allografts where the CsA treatment was discontinued at one week, enhancement of RCMV infection on the histological changes attributable to chronic kidney allograft rejection could not be demonstrated. Our results show that during CsA immunosuppression, RCMV infection enhances chronic kidney allograft rejection associated with increased interstitial inflammation as well as vascular endothelial and tubular epithelial ICAM-1 expression.

Ischemic colitis secondary to venous thrombosis. A rare presentation of cytomegalovirus vasculitis following renal transplantation

Gastrointestinal complications occur after renal transplantation in up to 16% of patients. Cytomegalovirus (CMV) vasculitis can affect the gastrointestinal tract with significant manifestations, including colonic ulceration, bleeding, and perforation. We present a case of CMV vasculitis in a renal transplant patient that caused middle and left colic vein thrombosis and resultant ischemic colitis. There was no evidence of arterial involvement. To our knowledge, this is the first reported case of ischemic colitis secondary to large vein thrombosis associated with CMV infection.

A foveal-sparing pattern of cytomegalovirus retinitis in the acquired immunodeficiency syndrome

PURPOSE

We describe the clinical course of 12 eyes of 10 patients in whom recurrent cytomegalovirus (CMV) retinitis exhibited a foveal-sparing pattern.

METHODS

We retrospectively reviewed the case records and photographic charts of 10 patients (12 eyes) with the acquired immunodeficiency syndrome (AIDS), in whom recurrent CMV retinitis exhibited a foveal-sparing pattern within 1500 mm of the foveola.

RESULTS

The site of primary retinitis was temporal in 10 eyes of nine patients in whom it was known. The median number of recurrences up to the observation of foveal-sparing retinitis was two (range one to eight), and five patients had active CMV retinitis despite treatment for at least two continuous months. Once established, the median rate of progression in a non-foveal vector was 2.3 times faster than toward the fovea, and the median time to reduction in acuity to < 6/30 (or death) was 11 to 14 weeks. Three eyes of three patients retained 6/30 or better acuity up to death. Foveal CMV retinitis ultimately reduced acuity to < 6/30 in five eyes. Six eyes suffered retinal detachment, involving the fovea in five, and being the primary reason for acuity of < 6/30 in four. Four patients suffered dose-limiting toxicity.

CONCLUSION

Foveal-sparing CMV retinitis arises in patients with recurrent CMV retinitis resistant to treatment ('clinically resistant'), particularly that which has arisen temporally. Despite its foveolar proximity, and ultimate significant loss of function, the pattern of progression allows for preservation of useful foveal vision for longer periods than would have been expected.

Membrane related effects in endothelial cells induced by human cytomegalovirus

Previously, we have reported on the increase in procoagulant activity of human umbilical vein endothelial cells (HUVEC) after infection with human cytomegalovirus (HCMV). When using microvascular endothelial cells from foreskin (MVEC), we also observe a significant increase in membrane perturbation and a concomittant increase in procoagulant activity. This effect is both observed with a laboratory HCMV strain (AD169) with low pathogenicity for endothelium and a HUVEC adapted strain (VHL-E) that readily infects endothelial cells. We compared the membrane perturbation of two types of endothelial cells, HUVEC and MVEC with human embryonal fibroblasts (HEF), being fully permissive for both strains. A membrane effect was only found in endothelial cells. Our results suggest that HCMV induces in MVEC more merocyanine-540 incorporation in the membrane as in HUVEC. The increase in the procoagulant activity induced by HCMV was more pronounced in MVEC than in HUVEC. Inactivated virus, as well as virus pre-incubated with heparin was unable to evoke membrane perturbation. It therefore appears that HCMV induces a rapid membrane response in vascular endothelium and that physical interaction of the virion and the endothelial cell is required to elicit this response.

The role of interferon beta in human cytomegalovirus-mediated inhibition of HLA DR induction on endothelial cells

Human cytomegalovirus (HCMV), a member of the virus family Herpesviridae that is associated with extensive worldwide morbidity and mortality in immunocompromised hosts, inhibits interferon-gamma (IFN gamma)-mediated induction of human leukocyte antigen (HLA) class II antigens on endothelial cells. In this study, the ability of HCMV-infected endothelial cells to synthesize interferon-beta (IFN beta), and the role of IFN beta in HCMV-mediated inhibition of HLA class II induction, was investigated. As determined by an encephalomyocarditis virus protection assay, HCMV-infected endothelial cell culture supernatants contained 240 IU/ml of IFN type I activity, of which 99.9% was IFN beta, as compared to the absence of IFN beta in mock-infected culture supernatants. UV-irradiated supernatants from HCMV-infected cultures inhibited induction of HLA class II in noninfected cultures by 24%. This inhibition could be abolished with 500 NU/ml of anti-IFN beta antibody. Addition of anti-IFN beta antibody directly to HCMV-infected cultures mitigated but did not abolish HLA class II antigen inhibition. Dual immunohistochemistry for HCMV and HLA DR demonstrated that infected cells, in contrast to noninfected cells, were rarely induced to express HLA class II even in the presence of anti-IFN beta antibody. These findings suggest that HCMV inhibits induction of HLA class II antigens by IFN beta dependent and independent mechanisms.

Detection of active cytomegalovirus infection in inflammatory aortic aneurysms with RNA polymerase chain reaction

PURPOSE

We previously reported the possible role of human cytomegalovirus in the pathogenesis of inflammatory aortic diseases. To further analyze the viral cause of human aortic diseases, in this study we examined the presence and the replication of human Herpesviridae in 60 aortic tissues, including 7 inflammatory aneurysms, 37 atherosclerotic aneurysms, and 16 normal aortas.

METHODS

To detect the genome of herpes simplex virus (type 1, type 2), cytomegalovirus, and Epstein-Barr virus, DNA polymerase chain reaction for each virus was performed. To analyze these herpesviral replications, the viral transcript was detected with RNA polymerase chain reaction.

RESULTS

The DNA polymerase chain reaction showed that either herpes simplex virus or cytomegalovirus was present more frequently in inflammatory (29% or 86%, respectively) and atherosclerotic aneurysms (27% or 65%, respectively) than in normal aortic tissues (6% or 31%, respectively), whereas the Epstein-Barr viral genome was not detected in any aortic tissue specimens. By the use of RNA polymerase chain reaction, only the cytomegaloviral transcript was recognized in 71% of the inflammatory aneurysms but was not recognized in any other tissue specimens. No other herpesviral transcripts were detected in any tissue specimens examined in this study.

CONCLUSIONS

Our results thus suggest that the human herpesviruses may play various roles in the pathogenicity of aortic diseases, in particular the replicating infections of the cytomegalovirus might potentially cause the formation of inflammatory aneurysms.

The effect of short-chain fatty acids on the susceptibility of human umbilical vein endothelial cells to human cytomegalovirus infection

We have compared the replication of three strains of human cytomegalovirus (HCMV), HCMV AD-169, HCMV Towne, or HCMV RC-256, an insertional mutant of Towne containing the LacZ gene of E. coli, in human umbilical vein endothelial cells (HUVEC) and human forskin fibroblasts (HFF). We also examine the effects of salts of short-chain fatty acids on the susceptibility of HUVEC to infection by HCMV. All three virus strains replicated in both cell types, but 10-to 100-fold less virus was produced in HUVEC cells than HFF. For all virus strains, expression of HCMV IE-1 antigen in HFF was > 70% 24 h after inoculation. In contrast, the number of HUVEC exhibiting IE-1 antigen at 24 h was < 15%. Treatment of HUVEC with sodium butyrate, sodium hexanoate, or sodium propionate prior to virus inoculation increased the IE-1 and late HCMV antigen expression in a dose- and time-dependent manner. Virus yield was also increased. This increased susceptibility was inhibited by cycloheximide and tunicamycin, indicating a requirement for new cellular protein synthesis. Treatment with both sodium hexanoate and propionate after virus inoculation increased HUVEC susceptibility to HCMV infection. Treatment of HUVEC with sodium butyrate after virus inoculation also increased HCMV IE-1 antigen expression, but only after removal of the drug. These studies demonstrate that the susceptibility of HUVEC to HCMV infection can be increased by the treatment of the host cell with salts of short-chain fatty acids, such as sodium butyrate, before or after virus inoculation.

Cytomegalovirus infection of vascular endothelial cells alters production of GM-CSF and G-CSF

Infection of human umbilical vein endothelial cells with the clinical isolate of human cytomegalovirus (HCMV; at a multiplicity of infection of 2) severely suppresses the production of granulocyte-CSF and granulocyte-macrophage-CSF at late stages of infection (6 days post infection onwards). The effect was produced by actively multiplying virus which indicates that HCMV antigen expression is important for this suppression. The suppression in the production of these two cytokines was not due to their accumulation inside the cell nor to cell damage or lysis after infection.

Interleukin-1 production and cell-activation response to cytomegalovirus infection of vascular endothelial cells

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.

An immortalized human fibroblast cell line is permissive for human cytomegalovirus infection

Human foreskin fibroblasts (HFF) were immortalized via retrovirus-mediated gene transfer of the E6 and E7 genes of human papillomavirus type 16. An immortalized fibroblast (IF) cell line which was morphologically akin to the parental cell line was isolated. The IF cell line was evaluated for permissiveness to human cytomegalovirus (HCMV) infection after the IF cell line surpassed the normal passage limitation of diploid fibroblasts. Western immunoblot analysis of representative HCMV-encoded immediate-early (72-kDa), early (gB), and late (gH) gene products demonstrated that the IF cell line produced these proteins analogous to those produced by the parental HFF cells. Similar quantities of infectious virus were produced in the IF and HFF cell lines as determined in one-step growth curve experiments. Compared with the HFF cells, morphologically identical plaques were produced in the IF cell line in approximately 10 to 12 days postinfection. These findings indicate that fibroblast cell lines immortalized with transforming genes of human papillomavirus retain complete permissiveness to HCMV infection and support plaque formation. The IF cell line will be useful for future genetic analysis of HCMV.

Three cases of varicella thrombophlebitis as a complication of varicella zoster virus infection

Three cases of deep venous thrombosis following varicella infection are described which were successfully treated with bed rest and anticoagulants. Two of these patients had severe pulmonary manifestations of varicella and the third was complicated by pulmonary embolism. Deep vein thrombosis is an uncommon systemic manifestation of varicella, possibly associated with vascular endothelium wall damage caused by varicella zoster virus infection.

Frosted branch angiitis associated with cytomegalovirus retinitis

We examined three patients with acquired immunodeficiency syndrome who had frosted branch angiitis associated with small patches of cytomegalovirus retinitis. Each patient had a low CD4-helper T-lymphocyte count and a T-lymphocyte helper-suppressor ratio of less than 0.1. Treatment with intravenous anticytomegalovirus antibiotics caused the vascular sheathing to resolve within two weeks in all three patients, but each patient continued to have a smoldering retinitis. Retinal biopsy in one of the patients demonstrated virions whose morphologic characteristics were consistent with cytomegalovirus on electron microscopy and the identity of which was confirmed by immunohistochemistry. Although frosted branch angiitis in otherwise healthy patients responds to corticosteroids, similar treatment with corticosteroids for frosted branch angiitis associated with cytomegalovirus retinitis in patients with AIDS does not seem to be indicated. Before corticosteroid treatment is started for a patient with the clinical signs and symptoms of frosted branch angiitis, careful medical examination of the patient is necessary.