SMAD proteins of oligodendroglial cells regulate transcription of JC virus early and late genes coordinately with the Tat protein of human immunodeficiency virus type 1

Transcriptomic Analysis Reveals Key Pathways Influenced by HIV-2 Vpx

Viral protein X (Vpx) is a unique accessory protein encoded by the genome of the human immunodeficiency virus type 2 (HIV-2) and lineages of the simian immunodeficiency virus of sooty mangabeys. So far, counteracting the cellular restriction factor SAMHD1 and mediating the efficient translocation of viral pre-integration complex have been recognized as key functions of Vpx; however, a thorough exploration of its effects on the cellular transcriptome and cytokine milieu has not yet been undertaken. In this study, we carried out the transcriptomic analysis of THP-1 cells and determined differential gene expressions induced by HIV-2 Vpx, utilizing vectors coding for the wild-type and K68-R70 functionally restricted proteins. Significantly altered genes were then validated and quantified through real-time quantitative PCR (qPCR); additionally, replication-competent virions were also used to confirm the findings. Moreover, we analyzed the effect of Vpx expression on the secretion of key cytokines in the medium of transfected cells. Our findings revealed that wild-type HIV-2 Vpx can significantly alter the expression of genes coding for helicases, zinc finger proteins, chaperons, transcription factors and proteins involved in DNA methylation. Differentially altered genes were involved in negative regulation of viral processes, the type I interferon-signaling pathway, DNA-template transcription, elongation, the positive regulation of interferon beta production and the negative regulation of innate immune response. Importantly, Vpx was also found to decrease the expression of HIV-1 Tat, possibly through the downregulation of a crucial splicing factor, required for the maturation of Tat. Additionally, studies on cellular cytokine milieu showed that this accessory protein induced key proinflammatory cytokines. Our study provides important information about the complex role played by HIV-2 Vpx in priming and taming the cellular environment to allow for the establishment of the infection.

HIV-1 Tat-induced disruption of epithelial junctions and epithelial-mesenchymal transition of oral and genital epithelial cells lead to increased invasiveness of neoplastic cells and the spread of herpes simplex virus and cytomegalovirus

Human immunodeficiency virus (HIV-1) transactivator Tat is a unique multi-functional viral protein secreted by infected cells. Although its primary function is to promote HIV-1 transcription, secreted Tat interacts with neighboring cells and induces numerous disease-associated pathological changes. Despite the substantial reduction of viral load and disease burden, Tat expression and secretion persist in people living with HIV who are undergoing treatment with highly effective combination antiretroviral therapy (cART). Tat interacts with both oral and genital epithelial cells and impairs their mucosal barrier functions, which facilitates the entry of other pathogenic viruses. Tat-mediated interactions with both human papillomavirus (HPV) -infected and HPV-negative neoplastic epithelial cells lead to epithelial-mesenchymal transition and increased invasiveness of malignant cells. Likewise, Tat-induced disruption of oral epithelial cell junctions leads to herpes simplex virus-1 (HSV-1) infection and spread via exposure of its receptor, nectin-1. HIV-1 Tat facilitates infection and spread of human cytomegalovirus (HCMV) by activating mitogen-activated protein kinases (MAPK) and promoting NF-κB signaling, both critical for the replication and production of progeny virions. HIV extracellular Tat also plays a critical role in human herpesvirus 8 (HHV8) -caused Kaposi sarcoma (KS) pathogenesis by synergizing with HHV-8 lytic proteins and promoting the proliferation, angiogenesis, and migration of endothelial cells. Collectively, these findings emphasize the critical impact of HIV-1 Tat on HIV/AIDS pathogenesis during the cART era and highlight the need for further research on the molecular mechanisms underlying Tat-mediated interactions with oral and genital mucosal epithelial cells.

JC polyomavirus: a short review of its biology, its association with progressive multifocal leukoencephalopathy, and the diagnostic value of different methods to manifest its activity or presence

INTRODUCTION

JC polyomavirus is the causative agent of progressive multifocal leukoencephalopathy (PML), a demyelinating disease resulting from the lytic infection of oligodendrocytes that may develop in immunosuppressed individuals: HIV1 infected or individuals under immunosuppressive therapies. Understanding the biology of JCPyV is necessary for a proper patient management, the development of diagnostic tests, and risk stratification.

AREAS COVERED

The review covers different areas of expertise including the genomic characterization of JCPyV strains detected in different body compartments (urine, plasma, and cerebrospinal fluid) of PML patients, viral mutations, molecular diagnostics, viral miRNAs, and disease.

EXPERT OPINION

The implementation of molecular biology techniques improved our understanding of JCPyV biology. Deep sequencing analysis of viral genomes revealed the presence of viral quasispecies in the cerebrospinal fluid of PML patients characterized by noncoding control region rearrangements and VP1 mutations. These neurotropic JCPyV variants present enhanced replication and an altered cell tropism that contribute to PML development. Monitoring these variants may be relevant for the identification of patients at risk of PML. Multiplex realtime PCR targeting both the LTAg and the archetype NCCR could be used to identify them. Failure to amplify NCCR should indicate the presence of a JCPyV prototype speeding up the diagnostic process.

Irrespective of Plaque Activity, Multiple Sclerosis Brain Periplaques Exhibit Alterations of Myelin Genes and a TGF-Beta Signature

In a substantial share of patients suffering from multiple sclerosis (MS), neurological functions slowly deteriorate despite a lack of radiological activity. Such a silent progression, observed in either relapsing-remitting or progressive forms of MS, is driven by mechanisms that appear to be independent from plaque activity. In this context, we previously reported that, in the spinal cord of MS patients, periplaques cover large surfaces of partial demyelination characterized notably by a transforming growth factor beta (TGF-beta) molecular signature and a decreased expression of the oligodendrocyte gene NDRG1 (N-Myc downstream regulated 1). In the present work, we re-assessed a previously published RNA expression dataset in which brain periplaques were originally used as internal controls. When comparing the mRNA profiles obtained from brain periplaques with those derived from control normal white matter samples, we found that, irrespective of plaque activity, brain periplaques exhibited a TGF-beta molecular signature, an increased expression of TGFB2 (transforming growth factor beta 2) and a decreased expression of the oligodendrocyte genes NDRG1 (N-Myc downstream regulated 1) and MAG (myelin-associated glycoprotein). From these data obtained at the mRNA level, a survey of the human proteome allowed predicting a protein-protein interaction network linking TGFB2 to the down-regulation of both NDRG1 and MAG in brain periplaques. To further elucidate the role of NDRG1 in periplaque-associated partial demyelination, we then extracted the interaction network linking NDRG1 to proteins detected in human central myelin sheaths. We observed that such a network was highly significantly enriched in RNA-binding proteins that notably included several HNRNPs (heterogeneous nuclear ribonucleoproteins) involved in the post-transcriptional regulation of MAG. We conclude that both brain and spinal cord periplaques host a chronic process of tissue remodeling, during which oligodendrocyte myelinating functions are altered. Our findings further suggest that TGFB2 may fuel such a process. Overall, the present work provides additional evidence that periplaque-associated partial demyelination may drive the silent progression observed in a subset of MS patients.

The oncogenic roles of JC polyomavirus in cancer

JC polyomavirus (JCPyV) belongs to the human polyomavirus family. Based on alternative splicing, the early region encodes the large and small T antigens, while the late region encodes the capsid structural proteins (VP1, VP2, and VP3) and the agnoprotein. The regulatory transcription factors for JCPyV include Sp1, TCF-4, DDX1, YB-1, LCP-1, Purα, GF-1, and NF-1. JCPyV enters tonsillar tissue through the intake of raw sewage, inhalation of air droplets, or parent-to-child transmission. It persists quiescently in lymphoid and renal tissues during latency. Both TGF-β1 and TNF-α stimulates JCPyV multiplication, while interferon-γ suppresses the process. The distinct distribution of caspid receptors (α-2, 6-linked sialic acid, non-sialylated glycosaminoglycans, and serotonin) determines the infection capabilities of JCPyV virions, and JCPyV entry is mediated by clathrin-mediated endocytosis. In permissive cells, JCPyV undergoes lytic proliferation and causes progressive multifocal leukoencephalopathy, while its DNA is inserted into genomic DNA and leads to carcinogenesis in non-permissive cells. T antigen targets p53, β-catenin, IRS, Rb, TGF-β1, PI3K/Akt and AMPK signal pathways in cancer cells. Intracranial injection of T antigen into animals results in neural tumors, and transgenic mice develop neural tumors, lens tumor, breast cancer, gastric, Vater’s, colorectal and pancreatic cancers, insulinoma, and hepatocellular carcinoma. Additionally, JCPyV DNA and its encoded products can be detected in the brain tissues of PML patients and brain, oral, esophageal, gastric, colorectal, breast, cervical, pancreatic, and hepatocellular cancer tissues. Therefore, JCPyV might represent an etiological risk factor for carcinogenesis and should be evaluated for early prevention, diagnosis, and treatment of cancers.

Determining host factors contributing to the reactivation of JC virus in kidney transplant recipients

BACKGROUND AND AIMS

The John Cunningham virus (JCV) is the established etiological agent of the polyomavirus-associated nephropathy among renal transplant recipients. In the present study, we aimed to determine the probable predictive factors leading to JCV replication in renal transplant patients.

MATERIAL AND METHODS

Urine and plasma samples were collected from a total of 120 consecutive renal-transplanted patients without preliminary screening from Jan 2018 to Mar 2019. After DNA extraction, the simultaneous detection and quantification of JCV and BK polyomavirus (BKV) were conducted using a Real-time quantitative PCR method. Moreover, statistical analyses were performed using the statistical software packages, SPSS version 21.

RESULTS

The prevalence of JCV viruria and viremia among renal transplant recipients were 26 (21.67%) and 20 (16.67%), respectively. A significant association was observed between the JCV and two risk factors, diabetes mellitus (P = 0.002) and renal stones (P = 0.015). The prevalence of JCV viremia among recipients who were grafted near time to sampling was significantly higher (P = 0.02). There was a statistically significant coexistence between BK and JC viruses among our patients (P = 0.029). The frequency of JCV viruria in males was reported almost three times more than in females (P = 0.005). The JCV shedding in urine was significantly associated with the tropical steroids like prednisolone acetate, which have been the standard regimen (P = 0.039). Multivariable analysis revealed duration of post-transplantation (OR, 0.89; P = 0.038), diabetes mellitus (OR, 1.85; P = 0.034), and renal stone (OR 1.10; P = 0.04) as independent risk factors associated with JCV viremia post-renal transplantation.

CONCLUSION

It seems that the discovery of potential risk factors, including immunological and non-immunological elements, may offer a possible preventive or therapeutic approach in the JCV disease episodes. The results of this study may also help clarify the probable clinical risk factors involving in progressive multifocal leukoencephalopathy development.

JCPyV NCCR analysis in PML patients with different risk factors: exploring common rearrangements as essential changes for neuropathogenesis

Background

During severe immunosuppression or treatment with specific biological drugs, human polyomavirus JC (JCPyV) may establish a lytic infection in oligodendrocytes, leading to progressive multifocal leukoencephalopathy (PML). Beyond AIDS, which represents the most common predisposing condition, several biological drugs have been associated to the development of PML, such as natalizumab, fingolimod and dimethyl fumarate, which have been showed to increase the risk of PML in the multiple sclerosis (MS) population. JCPyV non-coding control region (NCCR) can be found in two different forms: a virulent neurotropic pathogenic form and a latent non-pathogenic form. The neurotropic forms contain a rearranged NCCR and are typically found in the cerebrospinal fluid, brain or blood of PML patients.

Case presentation

We sequenced and critically examined JCPyV NCCR from isolates detected in the cerebrospinal fluid of four newly diagnosed progressive multifocal leukoencephalopathy patients: two HIV-positive and two HIV-negative multiple sclerosis patients. More complex NCCR rearrangements were observed in the two HIV-positive patients compared to the HIV-negative multiple sclerosis patients with PML.

Conclusions

The comparison of HIV-positive and HIV-negative MS patients with PML, allowed us to evidence the presence of a common pattern of JCPyV NCCR rearrangement, characterized by the deletion of the D-block, which could be one of the initial rearrangements of JCPyV NCCR needed for the development of PML.

Host-Immune Interactions in JC Virus Reactivation and Development of Progressive Multifocal Leukoencephalopathy (PML)

With the advent of immunomodulatory therapies and the HIV epidemic, the impact of JC Virus (JCV) on the public health system has grown significantly due to the increased incidence of Progressive Multifocal Leukoencephalopathy (PML). Currently, there are no pharmaceutical agents targeting JCV infection for the treatment and the prevention of viral reactivation leading to the development of PML. As JCV primarily reactivates in immunocompromised patients, it is proposed that the immune system (mainly the cellular-immunity component) plays a key role in the regulation of JCV to prevent productive infection and PML development. However, the exact mechanism of JCV immune regulation and reactivation is not well understood. Likewise, the impact of host factors on JCV regulation and reactivation is another understudied area. Here we discuss the current literature on host factor-mediated and immune factor-mediated regulation of JCV gene expression with the purpose of developing a model of the factors that are bypassed during JCV reactivation, and thus are potential targets for the development of therapeutic interventions to suppress PML initiation. Graphical Abstract.

Risk of Progressive Multifocal Leukoencephalopathy in the Combination Antiretroviral Therapy Era in the French Hospital Database on Human Immunodeficiency Virus (ANRS-C4)

Background

Risk factors for progressive multifocal leukoencephalopathy (PML) in individuals with human immunodeficiency virus (HIV) infection are poorly documented in the era of combination antiretroviral therapy (cART).

Methods

We studied HIV-1-infected individuals aged ≥15 years who had no history of PML and were prospectively followed up between 1997 and 2011 in the French Hospital Database on HIV (FHDH-ANRS CO4) cohort. Cox models were used to calculate adjusted hazard ratios (HRs), focusing on sub-Saharan origin, suggested to be protective, and recent cART initiation, potentially associated with an increased risk of PML.

Results

PML developed in 555 individuals, in 57 during the first 6 months of cART. From 1997-2000 to 2009-2011, the incidence fell from 1.15 (95% confidence interval [CI], .98-1.31) to 0.49 (.37-.61) per 1000 person-years. Sub-Saharan African origin had no clear influence (HR, 0.80; 95% CI, .58-1.11). Compared with men who have sex with men, injection drug users (IDUs) were at higher risk (HR, 1.80 [95% CI, 1.32-2.45] for male and 1.68 [1.13-2.48] for female IDUs). When IDUs were excluded, hepatitis C virus seropositivity was associated with an increased risk (HR, 1.40; 95% CI, 1.02-1.93). Compared with no cART initiation, initiation <6 months previously was associated with PML onset (HR, 4.91; 95% CI, 2.42-9.95).

Conclusions

Recent cART initiation is associated with an increased risk of PML, as are injection drug use and hepatitis C virus seropositivity. Sub-Saharan African origin had no protective effect.

Human Polyomavirus JCPyV and Its Role in Progressive Multifocal Leukoencephalopathy and Oncogenesis

The human neurotropic virus JCPyV, a member of the Polyomaviridiae family, is the opportunistic infectious agent of Progressive Multifocal Leukoencephalopathy (PML), a fatal disease seen in severe immunosuppressive conditions and, during the last decade, in patients undergoing immunotherapy. JCPyV is a ubiquitous pathogen with up to 85% of the adult population word-wide exhibiting antibodies against it. Early experiments demonstrated that direct inoculation of JCPyV into the brain of different species resulted in the development of brain tumors and other neuroectodermal-derived neoplasias. Later, several reports showed the detection of viral sequences in medulloblastomas and glial tumors, as well as expression of the viral protein T-Antigen. Few oncogenic viruses, however, have caused so much controversy regarding their role in the pathogenesis of brain tumors, but the discovery of new Polyomaviruses that cause Merkel cell carcinomas in humans and brain tumors in racoons, in addition to the role of JCPyV in colon cancer and multiple mechanistic studies have shed much needed light on the role of JCPyV in cancer. The pathways affected by the viral protein T-Antigen include cell cycle regulators, like p53 and pRb, and transcription factors that activate pro-proliferative genes, like c-Myc. In addition, infection with JCPyV causes chromosomal damage and T-Antigen inhibits homologous recombination, and activates anti-apoptotic proteins, such as Survivin. Here we review the different aspects of the biology and physiopathology of JCPyV.

FAST1 promotes the migration and invasion of colorectal cancer cells

BACKGROUND

The forkhead activin signal transducer 1 (FAST1) is involved in several oncogenic signaling pathways and its abnormal expression has been discovered in some cancers. Yet the role of FAST1 in colorectal cancer (CRC) remains largely unclear. Therefore, the goal of this study was to explore the function of FAST1 in CRC.

METHODS

In this study, we analyzed FAST1 expression and its relationship with clinicopathological parameters and prognostic significance in CRC via immunohistochemistry analysis. The effects and mechanisms of FAST1 on cell proliferation, migration and invasion were explored in vitro and in vivo.

RESULTS

We found that increased FAST1 as an independent prognostic factor was positively associated with TNM stage and pathological grade in CRC. FAST1 overexpression promoted the CRC cell proliferation, migration and invasion in vivo. Furthermore, mechanistic studies implicated that FAST1 enhanced the pulmonary metastasis of CRC cells through down-regulating E-cadherin levels.

CONCLUSIONS

In summary, FAST1 was significantly associated with CRC progression and could serve as an independent prognostic factor. FAST1 may be potential therapeutic target for CRC patients.

Tumor growth factor-β is an important factor for immunosuppression and tumorgenesis in Polyoma BK virus infection; a systematic review article

Polyoma BK virus (PBK) is a prevalent human specific virus and the cause of several malignancies in human. The main mechanisms used by PBK to induce/stimulate human cancers are yet to be clarified but it has been proposed that PBK may use several mechanisms to induce/stimulate cancers in human including attenuation of immune responses via up-regulation of immunosuppressor molecules. Transforming growth factor beta (TGF-β) is a key multifunctional factor from modulation of immunosurveillance to angiogenesis. The key roles of TGF-β in the progression of Th17 and T regulatory subsets, the most important immune cells involved in development of cancers, have been demonstrated. Thus, this review article aims to describe the mechanisms used by PBK in induction/stimulation of human cancers in TGF-β dependent manner..

Oligodendrocyte Injury and Pathogenesis of HIV-1-Associated Neurocognitive Disorders

Oligodendrocytes wrap neuronal axons to form myelin, an insulating sheath which is essential for nervous impulse conduction along axons. Axonal myelination is highly regulated by neuronal and astrocytic signals and the maintenance of myelin sheaths is a very complex process. Oligodendrocyte damage can cause axonal demyelination and neuronal injury, leading to neurological disorders. Demyelination in the cerebrum may produce cognitive impairment in a variety of neurological disorders, including human immunodeficiency virus type one (HIV-1)-associated neurocognitive disorders (HAND). Although the combined antiretroviral therapy has markedly reduced the incidence of HIV-1-associated dementia, a severe form of HAND, milder forms of HAND remain prevalent even when the peripheral viral load is well controlled. HAND manifests as a subcortical dementia with damage in the brain white matter (e.g., corpus callosum), which consists of myelinated axonal fibers. How HIV-1 brain infection causes myelin injury and resultant white matter damage is an interesting area of current HIV research. In this review, we tentatively address recent progress on oligodendrocyte dysregulation and HAND pathogenesis.

Human polyomaviruses and incidence of cutaneous squamous cell carcinoma in the New Hampshire skin cancer study

Squamous cell carcinoma (SCC) of the skin is a malignancy arising from epithelial keratinocytes. Experimental and epidemiologic evidence raise the possibility that human polyomaviruses (PyV) may be associated with the occurrence of SCC. To investigate whether the risk for SCC was associated with PyV infection, seropositivity to 10 PyV types was assessed following diagnosis in a population-based case-control study conducted in the United States. A total of 253 SCC cases and 460 age group and gender-matched controls were included. Antibody response against each PyV was measured using a multiplex serology-based glutathione S-transferase capture assay of recombinantly expressed VP1 capsid proteins. Odds ratios (OR) for SCC associated with seropositivity to each PyV type were estimated using logistic regression, with adjustment for potentially confounding factors. SCC cases were seropositive for a greater number of PyVs than controls (P = 0.049). Those who were JC seropositive had increased odds of SCC when compared to those who were JC seronegative (OR = 1.37, 95% CI: 0.98-1.90), with an increasing trend in SCC risk with increasing quartiles of seroreactivity (P for trend = 0.04). There were no clear associations between SCC risk and serostatus for other PyV types. This study provides limited evidence that infection with certain PyVs may be related to the occurrence of SCC in the general population of the United States.

Virological Mechanisms in the Coinfection between HIV and HCV

Due to shared transmission routes, coinfection with Hepatitis C Virus (HCV) is common in patients infected by Human Immunodeficiency Virus (HIV). The immune-pathogenesis of liver disease in HIV/HCV coinfected patients is a multifactorial process. Several studies demonstrated that HIV worsens the course of HCV infection, increasing the risk of cirrhosis and hepatocellular carcinoma. Also, HCV might increase immunological defects due to HIV and risk of comorbidities. A specific cross-talk among HIV and HCV proteins in coinfected patients modulates the natural history, the immune responses, and the life cycle of both viruses. These effects are mediated by immune mechanisms and by a cross-talk between the two viruses which could interfere with host defense mechanisms. In this review, we focus on some virological/immunological mechanisms of the pathogenetic interactions between HIV and HCV in the human host.

Surface-bound Tat inhibits antigen-specific CD8+ T-cell activation in an integrin-dependent manner

OBJECTIVE

The identification of still unrevealed mechanisms affecting the anti-HIV CD8 T-cell response in HIV-1 infection.

DESIGN

Starting from the observation that anti-Tat immunization is associated with improved CD8 T-cell immunity, we developed both in-vitro and ex-vivo assays to characterize the effects of extra-cellular Tat on the adaptive CD8 T-cell response.

METHODS

The effects of Tat on CD8 T-cell activation were assayed using CD8 T-cell clones specific for either cellular (MART-1) or viral (HIV-1 Nef) antigens, and HIV-1 Gag-specific CD8 T cells from HIV-1 patients.

RESULTS

The interaction between CD8 T lymphocytes and immobilized Tat, but not its soluble form, inhibits peptide-specific CD8 T-lymphocyte activation. The inhibition does not depend on Tat trans-activation activity, but on the interaction of the Tat RGD domain with α5β1 and αvβ3 integrins. Impaired CD8 T-cell activation was also observed in cocultures of CD8 T cells with HIV-1-infected cells. Anti-Tat Abs abrogate the inhibitory effect, consistently with the evidence that extracellular Tat accumulates on the cell membrane of virus-producing cells. The Tat-induced inhibition of cell activation associates with increased apoptosis of CD8 T cells. Finally, the inhibition of cell activation also takes place in Gag-specific CD8 T lymphocytes from HIV-1-infected patients.

CONCLUSION

Our results support the idea that CD8 T-cell apoptosis induced by surface-bound extracellular Tat can contribute to the dysregulation of the CD8 T-cell adaptive response against HIV as well as other pathogens present in AIDS patients.

Immune surveillance and response to JC virus infection and PML

The ubiquitous human polyomavirus JC virus (JCV) is the established etiological agent of the debilitating and often fatal demyelinating disease, progressive multifocal leukoencephalopathy (PML). Most healthy individuals have been infected with JCV and generate an immune response to the virus, yet remain persistently infected at subclinical levels. The onset of PML is rare in the general population, but has become an increasing concern in immunocompromised patients, where reactivation of JCV leads to uncontrolled replication in the CNS. Understanding viral persistence and the normal immune response to JCV provides insight into the circumstances which could lead to viral resurgence. Further, clues on the potential mechanisms of reactivation may be gleaned from the crosstalk among JCV and HIV-1, as well as the impact of monoclonal antibody therapies used for the treatment of autoimmune disorders, including multiple sclerosis, on the development of PML. In this review, we will discuss what is known about viral persistence and the immune response to JCV replication in immunocompromised individuals to elucidate the deficiencies in viral containment that permit viral reactivation and spread.

Human polyomavirus reactivation: disease pathogenesis and treatment approaches

JC and BK polyomaviruses were discovered over 40 years ago and have become increasingly prevalent causes of morbidity and mortality in a variety of distinct, immunocompromised patient cohorts. The recent discoveries of eight new members of the Polyomaviridae family that are capable of infecting humans suggest that there are more to be discovered and raise the possibility that they may play a more significant role in human disease than previously understood. In spite of this, there remains a dearth of specific therapeutic options for human polyomavirus infections and an incomplete understanding of the relationship between the virus and the host immune system. This review summarises the human polyomaviruses with particular emphasis on pathogenesis in those directly implicated in disease aetiology and the therapeutic options available for treatment in the immunocompromised host.

New insights on human polyomavirus JC and pathogenesis of progressive multifocal leukoencephalopathy

John Cunningham virus (JCV) is a member of the Polyomaviridae family. It was first isolated from the brain of a patient with Hodgkin disease in 1971, and since then the etiological agent of the progressive multifocal leukoencephalopathy (PML) was considered. Until the human immunodeficiency virus (HIV) pandemic, PML was rare: in fact HIV-induced immunodeficiency is the most common predisposing factor accounting for 85% of all instances of PML. This data led to intense research on JCV infection and resulted in better understanding of epidemiology and clinic-pathologic spectrum. Recently, cases of PML have been observed after the introduction of monoclonal antibodies, such as natalizumab, rituximab, efalizumab, and infliximab, in the treatment of autoimmune disease, underlining the important role of host immunity in PML pathogenesis. In this review current understanding of the JCV infection and the new findings relating to the pathogenesis of PML has been comprehensively revised, focusing our attention on the interaction between the cellular and viral molecular pathways implicated in the JCV infection and the modulating role of host immune surveillance in the viral reactivation from a latent state.

Neurofibromatosis type 2 tumor suppressor protein, NF2, induces proteasome-mediated degradation of JC virus T-antigen in human glioblastoma

Neurofibromatosis type 2 protein (NF2) has been shown to act as tumor suppressor primarily through its functions as a cytoskeletal scaffold. However, NF2 can also be found in the nucleus, where its role is less clear. Previously, our group has identified JC virus (JCV) tumor antigen (T-antigen) as a nuclear binding partner for NF2 in tumors derived from JCV T-antigen transgenic mice. The association of NF2 with T-antigen in neuronal origin tumors suggests a potential role for NF2 in regulating the expression of the JCV T-antigen. Here, we report that NF2 suppresses T-antigen protein expression in U-87 MG human glioblastoma cells, which subsequently reduces T-antigen-mediated regulation of the JCV promoter. When T-antigen mRNA was quantified, it was determined that increasing expression of NF2 correlated with an accumulation of T-antigen mRNA; however, a decrease in T-antigen at the protein level was observed. NF2 was found to promote degradation of ubiquitin bound T-antigen protein via a proteasome dependent pathway concomitant with the accumulation of the JCV early mRNA encoding T-antigen. The interaction between T-antigen and NF2 maps to the FERM domain of NF2, which has been shown previously to be responsible for its tumor suppressor activity. Co-immunoprecipitation assays revealed a ternary complex among NF2, T-antigen, and the tumor suppressor protein, p53 within a glioblastoma cell line. Further, these proteins were detected in various degrees in patient tumor tissue, suggesting that these associations may occur in vivo. Collectively, these results demonstrate that NF2 negatively regulates JCV T-antigen expression by proteasome-mediated degradation, and suggest a novel role for NF2 as a suppressor of JCV T-antigen-induced cell cycle regulation.

Effects of Tat proteins and Tat mutants of different human immunodeficiency virus type 1 clades on glial JC virus early and late gene transcription

Polyomavirus JC (JCV) is the aetiological agent of progressive multifocal leukoencephalopathy (PML), a frequently fatal infection of the brain afflicting nearly 4% of AIDS patients in the USA. Human immunodeficiency virus type 1 (HIV-1) Tat, acting together with cellular proteins at the JCV non-coding control region (NCCR), can stimulate JCV DNA transcription and replication. Tat in the brain is secreted by HIV-1-infected cells and incorporated by oligodendroglia, cells capable of infection by JCV. Thus far the effects of Tat on JCV have been studied primarily with protein encoded by the HIV-1 B clade most common in North America. Here, we determine the abilities of Tat from different HIV-1 clades to alter JCV early and late gene transcription and DNA replication initiated at the JCV origin. Tat from all clades tested stimulates both JCV early and late gene promoters, with clade B Tat being significantly most effective. Tat proteins from the HIV-1 clades display parallel patterns of differences in their effects on HIV-1 and JCV transcription, suggesting that Tat effects in both cases are mediated by the same cellular proteins. Clade B Tat is most effective at directing Smad mediators of tumour growth factor beta and cellular partner Purα to the NCCR. Tat proteins from all non-B clades inhibit initiation of JCV DNA replication. The effectiveness of HIV-1 clade B Tat at promoting JCV transcriptional and replicative processes highlights a need for further investigation to determine which molecular aspects of Tat from distinct HIV-1 substrains can contribute to the course of PML development in neuroAIDS.

Molecular biology, epidemiology, and pathogenesis of progressive multifocal leukoencephalopathy, the JC virus-induced demyelinating disease of the human brain

Progressive multifocal leukoencephalopathy (PML) is a debilitating and frequently fatal central nervous system (CNS) demyelinating disease caused by JC virus (JCV), for which there is currently no effective treatment. Lytic infection of oligodendrocytes in the brain leads to their eventual destruction and progressive demyelination, resulting in multiple foci of lesions in the white matter of the brain. Before the mid-1980s, PML was a relatively rare disease, reported to occur primarily in those with underlying neoplastic conditions affecting immune function and, more rarely, in allograft recipients receiving immunosuppressive drugs. However, with the onset of the AIDS pandemic, the incidence of PML has increased dramatically. Approximately 3 to 5% of HIV-infected individuals will develop PML, which is classified as an AIDS-defining illness. In addition, the recent advent of humanized monoclonal antibody therapy for the treatment of autoimmune inflammatory diseases such as multiple sclerosis (MS) and Crohn's disease has also led to an increased risk of PML as a side effect of immunotherapy. Thus, the study of JCV and the elucidation of the underlying causes of PML are important and active areas of research that may lead to new insights into immune function and host antiviral defense, as well as to potential new therapies.

The Tat protein of human immunodeficiency virus-1 enhances hepatitis C virus replication through interferon gamma-inducible protein-10

Background

Co-infection with human immunodeficiency virus-1 (HIV-1) and hepatitis C virus (HCV) is associated with faster progression of liver disease and an increase in HCV persistence. However, the mechanism by which HIV-1 accelerates the progression of HCV liver disease remains unknown.

Results

HIV-1/HCV co-infection is associated with increased expression of interferon gamma-induced protein-10 (IP-10) mRNA in peripheral blood mononuclear cells (PBMCs). HCV RNA levels were higher in PBMCs of patients with HIV-1/HCV co-infection than in patients with HCV mono-infection. HIV-1 Tat and IP-10 activated HCV replication in a time-dependent manner, and HIV-1 Tat induced IP-10 production. In addition, the effect of HIV-1 Tat on HCV replication was blocked by anti-IP-10 monoclonal antibody, demonstrating that the effect of HIV-1 Tat on HCV replication depends on IP-10. Taken together, these results suggest that HIV-1 Tat protein activates HCV replication by upregulating IP-10 production.

Conclusions

HIV-1/HCV co-infection is associated with increased expression of IP-10 mRNA and replication of HCV RNA. Furthermore, both HIV-1 Tat and IP-10 activate HCV replication. HIV-1 Tat activates HCV replication by upregulating IP-10 production. These results expand our understanding of HIV-1 in HCV replication and the mechanism involved in the regulation of HCV replication mediated by HIV-1 during co-infection.

Transforming growth factor beta-induced reactivation of Epstein-Barr virus involves multiple Smad-binding elements cooperatively activating expression of the latent-lytic switch BZLF1 gene

Transforming growth factor β (TGF-β) physiologically induces Epstein-Barr virus (EBV) lytic infection by activating the expression of EBV's latent-lytic switch BZLF1 gene. Liang et al. (J. Biol. Chem. 277:23345-23357, 2002) previously identified a Smad-binding element (SBE) within the BZLF1 promoter, Zp; however, it accounts for only 20 to 30% of TGF-β-mediated activation of transcription from Zp. Here, we identified additional factors responsible for the rest of this activation. The incubation of EBV-positive MutuI cells with a TGF-β neutralizing antibody or inhibitors of the TGF-β type I receptor (TβRI) or Smad3 eliminated the TGF-β-induced reactivation of EBV. The coexpression of Smad2, Smad3, and Smad4 together with a constitutively active form of TβRI induced 15- to 25-fold transcription from Zp in gastric carcinoma AGS cells. By electrophoretic mobility shift assays, we identified four additional Smad-binding elements, named SBE2 to SBE5. Substitution mutations in individual SBEs reduced Smad-mediated activation of Zp by 20 to 60%; together, these mutations essentially eliminated it. Chromatin immunoprecipitation assays confirmed that Smad4 newly bound the Zp region of the EBV genome following the incubation of MutuI cells with TGF-β. SBE2 overlaps the ZEB-binding ZV silencing element of Zp. Depending upon posttranslational modifications, Smad4 either competed with ZEB1 for binding or formed a complex with ZEB1 on the Zp ZV element in a cell-free assay system. In transiently transfected cells, exogenously expressed ZEB1 inhibited Smad-mediated transcriptional activation from Zp. We conclude that TGF-β induces EBV lytic reactivation via the canonical Smad pathway by activating BZLF1 gene expression through multiple SBEs acting in concert.

Tits and bits of HIV Tat protein

INTRODUCTION

HIV-Tat protein displays an array of functions that are essential for HIV replication. The structural flexibility of Tat protein has been regarded as one of the unique features responsible for sustaining diverse functions, from facilitated membrane-crossing ability to strong affinity for RNA binding.

AREAS COVERED

RNA binding ability and presence of multiple interacting domains in the same protein are very important properties of HIV-Tat protein. Tat protein has shown great ability to influence cellular and viral gene expression. We discuss the functions of HIV Tat protein, describing its structural significance, secretion and uptake of HIV Tat protein by immune cells, post-translational modifications and role of HIV Tat protein in HIV pathogenesis.

EXPERT OPINION

Perturbation in expression of many cytokines and chemokines by HIV-Tat protein exhibits downstream immune suppressive function as well as activation of several apoptotic genes. This explains the massive death of immune cells due to bystander effect of HIV Tat protein among HIV-infected patients.

Rearranged JC virus noncoding control regions found in progressive multifocal leukoencephalopathy patient samples increase virus early gene expression and replication rate

Polyomavirus JC (JCV) infects ∼ 60% of the general population, followed by asymptomatic urinary shedding in ∼ 20%. In patients with pronounced immunodeficiency, including HIV/AIDS, JCV can cause progressive multifocal leukoencephalopathy (PML), a devastating brain disease of high mortality. While JCV in the urine of healthy people has a linear noncoding control region called the archetype NCCR (at-NCCR), JCV in brain and cerebrospinal fluid (CSF) of PML patients bear rearranged NCCRs (rr-NCCRs). Although JCV NCCR rearrangements are deemed pathognomonic for PML, their role as a viral determinant is unclear. We sequenced JCV NCCRs found in CSF of eight HIV/AIDS patients newly diagnosed with PML and analyzed their effect on early and late gene expression using a bidirectional reporter vector recapitulating the circular polyomavirus early and late gene organization. The rr-NCCR sequences were highly diverse, but all increased viral early reporter gene expression in progenitor-derived astrocytes, glia-derived cells, and human kidney compared to the expression levels with the at-NCCR. The expression of simian virus 40 (SV40) large T antigen or HIV Tat expression in trans was associated with a strong increase of at-NCCR-controlled early gene expression, while rr-NCCRs were less responsive. The insertion of rr-NCCRs into the JCV genome backbone revealed higher viral replication rates for rr-NCCR compared to those of the at-NCCR JCV in human progenitor-derived astrocytes or glia cells, which was abrogated in SV40 large T-expressing COS-7 cells. We conclude that naturally occurring JCV rr-NCCR variants from PML patients confer increased early gene expression and higher replication rates compared to those of at-NCCR JCV and thereby increase cytopathology.

War and peace between microbes: HIV-1 interactions with coinfecting viruses

HIV-1 disrupts the homeostatic equilibrium between the host and coinfecting microbes, facilitating reactivation of persistent viruses and invasion by new viruses. These viruses usually accelerate HIV disease but occasionally create conditions detrimental for HIV-1. Understanding these phenomena may lead to anti-HIV-1 strategies that specifically target interactions between HIV-1 and coinfecting viruses.

High expression of MeCP2 in JC virus-infected cells of progressive multifocal leukoencephalopathy brains

Mutations of the methyl CpG binding protein 2 (MeCP2) gene are a major cause of Rett syndrome. To investigate whether the expression of this gene was related to JC virus (JCV) infection, we examined brains of four progressive multifocal leukoencephalopathy (PML) patients. JCV infection was confirmed by immunohistochemical labeling with antibodies against JCV VP1, agnoprotein and large T antigen. MeCP2 expression was examined by immunohistochemistry using a specific polyclonal antibody against MeCP2. In normal brains and uninfected cortices of PML brains, MeCP2 expression was observed in the nuclei of neurons, but not observed in glial and endothelial cell nuclei. However, in PML brains intense immunolabeling was observed in abnormally enlarged glial nuclei of JCV-infected cells. Double immunolabeling using antibodies against large T antigen (visualized as blue) and MeCP2 (visualised as red) revealed dark red JCV-infected nuclei, which confirmed that the JCV infected nuclei expressed MeCP2. We conclude that MeCP2 is highly expressed in the JCV-infected nuclei of PML brain and these results may provide a new insight into the mechanism which regulates the MeCP2 expression in glial cells by the infection of JCV.

SMAD4: a predictive marker of PDAC cell permissiveness for oncolytic infection with parvovirus H-1PV

Pancreatic ductal adenocarcinoma (PDAC) represents the eighth frequent solid tumor and fourth leading cause of cancer death. Because current treatments against PDAC are still unsatisfactory, new anticancer strategies are required, including oncolytic viruses. Among these, autonomous parvoviruses (PV), like MVMp (minute virus of mice) and H-1PV are being explored as candidates for cancer gene therapy. Human PDAC cell lines were identified to display various susceptibilities to an infection with H-1PV. The correlation between the integrity of the transcription factor SMAD4, mutated in 50% of all PDAC, and H-1PV permissiveness was particularly striking. Indeed, mutation or deletion of SMAD4 dramatically reduced the activity of the P4 promoter and, consequently, the accumulation of the pivotal NS1 protein. By means of DNA affinity immunoblotting, novel binding sites for SMAD4 and c-JUN transcription factors could be identified in the P4 promoter of H-1PV. The overexpression of wild-type SMAD4 in deficient cell lines (AsPC-1, Capan-1) stimulated the activity of the P4 promoter, whereas interference of endogenous SMAD4 function with a dominant-negative mutant decreased the viral promoter activity in wild-type SMAD4-expressing cells (Panc-1, MiaPaCa-2) reducing progeny virus production. In conclusion, the importance of members of the SMAD family for H-1PV early promoter P4 activity should guide us to select SMAD4-positive PDACs, which may be possible targets for an H-1PV-based cancer therapy.

JC virus-induced Progressive Multifocal Leukoencephalopathy

Progressive multifocal encephalopathy (PML) is a fatal demyelinating disease of the central nervous system (CNS), caused by the lytic infection of oligodendrocytes by a human polyomavirus, JC virus (JCV). PML is rare disease but mostly develops in patients with underlying immunosuppressive conditions, including Hodgkin's lymphoma, lymphoproliferative diseases, in those undergoing antineoplastic therapy and AIDS. However, consistent with the occurrence of PML under immunocompromised conditions, this disease seems to be also steadily increasing among autoimmune disease patients (multiple sclerosis and Crohn's disease), who are treated with antibody-based regimens (natalizumab, efalizumab and rituximab). This unexpected occurrence of the disease among such a patient population reconfirms the existence of a strong link between the underlying immunosuppressive conditions and development of PML. These recent observations have generated a new interest among investigators to further examine the unique biology of JCV.

Structural evaluation of new human polyomaviruses provides clues to pathobiology

In the past three years, remarkable discoveries have added three new human polyomaviruses (KI virus (KIV), WU virus (WUV) and Merkel cell virus (MCV)) to a class that previously had only two disease-causing members (BK virus (BKV) and JC virus (JCV)) identified. Two monkey polyomaviruses, simian virus (SV)40 and B-cell lymphotropic polyomavirus (LPV) are also present in humans. KIV and WUV lack the agnoprotein coding sequence and regulatory micro (mi)RNA clusters of BKV, JCV and SV40. MCV lacks the agnoprotein sequence but generates miRNAs. KIV, WUV and MCV are all widespread in humans. Although they have distinctive tissue tropisms, all these viruses are probably acquired in childhood. Of these viruses, only MCV has thus far been strongly linked to cancer. Marshalled evidence from diverse sources implicates MCV as an etiological agent of Merkel cell carcinoma. This review compares the structural features of the new and previously known polyomaviruses, with the aim of identifying approaches to molecular pathology.

Functions of Tat: the versatile protein of human immunodeficiency virus type 1

Human immunodeficiency virus type 1 (HIV-1) Tat is a multifunctional protein that contributes to several pathological symptoms of HIV-1 infection as well as playing a critical role in virus replication. Tat is a robust transactivating protein that induces a variety of effects by altering the expression levels of cellular and viral genes. The functions of Tat are therefore primarily related to its role in modulation of gene expression. In this review the functions of HIV-1 Tat that have been well documented, as well as a number of novel functions that have been proposed for this protein, are discussed. Since some of the functions of Tat vary in different cell types in a concentration-dependent manner and because Tat sometimes exerts the same activity through different pathways, study of this protein has at times yielded conflicting and controversial results. Due to its pivotal role in viral replication and in disease pathogenesis, Tat and the cellular pathways targeted by Tat are potential targets for new anti-HIV drugs.