Circulating endothelial giant cells permissive for human cytomegalovirus (HCMV) are detected in disseminated HCMV infections with organ involvement

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.

Whole Blood versus Plasma Samples-How Does the Type of Specimen Collected for Testing Affect the Monitoring of Cytomegalovirus Viremia?

Viral infections, or their reactivations, are one of the most important groups of transplantation complications that can occur among recipients of both hematopoietic cells and solid organ transplants. They are the most commonly caused by cytomegalovirus (CMV). Currently, the use of whole blood or plasma samples is recommended for CMV viral load monitoring. The aim of the study was to assess and compare the level of CMV DNA, depending on the type of clinical material—whole blood or plasma fraction derived from the same patient. The studies were carried out on 156 whole blood samples in which the presence of CMV genetic material was confirmed and the corresponding plasma samples from the same rounds of sampling. CMV DNA was not present in 59 (37.8%) of plasma samples compared to whole blood-positive counterparts. Of the samples positive in both types of clinical specimen, 77 (79.4%) had higher viral DNA levels in the whole blood samples. There were statistically significant differences in the detected CMV DNA load in the whole blood compared to plasma fraction counterparts (p < 0.001). The detected CMV DNA value is usually higher in whole blood compared to plasma samples of the same patient. Due to the variability in CMV viral load depending on the clinical material used for a particular patient, one type of specimen should be always used consequently for CMV viremia monitoring.

Transmission of cell-associated human cytomegalovirus isolates between various cell types using polymorphonuclear leukocytes as a vehicle

Polymorphonuclear leukocytes (PMNs) are regarded as vehicles for the hematogenous dissemination of human cytomegalovirus (HCMV). In cell culture, this concept has been validated with cell-free laboratory strains but not yet with clinical HCMV isolates that grow strictly cell-associated. We, therefore, aimed to evaluate whether PMNs can also transmit such isolates from initially infected fibroblasts to other cell types, which might further clarify the role of PMNs in HCMV dissemination and provide a model to search for potential inhibitors. PMNs, which have been isolated from HCMV-seronegative individuals, were added for 3 h to fibroblasts infected with recent cell-associated HCMV isolates, then removed and transferred to various recipient cell cultures. The transfer efficiency in the recipient cultures was evaluated by immunofluorescence staining of viral immediate early antigens. Soluble derivatives of the cellular HCMV entry receptor PDGFRα were analyzed for their potential to interfere with this transfer. All of five tested HCMV isolates could be transferred to fibroblasts, endothelial and epithelial cells with transfer rates ranging from 2 to 9%, and the transferred viruses could spread focally in these recipient cells within 1 week. The PDGFRα-derived peptides IK40 and GT40 reduced transfer by 40 and 70% when added during the uptake step. However, when added during the transfer step, only IK40 was effective, inhibiting transmission by 20% on endothelial cells and 50–60% on epithelial cells and fibroblasts. These findings further corroborate the assumption of cell-associated HCMV dissemination by PMNs and demonstrate that it is possible to inhibit this transmission mode.

Profiling the Blood Compartment of Hematopoietic Stem Cell Transplant Patients During Human Cytomegalovirus Reactivation

Human cytomegalovirus (HCMV) is a widespread pathogen establishing a latent infection in its host. HCMV reactivation is a major health burden in immunocompromised individuals, and is a major cause of morbidity and mortality following hematopoietic stem cell transplantation (HSCT). Here we determined HCMV genomic levels using droplet digital PCR in different peripheral blood mononuclear cell (PBMC) populations in HCMV reactivating HSCT patients. This high sensitivity approach revealed that all PBMC populations harbored extremely low levels of viral DNA at the peak of HCMV DNAemia. Transcriptomic analysis of PBMCs from high-DNAemia samples revealed elevated expression of genes typical of HCMV specific T cells, while regulatory T cell enhancers as well as additional genes related to immune response were downregulated. Viral transcript levels in these samples were extremely low, but remarkably, the detected transcripts were mainly immediate early viral genes. Overall, our data indicate that HCMV DNAemia is associated with distinct signatures of immune response in the blood compartment, however it is not necessarily accompanied by substantial infection of PBMCs and the residual infected PBMCs are not productively infected.

Circulating Endothelial Cells as a Marker of Endothelial Injury in Severe COVID -19

Beside the commonly described pulmonary expression of the coronavirus disease 2019 (COVID-19), major vascular events have been reported. The objective of this study was to investigate whether increased levels of circulating endothelial cells (CEC) might be associated with severe forms of COVID-19. Ninety-nine patients with COVID-19 were enrolled in this retrospective study. Patients in the intensive care units (ICU) had significantly higher CEC counts than non-ICU patients and the extent of endothelial injury was correlated with putative markers of disease severity and inflammatory cytokines. Altogether, these data provide in vivo evidence that endothelial injury is a key feature of COVID-19.

Circulating endothelial progenitor cells and endothelial cells in moyamoya disease

INTRODUCTION

There is no well-recognized biomarker for accurately predicting outcome in the presence of moyamoya disease (MMD), a progressive occlusive cerebrovascular disease of the internal carotid arteries or their branches. The aim of this study was to investigate the presence of endothelial progenitor cells (EPCs) and circulating endothelial cells (CECs) in MMD and correlate the findings with clinical features.

METHODS

Patients with MMD (n = 66) were compared with healthy controls (n = 81). Blood samples were obtained from an antecubital vein and analyzed using flow cytometry. EPCs were defined as CD31⁺ CD45^dim CD34^br CD133⁺ and CECs as CD31^br CD45^- CD34^dim CD133^- . Univariate and multivariate linear regression analyses were carried out.

RESULTS

The CEC counts were significantly higher in the patients than in the controls (p = 0.008). In multivariate analysis, EPC counts were independently associated with age of patients with MMD (p = 0.049) and CEC counts were independently negatively associated with concomitant disease such as hypertension, diabetes mellitus, and coronary heart disease (p = 0.034).

CONCLUSIONS

This is the first study to investigate the presence of CECs in the plasma of patients with MMD, and the amount of CECs was negatively correlated with concomitant disease in these patients.

There Is Always Another Way! Cytomegalovirus' Multifaceted Dissemination Schemes

Human cytomegalovirus (HCMV) is a β-herpes virus that is a significant pathogen within immune compromised populations. HCMV morbidity is induced through viral dissemination and inflammation. Typically, viral dissemination is thought to follow Fenner's hypothesis where virus replicates at the site of infection, followed by replication in the draining lymph nodes, and eventually replicating within blood filtering organs. Although CMVs somewhat follow Fenner's hypothesis, they deviate from it by spreading primarily through innate immune cells as opposed to cell-free virus. Also, in vivo CMVs infect new cells via cell-to-cell spread and disseminate directly to secondary organs through novel mechanisms. We review the historic and recent literature pointing to CMV's direct dissemination to secondary organs and the genes that it has evolved for increasing its ability to disseminate. We also highlight aspects of CMV infection for studying viral dissemination when using in vivo animal models.

The pentameric complex of human Cytomegalovirus: cell tropism, virus dissemination, immune response and vaccine development

Between the 1980s and 1990s, three assays were developed for diagnosis of human cytomegalovirus (HCMV) infections: leuko (L)-antigenemia, l-viremia and l-DNAemia, detecting viral protein pp65, infectious virus and viral DNA, respectively, in circulating leukocytes Repeated initial attempts to reproduce the three assays in vitro using laboratory-adapted strains and infected cell cultures were consistently unsuccessful. Results were totally reversed when wild-type HCMV strains were used to infect either fibroblasts or endothelial cells. Careful analysis and sequencing of plaque-purified viruses from recent clinical isolates drew attention to the ULb' region of the HCMV genome. Using bacterial artificial chromosome technology, it was shown by both gain-of-function and loss-of-function experiments that UL131-128 genes are indispensable for virus growth in endothelial cells and virus transfer to leukocytes. In addition, a number of clinical isolates passaged in human fibroblasts had lost both properties (leuko-tropism and endothelial cell-tropism) when displaying a mutation in the UL131-128 locus (referred to as UL128L). In the following years, it was shown that pUL128L was complexed with gH and gL to form the pentameric complex (PC), which is required to infect endothelial, epithelial and myeloid cells. The immune response to PC was studied extensively, particularly its humoral component, showing that the great majority of the neutralizing antibody response is directed to PC. Although anti-HCMV antibodies may act with other mechanisms than mere neutralizing activity, these findings definitely favour their protective activity, thus paving the way to the development of a potentially protective HCMV vaccine.

Enumeration of circulating endothelial cell frequency as a diagnostic marker in aortic valve surgery - a flow cytometric approach

Background

The frequency of circulating endothelial cells (CEC) in patients’ peripheral blood can be assessed as a direct marker of endothelial damage. However, conventional enumeration methods are extremely challenging. We developed a novel, automated approach to determine CEC frequencies and tested this method on two groups of patients undergoing conventional (CAVR) versus trans-catheter aortic valve implantation (TAVI).

Methods

CEC frequencies were assessed by a flow cytometric approach, including automated pre-enrichment of CD34 positive blood cell subpopulation and isotype controls. The efficacy and reproducibility of the CEC enumeration method was validated by spiking blood samples of healthy control donors with defined numbers of endothelial cells.

Results

CEC frequencies were significantly higher in the TAVI group before (9.8 ± 4.1 vs. 5.5 ± 2.2, p = 0.019) and 1 h after surgery (13.4 ± 5.1 vs. 8.2 ± 4.1, p = 0.030) corresponding to higher Euroscore, STS score in higher risk patients from the TAVI group. Five days after surgery, CEC frequencies became significantly higher in the more invasive CAVR group (39.0 ± 13.0 vs. 14.3 ± 4.4, p < 0.001) compared to minimally invasive TAVI approach.

Conclusions

The new flow cytometric approach might be a robust and reliable method for CEC enumeration. Initial results show that CEC frequency is a valid clinical marker for the assessment of pre-operative risk, invasiveness of surgical procedure and clinical outcome. Further studies are necessary to validate the practical clinical usefulness and the potential superiority compared to conventional markers.

Attenuation of chemokine receptor function and surface expression as an immunomodulatory strategy employed by human cytomegalovirus is linked to vGPCR US28

Background

Some herpesviruses like human cytomegalovirus (HCMV) encode viral G protein-coupled receptors that cause reprogramming of cell signaling to facilitate dissemination of the virus, prevent immune surveillance and establish life-long latency. Human GPCRs are known to function in complex signaling networks involving direct physical interactions as well as indirect crosstalk of orthogonal signaling networks. The human chemokine receptor CXCR4 is expressed on hematopoietic stem cells, leukocytes, endothelial and epithelial cells, which are infected by HCMV or display reservoirs of latency.

Results

We investigated the potential heteromerization of US28 with CXCR4 as well as the influence of US28 on CXCR4 signaling. Using Bioluminescence Resonance Energy Transfer and luciferase-complementation based methods we show that US28 expression exhibits negative effects on CXCR4 signaling and constitutive surface expression in HEK293T cells. Furthermore, we demonstrate that this effect is not mediated by receptor heteromerization but via signaling crosstalk. Additionally, we show that in HCMV, strain TB40E, infected HUVEC the surface expression of CXCR4 is strongly downregulated, whereas in TB40E-delUS28 infected cells, CXCR4 surface expression is not altered in particular at late time points of infection.

Conclusions

We show that the vGPCR US28 is leading to severely disturbed signaling and surface expression of the chemokine receptor CXCR4 thereby representing an effective mechanism used by vGPCRs to reprogram host cell signaling. In contrast to other studies, we demonstrate that these effects are not mediated via heteromerization.

Electronic supplementary material

The online version of this article (doi:10.1186/s12964-016-0154-x) contains supplementary material, which is available to authorized users.

Tetraspanin CD151 Promotes Initial Events in Human Cytomegalovirus Infection

Human cytomegalovirus (HCMV), a betaherpesvirus, can cause life-threatening disease in immunocompromised individuals. Viral envelope glycoproteins that mediate binding to and penetration into target cells have been identified previously. In contrast, cellular proteins supporting HCMV during entry are largely unknown. In order to systematically identify host genes affecting initial steps of HCMV infection, a targeted RNA interference screen of 96 cellular genes was performed in endothelial cells by use of a virus strain expressing the full set of known glycoprotein H and L (gH/gL) complexes. The approach yielded five proviral host factors from different protein families and eight antiviral host factors, mostly growth factor receptors. The tetraspanin CD151 was uncovered as a novel proviral host factor and was analyzed further. Like endothelial cells, fibroblasts were also less susceptible to HCMV infection after CD151 depletion. Virus strains with different sets of gH/gL complexes conferring either broad or narrow cell tropism were equally impaired. Infection of CD151-depleted cells by a fluorescent virus with differentially labeled capsid and envelope proteins revealed a role of CD151 in viral penetration but not in adsorption to the cell. In conclusion, the tetraspanin CD151 has emerged as a novel host factor in HCMV entry and as a putative antiviral target.

IMPORTANCE

At present, the events at the virus-cell interface and the cellular proteins involved during the HCMV entry steps are scarcely understood. In this study, several host factors with putative roles in this process were identified. The tetraspanin CD151 was discovered as a previously unrecognized proviral host factor for HCMV and was found to support viral penetration into the target cells. The findings of this study shed light on the cellular contribution during the initial steps of HCMV infection and open a new direction in HCMV research.

A permanently growing human endothelial cell line supports productive infection with human cytomegalovirus under conditional cell growth arrest

Infection of vascular endothelial cells (ECs) is assumed to contribute to dissemination of human cytomegalovirus (HCMV). Investigation of virus-host interactions in ECs such as human umbilical vein endothelial cells (HUVECs) is limited due to the low maximal passage numbers of these primary cells. We tested a conditionally immortalized EC line (HEC-LTT) and a permanent cell line (EA.hy926) for their susceptibility to HCMV infection. Both cell lines resembled HUVECs in that they allowed for entry and immediate early protein expression of highly endotheliotropic HCMV strains but not of poorly endotheliotropic strains, rendering them suitable for analysis of the viral entry mechanism in ECs. The late phase of viral replication and release, however, was supported by growth-controlled HEC-LTT cells but not by EA.hy926 cells. HEC-LTT cells support both the early and late phase of viral replication and release infectious progeny virus at titers comparable to primary HUVECs; thus, the HEC-LTT cell line is a cell culture model representing the full viral replicative cycle of HCMV in ECs. The implementation of permanent HEC-LTT and EA.hy926 cell lines in HCMV research will facilitate long-term approaches that are not feasible in primary HUVECs.

Analysis of human cytomegalovirus replication in primary cultured human corneal endothelial cells

Background/aims

Since the first case of human cytomegalovirus (HCMV)-induced corneal endotheliitis in which HCMV DNA was detected from the patient's aqueous humour using PCR, the clinical evidence for HCMV endotheliitis has been accumulating. However, it remains to be confirmed whether HCMV can efficiently replicate in corneal endothelial cells. We, therefore, sought to determine whether primary cultured human corneal endothelial cells (HCECs) could support HCMV replication.

Methods

Human foreskin fibroblasts (HFFs) have been shown to be fully permissive for HCMV replication, and are commonly used as an in vitro model for HCMV lytic replication. Therefore, primary cultured HCECs or HFFs were infected with the vascular endotheliotropic HCMV strain TB40/E or laboratory strain Towne. We then compared viral mRNA and protein expression, genome replication and growth between the TB40/E-infected and Towne-infected HCECs and HFFs.

Results

When HCECs were infected with TB40/E or Towne, rounded cells resembling owl's eyes as well as viral antigens were detected. Viral mRNA synthesis and protein expression proceeded efficiently in the HCECs and HFFs infected with TB40/E or Towne at a high multiplicity of infection (MOI). Similarly, the viral genome was also effectively replicated, with UL44—a viral DNA polymerase processivity factor—foci observed in the nuclei of HCECs. HCECs produced a substantial number of infectious virions after infection with TB40/E at both a high and low MOI.

Conclusions

Primary cultured HCECs could efficiently support HCMV replication after infection at both a high and low MOI.

Circulating cytomegalic cells in a patient with advanced HIV presenting with cytomegalovirus rhinosinusitis

We report a patient with newly diagnosed late-stage HIV presenting with fever, rhinosinusitis and cognitive impairment. Analysis of cerebrospinal fluid and nasal turbinate tissue confirmed cytomegalovirus (CMV) infection. CMV pp65 antigen assay conducted on peripheral blood leukocytes revealed large CMV infected mononuclear cells (diameter ∼ 50 μm) with an unusual cytoplasmic pattern of pp65 staining. These large cells were also seen in buffy coat Wright's stained smears; their size, morphology and pp65 antigen uptake pattern were consistent with CMV infected cytomegalic endothelial cells. While CMV sinus infections are occasionally encountered in AIDS patients, this is the first report to document CMV infection of the nasal mucosa with secondary sinusitis and chronic suppurative otitis media. Furthermore, the detection of circulating cytomegalic cells is described--a rare finding with pathological and clinical significance in immunocompromised patients with CMV disease.

Circulating endothelial cells and chronic kidney disease

Endothelial dysfunction may play a crucial role in initiation of the pathogenesis of vascular disease and atherosclerosis. The identification and quantification of circulating endothelial cells (CEC) have been developed as a novel marker of endothelial function. We describe, in great detail, mechanisms of endothelial dysfunction and CEC detachment. We also review the relationship between numbers of CEC and disease severity and response to treatment. In addition, we describe the possible clinical use of CEC in chronic kidney disease (CKD) and kidney transplantation. In summary, CEC have been developed as a novel approach to assess the endothelial damage. Measurement of the CEC level would provide an important diagnostic and prognostic value on the endothelium status and the long-term outcome of vascular dysfunction.

Effects of intrapulmonary viral tropism and cytokine expression on the histological patterns of cytomegalovirus pneumonia

Pulmonary cytomegalovirus (CMV) infection causes fatal CMV pneumonia (CMVp) in Immunocompromised patients; however, the mechanisms underlying CMV-Infection-Induced pulmonary lesion development remain largely unknown. We examined the relationship between CMVp patterns and Intrapulmonary viral tropism, Including expression of Inflammatory cytokines and related molecules. Double Immunohistochemistry of CMV antigen and cellular markers showed that epithelial tropism was associated with a diffuse alveolar damage (DAD) pattern (CMVp-DAD) while stromal tropism was associated with a predominantly interstitial inflammation/fibrosis (IIF) (CMVp-IIF) or a combination of DAD and IIF (CMVp-complex). Transforming growth factor (TGF)-β1 expression was relevant to CMV-induced tissue injury, and its expression was higher in CMVp-complex and CMVp-IIF than in CMVp-DAD. Expression of integrin β6 (ITGB6), an adhesion molecule and important activator of TGF-β1 in interstitial pneumonia, was lost in CMV-infected pneumocytes, especially CMVp-DAD, whereas CMV-negative pneumocytes in CMVp-complex and CMVp-IIF showed overexpression. Diffuse interleukin (IL)-8 up-regulation and strong expression were present in both CMV-infected pneumocytes and stromal cells only in CMVp-IIF cases with marked interstitial neutrophilic infiltration. On the basis of viral tropism and the expression of TGF-β1, ITGB6, and IL-8, we conclude that CMV-Infected pulmonary cells play an Important role in the development of diverse CMVp patterns.

A new approach for rapid and reliable enumeration of circulating endothelial cells in patients

BACKGROUND

Mature circulating endothelial cells (CECs) are surrogate markers of endothelial damage/dysfunction. A lack of standardized assays and consensus on CEC phenotype has resulted in a wide variation of reported CEC numbers (4-1300 per mL).

OBJECTIVES

Given the need for a quick, reliable, robust and validated CEC assay at an affordable price, we present a novel approach to enumerate CECs using a multi-parameter flow cytometric (FCM) method without immunological pre-enrichment.

METHODS

CECs were defined as CD34+, CD45neg, CD146+ and DNA+ events based on the immunophenotype of endothelial cells from vein-wall dissections. As CECs express high levels of CD34, we based our assay on absolute CD34 counts after analyzing all CD34 positive events in a total blood volume of 4 mL needed for a precise enumeration of CECs at a frequency of < 1 cell μL(-1).

RESULTS

The endothelial origin of CECs was confirmed by morphology, immunohistochemistry and gene expression. The new FCM assay was tested in parallel with a validated assay (i.e. CellSearch). CEC levels ranged from 4 to 79 CEC mL(-1) in healthy individuals and were significantly higher in patients with advanced solid malignancies (P = 0.0008) and in patients with hematological malignancies (P < 0.0001).

CONCLUSIONS

This flow cytometric method should be useful as a fast and economical assay to enumerate and characterize CECs.

Endothelial cells and CMV dissemination

Evaluation of: Sacher T, Andrassy J, Kalnins A et al. Shedding light on the elusive role of endothelial cells in cytomegalovirus dissemination. PLoS Pathog. 7(11), E1002366 (2011). Using the murine CMV animal model and the well-established model of Cre-lox-P-mediated green-fluorescence tagging of endothelial cell (EC)-derived mouse CMV to quantify the role of infected ECs in transplantation-associated CMV dissemination (in mice expressing Cre recombinase under the control of either the Tie2 or the Tek promoter selectively expressed in vascular EC-Tie-Cre and Tek-Cre mice), it was shown that EC-derived virus contributed to 50% of the total viral load during primary infection, and there was no preference for dissemination of EC-derived viruses over viruses produced by other cell types. In addition, during secondary viremia, there was only a negligible contribution of EC-derived virus to dissemination to other organs. These results are novel in the methodology employed and are somewhat interesting. However, the data are limited to the mouse model with a short-term follow-up, and the immunodeficient host has not yet been studied. In humans, these conclusions must be taken with caution. First, in primary infection occurring through natural routes, epithelial cells are infected first, then ECs, unless primary infection occurs through blood transfusion, in which case endothelial vascular cells may become infected first. In both cases, the virus transport occurs through the intervention of leukocytes, namely monocytes and polymorphonuclear leukocytes. As monocytes differentiate to macrophages, they become highly susceptible to human CMV replication inside organ tissues, while polymorphonuclear leukocytes are active in virus capturing from infected endothelial vascular cells and transporting to distant sites.

CMV infection attenuates the disease course in a murine model of multiple sclerosis

Recent evidence in multiple sclerosis (MS) suggests that active CMV infection may result in more benign clinical disease. The goal of this pilot study was to determine whether underlying murine CMV (MCMV) infection affects the course of the Theiler's murine encephalitis virus (TMEV) induced murine model of MS. A group of eight TMEV-infected mice were co-infected with MCMV at 2 weeks prior to TMEV infection while a second group of TMEV-infected mice received MCMV two weeks post TMEV. We also used 2 control groups, where at the above time points MCMV was replaced with PBS. Outcome measures included (1) monthly monitoring of disability via rotarod for 8 months; (2) in vivo MRI for brain atrophy studies and (3) FACS analysis of brain infiltrating lymphocytes at 8 months post TMEV infection. Co-infection with MCMV influenced the disease course in mice infected prior to TMEV infection. In this group, rotarod detectable motor performance was significantly improved starting 3 months post-infection and beyond (p≤0.024). In addition, their brain atrophy was close to 30% reduced at 8 months, but this was only present as a trend due to low power (p = 0.19). A significant reduction in the proportion of brain infiltrating CD3+ cells was detected in this group (p = 0.026), while the proportion of CD45+ Mac1+ cells significantly increased (p = 0.003). There was also a strong trend for a reduced proportion of CD4+ cells (p = 0.17) while CD8 and B220+ cell proportion did not change. These findings support an immunomodulatory effect of MCMV infection in this MS model. Future studies in this co-infection model will provide insight into mechanisms which modulate the development of demyelination and may be utilized for the development of novel therapeutic strategies.

Clinical value of circulating endothelial cell detection in oncology

Given the importance of tumor vasculature in tumor biology and as a target for treatment, there is an increasing need for biomarkers that reflect effects impacting tumor vasculature accurately. Circulating endothelial cells (CECs) increase in number as a result of vascular damage in cancer and several other diseases. CEC count constitutes a promising tool for monitoring disease activity with potential to assess prognosis and response to treatment. Here, we address the current state-of-the-art of CEC enumeration as a biomarker in clinical oncology. We focus on technical issues concerning CEC detection, review results from clinical studies and explore future potential applications.

Shedding light on the elusive role of endothelial cells in cytomegalovirus dissemination

Cytomegalovirus (CMV) is frequently transmitted by solid organ transplantation and is associated with graft failure. By forming the boundary between circulation and organ parenchyma, endothelial cells (EC) are suited for bidirectional virus spread from and to the transplant. We applied Cre/loxP-mediated green-fluorescence-tagging of EC-derived murine CMV (MCMV) to quantify the role of infected EC in transplantation-associated CMV dissemination in the mouse model. Both EC- and non-EC-derived virus originating from infected Tie2-cre(+) heart and kidney transplants were readily transmitted to MCMV-naïve recipients by primary viremia. In contrast, when a Tie2-cre(+) transplant was infected by primary viremia in an infected recipient, the recombined EC-derived virus poorly spread to recipient tissues. Similarly, in reverse direction, EC-derived virus from infected Tie2-cre(+) recipient tissues poorly spread to the transplant. These data contradict any privileged role of EC in CMV dissemination and challenge an indiscriminate applicability of the primary and secondary viremia concept of virus dissemination.

Mycoplasmal cerebral vasculopathy in a lymphoma patient: presumptive evidence of Mycoplasma pneumoniae microvascular endothelial cell invasion in a brain biopsy

A 73-year-old man had episodic encephalopathy, ataxia and neuropathy. Symptoms largely resolved but adenopathy later lead to the diagnosis of a low-grade follicular lymphoma. The neurological symptoms soon recurred with new pontine calcifications identified by computed tomography. Brain biopsy revealed microvascular endothelial cell nuclear changes. Electron microscopy identified small polymorphic bacteria without a cell wall and with terminal and attachment organelles within endothelial cells and clustered in some microvascular lumina. Immunostaining was positive for Mycoplasma pneumoniae and convalescent serum enzyme immunoassay was positive for M. pneumoniae IgG. The patient again recovered and he was neurologically stable 33 months after the initial episode. The ultrastructural findings of the bacterial cells are distinctive of some mycoplasmal species when compared to other small bacteria. Mycoplasma-like organisms are reported in four autopsied patients who had chronic encephalopathy, movement disorders, and some of the same light- and electron-microscopic findings in the brain as our patient. Direct neuroinvasion by Mycoplasma species has been suggested, while anatomic observations in our patient and in the four autopsy cases show microvascular invasion but not parenchymal invasion. Most mycoplasmal encephalitis may be immune-mediated. The frequency of neurovascular invasion is not known. It may be rare and it may persist.

Recombinant glycoprotein B vaccine formulation with Toll-like receptor 9 agonist and immune-stimulating complex induces specific immunity against multiple strains of cytomegalovirus

Natural human cytomegalovirus (CMV) infection is characterized by a strain-specific neutralizing antibody response. This is particularly relevant in clinical settings such as transplantation and pregnancy where reinfection with heterologous strains occurs and the immune system does not mount an effective response against the infecting strain due to underlying immunosuppression. There is an emerging argument that a CMV vaccine that induces high titres of cross-neutralizing antibodies will be more effective in protecting individuals from infection with antigenically different CMV strains. In addition, induction of cell-mediated immunity offers the additional advantage of targeting virus-infected cells. This study presents a novel formulation of a CMV vaccine that, by combining recombinant soluble gB protein with a Toll-like receptor 9 agonist (CpG ODN1826) and immune-stimulating complexes (AbISCO 100), was able to elicit strong polyfunctional CMV-specific cellular and cross-neutralizing humoral immune responses. These data demonstrated that prime-boost immunization of human leukocyte antigen (HLA)-A2 mice with gB protein in combination with CpG ODN1826 and AbISCO 100 induced long-lasting CMV-specific CD4(+) and CD8(+) T-cell and humoral responses. Furthermore, these responses neutralized infection with multiple strains of CMV expressing different gB genotypes and afforded protection against challenge with recombinant vaccinia virus encoding the gB protein. These observations argue that this novel vaccine strategy, if applied to humans, should facilitate the generation of a robust, pluripotent immune response, which may be more effective in preventing infection with multiple strains of CMV.

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.

Circulating endothelial cells are elevated in patients with type 1 diabetes mellitus

OBJECTIVE

Circulating endothelial cells (CECs) have emerged as vascular damage markers and are increased in type 2 diabetic patients. Since type 1 diabetes is associated with vascular damage, we hypothesized high CEC numbers in this patient population.

METHODS

Thirty-nine patients with type 1 diabetes and 39 controls were included. CECs were isolated using anti-CD146-coated Dynabeads, stained with Ulex lectin-1, and counted by fluorescence microscopy. Endothelial function was measured as flow-mediated dilation (FMD). Thiobarbituric acid reactive substances (TBARS), total glutathione levels (GSH), and paraoxonase (PON) activity levels were measured as oxidative stress markers.

RESULTS

Patients with type 1 diabetes mellitus had higher number of CECs (7.46+/-5.37 vs 2.13+/-1.13 cells/ml, P<0.001), lower FMD (7.87+/-2.19 vs 12.06+/-2.34%, P<0.001), higher TBARS (4.94+/-1.20 vs 3.07+/-0.75 nmol/MDA, P<0.001), lower GSH (206.12+/-98.06 vs 353.61+/-68.45 microM, P<0.001), and lower PON activity levels (89.10+/-17.82 vs 127.65+/-29.01 U/l, P<0.001) as compared to controls. There was positive correlation between CEC numbers and HbAlc levels (r=0.49, P=0.002). CECs and fasting glucose levels were not correlated. There was no correlation between the number of CECs and FMD. Furthermore, there were no correlations between the number of CECs and TBARS, GSH and PON activity levels. Multiple regression analysis showed that HbAlc levels (r(2)=0.40, P<0.009) were associated with CEC numbers.

CONCLUSION

CECs are elevated in patients with type 1 diabetes mellitus reflecting endothelial damage. This increase is dependent on long-term glucose control.

A prospective pilot study of circulating endothelial cells as a potential new biomarker in portal hypertension

BACKGROUND/AIMS

Peripheral circulating endothelial cells (CEC) have been proposed as a prognostic marker in cardiovascular diseases. Cirrhosis and portal hypertension are associated with vascular injury yet little is known about CEC count in these conditions. Therefore, we evaluated CEC count in patients with cirrhosis, and correlated it with markers of portal hypertension/disease severity.

PATIENTS/METHODS

Fifteen patients with cirrhosis/portal hypertension and 15 matched controls were prospectively recruited for study participation. An automated rare cell analysis system was used to enumerate CEC from peripheral blood and correlated with clinical features.

RESULTS

Median CEC levels were significantly higher in patients with cirrhosis as compared with controls (median [interquartile range (IQR)]; cirrhosis: 73.7 cells/4 ml [53.7-140.3]; controls: 28.7 cells/4 ml [21-58.7]; P=0.021). Ratio of CEC to platelet count (CEC/PC) also distinguished patients with cirrhosis from controls (IQR; cirrhosis: 0.723 [0.396-1.672]; controls: 0.126 [0.103-0.333]; P<0.001). Receiver operator characteristic analysis revealed that CEC cut-off of 42 cells/4 ml showed sensitivity of 87% and specificity of 74% for differentiating cirrhosis from controls (AUC: 0.74), while CEC/PC ratio at 0.21 showed sensitivity of 100% and specificity of 73% (AUC: 0.89). Furthermore, CEC/PC index was significantly elevated in patients with hepatic decompensation as defined by Child B/C (P<0.05). The intra- and interobserver variability correlation coefficients for CEC measurement were 0.9989 and 0.9986 respectively.

CONCLUSION

Median CEC count and CEC/PC ratio are significantly elevated in patients with cirrhosis, with CEC/PC also increased in patients with decompensated cirrhosis. These data provide rationale for larger validation studies to assess if CEC may have prognostic utility in patients with cirrhosis and portal hypertension.

Isolation of human monoclonal antibodies that potently neutralize human cytomegalovirus infection by targeting different epitopes on the gH/gL/UL128-131A complex

Human cytomegalovirus (HCMV) is a widely circulating pathogen that causes severe disease in immunocompromised patients and infected fetuses. By immortalizing memory B cells from HCMV-immune donors, we isolated a panel of human monoclonal antibodies that neutralized at extremely low concentrations (90% inhibitory concentration [IC(90)] values ranging from 5 to 200 pM) HCMV infection of endothelial, epithelial, and myeloid cells. With the single exception of an antibody that bound to a conserved epitope in the UL128 gene product, all other antibodies bound to conformational epitopes that required expression of two or more proteins of the gH/gL/UL128-131A complex. Antibodies against gB, gH, or gM/gN were also isolated and, albeit less potent, were able to neutralize infection of both endothelial-epithelial cells and fibroblasts. This study describes unusually potent neutralizing antibodies against HCMV that might be used for passive immunotherapy and identifies, through the use of such antibodies, novel antigenic targets in HCMV for the design of immunogens capable of eliciting previously unknown neutralizing antibody responses.

Impact of immunosuppressive treatment on endothelial biomarkers after kidney transplantation

Endothelial dysfunction occurs in hemodialysis and kidney-transplanted patients and can be enhanced by immunosuppressive therapy. Circulating endothelial cells (CEC), endothelial microparticles (EMP) and sVCAM-1 provide information on endothelium activation and damage. We compared the impact of two immunosuppressive regimens (CsA/Aza vs. Tac/MMF) on the kinetics of CEC, EMP and sVCAM-1 levels in 52 patients, both before graft and 3, 6, 9 and 12 months after graft, in reference to 50 healthy controls. CEC, EMP and sVCAM-1 levels were significantly decreased 1 year after transplantation (M12) as compared to pretransplant values. At M12, CEC and sVCAM-1 levels were significantly higher than those of controls whereas EMP reached normal values. Nine months postgraft, lower CEC and normalized EMP levels were found in patients receiving cyclosporine microemulsion/ azathioprine (CsA/Aza) when compared to patients treated with tacrolimus/ mycophenolate mofetil (Tac/MMF). Multivariate analysis evidenced positive correlations between CEC and history of cardiovascular diseases and between EMP and cytomegalovirus infection at M12. In conclusion, our combined analysis of endothelial injury markers confirms the favorable impact of renal transplantation on endothelium, and show that CEC levels discriminate treatment-associated endothelial toxicity. These results enlighten the potential of these noninvasive blood biomarkers in indexing vascular injury and optimize therapeutic options.

Manifestations of human cytomegalovirus infection: proposed mechanisms of acute and chronic disease

Infections with human cytomegalovirus (HCMV) are a major cause of morbidity and mortality in humans with acquired or developmental deficits in innate and adaptive immunity. In the normal immunocompetent host, symptoms rarely accompany acute infections, although prolonged virus shedding is frequent. Virus persistence is established in all infected individuals and appears to be maintained by both a chronic productive infections as well as latency with restricted viral gene expression. The contributions of the each of these mechanisms to the persistence of this virus in the individual is unknown but frequent virus shedding into the saliva and genitourinary tract likely accounts for the near universal incidence of infection in most populations in the world. The pathogenesis of disease associated with acute HCMV infection is most readily attributable to lytic virus replication and end organ damage either secondary to virus replication and cell death or from host immunological responses that target virus-infected cells. Antiviral agents limit the severity of disease associated with acute HCMV infections, suggesting a requirement for virus replication in clinical syndromes associated with acute infection. End organ disease secondary to unchecked virus replication can be observed in infants infected in utero, allograft recipients receiving potent immunosuppressive agents, and patients with HIV infections that exhibit a loss of adaptive immune function. In contrast, diseases associated with chronic or persistent infections appear in normal individuals and in the allografts of the transplant recipient. The manifestations of these infections appear related to chronic inflammation, but it is unclear if poorly controlled virus replication is necessary for the different phenotypic expressions of disease that are reported in these patients. Although the relationship between HCMV infection and chronic allograft rejection is well known, the mechanisms that account for the role of this virus in graft loss are not well understood. However, the capacity of this virus to persist in the midst of intense inflammation suggests that its persistence could serve as a trigger for the induction of host-vs-graft responses or alternatively host responses to HCMV could contribute to the inflammatory milieu characteristic of chronic allograft rejection.

CD146-based immunomagnetic enrichment followed by multiparameter flow cytometry: a new approach to counting circulating endothelial cells

BACKGROUND

Circulating endothelial cells (CECs) have emerged as non-invasive biomarkers of vascular dysfunction. The most widely used method for their detection is CD146-based immunomagnetic separation (IMS). Although this approach has provided consensus values in both normal and pathologic situations, it remains tedious and requires a trained operator.

OBJECTIVES

Our objective was to evaluate a new hybrid assay for CEC measurement using a combination of pre-enrichment of CD146+ circulating cells and multiparametric flow cytometry measurement (FCM).

PATIENTS AND METHODS

CECs were determined in peripheral blood from 20 healthy volunteers, 12 patients undergoing coronary angioplasty, and 30 renal transplant recipients, and blood spiked with cultured endothelial cells. CD146+ cells were isolated using CD146-coated magnetic nanoparticles and labeled using CD45-fluorescein isothiocyanate and CD146-PE or isotype control antibody and propidium iodide before FCM. The same samples were also processed using CD146-based immunomagnetic separation as the reference method.

RESULTS

The hybrid assay detected CECs, identified as CD45(dim)/CD146(bright)/propidium iodide(+), with high size-related scatter characteristics, and clearly discriminated these from CD45(bright)/CD146(dim) activated T lymphocytes. The method demonstrated both high recovery efficiency and good reproducibility. Both IMS and the hybrid assay similarly identified increased CEC levels in patients undergoing coronary angioplasty and renal transplantation, when compared to healthy controls. In patients, CEC values from these two methods were of the same order of magnitude and highly correlated. Bland-Altman analysis revealed poor statistical agreement between methods, flerrofluid-FCM providing higher values than IMS.

CONCLUSION

This new hybrid FCM assay constitutes an accurate alternative to visual counting of CECs following CD146-based IMS.

Entry route of HCMV into endothelial cells

Human cytomegalovirus (HCMV) is generally assumed to enter its target cells by direct fusion at the plasma membrane while sequestration and lysis of viral particles within endocytic vesicles has been suggested as an abortive entry pathway of fibroblast-adapted HCMV strains in endothelial cells. However, the finding that virions of a highly endotheliotropic strain are also found within endocytic vesicles at 10min after penetration together with the fact that the majority of these particles is translocated towards the nucleus indicates that endocytosis can be an effective entry route for HCMV in endothelial cells. HCMV-containing vesicles resemble endocytic vesicles reported for other herpesviruses with regard to size and structure suggesting a similar entry route for various herpesviruses in endocytically active cells.

The endothelium as a target for infections

The endothelial cells lining vascular and lymphatic vessels are targets of several infectious agents, including viruses and bacteria, that lead to dramatic changes in their functions. Understanding the pathophysiological mechanisms that cause the clinical manifestations of those infections has been advanced through the use of animal models and in vitro systems; however, there are also abundant studies that explore the consequences of endothelial infection in vitro without supporting evidence that endothelial cells are actual in vivo targets of infection in human diseases. This article defines criteria for considering an infection as truly endothelium-targeted and reviews the literature that offers insights into the pathogenesis of human endothelial-target infections.

Endothelial cells in peripheral blood of healthy subjects and patients with metastatic carcinomas

BACKGROUND

A lack of standardized assays and consensus of cell definition has lead to a wide variation in the reported range of circulating endothelial cells (CECs).

METHODS

An automated rare cell analysis system was used to enumerate nucleated, CD146+/CD105+/CD45- CECs in 4 mL of blood.

RESULTS

Recoveries of spiked HUVECs were linear over a range of 0-1,241 cells (R2>or=0.99) with recoveries of >or=70% at each spike level. Correlation coefficient values for interoperator variability and duplicate sample variation were (R2=0.99 and 0.90), respectively. Correlation of CEC counts between tubes 1-2 and 2-3 drawn from the same subject in sequence differed (R2=0.48 and 0.63, respectively). The normal CEC reference range established in 249 healthy donors was 1-20 CECs/mL blood. CEC counts were significantly higher in the 206 metastatic carcinoma patients (P<0.0001).

CONCLUSION

CECs can be accurately and reproducibly enumerated in blood and are elevated in metastatic carcinomas compared with healthy donors. Phlebotomy procedures can affect endothelial cell counts.

Circulating endothelial cells in cardiovascular disease

Quantification of circulating endothelial cells (CECs) in peripheral blood is developing as a novel and reproducible method of assessing endothelial damage/dysfunction. The CECs are thought to be mature cells that have detached from the intimal monolayer in response to endothelial injury and are a different cell population to endothelial progenitor cells (EPCs). The EPCs are nonleukocytes derived from the bone marrow that are believed to have proliferative potential and may be important in vascular regeneration. Currently accepted methods of CEC quantification include the use of immunomagnetic bead separation (with cell counting under fluorescence microscopy) and flow cytometry. Several recent studies have shown increased numbers of CECs in cardiovascular disease and its risk factors, such as unstable angina, acute myocardial infarction, stroke, diabetes mellitus, and critical limb ischemia, but no change in stable intermittent claudication, essential hypertension, or atrial fibrillation. Furthermore, CEC quantification at 48 h after acute myocardial infarction has been shown to be an accurate predictor of major adverse coronary events and death at both 1 month and 1 year. This article presents an overview of the pathophysiology of CECs in the setting of cardiovascular disease and a brief comparison with EPCs.

Positivity of cytomegalovirus antibodies predicts a better clinical and radiological outcome in multiple sclerosis patients

OBJECTIVES

To establish the relationship between the presence and titer of virus-specific serum- and cerebrospinal fluid (CSF)-antibodies in multiple sclerosis (MS) patients and disease severity measured with different quantitative magnetic resonance imaging (MRI) techniques.

METHODS

We investigated an association between clinical and MRI measures of disease activity and the presence and titer of IgG antibodies against seven common viruses (measles, rubella, herpes simplex virus type 1 and 2, varicella zoster virus, cytomegalovirus (CMV) and Epstein-Barr virus). One hundred and forty (90 female/50 male) patients with definite MS and 131 age and sex-matched controls participated in the study. Antibody positivity and titer were ascertained by the enzyme linked immunosorbent assay (ELISA) technique and clinical assessment was performed by evaluating the expanded disability status scale (EDSS) score and the lifetime relapse rate (LRR). T1- and T2-lesion loads (LL) and the brain parenchymal fraction (BPF) were calculated.

RESULTS

Multiple analyses showed that there was an association between antibody positivity against CMV and higher titer and better clinical and MRI outcomes. The cluster analyses indicated that patients positive for antibodies against CMV had significantly older age at onset (uncorr p = 0.001 and corr p = 0.009), lower LRR (uncorr p = 0.003 and corr p = 0.03) and higher BPF (uncorr p = 0.004 and pcorr p = 0.04). CMV-positive patients who had higher antibody titer showed lower T2-LL (uncorr p = 0.003 and corr p = 0.03) and higher BPF (uncorr p = 0.006 and corr p = 0.05).

DISCUSSION

Surprisingly, our results focused attention on the 'protective' role of a particular virus. CMV is probably capable of triggering some immunomodulating/immune evasion mechanisms which may decrease immune reactivity in MS patients. Further studies are needed to confirm and elucidate our study results on a larger sample of MS patients and in animal model studies.

Circulating endothelial cells: a novel marker of endothelial damage

Circulating endothelial cells (CECs) were first described over 30 years ago in smears of peripheral blood. Since then, more sophisticated techniques for CEC isolation have become available. In particular, immunomagnetic isolation and fluorescence-activated cell sorting (FACS) have been employed with success. We provide a short historical perspective and a comprehensive review on the subject. We review isolation and enumeration of CECs with an emphasis on CD146-driven immunomagnetic isolation and FACS. We describe, in great detail, advantages and pitfalls of both approaches and compare their specificity. Moreover, we provide a comprehensive list of clinical studies in this field and describe the possible clinical use of CECs. We also describe the phenotype of these cells and list typical surface markers. In addition, we review the phenotype of CECs and discuss mechanisms of detachment. We speculate about potential interactions between CECs and other cell subsets. We also describe other serum markers of endothelial damage and compare CECs with these markers. Finally, we highlight differences between circulating endothelial cells and endothelial progenitor cells. In summary, CECs must now be regarded as a sensitive and specific marker of endothelial damage. We emphasize that use of CECs in a clinical setting is on the horizon and pathogenetic clues may also be obtained.

Circulating Endothelial Cell Levels Correlate with Proinflammatory Cytokine Increase in the Acute Phase of Thermal Injury

Circulating endothelial cells (CECs) are increased in sickle cell disease, myocardial infarction, and acute lung injury. The purpose of this study was to determine whether CECs are a prognosticating marker for the development of pneumonia in burn patients with/without inhalation injury in addition to their relationship to proinflammatory cytokines. There were 24 patients: 6 with inhalation injury, 5 with burn only,and 13 with burn plus inhalation injury. CECs were measured by anchored cytometry (Clarient ChromaVision, San Juan Capistrano, CA). In addition, plasma levels of tumor necrosis factor-alpha, interferon-gamma, and interleukins (IL)-10, IL-6, IL-4, and IL-2 were compared with CEC levels. Patients with inhalation injury had a significant (P < .001) paucity of CECs compared with the thermally injured with inhalation. There was a statistically significant increase in inteferon-gamma, tumor necrosis factor-alpha, and IL-6, IL-4, and IL-2 compared with control patients (P < .01), with a concomitant increase in the number of CECs. The numbers of CEC levels did not prognosticate which patients would develop pneumonia. Burn patients with/without inhalation injury had concurrent increase in CECs and proinflammatory cytokines during the acute phase of injury.

Human cytomegalovirus UL130 protein promotes endothelial cell infection through a producer cell modification of the virion

Human cytomegalovirus (HCMV) growth in endothelial cells (EC) requires the expression of the UL131A-128 locus proteins. In this study, the UL130 protein (pUL130), the product of the largest gene of the locus, is shown to be a luminal glycoprotein that is inefficiently secreted from infected cells but is incorporated into the virion envelope as a Golgi-matured form. To investigate the mechanism of the UL130-mediated promotion of viral growth in EC, we performed a complementation analysis of a UL130 mutant strain. To provide UL130 in trans to viral infections, we constructed human embryonic lung fibroblast (HELF) and human umbilical vein endothelial cell (HUVEC) derivative cell lines that express UL130 via a retroviral vector. When the UL130-negative virus was grown in UL130-complementing HELF, the infectivity of progeny virions for HUVEC was restored to the wild-type level. In contrast, the infectivity of the UL130-negative virus for UL130-complementing HUVEC was low and similar to that of the same virus infecting control noncomplementing HUVEC. The UL130-negative virus, regardless of whether or not it had been complemented in the prior cycle, could form plaques only on UL130-complementing HUVEC, not control HUVEC. Because (i) both wild-type and UL130-transcomplemented virions maintained their infectivity for HUVEC after purification, (ii) UL130 failed to complement in trans the UL130-negative virus when it was synthesized in a cell separate from the one that produced the virions, and (iii) pUL130 is a virion protein, models are favored in which pUL130 acquisition in the producer cell renders HCMV virions competent for a subsequent infection of EC.

Diagnosis of human cytomegalovirus infections in the immunocompromised host

BACKGROUND

In the last decade several major advances have been made in the rapid diagnosis of human cytomegalovirus (HCMV) infections and disease in immunocompromised patients both at the immunological and molecular level.

OBJECTIVES

The objective was to review in some detail the new diagnostic tools allowing determination and quantitation of HCMV infection in blood of transplanted and AIDS patients.

STUDY DESIGN

The determination and quantitation as well as the clinical significance of antigenemia, viremia, HCMV-infected circulating endothelial cells (CEC) and DNAemia will be discussed in view of the therapeutic management of HCMV disease. Levels of viremia represent the number of p72-positive cultured fibroblasts inoculated with 2 x 10(5)PBL, while levels of antigenemia represent number of pp65-positive PBL/2 x 10(5) PBL examined. The number of CEC is determined simultaneously and in parallel with antigenemia. DNAemia, both qualitative and quantitative, can be determined by polymerase chain reaction (PCR) per 1 x 10(5)PBL. The clinical utility of determining either immediate-early or late mRNA is still debated.

RESULTS

In solid organ transplant recipients mean levels of viremia of 100 and of antigenemia of 400 correlate with onset of clinical symptoms. The time between first HCMV positivity and the onset of symptoms (>/= 10 days), together with the observation that most patients with reactivated infection clear virus without treatment, allowed the establishment of an antigenemia cut-off of 100 for the initiation of treatment. On the other hand, seronegative recipients of solid organs from seropositive donors must be treated preemptively, i.e. at first appearance of HCMV positivity in blood. Due to the risk of early appearance of HCMV pneumonia, the same preemptive approach must be used in bone-marrow transplant recipients. In acquired immunodeficiency syndrome (AIDS) patients with HCMV infection/disease, general criteria for initiation of treatment are more difficult to establish and treatment must be maintained. CEC are detected only in untreated disseminated HCMV infections with organ involvement. Qualitative DNA determination is useful only in special cases, such as in aqueous or vitreous humor of AIDS patients with HCMV retinitis. Quantitative DNA levels obtained by PCR are much more helpful for diagnosing HCMV disease and establishing initiation of treatment.

CONCLUSIONS

New diagnostic procedures currently ensure fine monitoring of HCMV infections/diseases and evaluation of the effect of specific antiviral treatment in the immunocompromised host.

Pathogenesis of human cytomegalovirus infection and cellular targets

In acquired immunodeficiency syndrome patients with human cytomegalovirus (HCMV), disseminated infection, and end-organ disease, autopsy findings show a generalized HCMV infection of endothelial cells. On the other hand, immunocompromised transplanted patients show presence of virus and virus products in peripheral blood leukocytes (PBL), when affected by a disseminated HCMV infection. All diagnostic assays are based on the detection of virus and viral components in PBL or whole blood, including polymorphonuclear leukocytes and monocytes. The interplay between endothelial cells and leukocytes represents the pathogenetic basis for all clinical syndromes originating during disseminated HCMV infections and is the trigger for the transmission of HCMV from mother to fetus during primary infections of pregnant women. The two biologic properties of endothelial cell tropism and leukocyte (polymorphonuclear- and monocyte-) tropism are shared by all recent clinical HCMV isolates, whereas they are missing in laboratory-adapted strains. The potential role of HCMV in the pathogenesis of atherosclerosis both in the immunocompetent (after angioplasty) and the heart transplant patient is receiving support from seroepidemiologic findings, in vivo animal models, in vitro data, and also some clinical observations. The interaction of endothelial cells and leukocytes with subsequent spreading of infection to smooth muscle cells may be a major pathogenetic mechanism at the basis of this important vascular disease.

Circulating endothelial cells: realities and promises in vascular disorders

Endothelial contribution to human vascular disorders is difficult to investigate, owing to the paucity of non-invasive methods and of specific endothelial markers . Circulating endothelial cells (CECs) might be used asa surrogate non-invasive marker for the study of vascular alterations. To address this problem, we produced an antibody against the endothelial molecule CD126 (S-Endol) and developed, in the nineties, an original and sensitive immunomagnetic separation assay. Using this approach, we demonstrated elevated number of CECs in clinical diseases linked with vascular injury like heart catheterization, sickle cell anemia,bacterial infection, thrombotic thrombocytopenic purpura or acute coronary syndromes. CECs correspond to very rare cells present in blood since levels in the range of 3 cells/ml are detectable in these pathologies. Several clinical interest of CECs will be discussed including their relevance as marker of disease activity, severity or treatment efficacy, or their use in diagnostic tests. The origin of endothelial cells in peripheral blood is difficult to establish. They could correspond to endothelial cells dislodged from the vessels in response to injury. It was subsequently shown that a subset of CECs comprised a population of bone marrow-derived endothelial progenitors that participate in angiogenesis. Identification of the origin and characteristics of CECs provides fascinating insights into endothelial cell pathophysiology. Moreover, CECs constitute original and promising tools for diagnosis, prognosis and therapy of vascular disorders.

Circulating endothelial cells are elevated in patients with type 2 diabetes mellitus independently of HbA(1)c

AIMS/HYPOTHESIS

Patients with diabetes mellitus are well known to be at high risk for vascular disease. Circulating endothelial cells (CECs) have been reported to be an ex vivo indicator of vascular injury. We investigated the presence of CECs in the peripheral blood of 25 patients with diabetes mellitus and in nine non-diabetic control donors.

METHODS

Endothelial cells were isolated from peripheral blood with anti-CD-146-coated immunomagnetic Dynabeads, and were stained with acridine orange dye and counted by fluorescence microscopy. The cells were also stained for von Willebrand factor and Ulex europaeus lectin 1.

RESULTS

Patients with diabetes mellitus had an elevated number of CECs (mean 69+/-30 cells/ml, range 35-126) compared with healthy controls (mean 10+/-5 cells/ml, range 3-18) (p<0.001). The increase in CECs did not correlate with the levels of HbA(1)c. Circulating endothelial cell numbers were elevated regardless of glucose levels, suggesting that, even with control of glucose levels, there is increased endothelial cell sloughing.

CONCLUSIONS

Our study suggests that the higher number of CECs in patients with type 2 diabetes may reflect ongoing vascular injury that is not directly dependent on glucose control.

Detached endothelial cells and microparticles as sources of tissue factor activity

INTRODUCTION

Cytokine activation of endothelial cell monolayers is associated with cell detachment, microparticle shedding from plasma membranes, and phosphatidylserine appearance in the plasma membrane outer leaflets. While tissue factor expression on activated endothelial cells and microparticles is well documented, the contribution of detached endothelial cells to tissue factor activity is less clear. We studied tissue factor expression and the role of tissue factor pathway inhibitor on adherent and detached endothelial cells and on microparticles following endothelial cell activation with TNF-alpha.

MATERIALS AND METHODS

Detached endothelial cells and microparticles were obtained from cultures of human umbilical vein endothelial cells by differential centrifugation of cell culture supernatant. For microparticle capture, an antibody directed against CD146 was used. Functional tissue factor activity was measured by chromogenic assay and tissue factor antigen by ELISA. Endothelial cell and microparticle morphology was examined by light and transmission electron microscopy.

RESULTS

After cell activation for 22 h, functional tissue factor activity was distributed as follows: 60%, adherent endothelial cells; 35%, detached cells; and 5%, microparticles. Tissue factor protein followed a similar distribution. Cell detachment was 47%. Electron microscopy demonstrated shedding of microparticles with a diameter of 0.1-0.6 mum. Cy3-annexin V revealed increased phosphatidylserine on activated adherent endothelial cells and microparticles. Pre-incubation of adherent and detached endothelial cells and microparticles with anti-tissue factor antibody blocked factor Xa production. Pre-incubation with anti-tissue factor pathway inhibitor antibody increased tissue factor activity of adherent endothelial cells 2.8-fold, detached cells 1.4-fold, and microparticles 45-fold.

CONCLUSIONS

Detached endothelial cells as well as microparticles from activated endothelial cell monolayers express tissue factor activity, and this activity on microparticles is markedly inhibited by microparticle-associated tissue factor pathway inhibitor.

Circulating endothelial (progenitor) cells reflect the state of the endothelium: vascular injury, repair and neovascularization

An increase in the number of circulating endothelial cells (CEC) and of bone marrow-derived endothelial progenitor cells (EPC) in the peripheral blood is associated with vascular injury, repair and neovascularization. The phenotype and number of CEC may serve as diagnostic or prognostic parameters of vascular injury and tumour growth. An increase in the number of EPC may reflect repair of ischaemic vascular injury, a finding which has resulted in the initiation of clinical cardiovascular pilot trials using cell therapy. However, there is no consensus on the exact phenotype of the EPC and haematopoietic stem cells (HSC) and therefore the best candidate cell for transplant has not been established. Although the use of peripheral blood stem cells following mobilization, or of ex vivo-expanded cells, may improve EPC-mediated vascular graft endothelialization or tissue vascularization, sustained EPC-induced neovascularization still needs to be proven. Flow cytometric characterization, in combination with functional assays, will further elucidate the phenotype of the CEC and EPC, thereby providing reliable detection to appreciate their role in vascular diseases and cancer and to evaluate and, if possible, improve their therapeutic potential.

Murine cytomegalovirus (MCMV) spreads to and replicates in the retina after endotoxin-induced disruption of the blood-retinal barrier of immunosuppressed BALB/c mice

The goal of this study was to determine whether disruption of the blood-retinal barrier (BRB) facilitates spread of MCMV to the retina in immunosuppressed (IS) BALB/c mice. IS mice were inoculated intravenously (i.v.) with murine cytomegalovirus (MCMV) or with macrophages infected with MCMV for 4 days in vitro. The BRB was disrupted by injection of sodium iodate (i.v.) or lipopolysaccharide (LPS, i.v. or anterior chamber). Frozen sections of ocular tissue were examined for MCMV antigens. The results showed that MCMV-infected cells were observed only in the choroid and ciliary body in IS mice with an intact BRB. After LPS injection, a few positive cells were observed in the retina of IS mice after i.v. injection of MCMV. In lipopolysaccharide (LPS)-treated IS mice, a few PKH-26-positive macrophages or MCMV-positive cells were observed in the retina at 1 or 2 days after injection of macrophages. No PKH-26-positive cells or virus-infected cells were noted in the retina of phosphate-buffered saline (PBS)-treated mice. Ten days after injection of virus-infected macrophages, MCMV-infected cells were observed in choroid and ciliary body of both LPS- and PBS-treated mice, but they were observed in the retina only in LPS-treated mice. The results support the idea that disruption of the BRB allows MCMV to spread to the retina of IS mice and that monocytes/macrophages disseminate MCMV to the retina in mice with a disrupted BRB. By extrapolation, damage to the BRB in immunosuppressed patients may facilitate spread of CMV-infected monocytes/macrophages to the retina.

Counting the cost: markers of endothelial damage in hematopoietic stem cell transplantation

During hematopoietic stem cell transplantation (HSCT), endothelial damage is the pathological hallmark of veno-occlusive disease of the liver, thrombotic microangiopathy, capillary leak syndrome and graft-versus-host disease. Events prior to conditioning, the conditioning regimen itself as well as calcineurin inhibitors may all induce endothelial damage. Unfortunately, the relative importance of these factors and their interactions, the time frame of endothelial damage and individual susceptibility remain unknown. Moreover, it is conceivable that conditioning regimens differ markedly in their propensity to initiate endothelial damage. Monitoring endothelial damage and response to treatment is hampered by the current lack of suitable markers. In this regard, an ideal marker should be sensitive and specific and indicate the development of an endothelial disorder prior to the onset of symptoms and organ dysfunction. Soluble markers, such as thrombomodulin, are easily amenable with immunoassays; yet, the interpretation of their levels is hampered by the influence of comorbidity. Evaluation of circulating endothelial cells in HSCT demonstrated a marked and dose-dependent increase in cell numbers after conditioning. The challenge ahead is to establish and evaluate novel markers of endothelial damage to permit early detection of disease, monitor response to treatment and evaluate different conditioning regimens.