Cytomegalovirus induced up-regulation of LFA-3 (CD58) and ICAM-1 (CD54) is a direct viral effect that is not prevented by ganciclovir or foscarnet treatment

CD58 Immunobiology at a Glance

The glycoprotein CD58, also known as lymphocyte-function antigen 3 (LFA-3), is a costimulatory receptor distributed on a broad range of human tissue cells. Its natural ligand CD2 is primarily expressed on the surface of T/NK cells. The CD2-CD58 interaction is an important component of the immunological synapse (IS) that induces activation and proliferation of T/NK cells and triggers a series of intracellular signaling in T/NK cells and target cells, respectively, in addition to promoting cell adhesion and recognition. Furthermore, a soluble form of CD58 (sCD58) is also present in cellular supernatant in vitro and in local tissues in vivo. The sCD58 is involved in T/NK cell-mediated immune responses as an immunosuppressive factor by affecting CD2-CD58 interaction. Altered accumulation of sCD58 may lead to immunosuppression of T/NK cells in the tumor microenvironment, allowing sCD58 as a novel immunotherapeutic target. Recently, the crucial roles of costimulatory molecule CD58 in immunomodulation seem to be reattracting the interests of investigators. In particular, the CD2-CD58 interaction is involved in the regulation of antiviral responses, inflammatory responses in autoimmune diseases, immune rejection of transplantation, and immune evasion of tumor cells. In this review, we provide a comprehensive summary of CD58 immunobiology.

Control of viral infections by epigenetic-targeted therapy

Epigenetics is defined as the science that studies the modifications of gene expression that are not owed to mutations or changes in the genetic sequence. Recently, strong evidences are pinpointing toward a solid interplay between such epigenetic alterations and the outcome of human cytomegalovirus (HCMV) infection. Guided by the previous possibly promising experimental trials of human immunodeficiency virus (HIV) epigenetic reprogramming, the latter is paving the road toward two major approaches to control viral gene expression or latency. Reactivating HCMV from the latent phase ("shock and kill" paradigm) or alternatively repressing the virus lytic and reactivation phases ("block and lock" paradigm) by epigenetic-targeted therapy represent encouraging options to overcome latency and viral shedding or otherwise replication and infectivity, which could lead eventually to control the infection and its complications. Not limited to HIV and HCMV, this concept is similarly studied in the context of hepatitis B and C virus, herpes simplex virus, and Epstein-Barr virus. Therefore, epigenetic manipulations stand as a pioneering research area in modern biology and could constitute a curative methodology by potentially consenting the development of broad-spectrum antivirals to control viral infections in vivo.

Absence of interaction between porcine endogenous retrovirus and porcine cytomegalovirus in pig-to-baboon renal xenotransplantation in vivo

BACKGROUND

Studies of xenotransplantation from swine have identified porcine viruses as potential barriers to clinical trials. The biology of these viruses has not been extensively investigated in the in vivo xeno-environment. Enhancement of viral gene expression by viral and cellular factors acting in trans has been demonstrated for certain viruses, including bidirectional interactions between human herpesviruses and endogenous (HERV) and exogenous (HIV) retroviruses. Both porcine cytomegalovirus (PCMV) and porcine endogenous retrovirus (PERV) infections have been identified in xenografts from swine. PERV receptors exist on human cells with productive infection in vitro in permissive human target cell lines. PCMV is largely species-specific with infection restricted to the xenograft in pig-to-baboon transplants. It is unknown whether coinfection by PCMV affects the replication of PERV within xenograft tissues which might have implications for the risk of retroviral infection in the human host.

METHODS

A series of 11 functioning, life-supporting pig-to-baboon kidney xenografts from PERV-positive miniature swine were studied with and without PCMV co-infection. Frozen biopsy samples were analyzed using quantitative, real-time PCR with internal controls.

RESULTS

PERV replication was not altered in the presence of PCMV coinfection (P = .70). The absence of variation with coinfection was confirmed when PERV quantitation was expressed relative to simultaneous cellular GAPDH levels with or without PCMV coinfection (P = .59).

CONCLUSIONS

PCMV coinfection does not alter the replication of PERV in life-supporting renal xenotransplantation in vivo in baboons.

Epigenetically repressing human cytomegalovirus lytic infection and reactivation from latency in THP-1 model by targeting H3K9 and H3K27 histone demethylases

Human Cytomegalovirus (hCMV) infects a broad range of the population and establishes life-long latency in the infected individuals. Periodically the latently infected virus can reactivate and becomes a significant cause of morbidity and mortality in immunocompromised individuals. In latent infection, the viral genome is suppressed in a heterochromatic state and viral gene transcription is silenced. Upon reactivation, the repressive chromatin is remodeled to an active form, allowing viral lytic gene transcription, initiated by the expression of viral Immediate Early (IE) genes. During this process, a number of histone modification enzymes, including histone demethylases (HDMs), play important roles in driving IE expression, but the mechanisms involved are not fully understood. To get a better understanding of these mechanisms, we focused on two HDMs, KDM4 and KDM6, which reverse the repressive histone H3-lysine 9 and lysine 27 methylation, respectively. Our studies show that in lytic infection, both demethylases are important in the activation of viral IE gene expression. Simultaneous disruption of both via genetic or chemical methods leads to severely impaired viral IE gene expression and viral replication. Additionally, in an experimental latency-reactivation model in THP-1 cells, the KDM6 family member JMJD3 is induced upon viral reactivation and its knockdown resulted in reduced IE gene transcription. These findings suggest pharmacological inhibition of these HDMs may potentially block hCMV lytic infection and reactivation, and control the viral infection associated diseases, which are of significant unmet medical needs.

CD2-CD58 interactions are pivotal for the activation and function of adaptive natural killer cells in human cytomegalovirus infection

The existence and expansion of adaptive NK-cell subsets have been linked to HCMV infection. Phenotypically, a majority of adaptive NK cells expresses the activating receptor NKG2C and CD57. Some of the molecular factors driving the expansion of NKG2C⁺ CD57⁺ NK cells in HCMV infection have been identified. The direct interaction of adaptive NK cells with HCMV-infected cells, preceding the expansion, however, remains less studied. Recently, adaptive NK cells were reported to express higher levels of the co-activating receptor CD2. We explored whether CD2 was directly involved in the response of adaptive NK cells to HCMV. In a co-culture system of human PBMCs and productively infected fibroblasts, we observed an upregulation of CD69, CD25, and HLA-DR on all NK cells. However, only in adaptive NK cells was this increase largely blocked by antibodies against CD2 and CD58. Functionally, this blockade also resulted in diminished production of IFN-γ and TNF-α by adaptive human NK cells in response to HCMV-infected cells. Our results demonstrate that binding of CD2 to upregulated CD58 on infected cells is a critical event for antibody-mediated activation and subsequent effector functions of adaptive NKG2C⁺ CD57⁺ NK cells during the antiviral response.

A new Western blot assay for the detection of porcine cytomegalovirus (PCMV)

Porcine cytomegalovirus (PCMV) may be harmful for human recipients if xenotransplantation using pig cell, tissue or organ will be performed transmitting the virus from donor pigs to human recipients. PCMV is widespread in pigs and closely related to human pathogenic herpesviruses, however there are no data concerning infection of humans. In contrast, recently it had been shown that transplantation of organs from pigs infected with PCMV into non-human primate recipients resulted in a significant reduction of the survival time compared with the transplantation of organs from uninfected pigs. To prevent transmission of PCMV in future pig to human xenotransplantations, sensitive and specific detection methods should be used. Here a new Western blot assay using recombinant proteins corresponding to two domains of the glycoprotein gB of PCMV is described. With this assay, the presence of PCMV-specific antibodies in different pig breeds was analysed. Antibodies were detected in a high percentage of animals, in one breed up to 85%.

A CD2 high-expressing stress-resistant human plasmacytoid dendritic-cell subset

Human plasmacytoid dendritic cells (pDCs) were considered to be a phenotypically and functionally homogeneous cell population; however, recent analyses indicate potential heterogeneity. This is of major interest, given their importance in the induction of anti-viral responses and their role in creating immunologically permissive environments for human malignancies. For this reason, we investigated the possible presence of human pDC subsets in blood and bone marrow, using unbiased cell phenotype clustering and functional studies. This defined two major functionally distinct human pDC subsets, distinguished by differential expression of CD2. The CD2(hi) and CD2(lo) pDCs represent discontinuous subsets, each with hallmark pDC functionality, including interferon-alpha production. The rarer CD2(hi) pDC subset demonstrated a significant survival advantage over CD2(lo) pDC during stress and upon exposure to glucocorticoids (GCs), which was associated with higher expression of the anti-apoptotic molecule BCL2. The differential sensitivity of these two human pDC subsets to GCs is demonstrated in vivo by a relative increase in CD2(hi) pDC in multiple myeloma patients treated with GCs. Hence, the selective apoptosis of CD2(lo) pDC during stress represents a novel mechanism for the control of innate responses.

Porcine cytomegalovirus infection is associated with early rejection of kidney grafts in a pig to baboon xenotransplantation model

BACKGROUND

Recent survivals of our pig-to-baboon kidney xenotransplants have been markedly shorter than the graft survivals we previously reported. The discovery of high levels of porcine cytomegalovirus (pCMV) in one of the rejected xenografts led us to evaluate whether this reduction in graft survival might be because of the inadvertent introduction of pCMV into our α1,3-galactosyltransferase gene knockout swine herd.

METHODS

Archived frozen sections of xeno-kidney grafts over the past 10 years were analyzed for the presence of pCMV, using real-time polymerase chain reaction. Three prospective pig-to-baboon renal transplants using kidneys from swine delivered by cesarean section (C-section) and raised in isolation were likewise analyzed.

RESULTS

Kidney grafts, from which 8 of the 18 archived samples were derived were found to be pCMV-negative, showed a mean graft survival of 48.3 days and were from transplants performed before 2008. None showed signs of disseminated intravascular coagulopathy and were lost because of proteinuria or infectious complications. In contrast, 10 of the archived samples were pCMV positive, were from kidney transplants with a mean graft survival of 14.1 days, had been performed after 2008, and demonstrated early vascular changes and decreased platelet counts. Three prospective xenografts from swine delivered by C-section were pCMV negative and survived an average of 53.0 days.

CONCLUSIONS

Decreased survivals of α1,3-galactosyltransferase gene knockout renal xenografts in this laboratory correlate temporally with latent pCMV in the donor animals and pCMV in the rejected xeno-kidneys. Transmission of pCMV to swine offspring may be avoided by C-section delivery and scrupulous isolation of donor animals.

Managing complications following lung transplantation

Lung transplantation has become a proven therapeutic option for patients with end-stage lung disease, extending life and providing improved quality of life to those who otherwise would continue to be breathless and oxygen-dependent. Over the past 20 years, considerable experience has been gained in understanding the multitude of medical and surgical issues that impact upon patient survival. Today, clinicians have an armamentarium of tools to manage diverse problems such as primary graft dysfunction, acute and chronic allograft rejection, airway anastomotic issues, infectious complications, renal dysfunction, diabetes and osteoporosis, hematological and gastrointestinal problems, malignancy, and other unique issues that confront immunosuppressed solid organ transplant recipients.

Susceptibility of human pancreatic β cells for cytomegalovirus infection and the effects on cellular immunogenicity

OBJECTIVES

Human cytomegalovirus (HCMV) infection has been suggested to be a causal factor in the development of type 1 diabetes, posttransplantation diabetes, and the failure of islet allografts. This effect of CMV has been interpreted as an indirect effect on the immune system rather than direct infection-induced cell death. In the present study, we investigated (i) the susceptibility of β cells to HCMV infection, (ii) regulation of immune cell-activating ligands, (iii) release of proinflammatory cytokines, and (iv) the effects on peripheral blood mononuclear cell (PBMC) activation.

METHODS

CM insulinoma cells and primary β cells were HCMV-infected in vitro using a laboratory and a clinical HCMV strain. The susceptibility to infection was measured by the expression of viral genes and proteins. Furthermore, expression levels of Major Histocompatibility Complex I, Intracellular Adhesion Molecule-1, and Lymphocyte Function Associated Antigen-3 and the release of proinflammatory cytokines were determined. In addition, PBMC activation to HCMV-infected β cells was determined.

RESULTS

β Cells were susceptible to HCMV infection. Moreover, the infection increased the cellular immunogenicity, as demonstrated by an increased MHC I and ICAM-1 expression and an increased proinflammatory cytokine release. Human cytomegalovirus-infected CM cells potently activated PBMCs. The infection-induced effects were dependent on both viral "sensing" and viral replication.

CONCLUSIONS

In vivo β-cell HCMV infection and infection-enhanced cellular immunogenicity may have important consequences for native or transplanted β-cell survival.

Human cytomegalovirus IE1 protein elicits a type II interferon-like host cell response that depends on activated STAT1 but not interferon-γ

Human cytomegalovirus (hCMV) is a highly prevalent pathogen that, upon primary infection, establishes life-long persistence in all infected individuals. Acute hCMV infections cause a variety of diseases in humans with developmental or acquired immune deficits. In addition, persistent hCMV infection may contribute to various chronic disease conditions even in immunologically normal people. The pathogenesis of hCMV disease has been frequently linked to inflammatory host immune responses triggered by virus-infected cells. Moreover, hCMV infection activates numerous host genes many of which encode pro-inflammatory proteins. However, little is known about the relative contributions of individual viral gene products to these changes in cellular transcription. We systematically analyzed the effects of the hCMV 72-kDa immediate-early 1 (IE1) protein, a major transcriptional activator and antagonist of type I interferon (IFN) signaling, on the human transcriptome. Following expression under conditions closely mimicking the situation during productive infection, IE1 elicits a global type II IFN-like host cell response. This response is dominated by the selective up-regulation of immune stimulatory genes normally controlled by IFN-γ and includes the synthesis and secretion of pro-inflammatory chemokines. IE1-mediated induction of IFN-stimulated genes strictly depends on tyrosine-phosphorylated signal transducer and activator of transcription 1 (STAT1) and correlates with the nuclear accumulation and sequence-specific binding of STAT1 to IFN-γ-responsive promoters. However, neither synthesis nor secretion of IFN-γ or other IFNs seems to be required for the IE1-dependent effects on cellular gene expression. Our results demonstrate that a single hCMV protein can trigger a pro-inflammatory host transcriptional response via an unexpected STAT1-dependent but IFN-independent mechanism and identify IE1 as a candidate determinant of hCMV pathogenicity.

Effects of acute cytomegalovirus infection on rat islet allograft survival

Transplantation of pancreatic islets is a promising therapy for the treatment of type 1 diabetes mellitus. However, long-term islet graft survival rates are still unsatisfactory low. In this study we investigated the role of cytomegalovirus (CMV) in islet allograft failure. STZ-diabetic rats received an allogenic islet graft in combination with either an acute CMV infection or control infection. A third group received ganciclovir treatment in addition to the CMV infection. Graft function was assessed by measuring basal blood glucose levels. After sacrifice, the islet grafts were retrieved for analysis of infection and leukocyte infiltration. CMV-infected recipients demonstrated accelerated islet graft failure compared to noninfected controls. CMV infection of the graft was only observed prior to complete graft failure. Quantification of the leukocyte infiltration demonstrated increased CD8(+) T-cell and NK cell infiltration in the CMV-infected grafts compared to the controls. This suggests that CMV infection accelerates immune-mediated graft destruction. Antiviral ganciclovir treatment did not prevent accelerated graft failure, despite effectively decreasing the grade of infection. Our data confirm the recently published CITR data, which state that CMV is an independent risk factor for failure of islet grafts. Also, our data demonstrate that new approaches for preventing virus-induced islet allograft failure may be required.

Pneumonitis in human cytomegalovirus infection

Human cytomegalovirus (HCMV) is a beta herpes virus with a double stranded DNA genome of 240kbp. The virus is prevalent and establishes a latent infection in most adults. HCMV is an opportunistic pathogen for patients with impaired cellular immunity. HCMV pneumonia is a common presentation of HCMV disease in immunocompromised patients. The incidence of HCMV pneumonitis can be as high as 90% in lung transplant recipients. This paper takes a fresh look at the challenging perspectives of molecular, immunologic, cellular, diagnostic, clinical, and therapeutic characteristics of HCMV infection as future targets for development of antiviral strategies.

Rat pancreatic beta cells and cytomegalovirus infection

OBJECTIVES

Cytomegalovirus (CMV) infection has been suggested to accelerate beta-cell destruction and thereby to contribute to new-onset diabetes and failure of islet allografts in both humans and rodents. Surprisingly, direct CMV infection of beta cells has received only minor attention. Therefore, we investigated the susceptibility of rat beta cells for rat CMV (RCMV) infection and the direct effects on the regulation of immune cell-activating ligands.

METHODS

Primary rat beta cells, the rat beta-cell line Rin-m5F, and fibroblasts were RCMV-infected in vitro. The viral gene and protein expression levels were determined as a measure for RCMV susceptibility. Gene expression levels of intracellular adhesion molecule 1, lymphocyte function associated antigen 3, rat major histocompatibility complex region A, rat major histocompatibility complex region E, toll like receptor 2, and clustered domain 14 were determined as a measure for cellular immunogenicity.

RESULTS

We demonstrate that beta cells are susceptible for RCMV infection but allow only low levels of viral gene expression. In contrast, infected fibroblasts demonstrated productive viral infection and formation of viral progeny. After RCMV infection, beta-cell immunogenicity was markedly increased, as demonstrated by the increased cellular expression of immune cell-activating ligands.

CONCLUSIONS

Direct beta-cell infection by RCMV and subsequent low-grade viral gene expression may lead to increased immunogenicity of native or transplanted beta cells in vivo. An infection-induced enhanced beta-cell recognizability may have important consequences for beta-cell survival and the development of diabetes or rejection of islet grafts.

A lower incidence of cytomegalovirus infection in de novo heart transplant recipients randomized to everolimus

BACKGROUND

Cytomegalovirus (CMV) infection in recipients of cardiac transplants is associated with higher rates of morbidity. A recent phase III trial showed highly significantly (P<0.001) lower CMV rates with the proliferation signal inhibitor everolimus compared to azathioprine (AZA). To better define this association, data on CMV risk factors were collected retrospectively and analyzed.

METHODS

Data on CMV risk factors from a multicenter phase III trial on de novo heart transplant recipients (n=634) receiving a triple immunosuppressive regimen randomized to everolimus 1.5 mg/day (group 1), everolimus 3 mg/day (group 2), or AZA (group 3) were merged with prospectively collected CMV-related outcome data and analyzed.

RESULTS

CMV-positive donors (D+) and CMV-negative recipients (R-) were evenly distributed across groups 1-3 at 36/209 (17.2%), 48/211 (22.7%), and 38/214 (17.8%), respectively. CMV prophylaxis had been given for a mean (SD) of 175 (127.8), 183 (137.1), and 177 (132.9) days, respectively. In the high-risk D+/R- subgroup with prophylaxis, the proportions of patients with CMV infection compared with group 3 (12/29 [41.4%]) were 3/25 (12.0%) in group 1 (P=0.031) and 6/36 (16.7%) in group 2 (P=0.049). In D+/R+ subgroups either with or without prophylaxis, the everolimus groups had less CMV disease (P<0.001). The incidence of CMV syndrome, organ involvement, and laboratory evidence was lower with everolimus use compared to AZA.

CONCLUSIONS

Everolimus is associated with lower rates of CMV infection, syndrome, or organ involvement, suggesting an additional advantage from the use of everolimus in cardiac transplant recipients.

Targeting the NF-kappaB pathway through pharmacological inhibition of IKK2 prevents human cytomegalovirus replication and virus-induced inflammatory response in infected endothelial cells

Endothelial cells are important reservoirs for human cytomegalovirus (HCMV) replication, dissemination and persistence. HCMV infection of endothelial cells has been associated with a proinflammatory response characterized by an increased expression of chemokines and adhesion molecules and modulation of angiogenesis. Many of the host proinflammatory genes augmented in HCMV-infected endothelial cells are regulated, at least in part, by the NF-kappaB pathway. HCMV is a potent activator of NF-kappaB through the IKK-IkappaB signaling axis. To explore whether inhibition of HCMV-induced NF-kappaB activation may interfere with the onset of virus-associated inflammatory response, we measured the effects of the specific IKK2 inhibitor AS602868 on the expression of a panel of proinflammatory genes in HUVEC cells infected with a clinical isolate. Treatment of infected HUVEC with AS602868 was shown to impair HCMV-induced NF-kappaB activity, IE gene expression, viral replication and to prevent HCMV-induced upregulation of ICAM-1, IL-8, RANTES, IP-10, I-TAC and COX-2 gene expression. Consistent with these results, HCMV-mediated upregulation of another NF-kappaB-dependent gene, the plasminogen inhibitor type-1, a regulatory factor of endothelial proliferation and angiogenesis, was abrogated by AS602868. These results suggest that inhibition of HCMV-induced IKK-NF-kappaB activation may be of interest to limit the virus-induced inflammatory response of infected endothelial cells.

A multiparametric flow cytometry method for detection of modifications of antigen expression in polymorphonuclear cells infected by human cytomegalovirus

Human cytomegalovirus (CMV) has been shown to alter adhesion molecule expression on permissive cells such as endothelial cells. The aim of the present study was to investigate expression of receptors for these molecules on CMV infected polymorphonuclear leukocytes (PMNLs). CMV-induced variations on cellular integrin expression were examined using an in vitro system to obtain infected PMNLs. A triparametric flow cytometry approach was developed, which allows combined detection, in a single experiment, of both viral intranuclear antigen in the selected PMNLs and cellular CD11/CD18 expression. Comparison of infected PMNLs with uninfected cells showed a decrease of up to 50% in the expression of CD11b, CD11c, and CD18. This study thus demonstrates that the presence of CMV in PMNLs, which characterizes active infection, modifies the expression of integrins and may thus affect cell-to-cell interactions and immune functions.

The Impact of Pretransplant Cytomegalovirus Infection on Acute Renal Allograft Rejection

BACKGROUND

The role of cytomegalovirus (CMV) infection in renal allograft rejection remains controversial; moreover, there are few studies on pretransplant infections. This study sought to investigate whether pretransplant CMV infections had negative effects on acute rejection episodes (ARE) and to evaluate the effect of preemptive treatment.

METHODS

This retrospective single-center study of 416 transplant recipients from October 1, 2000 to September 1, 2003 had CMV infections diagnosed by CMV antigenemia tests. The incidences of ARE were compared between CMV-infected and noninfected groups. Risk factors for ARE were analyzed. Based on preemptive treatment, pretransplant CMV-infected recipients were divided into ganciclovir-treated and nontreated groups and the incidence of ARE was compared between the two groups.

RESULTS

One hundred eighty four recipients had CMV infections pretransplant; the infection rate was 44.2%. Fifty five recipients had ARE among the pretransplant CMV-positive group, which was significantly higher than that in the noninfected group (29.9% vs 19.5%, P = .014). But the rejection subgroups and renal function recovery had no significant differences. While the presence of pretransplant infection was an independent predictor of ARE (RR = 1.807), severity showed no significant impact on ARE. Among 184 pretransplant CMV infection recipients, the incidences of ARE were 14.3% and 18.0% in ganciclovir-treated versus nontreated patients, respectively (P = .650).

CONCLUSIONS

Pretransplant CMV-positive recipients were at greater risk of ARE. Pretransplant CMV infection was an independent risk factor for ARE. Preemptive antiviral treatment did not show protective effects against ARE related to CMV infection-mediated immunological injuries.

Human cytomegalovirus downregulates complement receptors (CR3, CR4) and decreases phagocytosis by macrophages

Human cytomegalovirus (HCMV) infection is associated with an increased susceptibility to opportunistic infections. Although the subversion of adaptive immune responses has been extensively studied, the consequences of HCMV infection on natural immune responses are not well documented. A striking selective downmodulation of CD11b/CD18 (CR3) or CD11c/CD18 (CR4) was found upon HCMV infection, on two models, the monocytic THP-1 cell line and monocyte- derived macrophages. HCMV-infected macrophages have an altered adhesion/phagocytic capacity to Candida albicans, a pathogen responsible for some opportunistic infections in immunocompromised patients. These results suggest a new mechanism implicated in the augmentation of opportunistic infections in HCMV patients.

Human cytomegalovirus-induced upregulation of intercellular cell adhesion molecule-1 on villous syncytiotrophoblasts

Human cytomegalovirus (HCMV) is secreted apically from villous trophoblasts, thus congenital infection is not likely to occur by basal release across the basement membrane. As an alternative route, we hypothesize that an HCMV-infected villous syncytiotrophoblast (ST) upregulates intercellular adhesion molecule (ICAM)-1, causing blood monocytes to bind to the ST and induce apoptosis. Purified (>99.99%) populations of human villous trophoblasts were differentiated into an ST-like culture, infected with HCMV strain AD169, and assessed for ICAM-1 expression by immunofluorescence. Infection strongly upregulated ICAM-1 24 h after challenge. ICAM-1 was also stimulated by transfection with viral genes IE2-55, IE1-72, and IE2-86, but not by UV-inactivated virus. Infection with a green fluorescent protein recombinant virus allowed infection and ICAM-1 expression to be topographically located. We found that ICAM-1 was expressed on both infected and noninfected cells. Furthermore, antibody to tumor necrosis factor (TNF)alpha and, to a lesser extent, interleukin (IL)1 beta inhibited ICAM-1 upregulation on noninfected cells but not on infected cells. We conclude that HCMV IE proteins stimulate ICAM-1 expression on villous trophoblasts by paracrine release of TNF alpha and IL1 beta, as well as by a direct effect on infected cells.

Pulmonary involvement during cytomegalovirus infection in immunosuppressed patients

Although cytomegalovirus (CMV) pulmonary involvement after solid organ transplantation is infrequently seen nowadays, CMV pneumonitis is still a potential lethal complication. Introduction of the pp65 antigenemia assay enabled early and rapid diagnosis of CMV viremia in transplant patients prior to symptoms. Also, in asymptomatic patients with CMV viremia, a decreased pulmonary diffusion capacity could be demonstrated. In this review, we discuss clinical and subclinical pulmonary involvement of CMV infection in the immunocompromised host with an emphasis on transplant recipients. The clinical course, diagnosis, therapy, prophylaxis, and pathophysiology of CMV pneumonitis are discussed.

Viral chemokine receptors and chemokines in human cytomegalovirus trafficking and interaction with the immune system. CMV chemokine receptors

The ubiquitous, opportunistic pathogen human cytomegalovirus (CMV) encodes several proteins homologous to those of the host organism. Four different CMV genes encode chemokine receptor-like peptides. These genes, UL33, UL78, US27, and US28, are expressed at various stages of infection in vitro. Their functions remain largely unknown. To date, chemokine binding and signalling has only been demonstrated for the US28 gene product. Putative ligands for the other CMV-encoded chemokine receptors are discussed on basis of phylogenetic analysis. The potential roles of these receptors in virus trafficking, persistence, and immune evasion are summarized. Similarly, modulation of expression of the host chemokines IL-8, MCP-1a and RANTES in relation to viral dissemination and persistence is reviewed.

Upregulation of CD40 expression on endothelial cells infected with human cytomegalovirus

CD40 has been identified as an important molecule for a number of processes, such as immune responses, inflammation, and the activation of endothelia. We investigated CD40 in endothelial cells (EC) following infection with an endotheliotropic strain of human cytomegalovirus (HCMV). Between 8 and 72 h postinfection, we observed a significant increase in CD40 levels on the surface of infected EC, as measured by fluorescence-activated cell sorting analysis. As a consequence of CD40 upregulation, increased levels of E-selectin were found on infected EC after stimulation with CD154-expressing T cells. Enhanced expression of CD40 was specific for EC, since infection of fibroblasts did not result in the upregulation of CD40. The addition of neutralizing antibodies as well as UV inactivation of virus completely prevented the upregulation of CD40 on EC. Also, laboratory-adapted HCMV strain AD169 was not able to induce CD40 on EC. De novo protein synthesis was necessary for the increased surface expression. At early times (4 to 24 h) postinfection, this change was not accompanied by increased levels of CD40 protein or mRNA. At late times (48 to 96 h) postinfection, increased amounts of CD40 protein and mRNA were detected. Immunohistochemical analysis of infected tissues demonstrated elevated levels of CD40 on HCMV-infected EC in vivo. Thus, infection of EC by HCMV may result in the activation of endothelia and in the augmentation of inflammatory processes.

Cytomegalovirus seromismatching increases the risk of acute renal allograft rejection

BACKGROUND

There is an association between cytomegalovirus (CMV) infection or disease and acute allograft rejection in the setting of renal transplantation. There is, however, debate regarding the nature of this association, with evidence supporting both a "forward" relationship (CMV infection or disease precedes acute rejection) and a "backward" relationship (CMV infection or disease follows acute rejection). The objective of this study was to determine whether CMV matching had an independent effect on the risk of acute renal allograft rejection, which would support the view that CMV infection or disease is a risk factor for acute rejection.

METHODS

Retrospective single center study (using a prospectively maintained database) of 333 first cadaveric transplant recipients from January 1st 1991 to December 31st 1997. Primary end-point was incidence of acute rejection, diagnosed clinically or by renal biopsy, for different groups formed on the basis of CMV seromatching.

RESULTS

One hundred and ninety-four patients (58.3%) had at least one acute rejection episode. CMV seromismatched patients (donor +/recipient-) had a significantly higher rate of acute rejection than non-seromismatched patients (72.6% vs. 54.2%, P=0.005). Using multiple logistic regression, CMV seromismatch, delayed graft function, and biological induction were identified as independent predictors of acute rejection. The adjusted odds ratios for these were 2.28, 1.65, and 0.52, respectively.

CONCLUSIONS

Patients who are CMV seromismatched are at higher risk of acute renal allograft rejection. This finding suggests that CMV infection or disease is a risk factor for acute rejection.

The role of immune reconstitution in cytomegalovirus infection

Cytomegalovirus (CMV) causes high morbidity and mortality in immunocompromised patients. The host immune response to CMV comprises specific and nonspecific cellular and humoral responses, but current knowledge supports a protective role only for cell-mediated immune responses. Although complete CMV eradication is unusual even in immunocompetent hosts, its morbidity can be limited by CMV-specific CD8+ cytotoxic lymphocytes supported by CD4+-mediated T lymphocyte helper activity. In patients with congenital or acquired deficiencies of cell-mediated immunity, recovery of CD4+ lymphocyte numbers and/or function coincides with cessation of CMV-associated morbidity. However, an immunological test that can predict protection against CMV disease across different types of high-risk patients is not yet available. In recent years, the introduction of antivirals active against CMV has improved the outcome of CMV disease. In addition, there is a continuous effort to develop CMV-specific immune-based therapies including vaccines and immune modulators such as cytokines, which may be of supplemental benefit in the control of CMV disease.

Infections and solid organ transplant rejection: a cause-and-effect relationship?

Although evidence is far from being conclusive, several studies have suggested that infections could trigger rejection in different transplant settings. In this review we examine the evidence linking cytomegalovirus (CMV), adenovirus, enterovirus, parvovirus, and herpes simplex virus infections to the vasculopathy leading to cardiac allograft rejection, the association between CMV and chronic kidney, lung, and liver graft rejection, and the association of human herpesvirus 6 reactivation with CMV-related disease in kidney and liver transplant recipients. We also review the numerous antiviral prophylactic or pre-emptive treatments in use to control CMV infection, and suggest that they do not limit immune reactions leading to graft rejection or lower the risk of developing post-transplantation atherosclerosis in allograft recipients. Finally, we emphasise the need for prospective, international studies to clarify the role of infections in transplant rejection, to look at virus-to-virus interactions, and to establish specific therapeutic strategies. Such strategies must not rely exclusively on expensive antiviral agents but also on vaccination or other, innovative approaches, such as the use of agents able to inhibit the activity of natural killer cells, which might have an important role in acute allograft rejection.

Proteasome Inhibitors: A Novel Tool to Suppress Human Cytomegalovirus Replication and Virus-Induced Immune Modulation

Recently, we like others, demonstrated that systemic inflammation is the most important mechanism involved in (re)activation of human cytomegalovirus (HCMV) in both immunocompromised and immunocompetent patients. By in vitro studies the eukaryotic transcription factor NF-κB could be identified as the key mediator of TNF-α- and IE1-dependent stimulation of the HCMV IE1/2 enhancer/promoter activity, which is crucial for initiation of viral gene expression during reactivation from latency as well as productive infection. The enzymatic proteasome complex plays a central role in regulating intracellular processes, including the activation of NF-κB. As present antiviral strategies target mainly late events in HCMV replication (DNA replication, virus assembly) that do not completely prevent virus mediated immunopathogenesis, we wondered whether proteasome inhibitors might be a novel tool for targeting the interaction between inflammation and HCMV (re)activation. Here, proteasome inhibitors like MG132, PSI, II and III (MG262) have been shown to block both TNF-α-associated up-regulation of the HCMV IE1/2 enhancer/promoter in monocytic cells in an in vitro transient transfection system and HCMV replication in permissive human embryonal lung fibroblasts. Importantly, ganciclovir-resistant HCMV strains are sensitive to proteasome inhibitors. The effect of proteasome inhibitors on HCMV replication was found to be specific as replication of other herpes viruses, like HSV-1 and HSV-2, under identical experimental conditions was not influenced. Inhibition of HCMV replication correlated with a delayed and significantly reduced expression of IE proteins, particularly of the IE2 protein, suggesting that MG132 blocks HCMV replication at an immediate early stage of infection. Early and late protein synthesis as shown exemplary for the pp52 (DNA-binding protein) and p68 (structural protein) protein production and viral DNA synthesis were also inhibited. Suppression of HCMV replication could be correlated with an increased cytosolic accumulation of IκB as well as a reduced NF-κB binding activity in nuclear extracts of MG132-treated cells, which mainly regards NF-κB p50. MG132 also reduced the immune modulatory activity of the virus by abrogating virus-induced up-regulation of cellular ICAM-1. These data suggest that short-term therapy with proteasome inhibitors might be an alternative strategy to prevent (re)activation, replication and immune modulatory activity of HCMV in patients with systemic inflammation.

Equid herpesvirus 1 infection of endothelial cells requires activation of putative adhesion molecules: an in vitro model

Antisera to activated equine endothelial cells, which detected surface molecules of 116 kD, 97 kD, 42 kD and 38 kD, were made to investigate the role of endothelial adhesion molecules in equid herpes virus 1 infection. These putative adhesion molecules could be induced by 17-beta oestradiol, chorionic gonadotrophin, or IL-2, as well as by LPS and PWM. In an in vitro flow system, using equine veins or arteries, equid herpesvirus 1 in leucocytes was only transferred to infect endothelial cells if both leucocytes and endothelial cells expressed these surface molecules. Blocking of the membrane molecules with polyclonal antibodies prevented transfer of virus to the endothelial cells, indicating that the adhesion molecules had a key role in effecting transfer of virus. These in vitro observations give particular insight into the reports that in the natural course of infection in horses infection of endothelial cells is restricted to certain tissues, and in a wider context the results illustrate the complexity of factors that may direct tissue tropism.

Human cytomegalovirus-mediated induction of MIF in fibroblasts

Human cytomegalovirus (HCMV) infection of fibroblasts induces the proinflammatory mediator macrophage migration inhibitory factor (MIF). Our in vitro experiments show that active HCMV infection alone is required to induce an early and sustained induction of MIF mRNA and protein production. Unlike in other infection models, in which MIF has been described to be released from preformed stores, our data conclusively show that HCMV infection triggers de novo synthesis and subsequent secretion of MIF. The kinetics of MIF protein production during HCMV infection points to an efficacious immune modulation, in which lymphocytes and monocytes are initially recruited by the early release of chemokines to sites of infection and locally activated by increasing concentrations of MIF.

Antiviral and immunomodulatory activity of the metal chelator ethylenediaminedisuccinic acid against cytomegalovirus in vitro and in vivo

Antiviral activity of the metal chelator ethylenediaminedisuccinic acid (EDDS) was examined in vitro against human cytomegalovirus (HCMV) wild type strains and strains that are resistant against ganciclovir (GCV) and cidofovir (HPMPC). EDDS inhibited the replication of wild-type as well as GCV- and HPMPC-resistant strains with a 50% effective concentration of 7.4-12 microg/ml. At concentrations of 100 microg/ml EDDS, unlike GCV or HPMPC, suppressed HCMV-induced up-regulation of intercellular adhesion molecule-1 (ICAM-1) and reduced T-cell adhesion to HCMV-infected cells in a monolayer adhesion model. In vitro EDDS inhibited murine cytomegalovirus (MCMV) replication (EC50 8.6 microg/ml) and caused in mice some protection against MCMV induced mortality at a non-toxic dose. Since immunopathological factors may play a significant role in HCMV disease it will be of interest to further study whether EDDS is effective in terms of modulation of inflammatory responses to HCMV infections.

T-cell activation response to allogeneic CMV-infected endothelial cells is not prevented by ganciclovir or foscarnet: implications for transplant vascular sclerosis

BACKGROUND

Cytomegalovirus (CMV), a common infectious complication in transplant recipients, has been implicated as an exacerbating agent in the development of transplant vascular sclerosis (TVS); however, mechanisms defining this role remain to be fully resolved. Our previous studies suggest that CMV-infected graft endothelial cells (EC) can initiate a host T-cell activation cascade, and that cytokines produced as a consequence enhance graft endothelial alloimmunogenicity. Because antiviral therapy has not uniformly attenuated CMV-associated risk of TVS development, we have tested the hypothesis that antiviral agents do not affect T-cell activation by allogeneic CMV-infected EC.

METHODS

Human umbilical vein EC, inoculated with CMV VHL/E and incubated in the presence or absence of ganciclovir (GCV) or foscarnet (PFA), were cocultured with CMV-seropositive or -seronegative donor-derived T cells in the presence of these agents, then labeled with [(3)H]thymidine. Cocultures were harvested, and radiolabel incorporation was assayed by scintillation counting.

RESULTS

Limiting dilution analysis demonstrated that proliferation frequencies of CMV-seropositive donor-derived T cells in response to CMV-infected EC (approximately 80 cells/106, compared with approximately 4 cells/10(6) in response to uninfected EC) were not significantly modified by GCV (approximately 86 cells/10(6)) or PFA (approximately 82 cells/10(6)). Likewise, T-cell proliferation curves generated in response to stimulator cell titrations were essentially identical regardless of drug treatment.

CONCLUSIONS

Results of these experiments suggest that although these drugs limit CMV replication and dissemination, they do not attenuate the inflammatory potential of infected EC, a force that may be a major factor in CMV-mediated exacerbation of the development of TVS.

Human cytomegalovirus infection of bone marrow myofibroblasts enhances myeloid progenitor adhesion and elicits viral transmission

Human cytomegalovirus (CMV) infection of bone marrow transplant recipients can cause pancytopenia, as well as life-threatening interstitial pneumonia. CMV replicates actively in bone marrow stromal cells, whereas it remains latent in hematopoietic progenitors. Our aim was to study the influence of CMV infection on adherence of CD34(+) cells to the myofibroblastic component of human bone marrow and examine transmission of virus from myofibroblasts to CD34(+) cells. We show that smooth actin, but not fibronectin, organization is markedly modified by CMV infection of bone marrow stromal myofibroblasts. Nonetheless, CMV infection led to increased adherence of the CD34(+) progenitor cell line, KG1a, relative to adherence to uninfected myofibroblasts from the same donors. Adherence of CD34(+) cells to infected bone marrow myofibroblasts resulted in transfer of virions and viral proteins through close cell-to-cell contacts. This phenomenon may play a role in the pathophysiology of CMV bone marrow infection and in eventual virus dissemination.

Cytomegalovirus in renal transplantation

Cytomegalovirus (CMV) was first isolated from the salivary gland and kidney of two dying infants with cytomegalic inclusion bodies and reported in 1956 (1). Two other laboratories isolated CMV at approximately the same time. Thus, CMV was initially called "salivary gland virus" or "salivary gland inclusion disease virus". In 1960, Weller et al. (2) proposed the use of the term cytomegalovirus. Klemola and Kaarianinen (3) first described CMV mononucleosis, the principal presentation of previously healthy individuals, in 1965. CMV was first isolated in a renal transplant patient in 1965,

Inhibition of cytomegalovirus immediate early gene expression: a therapeutic option?

The replication cycle of the human cytomegalovirus (HCMV) is characterized by the expression of immediate early (IE), early (E), and late (L) gene regions. Current antiviral strategies are directed against the viral DNA polymerase expressed during the early phase of infection. The regulation of the IE-1 and IE-2 gene expression is the key to latency and active replication due to their transactivating and repressing functions. There is growing evidence that the pathogenic features of HCMV are largely due to the abilities of IE-1 and IE-2 to transactivate cellular genes. Consequently, current drugs used to inhibit HCMV infection would have no impact on IE-1 and IE-2-induced effects that are produced before the early phase. Moreover, when HCMV DNA replication is inhibited, IE gene products accumulate in infected cells causing disturbances of host cell functions. This review summarizes the biological functions of HCMV-IE gene expression, their relevance in pathogenesis, as well as efforts to develop novel treatment strategies directed against HCMV-IE expression.

Antioxidant effect of estrogen on cytomegalovirus-induced gene expression in coronary artery smooth muscle cells

BACKGROUND

Pathogens infecting the arterial wall with resultant inflammation may contribute to atherogenesis. Human coronary artery smooth muscle cells (SMCs) infected with human cytomegalovirus (CMV) demonstrate a rapid increase in reactive oxygen species (ROSs), with activation of genes involved in viral replication and inflammation. Because estrogen appears to have antioxidant properties, we wished to determine whether this hormone attenuates SMC responses to CMV infection.

METHODS AND RESULTS

Using confocal microscopy and an intracellular fluorescent dye activated by ROSs, we found that 17beta-estradiol (0.1 to 10 nmol/L) and its stereoisomer 17alpha-estradiol (which has low affinity for the estrogen receptor) dose-dependently inhibited ROS generation in CMV-infected SMCs. These effects were not blocked by the estrogen receptor inhibitor ICI 182,780. 3-Methoxyestrone, which lacks the phenolic hydroxyl group, did not interfere with ROS generation. We found that 17beta-estradiol and 17alpha-estradiol, but not 3-methoxyestrone, prevented binding of nuclear factor (NF)-kappaB to DNA. Furthermore, in SMCs transfected with the reporter constructs 3XkappaB-CAT, MIEP-CAT, or ICAM-CAT, cotransfection with a CMV-IE72 expression plasmid caused promoter and CAT activation. Treatment with 17beta-estradiol and 17alpha-estradiol, but not 3-methoxyestrone, inhibited CAT activity and, in CMV-infected SMCs, prevented IE72 and ICAM-1 protein expression and cytopathic effects.

CONCLUSIONS

These findings indicate that estrogen molecules with an A-ring hydroxyl group have estrogen receptor-independent anti-CMV effects at physiological concentrations by inhibiting ROS generation, NF-kappaB activation, NF-kappaB-dependent transcription, and viral replication. To the extent that chronic infection of the vascular wall with CMV contributes to atherogenesis, these antioxidant actions of estrogen may be of therapeutic importance.

Induction of vascular adhesion protein-1 during liver allograft rejection and concomitant cytomegalovirus infection in rats

Vascular adhesion protein-1 (VAP-1) is an adhesion molecule controlling lymphocyte recirculation through high endothelial venules of the lymph nodes. It has also been shown to be induced and to mediate lymphocyte adhesion at sites of inflammation. We studied the expression of VAP-1 and two other inducible adhesion molecules ICAM-1 and VCAM-1 in our experimental model of rat liver allograft rejection and, in addition, the effect of concomitant rat cytomegalovirus (RCMV) infection on this expression. Expression of VAP-1, ICAM-1, and VCAM-1 was studied in rat liver allografts with or without RCMV infection, isografts, and normal rat liver. Immunoperoxidase technique and monoclonal antibodies including a novel anti-VAP-1 reagent were used. VAP-1 expression was induced by acute rejection in sinusoids, hepatocytes, and also in bile ducts, when compared to the isografts or normal liver, where only blood vessels were consistently positive. Sinusoidal and hepatocyte expression of VAP-1 was prolonged by the presence of RCMV. ICAM-1 and VCAM-1 expression was also induced by acute rejection. However, RCMV increased sinusoidal VCAM-1 expression compared to uninfected grafts. The present experimental study shows that VAP-1 is up-regulated in acute rejection of liver allografts, and that this up-regulation is prolonged by RCMV infection.

Chemokines and soluble adhesion molecules in renal transplant recipients with cytomegalovirus infection

Cytomegalovirus (CMV) infection is associated with leucocyte infiltration in various organs, which supports a role for chemokines and adhesion molecules in the pathogenesis of CMV infection. In a prospectively conducted study of renal transplant recipients, 10 patients with CMV disease, five patients with asymptomatic CMV infection and 10 patients who did not have any CMV infection were included. During CMV infection, and in particular during CMV disease, plasma levels of the chemokines IL-8, macrophage inflammatory protein-1alpha (MIP-1alpha) and monocyte chemotactic protein-1 (MCP-1) and the soluble adhesion molecules vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1) and L-selectin increased and were positively correlated with the degree of CMV pp65 antigenaemia. Furthermore, a decrease in plasma levels of these chemokines and adhesion molecules was observed following ganciclovir therapy in the patients with CMV disease. This could suggest a role for these molecules in the pathogenesis of CMV infection.

Exploitation of cellular signaling and regulatory pathways by human cytomegalovirus

Human cytomegalovirus is a ubiquitous human pathogen that is the leading viral cause of birth defects. It also causes significant morbidity and mortality in both chemically and virally immunosuppressed individuals. Recent studies have begun to elucidate the interplay between this virus and its host cell on a molecular level. The interactions begin upon contact with the cell membrane, involve multiple processes including cell signaling, cell-cycle control and immune response mechanisms, and culminate in a productive infection.

The antisense oligonucleotide ISIS 2922 prevents cytomegalovirus-induced upregulation of IL-8 and ICAM-1 in cultured human fibroblasts

Human cytomegalovirus (HCMV) infection is associated with excessive proinflammatory immune responses such as cytokine/chemokine production or upregulation of adhesion molecules on the host cells. It is assumed that these features of HCMV-related immunopathology can not be treated effectively with currently available anti HCMV drugs. In the present study the efficacy of ganciclovir (GCV), foscarnet (PFA), cidofovir (HPMPC), and ISIS 2922, an antisense oligonucleotide complementary to HCMV immediate-early (IE) mRNA, was investigated on HCMV-induced secretion and functional activity of the C-X-C chemokine IL-8 and the expression of the intercellular adhesion molecule-1 (ICAM-1). As compared with mock-infected cells IL-8 production was increased up to 9-fold and ICAM-1 expression up to 4-fold in HCMV-infected fibroblasts. Treatment of infected cells with GCV (40 microM), PFA (200 microM) or HPMPC (2 microM) suppressed completely virus replication as demonstrated by quantification of late (L) antigen expression and infectious virus production. These drugs, however, failed to inhibit IE antigen expression and did not prevent HCMV-induced upregulation of IL-8 and ICAM-1. In contrast, ISIS 2922 (1 microM) suppressed both IE and L antigen expression by 99% and inhibited infectious virus production by 10(4)-fold. Moreover, ISIS 2922 significantly suppressed HCMV-induced upregulation of both IL-8 and ICAM-1 expression on the transcriptional and on the protein level. Our results indicate that ISIS 2922 but not inhibitors of HCMV DNA prevents HCMV-induced upregulation of IL-8 and ICAM-1, both hallmarks of inflammatory processes. Thus, inhibition of HCMV IE expression with ISIS 2922 may be an important strategy for the treatment of HCMV-related immunopathogenesis.

Attenuation of cytomegalovirus-induced endothelial intercellular adhesion molecule-1 mRNA/protein expression and T lymphocyte adhesion by a 2'-O-methoxyethyl antisense oligonucleotide

BACKGROUND

Intercellular adhesion molecule-1 (ICAM-1) is strongly induced under inflammatory conditions associated with allograft rejection, thereby promoting leukocyte recruitment and activation at the site of inflammation. Enhancement of ICAM-1 expression can also be the result of viral infection, in particular human cytomegalovirus (CMV), a frequent source of complications in the transplant recipient. In vitro studies have shown that CMV infection of endothelial cells (EC) results in the direct enhancement of ICAM-1 expression and consequent leukocyte adhesion/activation suggesting mechanisms by which CMV exacerbates graft vascular disease. Although treatment of EC with ICAM-1-specific antisense oligonucleotides has been shown to attenuate ICAM-1 induction under simulated inflammatory conditions (i.e., TNF-alpha), no studies have addressed their effectiveness on virally-induced ICAM-1 expression.

RESULTS

In the current investigation, we show that the progressive increase in endothelial ICAM-1 protein expression that follows inoculation with CMV correlates with a progressive accumulation of ICAM-1 mRNA. Furthermore, we demonstrate that treatment of EC with a partially 2'-O-methoxyethyl modified ICAM-1-specific antisense oligonucleotide before viral inoculation significantly reduces CMV-associated induction of ICAM-1 protein and mRNA expression. Finally, we show that antisense-mediated attenuation in ICAM-1 expression results in a significant reduction of T lymphocyte adhesion to CMV-infected EC monolayers, an interaction that has been implicated in allogeneic T lymphocyte activation, in viral transmission to transiently adherent leukocytes and subsequent hematogenous dissemination.

CONCLUSIONS

These findings demonstrate for the first time that antisense oligonucleotides can effectively reverse virally-induced host cellular protein expression, specifically ICAM-1, as well as consequent T lymphocytes adhesion, thus broadening the potential clinical utility of antisense oligonucleotides.

Antiviral and immunomodulatory effects of desferrioxamine in cytomegalovirus-infected rat liver allografts with rejection

BACKGROUND

Cytomegalovirus (CMV) infection is associated with acute and chronic allograft rejection. We have recently shown that rat CMV increases portal inflammation and bile duct destruction in a model of rat liver allograft rejection. Desferrioxamine (DFO), an iron chelator and antioxidant, has recently been demonstrated to have antiviral as well as immunomodulatory effects in vitro. We therefore investigated whether DFO inhibits (a) CMV infection and (b) graft destruction in our rat model.

METHOD

One day after liver transplantation, PVG (RT1c) into BN(RT1n), the rats were infected with rat CMV (RCMV, Maastricht strain; 10(5) plaque-forming units i.p.). The effects of 100 mg/kg body weight and 200 mg/kg body weight DFO were examined.

RESULTS

In the untreated group, the grafts were uniformly RCMV culture-positive. In the group receiving 200 mg/kg DFO, RCMV replication was effectively inhibited. Inflammatory response in the graft, and especially the number of macrophages, was significantly reduced by DFO. Portal inflammation and bile duct destruction were also significantly reduced. In the untreated group, the bile duct epithelial cells were found to be strongly positive for tumor necrosis factor-alpha and this expression was clearly decreased by DFO. In addition, DFO significantly inhibited vascular cell adhesion molecule-1 expression on sinusoidal endothelial cells.

CONCLUSIONS

Our in vivo transplant study strongly supports the inhibitory effects of metal chelators on CMV infection and their possible usefulness in the treatment of CMV-induced pathogenic changes.

Identification of Three HLA-A*0201-Restricted Cytotoxic T Cell Epitopes in the Cytomegalovirus Protein pp65 That Are Conserved Between Eight Strains of the Virus

The Ag specificity of the CTL response against CMV is directed almost entirely to a single CMV tegument protein, the phosphoprotein pp65. We report the identification of three peptides derived from the protein pp65 that displayed a high or intermediate binding to HLA-A*0201 molecules, which were also able to induce an in vitro CTL response in peripheral blood lymphocytes from CMV seropositive individuals. The peptide-specific CTLs generated were capable of recognizing the naturally processed pp65 either presented by CMV-infected cells or by cells infected with an adenovirus construct expressing pp65 in an HLA-A*0201-restricted manner. Thus, we were able to demonstrate responses to subdominant CTL epitopes in CMV-pp65 that were not detected in polyclonal cultures obtained by conventional stimulations. We also found that the amino acid sequences of the three peptides identified as HLA-A*0201-restricted CTL epitopes were conserved among different wild-type strains of CMV obtained from renal transplant patients, an AIDS patient, and a congenitally infected infant, as well as three laboratory strains of the virus (AD169, Towne and Davis). These observations suggest that these pp65 CTL peptide epitopes could potentially be used as synthetic peptide vaccines or for other therapeutic strategies aimed at HLA-A*0201-positive individuals, who represent ∼40% of the European Caucasoid population. However, strain variation must be taken in consideration when the search for CTL epitopes is extended to other HLA class I alleles, because these mutations may span potential CTL epitopes for other HLA molecules, as it is described in this study.

Cytomegalovirus infection of bile duct epithelial cells, hepatic artery and portal venous endothelium in relation to chronic rejection of liver grafts

BACKGROUND/AIM

Chronic rejection is an important cause of graft loss following liver transplantation. A number of risk factors for chronic rejection have been identified previously, albeit inconsistently. These include cytomegalovirus infection detected by a number of different techniques, including immunohistochemical staining and in situ hybridisation of liver grafts. However, tissue-based techniques for the detection of CMV have not been applied to grafts lost to conditions other than chronic rejection. The purpose of this study was to investigate the relationship between the presence of cytomegalovirus infection detected by in situ hybridisation and immunohistochemistry with respect to graft outcome, the presence of cytomegalovirus infection detected by other techniques and in addition, the type of infected cell.

METHODS

The 29 patients studied included 15 patients who lost their primary liver graft to chronic rejection in 8 cases, to hepatic artery thrombosis in 4 cases and to causes other than chronic rejection or hepatic artery thrombosis in 3 further cases. In each case, sections containing septal or large ducts and vessels were selected (usually blocks) since these may be more representative. Needle biopsies from 14 further patients who ultimately achieved satisfactory graft function served as control tissue. Of these, ten had evidence of cytomegalovirus infection at the time of study by serum/urine PCR, DEAFF testing or seroconversion, while 4 patients had no evidence of cytomegalovirus infection according to these techniques.

RESULTS

Cytomegalovirus infection was detected in the liver of 12 of the 29 patients. These included 8/15 grafts lost, which comprised 3/8 with chronic rejection, 2/3 with hepatic artery thrombosis and 3/4 with grafts lost to other causes, as well as 4/14 who retained grafts. CMV was detected most commonly in association with symptomatic infection and notably was detected only by in situ hybridisation in two cases. Predominant cell types that contained cytomegalovirus were hepatocytes and mononuclear cells. However, bile duct epithelial cells, hepatic artery endothelial cells and portal venous endothelial cells also contained cytomegalovirus in some cases.

CONCLUSIONS

These data support previous studies that cytomegalovirus infection is detectable in patients with chronic rejection and are consistent with the theory that CMV is involved in chronic rejection. However, cytomegalovirus infection was detected in explanted grafts lost to conditions other than chronic rejection, and the association may not be causal but a consequence of graft injury.

Target structures of the CD8(+)-T-cell response to human cytomegalovirus: the 72-kilodalton major immediate-early protein revisited

Cell-mediated immunity plays an essential role in the control of infection with the human cytomegalovirus (HCMV). However, only a few CD8(+)-T-cell epitopes are known, with the majority being contained in the pp65 phosphoprotein, which is believed to dominate the CD8(+)-T-cell response to HCMV. Here, we have readdressed the issue of CD8(+) T cells specific for the 72-kDa major immediate-early protein (IE-1), which is nonstructural but is found very early and throughout the replicative cycle. Using a novel flow-cytometric assay, we were able to identify CD8(+)-T-cell epitopes (by IE-1 peptide-specific induction of cytokine synthesis) and simultaneously measure the frequency of cells directed against them. For this purpose, 81 pentadecamer peptides covering the complete 491-amino-acid sequence of IE-1 were tested on peripheral blood mononuclear cells of anti-HCMV immunoglobulin G-seropositive donors. At least 10 new epitopes were identified, and the fine specificity and presenting HLA molecule of the first of them was determined. The frequencies of CD8(+) T cells directed against IE-1 were similar to those directed against pp65 in donors tested with known pp65-derived peptides. Importantly, additional testing of a corresponding set of peptides covering the complete sequence of pp65 on 10 of these donors identified individuals whose CD8(+) T cells recognized IE-1 but not pp65 and vice versa, clearly illustrating that either protein may be a major target. In summary, our results suggest that IE-1 is far more important as a CD8(+)-T-cell target than current opinion suggests.

Mechanisms of human cytomegalovirus (HCMV) (re)activation and its impact on organ transplant patients

Human cytomegalovirus (HCMV) infection plays an important role in transplant patients. Its impact is both direct and indirect. This review focuses on new aspects of HCMV (re)activation and HCMV related pathology, particularly HCMV-associated renal allograft injury. During the last two years we have learned that HCMV is more frequently (re)activated, even in healthy people, than previously expected. Inflammatory as well as stress mediators and some drugs may (re)activate the virus by using distinct intracellular pathways. Commonly, HCMV (re)activation is accompanied by HCMV antigenemia/DNAemia, suggesting that precursor cells in the bone marrow play an important role as a reservoir of latent virus. However, local HCMV (re)activation (colon, lung) without detection of active HCMV infection in the peripheral blood is possible. In healthy people a sufficient type 1 T-cell response controls the active HCMV infection, while in patients with severe immune deficiency (AIDS, high-dose immunosuppression) the virus can spread in an uncontrolled fashion and induce 'classic' HCMV disease. In patients with moderate immune deficiency (e.g. long-term transplant patients on low-dose immunosuppression) virus spreading is controlled but the elimination of cells harboring the active virus may be insufficient. The resulting persistent HCMV antigenemia may induce chronic inflammatory processes leading to tissue injury, particularly in the allograft. Therefore, antiviral therapy may be useful in patients suffering from graft deterioration with otherwise clinically symptomless HCMV infection. HCMV-related immune deficiency with an increased risk of developing bacterial/fungal superinfections is frequently seen in patients with symptomatic HCMV disease but not in asymptomatic CMV antigenemia. The risk of developing superinfections can be predicted by flow-cytometric monitoring of peripheral blood monocytes.