Human herpesvirus 8 acute infection of endothelial cells induces monocyte chemoattractant protein 1-dependent capillary-like structure formation: role of the IKK/NF-kappaB pathway

Recent Updates on Viral Oncogenesis: Available Preventive and Therapeutic Entities

Human viral oncogenesis is a complex phenomenon and a major contributor to the global cancer burden. Several recent findings revealed cellular and molecular pathways that promote the development and initiation of malignancy when viruses cause an infection. Even, antiviral treatment has become an approach to eliminate the viral infections and prevent the activation of oncogenesis. Therefore, for a better understanding, the molecular pathogenesis of various oncogenic viruses like, hepatitis virus, human immunodeficiency viral (HIV), human papillomavirus (HPV), herpes simplex virus (HSV), and Epstein-Barr virus (EBV), could be explored, especially, to expand many potent antivirals that may escalate the apoptosis of infected malignant cells while sparing normal and healthy ones. Moreover, contemporary therapies, such as engineered antibodies antiviral agents targeting signaling pathways and cell biomarkers, could inhibit viral oncogenesis. This review elaborates the recent advancements in both natural and synthetic antivirals to control viral oncogenesis. The study also highlights the challenges and future perspectives of using antivirals in viral oncogenesis.

Evaluation of the effects in the <i>in vitro</i> system of synthetic thymic hexapeptide on the expression levels of NF-κB, IFNα/βR and CD119 neutrophilic granulocytes in patients with chronic herpes viral co-infections

Background. Strategies used by herpes viruses with human cells are complex and multifaceted. On one hand, inborn defects in antiviral immune defense have been unveiled, which also affect interferon (IFN) system underlying development of chronic recalcitrant relapsing viral infections such as remittent respiratory viral infections, herpesvirus infections, and papillomavirus infections. On the other hand, numerous viruses are able to damage both immune system and IFN network. During inborn and acquired defects in IFN network, inborn or induced mutation in gene products involved in signaling cascades aimed at upregulating gene expression responsible for IFN production are observed. One of the strategies used by diverse viruses is altering some signaling pathways resulting in activated transcription factors including nuclear factor NF-kB. However, antiviral mechanisms executed by neutrophilic granulocytes (NGs), particularly affecting NF-kB expression have not been elucidated. Aim of the study: to study in vitro features of NF-kB expression and number of neutrophilic granulocytes (NG) expressing membrane IFN/R and IFNR in patients with atypical chronic active herpes virus infections (AChA-HVI), followed by assessing an effect of arginyl-alpha-aspartyl-lysyl-valyl-tyrosyl-arginine hexapeptide (HP), a synthetic analogue of the active center of the thymopoietin (active substance of drug Imunofan, Russia), on the expression of NG NF-kB and IFN/R and IFNR. Materials and methods. We observed 25 patients of both sexes aged 23 to 64 years with AChA-HVI, manifested by chronic fatigue syndrome and cognitive disorders. Study design: stage 1 clinical, ELISA, PCR methods, FC was used. Stage 2 the in vitro experiment: 32 blood samples from 8 healthy adults and 375 blood samples from 25 patients with AChA-HVI were analyzed: % NG expressing NF-kB, IFN/R, IFNR and the relevant MFI levels by using FC before and after incubation with HP. Results. Our study demonstrated low level (MFI) of NF-kB expression in 100% NG associated with decreased % of NG expressing IFN/R and IFNR in all patients with AChA-HVI and low serum level for IFN and IFN in comparison with healthy individuals. In the in vitro experiment there was shown that 100% of NG expressed NF-kB after exposure to HP. However, only 48% patients (SG 2) restored NF-kB expression level (MFI) to normal range and 52% of cases (SG 1) had no response. HP increased % of NG expressing IFN/R in SG 2 and increased % of NG expressing IFNR in SG 1. Conclusions. It was shown, that influence of HP in vitro has ambiguous effects on the expression of NF-kB, % of NG expressing IFN/R and IFNR in patients with AChA-HVI. We assume that different NF-kB response to HP is associated with inborn or secondary NF-kB deficiency.

SARS-CoV-2 Infection Remodels the Phenotype and Promotes Angiogenesis of Primary Human Lung Endothelial Cells

SARS-CoV-2-associated acute respiratory distress syndrome (ARDS) and acute lung injury are life-threatening manifestations of severe viral infection. The pathogenic mechanisms that lead to respiratory complications, such as endothelialitis, intussusceptive angiogenesis, and vascular leakage remain unclear. In this study, by using an immunofluorescence assay and in situ RNA-hybridization, we demonstrate the capability of SARS-CoV-2 to infect human primary lung microvascular endothelial cells (HL-mECs) in the absence of cytopathic effects and release of infectious particles. Preliminary data point to the role of integrins in SARS-CoV-2 entry into HL-mECs in the absence of detectable ACE2 expression. Following infection, HL-mECs were found to release a plethora of pro-inflammatory and pro-angiogenic molecules, as assessed by microarray analyses. This conditioned microenvironment stimulated HL-mECs to acquire an angiogenic phenotype. Proteome analysis confirmed a remodeling of SARS-CoV-2-infected HL-mECs to inflammatory and angiogenic responses and highlighted the expression of antiviral molecules as annexin A6 and MX1. These results support the hypothesis of a direct role of SARS-CoV-2-infected HL-mECs in sustaining vascular dysfunction during the early phases of infection. The construction of virus-host interactomes will be instrumental to identify potential therapeutic targets for COVID-19 aimed to inhibit HL-mEC-sustained inflammation and angiogenesis upon SARS-CoV-2 infection.

Epstein-Barr virus infection modulates blood-brain barrier cells and its co-infection with Plasmodium falciparum induces RBC adhesion

Plasmodium falciparum infection-mediated Epstein-Barr virus (EBV) reactivation is well established in malaria-endemic countries. We hypothesize that, during malaria onset, the reactivated EBV can infect human brain microvascular endothelial cells (HBECs). This may cause severe cerebral manifestations. We infected HBECs with EBV in vitro. The subsequent gene expression pattern of EBV, inflammatory and endothelial markers was analysed using qRT-PCR. Further, a wound-healing assay for cells maintaining blood-brain barrier (BBB) integrity was performed to investigate the effect of EBV-infected HBECs secretions. The RBC adhesion assay was conducted to assess RBC attachment onto HBECs during EBV and P. falciparum mono- and co-infection. Our experiments revealed that EBV infection of HBECs significantly elevated several inflammatory (TNFα, CCL2) and endothelial (integrin β3, PECAM, VEGFA, VWF, claudin-5, cx37) markers. The EBV-infected HBECs secretion significantly reduced migration of HBECs, glial and neuronal cells. Additionally, EBV-P. falciparum co-infection significantly (P < 0.05) enhanced RBC adhesion to HBECs compared to mono-infection scenarios. Conclusively, the EBV infection of HBECs led to endothelial activation and modulated the BBB microenvironment. The EBV-P. falciparum co-infection scenario increased RBC adhesion on ECs which is a hallmark of cerebral malaria. Together with malaria, EBV infection can aid in exacerbation of cerebral malaria pathology.

Novel Functions and Virus-Host Interactions Implicated in Pathogenesis and Replication of Human Herpesvirus 8

Human herpesvirus 8 (HHV-8) is classified as a γ2-herpesvirus and is related to Epstein-Barr virus (EBV), a γ1-herpesvirus. One important aspect of the γ-herpesviruses is their association with neoplasia, either naturally or in animal model systems. HHV-8 is associated with B-cell-derived primary effusion lymphoma (PEL) and multicentric Castleman's disease (MCD), endothelial-derived Kaposi's sarcoma (KS), and KSHV inflammatory cytokine syndrome (KICS). EBV is also associated with a number of B-cell malignancies, such as Burkitt's lymphoma, Hodgkin's lymphoma, and posttransplant lymphoproliferative disease, in addition to epithelial nasopharyngeal and gastric carcinomas. Despite the similarities between these viruses and their associated malignancies, the particular protein functions and activities involved in key aspects of virus biology and neoplastic transformation appear to be quite distinct. Indeed, HHV-8 specifies a number of proteins for which counterparts had not previously been identified in EBV, other herpesviruses, or even viruses in general, and these proteins are believed to play vital functions in virus biology and to be involved centrally in viral pathogenesis. Additionally, a set of microRNAs encoded by HHV-8 appears to modulate the expression of multiple host proteins to provide conditions conductive to virus persistence within the host and possibly contributing to HHV-8-induced neoplasia. Here, we review the molecular biology underlying these novel virus-host interactions and their potential roles in both virus biology and virus-associated disease.

The interplay between EBV and KSHV viral products and NF-κB pathway in oncogenesis

Among the DNA tumor viruses Epstein-Barr virus (EBV) and Kaposi sarcoma herpesvirus (KSHV), account for a considerable percentage of virus-associated cancers. Deregulation of transcription factors signaling pathways is one of the most significant oncogenic characteristics of EBV and KSHV. NF-κB is a transcription factor that play a remarkable role in oncogenesis because of its function as a master regulator of a spectrum of genes involved in physiological and pathophysiological process. Constitutive activation of NF-κB is a frequent and well-described event in many human malignancies. Compelling evidence represent EBV and KSHV are capable of targeting different components of NF-κB cascade. Here, we summarized recent findings to clarify the precise relationship between dysregulation of NF-κB and EBV and KSHV-related malignancies. This essay also emphasizes on contribution of various viral products in developing cancer through alteration of NF-κB signaling pathway.

KSHV dysregulates bulk macroautophagy, mitophagy and UPR to promote endothelial to mesenchymal transition and CCL2 release, key events in viral-driven sarcomagenesis

Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent of KS, an aggressive neoplasm that mainly occurs in immune-compromised patients. Spindle cells represent the main feature of this aggressive malignancy and arise from KSHV-infected endothelial cells undergoing endothelial to mesenchymal transition (EndMT), which changes their cytoskeletal composition and organization. As in epithelial to mesenchymal transition (EMT), EndMT is driven by transcription factors such as SNAI1 and ZEB1 and implies a cellular reprogramming mechanism regulated by several molecular pathways, particularly PI3K/AKT/MTOR. Here we found that KSHV activated MTOR and its targets 4EBP1 and ULK1 and reduced bulk macroautophagy and mitophagy to promote EndMT, activate ER stress/unfolded protein response (UPR), and increase the release of the pro-angiogenic and pro-inflammatory chemokine CCL2 by HUVEC cells. Our study suggests that the manipulation of macroautophagy, mitophagy and UPR and the interplay between the three could be a promising strategy to counteract EndMT, angiogenesis and inflammation, the key events of KSHV-driven sarcomagenesis.

Human Herpesvirus 8 and Host-Cell Interaction: Long-Lasting Physiological Modifications, Inflammation and Related Chronic Diseases

Oncogenic and latent-persistent viruses belonging to both DNA and RNA groups are known to cause serious metabolism alterations. Among these, the Human Herpesvirus 8 (HHV8) infection induces stable modifications in biochemistry and cellular metabolism, which in turn affect its own pathological properties. HHV8 enhances the expression of insulin receptors, supports the accumulation of neutral lipids in cytoplasmic lipid droplets and induces alterations in both triglycerides and cholesterol metabolism in endothelial cells. In addition, HHV8 is also known to modify immune response and cytokine production with implications for cell oxidative status (i.e., reactive oxygen species activation). This review underlines the recent findings regarding the role of latent and persistent HHV8 viral infection in host physiology and pathogenesis.

Human Herpesvirus 8 infection may contribute to oxidative stress in diabetes type 2 patients

OBJECTIVE

To investigate the link between Human Herpesvirus 8 (HHV8) infection and plasma oxidative stress in patients with diabetes mellitus type 2 (DM2).

RESULTS

Blood samples collected from DM2 and control subjects were screened for the presence of antibodies against HHV8 and for biomarkers of oxidative stress. We determined the products of radical damage on the plasma lipid fraction, such as malondialdehyde (MDA), fatty acid hydroperoxides (HP) and 7-ketocholesterol (7-keto), the oxidation products of unsaturated fatty acids (UFA) and cholesterol, respectively. The level of plasma antioxidant α-tocopherol (α-toc) was also assessed. Relevant differences were observed in the redox status in DM2 and either HHV8-positive or -negative control subjects. The level of α-toc significantly decreased in both DM2 and HHV8-positive subjects. Levels of MDA, HP and 7-keto were much higher in HHV8-positive and DM2 subjects, indicating that plasma oxidative stress is a common feature in both DM2 and HHV8-infection. In addition, 7-keto was further increased in HHV8-positive DM2 patients. We hypothesized that the HHV8-infection may contribute to the production of ROS, and hence to the oxidative stress closely related to the pathogenesis and development of DM2.

HHV-6A Infection and Systemic Sclerosis: Clues of a Possible Association

Systemic sclerosis (SSc) is an autoimmune disease characterized by vasculopathy, excessive extracellular matrix deposition, and fibrosis of the skin and internal organs. Several infectious agents, including human herpesvirus-6 (HHV-6), have been suggested as possible triggering factors, but a direct association is still missing. We characterized 26 SSc patients for the presence of HHV-6 in tissues and blood, the anti-HHV-6 response, HLA-G plasma levels, and KIR typing. Given the prominent role of endothelial cells (EC) in SSc pathogenesis, along with HHV-6 tropism for EC, we also investigated the expression of pro-fibrosis factors in HHV-6 infected EC. Results showed the presence of HHV-6A in skin biopsies, and an increased virus load was associated with disease severity and poor natural killer (NK) response against the virus, particularly in subjects exhibiting a KIR2 phenotype. HLA-G plasma levels were significantly higher in HHV-6A/B-KIR2 positive SSc patients and in vitro HHV-6A infection-induced pro-fibrosis factors expression in EC, supporting its role in the development of the fibrosing process. Our data suggest an association between virus infection/reactivation and disease, opening the way to future studies to understand the mechanisms by which HHV-6A might contribute to the multifactorial pathogenesis of SSc.

Modulation of Angiogenic Processes by the Human Gammaherpesviruses, Epstein-Barr Virus and Kaposi's Sarcoma-Associated Herpesvirus

Angiogenesis is the biological process by which new blood vessels are formed from pre-existing vessels. It is considered one of the classic hallmarks of cancer, as pathological angiogenesis provides oxygen and essential nutrients to growing tumors. Two of the seven known human oncoviruses, Epstein–Barr virus (EBV) and Kaposi’s sarcoma-associated herpesvirus (KSHV), belong to the Gammaherpesvirinae subfamily. Both viruses are associated with several malignancies including lymphomas, nasopharyngeal carcinomas, and Kaposi’s sarcoma. The viral genomes code for a plethora of viral factors, including proteins and non-coding RNAs, some of which have been shown to deregulate angiogenic pathways and promote tumor growth. In this review, we discuss the ability of both viruses to modulate the pro-angiogenic process.

Human Herpesvirus 6A and 6B inhibit in vitro angiogenesis by induction of Human Leukocyte Antigen G

We have previously reported that human herpesvirus 6 (HHV-6) infection of endothelial cells (ECs) induces the loss of angiogenic properties, through the expression of HHV-6 U94, possibly associated to the release of a soluble mediator. It is also known that the soluble isoform of HLA-G exhibits an anti-angiogenic function, important in implantation, transplantation and neoplastic development. In this study, we analyzed the expression of HLA-G in HHV-6 infected ECs, showing that both HHV-6A and HHV-6B infection induce a potent up-modulation of HLA-G, including both membrane and soluble isoforms. Interestingly, HHV-6A and HHV-6B induced different isoforms of HLA-G. The virus-induced increase of HLA-G was likely due to the expression of the U94 viral gene, that by itself was able to reproduce the effect of whole virus. The effect of U94 was mediated by human transcription factor ATF3, that induced HLA-G activation by recognizing a consensus sequence on its promoter. Virus-induced inhibition of ECs angiogenic ability directly correlated to HLA-G expression and release, and the addition of anti-HLA-G antibody restored the angiogenic properties of HHV6-infected ECs. The induction of HLA-G expression in ECs might represent an important mediator of HHV-6 induced effects.

Relapses of primary cutaneous anaplastic large-cell lymphoma in a female immunocompetent patient with persistent chlamydophila pneumoniae and human herpesvirus 8 infection

Background

We have previously reported the case of an immunocompetent female patient with a primary cutaneous CD30+ anaplastic large-cell lymphoma (PCALCL) located on her upper right eyelid characterized by the presence of a concurrent active infection by C. pneumoniae and Human herpesvirus 8 (HHV8). This finding suggested for the first time a possible association of C. pneumoniae and/or HHV8 infection, or both together, with PCALCL pathogenesis in non-immunocompromised and HIV-negative subjects. The subsequent course of the same patient’s medical history is herein reported.

Findings

During the 4 years following the surgical excision of the first PCALCL, the patient developed five further skin lesions located at different anatomical sites, all histologically proven as PCALCLs. The patient underwent several cycles of doxycycline as prophylaxis against Chlamydia. Skin presence of Chlamydia spp and HHV8 was investigated in all recurrences as well as in routine control blood samples. Amplification fragments corresponding to Chlamydia were found in all skin tissues analysed except one (4/5; 80 %), whereas it was not detected in any of the peripheral blood mononuclear cell samples. Conversely, HHV8 was detected in 2/5 (40 %) of the skin biopsies, including the sample negative for Chlamydia, but in all the blood samples analysed.

Conclusions

These findings further support the hypothesis of a potential role of C. pneumoniae and HHV8 infection in the development and course of the described cutaneous lymphoma. A reciprocally promoting interaction between the two pathogens may be supposed to be relevant for PCALC occurrence and relapse.

High prevalence of specific KIR types in patients with HHV-8 positive cutaneous vascular lesions: a possible predisposing factor?

Human herpesvirus 8 (HHV8) has been hypothesized to be a potential cofactor for the development of diverse cutaneous vascular proliferative lesions, including eruptive cherry angiomas. Recent reports evidenced the influence of killer cell immunoglobulin-like receptor (KIR) gene diversity in defining the susceptibility to symptomatic herpesvirus infections. In this study, skin samples from vascular lesions and healthy controls were characterized simultaneously for the presence of HHV8 and for the KIR genotype, focusing upon the presence of the KIR2DL2/DS2 and KIR2DL3 genes, which have been associated to herpesvirus susceptibility. The results showed that about 64 % of the vascular lesions resulted positive for the presence of HHV8, whereas no control healthy skin samples harbored HHV8 DNA. HHV8-positive patients had a significantly increased frequency of KIR2DL2/DS2 homozigosity and a concomitant decrease of the homozygous KIR2DL3 genotype, compared to healthy controls or HHV8-negative patients. Notably, the simultaneous presence of KIR2DL2/DS2 homozygosity and HHV8 infection resulted in a significantly increased risk to develop cutaneous lesions (OR 5.7) compared to the individual factors alone, suggesting that specific KIR genotypes might predispose to HHV8 symptomatic infection, allowing the virus to exert its angioproliferative activity at skin level.

Inhibition of viral protein translation by indomethacin in vesicular stomatitis virus infection: role of eIF2α kinase PKR

Indomethacin, a cyclooxygenase‐1 and ‐2 inhibitor widely used in the clinic for its potent anti‐inflammatory/analgesic properties, possesses antiviral activity against several viral pathogens; however, the mechanism of antiviral action remains elusive. We have recently shown that indomethacin activates the double‐stranded RNA (dsRNA)‐dependent protein kinase R (PKR) in human colon cancer cells. Because of the important role of PKR in the cellular defence response against viral infection, herein we investigated the effect of indomethacin on PKR activity during infection with the prototype rhabdovirus vesicular stomatitis virus. Indomethacin was found to activate PKR in an interferon‐ and dsRNA‐independent manner, causing rapid (< 5 min) phosphorylation of eukaryotic initiation factor‐2 α‐subunit (eIF2α). These events resulted in shutting off viral protein translation and blocking viral replication (IC₅₀ = 2 μM) while protecting host cells from virus‐induced damage. Indomethacin did not affect eIF2α kinases PKR‐like endoplasmic reticulum‐resident protein kinase (PERK) and general control non‐derepressible‐2 (GCN2) kinase, and was unable to trigger eIF2α phosphorylation in the presence of PKR inhibitor 2‐aminopurine. In addition, small‐interfering RNA‐mediated PKR gene silencing dampened the antiviral effect in indomethacin‐treated cells. The results identify PKR as a critical target for the antiviral activity of indomethacin and indicate that eIF2α phosphorylation could be a key element in the broad spectrum antiviral activity of the drug.

Neutral lipid alterations in human herpesvirus 8-infected HUVEC cells and their possible involvement in neo-angiogenesis

Background

Human Herpesvirus 8 (HHV8), the causative agent of Kaposi’s sarcoma, induces an intense modification of lipid metabolism and enhances the angiogenic process in endothelial cells. In the present study, neutral lipid (NL) metabolism and angiogenesis were investigated in HHV8-infected HUVEC cells. The viral replication phases were verified by rtPCR and also by K8.1 and LANA immunostaining.

Results

Lipid droplets (Nile Red) were higher in all phases and NL staining (LipidTOX) combined with viral-antigen detection (immunofluorescence) demonstrated a NL content increase in infected cells. In particular, triglyceride synthesis increases in the lytic phase, whereas cholesteryl ester synthesis rises in the latent one. Moreover, the inhibition of cholesterol esterification reduces neo-tubule formation mainly in latently infected cells.

Conclusions

We suggest that a reprogramming of cholesteryl ester metabolism is involved in regulating neo-angiogenesis in HHV8-infected cells and plays a likely role in the high metastatic potential of derived-tumours.

The Role of Human Herpesvirus 8 in Diabetes Mellitus Type 2: State of the Art and a Medical Hypothesis

Diabetes is a common chronic disease due to an altered glucose metabolism, caused by the quantitative and/or qualitative dysfunction of the insulin hormone. Two types of diabetes are recognized: juvenile diabetes, or type 1, which has an autoimmune origin, and adult diabetes, or type 2 (DMT2), which covers 90-95 % of all diabetic patients.The causes of DMT2 are not yet clear: heredity, life style, nutrition, and environment are considered the main risk factors. Several viral infections, namely cytomegalovirus, coxsackie and other enteroviruses, rubella and hepatitis C virus, have been claimed to be associated with some forms of diabetes. The direct role of viruses as a cause or as a risk of type 1 diabetes has been amply described in several recent reviews. Therefore, this review focuses attention on the role of a human herpes pathogenic virus in the onset of DMT2. By carrying out an analysis of recent literature, we describe the findings reported on an extremely deceitful virus, such as Human Herpes virus 8, and present a medical hypothesis on a possible relationship between this virus and DMT2.

ERK-dependent downregulation of the atypical chemokine receptor D6 drives tumor aggressiveness in Kaposi sarcoma

D6 is an atypical chemokine receptor acting as a decoy and scavenger for inflammatory CC chemokines expressed in lymphatic endothelial cells. Here, we report that D6 is expressed in Kaposi sarcoma (KS), a tumor ontogenetically related to the lymphatic endothelium. Both in human tumors and in an experimental model, D6 expression levels were inversely correlated with tumor aggressiveness and increased infiltration of proangiogenic macrophages. Inhibition of monocyte recruitment reduced the growth of tumors, while adoptive transfer of wild-type, but not CCR2(-/-) macrophages, increased the growth rate of D6-competent neoplasms. In the KS model with the B-Raf V600E-activating mutation, inhibition of B-Raf or the downstream ERK pathway induced D6 expression; in progressing human KS tumors, the activation of ERK correlates with reduced levels of D6 expression. These results indicate that activation of the K-Ras-B-Raf-ERK pathway during KS progression downregulates D6 expression, which unleashes chemokine-mediated macrophage recruitment and their acquisition of an M2-like phenotype supporting angiogenesis and tumor growth. Combined targeting of CCR2 and the ERK pathway should be considered as a therapeutic option for patients with KS.

Molecular biology of human herpesvirus 8: novel functions and virus-host interactions implicated in viral pathogenesis and replication

Human herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus (KSHV), is the second identified human gammaherpesvirus. Like its relative Epstein-Barr virus, HHV-8 is linked to B-cell tumors, specifically primary effusion lymphoma and multicentric Castleman's disease, in addition to endothelial-derived KS. HHV-8 is unusual in its possession of a plethora of "accessory" genes and encoded proteins in addition to the core, conserved herpesvirus and gammaherpesvirus genes that are necessary for basic biological functions of these viruses. The HHV-8 accessory proteins specify not only activities deducible from their cellular protein homologies but also novel, unsuspected activities that have revealed new mechanisms of virus-host interaction that serve virus replication or latency and may contribute to the development and progression of virus-associated neoplasia. These proteins include viral interleukin-6 (vIL-6), viral chemokines (vCCLs), viral G protein-coupled receptor (vGPCR), viral interferon regulatory factors (vIRFs), and viral antiapoptotic proteins homologous to FLICE (FADD-like IL-1β converting enzyme)-inhibitory protein (FLIP) and survivin. Other HHV-8 proteins, such as signaling membrane receptors encoded by open reading frames K1 and K15, also interact with host mechanisms in unique ways and have been implicated in viral pathogenesis. Additionally, a set of micro-RNAs encoded by HHV-8 appear to modulate expression of multiple host proteins to provide conditions conducive to virus persistence within the host and could also contribute to HHV-8-induced neoplasia. Here, we review the molecular biology underlying these novel virus-host interactions and their potential roles in both virus biology and virus-associated disease.

YGLF motif in the Kaposi sarcoma herpes virus G-protein-coupled receptor adjusts NF-κB activation and paracrine actions

Kaposi sarcoma (KS) and primary effusion lymphoma (PEL) are two pathologies associated with KS herpes virus (KSHV/HHV-8) infection. KSHV genome contains several oncogenes, among which, the viral G-protein-coupled receptor (vGPCR open reading frame 74) has emerged as a major factor in KS pathogenicity. Indeed, vGPCR is a constitutively active receptor, whose expression is sufficient to drive cell transformation in vitro and tumour development in mice. However, neither the role of vGPCR in KSHV-infected B-lymphocytes nor the molecular basis for its constitutive activation is well understood. Here, we show that vGPCR expression contributes to nuclear factor-κB (NF-κB)-dependent cellular survival in both PEL cells and primary B cells from HIV-negative KS patients. We further identified within vGPCR an AP2 consensus binding motif, Y326GLF, that directs its localization between the plasma membrane and clathrin-coated vesicles. The introduction of a mutation in this site (Y326A) increased NF-κB activity and proinflammatory cytokines production. This correlated with exacerbated morphological rearrangement, migration and proliferation of non-infected monocytes. Collectively, our work raises the possibility that KSHV-infected B-lymphocytes use vGPCR to impact ultimately the immune response and communication within the tumour microenvironment in KSHV-associated pathologies.

Detection of Chlamydophila pneumoniae and human herpesvirus 8 in primary cutaneous anaplastic large-cell lymphoma: a case report

Background

The etiology of primary cutaneous anaplastic large-cell CD30+ lymphoma is largely unknown, and although an infectious involvement has been suspected, the implication of infectious agents in its pathogenesis is still unclear.

Findings

We report the case of a HIV-negative patient referred to our hospital with a rapidly enlarging skin tumor on her upper eyelid. Surgical excision was performed and histological analysis evidenced a primary cutaneous anaplastic large-cell lymphoma. Due to the ocular localization and to the prominent angiogenic component of the lesion, molecular analyses for the detection of Chlamydophila pneumoniae and HHV8 were performed, revealing the presence of an infection by both pathogens in surgical biopsy and in peripheral blood mononuclear cells.

Conclusions

These findings suggest for the first time a possible association of C. pneumoniae and/or HHV8 infection, or both together, with primary cutaneous anaplastic large-cell lymphoma in non-immunocompromised and HIV-negative subjects. This potential pathogenic association, if confirmed, could provide potential indications for future therapy.

Susceptibility of human placenta derived mesenchymal stromal/stem cells to human herpesviruses infection

Fetal membranes (FM) derived mesenchymal stromal/stem cells (MSCs) are higher in number, expansion and differentiation abilities compared with those obtained from adult tissues, including bone marrow. Upon systemic administration, ex vivo expanded FM-MSCs preferentially home to damaged tissues promoting regenerative processes through their unique biological properties. These characteristics together with their immune-privileged nature and immune suppressive activity, a low infection rate and young age of placenta compared to other sources of SCs make FM-MSCs an attractive target for cell-based therapy and a valuable tool in regenerative medicine, currently being evaluated in clinical trials. In the present study we investigated the permissivity of FM-MSCs to all members of the human Herpesviridae family, an issue which is relevant to their purification, propagation, conservation and therapeutic use, as well as to their potential role in the vertical transmission of viral agents to the fetus and to their potential viral vector-mediated genetic modification. We present here evidence that FM-MSCs are fully permissive to infection with Herpes simplex virus 1 and 2 (HSV-1 and HSV-2), Varicella zoster virus (VZV), and Human Cytomegalovirus (HCMV), but not with Epstein-Barr virus (EBV), Human Herpesvirus-6, 7 and 8 (HHV-6, 7, 8) although these viruses are capable of entering FM-MSCs and transient, limited viral gene expression occurs. Our findings therefore strongly suggest that FM-MSCs should be screened for the presence of herpesviruses before xenotransplantation. In addition, they suggest that herpesviruses may be indicated as viral vectors for gene expression in MSCs both in gene therapy applications and in the selective induction of differentiation.

Inhibition of apelin expression switches endothelial cells from proliferative to mature state in pathological retinal angiogenesis

The recruitment of mural cells such as pericytes to patent vessels with an endothelial lumen is a key factor for the maturation of blood vessels and the prevention of hemorrhage in pathological angiogenesis. To date, our understanding of the specific trigger underlying the transition from cell growth to the maturation phase remains incomplete. Since rapid endothelial cell growth causes pericyte loss, we hypothesized that suppression of endothelial growth factors would both promote pericyte recruitment, in addition to inhibiting pathological angiogenesis. Here, we demonstrate that targeted knockdown of apelin in endothelial cells using siRNA induced the expression of monocyte chemoattractant protein-1 (MCP-1) through activation of Smad3, via suppression of the PI3K/Akt pathway. The conditioned medium of endothelial cells treated with apelin siRNA enhanced the migration of vascular smooth muscle cells, through MCP-1 and its receptor pathway. Moreover, in vivo delivery of siRNA targeting apelin, which causes exuberant endothelial cell proliferation and pathological angiogenesis through its receptor APJ, led to increased pericyte coverage and suppressed pathological angiogenesis in an oxygen-induced retinopathy model. These data demonstrate that apelin is not only a potent endothelial growth factor, but also restricts pericyte recruitment, establishing a new connection between endothelial cell proliferation signaling and a trigger of mural recruitment.

Herpesviruses and the microbiome

The focus of this article will be to examine the role of common herpesviruses as a component of the microbiome of atopic patients and to review clinical observations suggesting that atopic patients might be predisposed to more severe and atypical herpes-related illness because their immune response is biased toward a TH2 cytokine profile. Human populations are infected with 8 herpesviruses, including herpes simplex virus HSV1 and HSV2 (also termed HHV1 and HHV2), varicella zoster virus (VZV or HHV3), EBV (HHV4), cytomegalovirus (HHV5), HHV6, HHV7, and Kaposi sarcoma-associated herpesvirus (termed KSV or HHV8). Herpesviruses are highly adapted to lifelong infection of their human hosts and thus can be considered a component of the human "microbiome" in addition to their role in illness triggered by primary infection. HSV1 and HSV2 infection and reactivation can present with more severe cutaneous symptoms termed eczema herpeticum in the atopic population, similar to the more severe eczema vaccinatum, and drug reaction with eosinophilia and systemic symptoms syndrome (DRESS) is associated with reactivation of HSV6 and possibly other herpesviruses in both atopic and nonatopic patients. In this review evidence is reviewed that primary infection with herpesviruses may have an atypical presentation in the atopic patient and conversely that childhood infection might alter the atopic phenotype. Reactivation of latent herpesviruses can directly alter host cytokine profiles through viral expression of cytokine-like proteins, such as IL-10 (EBV) or IL-6 (cytomegalovirus and HHV8), viral encoded and secreted siRNA and microRNAs, and modulation of expression of host transcription pathways, such as nuclear factor κB. Physicians caring for allergic and atopic populations should be aware of common and uncommon presentations of herpes-related disease in atopic patients to provide accurate diagnosis and avoid unnecessary laboratory testing or incorrect diagnosis of other conditions, such as drug allergy or autoimmune disease. Antiviral therapy and vaccines should be administered promptly when indicated clinically.

Professional antigen presenting cells in human herpesvirus 8 infection

Professional antigen presenting cells (APC), i.e., dendritic cells (DC), monocytes/macrophages, and B lymphocytes, are critically important in the recognition of an invading pathogen and presentation of antigens to the T cell-mediated arm of immunity. Human herpesvirus 8 (HHV-8) is one of the few human viruses that primarily targets these APC for infection, altering their cytokine profiles, manipulating their surface expression of MHC molecules, and altering their ability to activate HHV-8-specific T cells. This could be why T cell responses to HHV-8 antigens are not very robust. Of these APC, only B cells support complete, lytic HHV-8 infection. However, both complete and abortive virus replication cycles in APC could directly affect viral pathogenesis and progression to Kaposi's sarcoma (KS) and HHV-8-associated B cell cancers. In this review, we discuss the effects of HHV-8 infection on professional APC and their relationship to the development of KS and B cell lymphomas.

Curcumin inhibits Rift Valley fever virus replication in human cells

Rift Valley fever virus (RVFV) is an arbovirus that is classified as a select agent, an emerging infectious virus, and an agricultural pathogen. Understanding RVFV-host interactions is imperative to the design of novel therapeutics. Here, we report that an infection by the MP-12 strain of RVFV induces phosphorylation of the p65 component of the NFκB cascade. We demonstrate that phosphorylation of p65 (serine 536) involves phosphorylation of IκBα and occurs through the classical NFκB cascade. A unique, low molecular weight complex of the IKK-β subunit can be observed in MP-12-infected cells, which we have labeled IKK-β2. The IKK-β2 complex retains kinase activity and phosphorylates an IκBα substrate. Inhibition of the IKK complex using inhibitors impairs viral replication, thus alluding to the requirement of an active IKK complex to the viral life cycle. Curcumin strongly down-regulates levels of extracellular infectious virus. Our data demonstrated that curcumin binds to and inhibits kinase activity of the IKK-β2 complex in infected cells. Curcumin partially exerts its inhibitory influence on RVFV replication by interfering with IKK-β2-mediated phosphorylation of the viral protein NSs and by altering the cell cycle of treated cells. Curcumin also demonstrated efficacy against ZH501, the fully virulent version of RVFV. Curcumin treatment down-regulated viral replication in the liver of infected animals. Our data point to the possibility that RVFV infection may result in the generation of novel versions of host components (such as IKK-β2) that, by virtue of altered protein interaction and function, qualify as unique therapeutic targets.

KSHV Induction of Angiogenic and Lymphangiogenic Phenotypes

Kaposi’s sarcoma (KS) is a highly vascularized tumor supporting large amounts of neo-angiogenesis. The major cell type in KS tumors is the spindle cell, a cell that expresses markers of lymphatic endothelium. KSHV, the etiologic agent of KS, is found in the spindle cells of all KS tumors. Considering the extreme extent of angiogenesis in KS tumors at all stages it has been proposed that KSHV directly induces angiogenesis in a paracrine fashion. In accordance with this theory, KSHV infection of endothelial cells in culture induces a number of host pathways involved in activation of angiogenesis and a number of KSHV genes themselves can induce pathways involved in angiogenesis. Spindle cells are phenotypically endothelial in nature, and therefore, activation through the induction of angiogenic and/or lymphangiogenic phenotypes by the virus may also be directly involved in spindle cell growth and tumor induction. Accordingly, KSHV infection of endothelial cells induces cell autonomous angiogenic phenotypes to activate host cells. KSHV infection can also reprogram blood endothelial cells to lymphatic endothelium. However, KSHV induces some blood endothelial specific genes upon infection of lymphatic endothelial cells creating a phenotypic intermediate between blood and lymphatic endothelium. Induction of pathways involved in angiogenesis and lymphangiogenesis are likely to be critical for tumor cell growth and spread. Thus, induction of both cell autonomous and non-autonomous changes in angiogenic and lymphangiogenic pathways by KSHV likely plays a key role in the formation of KS tumors.

Activating transcription factor 4 (ATF4) is upregulated by human herpesvirus 8 infection, increases virus replication and promotes proangiogenic properties

Human herpesvirus 8 (HHV-8) triggers proangiogenic behaviour in endothelial cells by inducing monocyte chemoattractant protein 1 (MCP-1) through activation of Nuclear Factor κB (NF-κB). However, NF-κB inhibition still results in partial MCP-1 induction and consequent angiogenesis, suggesting the involvement of another transcriptional pathway. We analysed activating transcription factor 4 (ATF4), since it is central in the cellular response to stress and is involved in angiogenesis. The results show that HHV-8 upregulates ATF4 expression, which in turn promotes HHV-8 infection, and induces MCP-1 production and proangiogenic properties in endothelial cells. By contrast, ATF4 silencing decreases virus replication and inhibits virus-induced MCP-1 production and induction of tube-like structures. Therefore, ATF4 plays a role in HHV-8 replication and associated virus-induced angiogenesis. The elucidation of molecular pathways involved in this process will result in a better understanding of the virus-induced angiogenic process and might help in designing novel therapies to reduce tumour growth.

Kaposi's sarcoma-associated herpesvirus infection of endothelial cells inhibits neutrophil recruitment through an interleukin-6-dependent mechanism: a new paradigm for viral immune evasion

Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiological agent of Kaposi's sarcoma (KS), an endothelial cell (EC) neoplasm characterized by dysregulated angiogenesis and inflammation. KSHV infection of EC causes production of proinflammatory mediators, regarded as possible initiators of the substantial mononuclear leukocyte recruitment seen in KS. Conversely, KSHV immune evasion strategies exist, such as degradation of EC leukocyte adhesion receptors by viral proteins. Here, we report the effects of KSHV infection of primary EC on recruitment of flowing leukocytes. Infection did not initiate adhesion of any leukocyte subset per se. However, on cytokine-stimulated EC, KSHV specifically inhibited neutrophil, but not PBL or monocyte, transmigration, an observation consistent with the inflammatory cell profile found in KS lesions in vivo. This inhibition could be recapitulated on uninfected EC using supernatant from infected cultures. These supernatants contained elevated levels of human interleukin 6 (hIL-6), and both the KSHV- and the supernatant-induced inhibitions of neutrophil transmigration were abrogated in the presence of a hIL-6 neutralizing antibody. Furthermore, preconditioning of EC with hIL-6 mimicked the effect of KSHV. Using RNA interference (RNAi), we show that upregulation of suppressor of cytokine signaling 3 (SOCS3) was necessary for this effect of hIL-6. These studies reveal a novel paracrine mode of KSHV immune evasion, resulting in reduced recruitment of neutrophils, a cell type whose antiviral and antitumor roles are becoming increasingly appreciated. Moreover, the findings have implications for our understanding of the contribution of hIL-6 to the pathogenesis of other inflammatory disorders and tumors in which this cytokine is abundant.

Vascular endothelial cells cultured from patients with cerebral or uncomplicated malaria exhibit differential reactivity to TNF

Plasmodium falciparum malaria is a major cause of morbidity and mortality in African children, and factors that determine the development of uncomplicated (UM) versus cerebral malaria (CM) are not fully understood. We studied the ex vivo responsiveness of microvascular endothelial cells to pro-inflammatory stimulation and compared the findings between CM and UM patients. In patients with fatal disease we compared the properties of vascular endothelial cells cultured from brain tissue to those cultured from subcutaneous tissue, and found them to be very similar. We then isolated, purified and cultured primary endothelial cells from aspirated subcutaneous tissue of patients with CM (EC(CM) ) or UM (EC(UM) ) and confirmed the identity of the cells before analysis. Upon TNF stimulation in vitro, EC(CM) displayed a significantly higher capacity to upregulate ICAM-1, VCAM-1 and CD61 and to produce IL-6 and MCP-1 but not RANTES compared with EC(UM) . The shedding of endothelial microparticles, a recently described parameter of severity in CM, and the cellular level of activated caspase-3 were both significantly greater in EC(CM) than in EC(UM) . These data suggest that inter-individual differences in the endothelial inflammatory response to TNF may be an additional factor influencing the clinical course of malaria.

Regulation of tumor necrosis factor-like weak inducer of apoptosis receptor protein (TWEAKR) expression by Kaposi's sarcoma-associated herpesvirus microRNA prevents TWEAK-induced apoptosis and inflammatory cytokine expression

Kaposi's sarcoma (KS)-associated herpesvirus (KSHV) is the causative agent of KS, the second most common AIDS-associated malignancy. KSHV expresses at least 18 different mature microRNAs (miRNAs) during latency. To identify cellular targets of KSHV miRNAs, we have analyzed a previously reported series of microarrays examining changes in cellular gene expression in the presence of KSHV miRNAs. Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) receptor (TWEAKR) was among the most consistently and robustly downregulated genes in the presence of KSHV miR-K12-10a (miR-K10a). Results from luciferase assays with reporter plasmids containing the 3' untranslated region (UTR) of TWEAKR suggest a targeting of TWEAKR by miR-K10a. The mutation of two predicted miR-K10a recognition sites within the 3' UTR of TWEAKR completely disrupts inhibition by miR-K10a. The expression of TWEAKR was downregulated in cells transfected with miR-K10a as well as during de novo KSHV infection. In a KS tumor-derived endothelial cell line, the downregulation of TWEAKR by miR-K10a resulted in reduced levels of TWEAK-induced caspase activation. In addition, cells transfected with miR-K10a showed less induction of apoptosis by annexin V staining and terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) assays. Finally, the downregulation of TWEAKR by miR-K10a in primary human endothelial cells resulted in a decrease in levels of expression of the proinflammatory cytokines interleukin-8 (IL-8) and monocyte chemoattractant protein 1 (MCP-1) in response to TWEAK. These results identify and validate an important cellular target of KSHV miRNAs. Furthermore, we demonstrate that a viral miRNA protects cells from apoptosis and suppresses a proinflammatory response, which may have significant implications in the complex context of KS lesions.

Induction of angiogenic chemokine CCL2 by human herpesvirus 8 chemokine receptor

Human herpesvirus 8 (HHV-8) is associated with Kaposi's sarcoma (KS), an endothelial cell lesion believed to be initiated and driven primarily by cytokine dysregulation. Among the viral proteins suspected as contributing to viral pathogenesis is the lytically expressed viral G protein-coupled receptor (vGPCR), which can induce various cellular cytokines. CC ligand-2 (CCL2/MCP-1) is a vGPCR-regulated angiogenic chemokine found at elevated levels in KS lesions and induced by HHV-8 infection of endothelial cells. Here we show that vGPCR induces CCL2 in endothelial cells via activation of C/EBPbeta and that vGPCR and C/EBPbeta are critical components of CCL2 induction by HHV-8 infection of endothelial cultures. To our knowledge, this is the first report of vGPCR-mediated cytokine induction, and its characterization, in the context of virus infection. Our results identify a mechanism by which vGPCR can contribute, in a host cell shutoff-independent manner, to viral pathogenesis.

Integrated microarray and multiplex cytokine analyses of Kaposi's Sarcoma Associated Herpesvirus viral FLICE Inhibitory Protein K13 affected genes and cytokines in human blood vascular endothelial cells

Background

Kaposi's sarcoma (KS) associated herpesvirus (KSHV) is the etiological agent of KS, a neoplasm characterized by proliferating spindle cells, extensive neoangiogenesis and a prominent inflammatory infiltrate. Infection of blood vascular endothelial cells with KSHV in vitro results in their spindle cell transformation, which is accompanied by increased expression of inflammatory chemokines and cytokines, and acquisition of lymphatic endothelial markers. Mimicking the effect of viral infection, ectopic expression of KSHV-encoded latent protein vFLIP K13 is sufficient to induce spindle transformation of vascular endothelial cells. However, the effect of K13 expression on global gene expression and induction of lymphatic endothelial markers in vascular endothelial cells has not been studied.

Methods

We used gene array analysis to determine change in global gene expression induced by K13 in human vascular endothelial cells (HUVECs). Results of microarray analysis were validated by quantitative RT-PCR, immunoblotting and a multiplex cytokine array.

Results

K13 affected the expression of several genes whose expression is known to be modulated by KSHV infection, including genes involved in immune and inflammatory responses, anti-apoptosis, stress response, and angiogenesis. The NF-κB pathway was the major signaling pathway affected by K13 expression, and genetic and pharmacological inhibitors of this pathway effectively blocked K13-induced transcriptional activation of the promoter of CXCL10, one of the chemokines whose expression was highly upregulated by K13. However, K13, failed to induce expression of lymphatic markers in blood vascular endothelial cells.

Conclusion

While K13 may account for change in the expression of a majority of genes observed following KSHV infection, it is not sufficient for inducing lymphatic reprogramming of blood vascular endothelial cells.

Thiazolides, a new class of anti-influenza molecules targeting viral hemagglutinin at the post-translational level

The emergence of highly contagious influenza A virus strains, such as the new H1N1 swine influenza, represents a serious threat to global human health. Efforts to control emerging influenza strains focus on surveillance and early diagnosis, as well as development of effective vaccines and novel antiviral drugs. Herein we document the anti-influenza activity of the anti-infective drug nitazoxanide and its active circulating-metabolite tizoxanide and describe a class of second generation thiazolides effective against influenza A virus. Thiazolides inhibit the replication of H1N1 and different other strains of influenza A virus by a novel mechanism: they act at post-translational level by selectively blocking the maturation of the viral hemagglutinin at a stage preceding resistance to endoglycosidase H digestion, thus impairing hemagglutinin intracellular trafficking and insertion into the host plasma membrane, a key step for correct assembly and exit of the virus from the host cell. Targeting the maturation of the viral glycoprotein offers the opportunity to disrupt the production of infectious viral particles attacking the pathogen at a level different from the currently available anti-influenza drugs. The results indicate that thiazolides may represent a new class of antiviral drugs effective against influenza A infection.

Induction of CCL20 production by Kaposi sarcoma-associated herpesvirus: role of viral FLICE inhibitory protein K13-induced NF-kappaB activation

Kaposi sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8, is the etiologic agent of Kaposi sarcoma (KS), an angioproliferative lesion characterized by dramatic angiogenesis and inflammatory infiltration. In this study, we report that expression of chemokine CCL20, a potent chemoattractant of dendritic cells and lymphocytes, is strongly induced in cultured cells either by KSHV infection or on ectopic expression of viral FLICE inhibitory protein K13. This induction is caused by transcriptional activation of CCL20 gene, which is mediated by binding of the p65, p50, and c-Rel subunits of the transcription factor nuclear factor-kappaB (NF-kappaB) to an atypical NF-kappaB-binding site present in the CCL20 gene promoter. The CCL20 gene induction is defective in K13 mutants that lack NF-kappaB activity, and can be blocked by specific genetic and pharmacologic inhibitors of the NF-kappaB pathway. CCR6, the specific receptor for CCL20, is also induced in cultured cells either by KSHV infection or on K13 expression. Finally, expression of CCL20 and CCR6 is increased in clinical samples of KS. These results suggest that KSHV and K13-mediated induction of CCL20 and CCR6 may contribute to the recruitment of dendritic cells and lymphocytes into the KS lesions, and to tumor growth and metastases.

Impact of Monocyte Chemoattractant Protein-1 Deficiency on Cerebral Aneurysm Formation

Background and Purpose— Recent studies have suggested that chronic inflammation actively participates in cerebral aneurysm (CA) formation. Macrophages accumulate in CA walls and express proinflammatory genes promoting CA progression, but the molecular mechanisms of monocyte/macrophage recruitment into CA walls remain to be elucidated.

Methods— Monocyte chemoattractant protein-1 (MCP-1) expression in experimentally induced CAs was assessed by immunohistochemistry and Western blotting. The role of MCP-1 in CA formation was examined by MCP-1 −/− mice and a plasmid DNA encoding a dominant negative mutant of MCP-1 (7ND). MCP-1 expression in human CAs was examined by immunohistochemistry.

Results— MCP-1 expression was upregulated in aneurysmal walls at the early stage of CA formation. MCP-1 −/− mice exhibited a significant decrease of CA formation and macrophage accumulation with decreased expression of matrix metalloproteinase-2, -9, and inducible nitric oxide synthase. Immunohistochemistry for the DNA binding form of nuclear factor-kappa B showed nuclear factor-kappa B activation in MCP-1-expressing cells. Blockade of MCP-1 activity by 7ND resulted in the inhibition of CA progression in rats. In human CAs, MCP-1 was also expressed in CA walls.

Conclusions— These data suggest that MCP-1 plays a crucial role in CA formation as a major chemoattractant for monocyte/macrophage. MCP-1 expression in CA walls is induced through nuclear factor-kappa B activation. MCP-1 may be a novel therapeutic target of medical treatment preventing CA progression.

NF-kappaB serves as a cellular sensor of Kaposi's sarcoma-associated herpesvirus latency and negatively regulates K-Rta by antagonizing the RBP-Jkappa coactivator

Successful viral replication is dependent on a conducive cellular environment; thus, viruses must be sensitive to the state of their host cells. We examined the idea that an interplay between viral and cellular regulatory factors determines the switch from Kaposi's sarcoma-associated herpesvirus (KSHV) latency to lytic replication. The immediate-early gene product K-Rta is the first viral protein expressed and an essential factor in reactivation; accordingly, this viral protein is in a key position to serve as a viral sensor of cellular physiology. Our approach aimed to define a host transcription factor, i.e., host sensor, which modulates K-Rta activity on viral promoters. To this end, we developed a panel of reporter plasmids containing all 83 putative viral promoters for a comprehensive survey of the response to both K-Rta and cellular transcription factors. Interestingly, members of the NF-kappaB family were shown to be strong negative regulators of K-Rta transactivation for all but two viral promoters (Ori-RNA and K12). Recruitment of K-Rta to the ORF57 and K-bZIP promoters, but not the K12 promoter, was significantly impaired when NF-kappaB expression was induced. Many K-Rta-responsive promoters modulated by NF-kappaB contain the sequence of the RBP-Jkappa binding site, a major coactivator which anchors K-Rta to target promoters via consensus motifs which overlap with that of NF-kappaB. Gel shift assays demonstrated that NF-kappaB inhibits the binding of RBP-Jkappa and forms a complex with RBP-Jkappa. Our results support a model in which a balance between K-Rta/RBP-Jkappa and NF-kappaB activities determines KSHV reactivation. An important feature of this model is that the interplay between RBP-Jkappa and NF-kappaB on viral promoters controls viral gene expression mediated by K-Rta.

vFLIP from KSHV inhibits anoikis of primary endothelial cells

Kaposi's sarcoma-associated herpesvirus (KSHV or HHV-8) infection of endothelial cells is an early event in the aetiology of the endothelial cell tumour Kaposi's sarcoma (KS). We have examined the effect of the KSHV latent protein viral FLICE-like inhibitory protein (vFLIP) on dermal microvascular endothelial cell (MVEC) survival as vFLIP is expressed in the KSHV-infected cells within KS lesions. To do this, we have used a lentiviral vector to express vFLIP in MVECs in the absence of other KSHV proteins. vFLIP activates the classical NF-κB pathway in MVECs and causes nuclear translocation of RelA/p65. This NF-κB activation prevents detachment-induced apoptosis (anoikis) of MVECs but does not inhibit apoptosis induced by removal of essential survival factors, including vascular endothelial growth factor (VEGF). vFLIP expression inhibits anoikis in part by inducing the secretion of an additional paracrine survival factor(s). The implications of these results for KS development are discussed.

Retinoic Acid Analogues Inhibit Human Herpesvirus 8 Replication

Background

Retinoids have a pronounced antiviral effect against several viruses. In this study we aimed to investigate the effect of retinoids on human herpesvirus 8 (HHV-8).

Methods

A panel of retinoic acid compounds were tested for their antiviral activity against HHV-8 in human umbilical vascular endothelial cells (HUVECs) and in a human epithelial cell line. The presence, transcription and antigen expression of HHV-8 in infected cells – in the presence or absence of retinoic acid compounds – were evaluated by PCR, reverse transcriptase PCR and immunofluorescence assays; HHV-8 viral load was determined by real-time quantitative PCR. Angiogenesis induced by HHV-8 was also assessed using Cultrex® basement membrane extract.

Results

The compounds tested specifically inhibited viral promoters, during the early and late phases of infection in both cell systems tested, and resulted in up to 100fold reduction of viral titre and release of progeny virus. The inhibition of viral replication induced by retinoids in endothelial cells, the primary target of HHV-8-driven transformation in Kaposi's Sarcoma, prevented endothelial cells from developing spindle morphology and in vitro tube formation, characteristic changes associated with HHV-8 infection and transformation.

Conclusions

We show that retinoids inhibit HHV-8 replication and identify new retinoid compounds with a strong antiviral effect. Selective retinoids, particularly those with retinoic acid receptor agonist activity, may be good candidates for the development of antiviral drugs.

MCP-1 Promoter Polymorphism at 2518 is associated with metastasis of nasopharyngeal carcinoma after treatment

PURPOSE

We herein examined whether the single nucleotide polymorphism (SNP) at -2518 of the MCP-1 gene promoter region influences clinical outcomes among nasopharyngeal carcinoma (NPC) patients.

EXPERIMENTAL DESIGN

The study population consisted of 411 NPC patients without metastasis at diagnosis. All patients were treated at the Chang Gung Memorial Hospital from March 1994 to November 2004. The MCP-1 SNP-2518 genotype of each patient was determined by TaqMan genotyping kit. Statistical analyses were conducted to compare disease-specific survival (DSS), progression-free survival (PFS), local recurrence-free survival (LRFS), and distant metastasis-free survival (DMFS) of patients according to genotype. MCP-1 expression in tumor biopsies was examined by immunohistochemistry.

RESULTS

Among 411 NPC patients, carriers of AA and AG genotypes were prone to distant metastasis than that of GG genotype (hazard ratio, 2.21; P = 0.017, and hazard ratio, 2.23; P = 0.005, for AA and AG genotype, respectively) after initial radiotherapy. No genotype-specific significant difference was found in DSS, PFS, and LRFS. Furthermore, immunohistochemistry revealed that MCP-1 expression level was higher in NPC tumor cells from GG carriers compared with those from AA and AG carriers.

CONCLUSIONS

MCP-1 SNP-2518 may be a valuable genetic marker for assessing the risk of developing distant metastasis after the radiotherapy in NPC patients. Carriers of A allele may require more aggressive chemotherapy implicating a potential marker for personalized medicine. We speculate that a regulatory SNP may be associated with the distant metastasis of NPC. Validation studies are warranted.

PAX2 expression by HHV-8-infected endothelial cells induced a proangiogenic and proinvasive phenotype

In the present study, we evaluated whether infection of microvascular endothelial cells (HMECs) with HHV-8 can trigger the expression of PAX2 oncogene and whether PAX2 protein is involved in HHV-8-induced transformation of HMECs. We found that HHV-8 infection induced the expression of both the PAX2 gene and PAX2 protein in HMECs but failed to induce PAX2 protein in HMECs stably transfected with PAX2 antisense (HMEC-AS). HHV-8-infected HMECs but not HMEC-AS acquired proinvasive proadhesive properties, enhanced survival and in vitro angiogenesis, suggesting a correlation between PAX2 expression and the effects triggered by HHV-8 infection. When HMEC-expressing PAX2 by stable transfection with PAX2 sense gene or by HHV-8 infection were implanted in vivo in severe combined immunodeficient (SCID) mice, enhanced angiogenesis and proliferative lesions resembling KS were observed. HHV-8-infected HMEC-AS failed to induce angiogenesis and KS-like lesions. These results suggest that the expression of PAX2 is required for the proangiogenic and proinvasive changes induced by HHV-8 infection in HMECs. In conclusion, HHV-8 infection may activate an embryonic angiogenic program in HMECs by inducing the expression of PAX2 oncogene.

Parotid localized Castleman’s disease and HHV-8 infection: a case report

Castleman's disease (CD) is an unusual massive proliferation of lymphoid tissue distinct in two clinical forms, localized and multicentric. The multicentric form has been related to human herpesvirus 8 (HHV-8), especially in HIV-infected patients, whereas the localized form of CD is still unrelated to viral pathogens. We report a case of a HIV-negative 16-year-old male referred to our hospital with a 12-month history of a painless swelling in his right parotid region. A parotidectomy was performed, and histological analysis evidenced a localized CD. The search for HHV-8 revealed an active virus infection. The patient was commenced on corticosteroid therapy and a follow-up was performed every 6 months. The patient was commenced on corticosteroid therapy and there has been no recurrence after 24 months. The authors report a case of localized parotid CD in a patient with evidence of an active HHV-8 infection. The results of this study does for the first time suggest an association between HHV-8 and localized CD in HIV-negative subjects.

Kaposi's sarcoma-associated herpesvirus induces sustained NF-kappaB activation during de novo infection of primary human dermal microvascular endothelial cells that is essential for viral gene expression

In vitro Kaposi's sarcoma-associated herpesvirus (KSHV) infection of primary human dermal microvascular endothelial (HMVEC-d) cells and human foreskin fibroblast (HFF) cells is characterized by the induction of preexisting host signal cascades, sustained expression of latency-associated genes, transient expression of a limited number of lytic genes, and induction of several cytokines, growth factors, and angiogenic factors. Since NF-kappaB is a key molecule involved in the regulation of several of these factors, here, we examined NF-kappaB induction during de novo infection of HMVEC-d and HFF cells. Activation of NF-kappaB was observed as early as 5 to 15 min postinfection by KSHV, and translocation of p65-NF-kappaB into nuclei was detected by immunofluorescence assay, electrophoretic mobility shift assay, and p65 enzyme-linked immunosorbent assay. IkappaB phosphorylation inhibitor (Bay11-7082) reduced this activation significantly. A sustained moderate level of NF-kappaB induction was seen during the observed 72 h of in vitro KSHV latency. In contrast, high levels of ERK1/2 activation at earlier time points and a moderate level of activation at later times were observed. p38 mitogen-activated protein kinase was activated only at later time points, and AKT was activated in a cyclic manner. Studies with UV-inactivated KSHV suggested a role for virus entry stages in NF-kappaB induction and a requirement for KSHV viral gene expression in sustained induction. Inhibition of NF-kappaB did not affect target cell entry by KSHV but significantly reduced the expression of viral latent open reading frame 73 and lytic genes. KSHV infection induced the activation of several host transcription factors, including AP-1 family members, as well as several cytokines, growth factors, and angiogenic factors, which were significantly affected by NF-kappaB inhibition. These results suggest that during de novo infection, KSHV induces sustained levels of NF-kappaB to regulate viral and host cell genes and thus possibly regulates the establishment of latent infection.