Interferon- alpha and - beta restrict polyomavirus JC replication in primary human fetal glial cells: implications for progressive multifocal leukoencephalopathy therapy

Pathogenicity of Avian Polyomaviruses and Prospect of Vaccine Development

Polyomaviruses are nonenveloped icosahedral viruses with a double-stranded circular DNA containing approximately 5000 bp and 5–6 open reading frames. In contrast to mammalian polyomaviruses (MPVs), avian polyomaviruses (APVs) exhibit high lethality and multipathogenicity, causing severe infections in birds without oncogenicity. APVs are classified into 10 major species: Adélie penguin polyomavirus, budgerigar fledgling disease virus, butcherbird polyomavirus, canary polyomavirus, cormorant polyomavirus, crow polyomavirus, Erythrura gouldiae polyomavirus, finch polyomavirus, goose hemorrhagic polyomavirus, and Hungarian finch polyomavirus under the genus Gammapolyomavirus. This paper briefly reviews the genomic structure and pathogenicity of the 10 species of APV and some of their differences in terms of virulence from MPVs. Each gene’s genomic size, number of amino acid residues encoding each gene, and key biologic functions are discussed. The rationale for APV classification from the Polyomavirdae family and phylogenetic analyses among the 10 APVs are also discussed. The clinical symptoms in birds caused by APV infection are summarized. Finally, the strategies for developing an effective vaccine containing essential epitopes for preventing virus infection in birds are discussed. We hope that more effective and safe vaccines with diverse protection will be developed in the future to solve or alleviate the problems of viral infection.

Single-Molecule RNA Sequencing Reveals IFNγ-Induced Differential Expression of Immune Escape Genes in Merkel Cell Polyomavirus-Positive MCC Cell Lines

Merkel cell carcinoma (MCC) is a rare and highly aggressive cancer, which is mainly caused by genomic integration of the Merkel cell polyomavirus and subsequent expression of a truncated form of its large T antigen. The resulting primary tumor is known to be immunogenic and under constant pressure to escape immune surveillance. Because interferon gamma (IFNγ), a key player of immune response, is secreted by many immune effector cells and has been shown to exert both anti-tumoral and pro-tumoral effects, we studied the transcriptomic response of MCC cells to IFNγ. In particular, immune modulatory effects that may help the tumor evade immune surveillance were of high interest to our investigation. The effect of IFNγ treatment on the transcriptomic program of three MCC cell lines (WaGa, MKL-1, and MKL-2) was analyzed using single-molecule sequencing via the Oxford Nanopore platform. A significant differential expression of several genes was detected across all three cell lines. Subsequent pathway analysis and manual annotation showed a clear upregulation of genes involved in the immune escape of tumor due to IFNγ treatment. The analysis of selected genes on protein level underlined our sequencing results. These findings contribute to a better understanding of immune escape of MCC and may help in clinical treatment of MCC patients. Furthermore, we demonstrate that single-molecule sequencing can be used to assess characteristics of large eukaryotic transcriptomes and thus contribute to a broader access to sequencing data in the community due to its low cost of entry.

Virus-Induced Tumorigenesis and IFN System

Oncogenic viruses favor the development of tumors in mammals by persistent infection and specific cellular pathways modifications by deregulating cell proliferation and inhibiting apoptosis. They counteract the cellular antiviral defense through viral proteins as well as specific cellular effectors involved in virus-induced tumorigenesis. Type I interferons (IFNs) are a family of cytokines critical not only for viral interference but also for their broad range of properties that go beyond the antiviral action. In fact, they can inhibit cell proliferation and modulate differentiation, apoptosis, and migration. However, their principal role is to regulate the development and activity of most effector cells of the innate and adaptive immune responses. Various are the mechanisms by which IFNs exert their effects on immune cells. They can act directly, through IFN receptor triggering, or indirectly by the induction of chemokines, the secretion of further cytokines, or by the stimulation of cells useful for the activation of particular immune cells. All the properties of IFNs are crucial in the host defense against viruses and bacteria, as well as in the immune surveillance against tumors. IFNs may be affected by and, in turn, affect signaling pathways to mediate anti-proliferative and antiviral responses in virus-induced tumorigenic context. New data on cellular and viral microRNAs (miRNAs) machinery, as well as cellular communication and microenvironment modification via classical secretion mechanisms and extracellular vesicles-mediated delivery are reported. Recent research is reviewed on the tumorigenesis induced by specific viruses with RNA or DNA genome, belonging to different families (i.e., HPV, HTLV-1, MCPyV, JCPyV, Herpesviruses, HBV, HCV) and the IFN system involvement.

IFNα and β Mediated JCPyV Suppression through C/EBPβ-LIP Isoform

Polyomavirus JC (JCPyV) causes the demyelinating disease progressive multifocal leukoencephalopathy (PML). JCPyV infection is very common in childhood and, under conditions of severe immunosuppression, JCPyV may reactivate to cause PML. JC viral proteins expression is regulated by the JCPyV non-coding control region (NCCR), which contains binding sites for cellular transcriptional factors which regulate JCPyV transcription. Our earlier studies suggest that JCPyV reactivation occurs within glial cells due to cytokines such as TNF-α which stimulate viral gene expression. In this study, we examined interferon-α (IFNα) or β (IFNβ) which have a negative effect on JCPyV transcriptional regulation. We also showed that these interferons induce the endogenous liver inhibitory protein (LIP), an isoform of CAAT/enhancer binding protein beta (C/EBPβ). Treatment of glial cell line with interferons increases the endogenous level of C/EBPβ-LIP. Furthermore, we showed that the negative regulatory role of the interferons in JCPyV early and late transcription and viral replication is more pronounced in the presence of C/EBPβ-LIP. Knockdown of C/EBPβ-LIP by shRNA reverse the inhibitory effect on JCPyV viral replication. Therefore, IFNα and IFNβ negatively regulate JCPyV through induction of C/EBPβ-LIP, which together with other cellular transcriptional factors may control the balance between JCPyV latency and activation.

The Small t Antigen of JC Virus Antagonizes RIG-I-Mediated Innate Immunity by Inhibiting TRIM25's RNA Binding Ability

JC polyomavirus (JCV), a DNA virus that leads to persistent infection in humans, is the causative agent of progressive multifocal leukoencephalopathy, a lethal brain disease that affects immunocompromised individuals. Almost nothing is currently known about how JCV infection is controlled by the innate immune response and, further, whether JCV has evolved mechanisms to antagonize antiviral immunity. Here, we show that the innate immune sensors retinoic acid-inducible gene I (RIG-I) and cGMP-AMP synthase (cGAS) control JCV replication in human astrocytes. We further identify that the small t antigen (tAg) of JCV functions as an interferon (IFN) antagonist by suppressing RIG-I-mediated signal transduction. JCV tAg interacts with the E3 ubiquitin ligase TRIM25, thereby preventing its ability to bind RNA and to induce the K63-linked ubiquitination of RIG-I, which is known to facilitate RIG-I-mediated cytokine responses. Antagonism of RIG-I K63-linked ubiquitination and antiviral signaling is also conserved in the tAg of the related polyomavirus BK virus (BKV). These findings highlight how JCV and BKV manipulate a key innate surveillance pathway, which may stimulate research into designing novel therapies.IMPORTANCE The innate immune response is the first line of defense against viral pathogens, and in turn, many viruses have evolved strategies to evade detection by the host's innate immune surveillance machinery. Investigation of the interplay between viruses and the innate immune response provides valuable insight into potential therapeutic targets against viral infectious diseases. JC polyomavirus (JCV) is associated with a lifelong, persistent infection that can cause a rare neurodegenerative disease, called progressive multifocal leukoencephalopathy, in individuals that are immunosuppressed. The molecular mechanisms of JCV infection and persistence are not well understood, and very little is currently known about the relevance of innate immunity for the control of JCV replication. Here, we define the intracellular innate immune sensors responsible for controlling JCV infection and also demonstrate a novel mechanism by which a JCV-encoded protein acts as an antagonist of the type I interferon-mediated innate immune response.

Lipid-specific IgMs induce antiviral responses in the CNS: implications for progressive multifocal leukoencephalopathy in multiple sclerosis

Progressive multi-focal leukoencephalopathy (PML) is a potentially fatal encephalitis caused by JC polyomavirus (JCV). PML principally affects people with a compromised immune system, such as patients with multiple sclerosis (MS) receiving treatment with natalizumab. However, intrathecal synthesis of lipid-reactive IgM in MS patients is associated with a markedly lower incidence of natalizumab-associated PML compared to those without this antibody repertoire. Here we demonstrate that a subset of lipid-reactive human and murine IgMs induce a functional anti-viral response that inhibits replication of encephalitic Alpha and Orthobunyaviruses in multi-cellular central nervous system cultures. These lipid-specific IgMs trigger microglia to produce IFN-β in a cGAS-STING-dependent manner, which induces an IFN-α/β-receptor 1-dependent antiviral response in glia and neurons. These data identify lipid-reactive IgM as a mediator of anti-viral activity in the nervous system and provide a rational explanation why intrathecal synthesis of lipid-reactive IgM correlates with a reduced incidence of iatrogenic PML in MS.

Dimethyl fumarate potentiates oncolytic virotherapy through NF-κB inhibition

Resistance to oncolytic virotherapy is frequently associated with failure of tumor cells to get infected by the virus. Dimethyl fumarate (DMF), a common treatment for psoriasis and multiple sclerosis, also has anticancer properties. We show that DMF and various fumaric and maleic acid esters (FMAEs) enhance viral infection of cancer cell lines as well as human tumor biopsies with several oncolytic viruses (OVs), improving therapeutic outcomes in resistant syngeneic and xenograft tumor models. This results in durable responses, even in models otherwise refractory to OV and drug monotherapies. The ability of DMF to enhance viral spread results from its ability to inhibit type I interferon (IFN) production and response, which is associated with its blockade of nuclear translocation of the transcription factor nuclear factor κB (NF-κB). This study demonstrates that unconventional application of U.S. Food and Drug Administration-approved drugs and biological agents can result in improved anticancer therapeutic outcomes.

Isolation and characterization of an Aves polyomavirus 1 from diseased budgerigars in China

Aves polyomavirus 1 (APV) causes inflammatory disease in psittacine birds, especially in young budgerigar. In this study, an APV virus (SD18 strain) was isolated from a diseased psittacine birds breeding facility. The full genome (4981 bp) of SD18 was determined and analyzed. Phylogenetic analysis of full genome sequences indicated all the APV strains form two groups. The SD18 strain showed close relationship with APV isolated from Poland, however, the other Chinese strains are located in group II, which suggested different genotypes APVs are co-circulating in China. Compared with the consensus sequence of APV full genome, the SD18 strain contains 13 nucleotide mutations, and 2 unique amino acid substitutions (R179M and Q382K) located in VP2/3 and Large T proteins. To explore the pathogenicity of the virus, the SD18 strain was used to challenge 2-week-old budgerigars. All infected birds died no later than 5 days post infection, and virus was detected in multiple organs including brain, heart, ingluvies, liver, and intestine, which indicated that SD18 is fatal and causes systemic infection in young budgerigar. In vitro studies showed that SD18 replicated efficiently in CEF cells and reached the highest viral titers at 9 days post infection. Notably, replication of SD18 stimulated IFN-β response in CEF cells and overexpression of the VP4 or VP4Delta proteins significantly inhibited IFN-β promoter activation, which could be the strategy of APV to escape from the host innate immunity.

TLR3 agonism re-establishes CNS immune competence during α4-integrin deficiency

OBJECTIVE

Natalizumab blocks α4-integrin-mediated leukocyte migration into the central nervous system (CNS). It diminishes disease activity in multiple sclerosis (MS), but carries a high risk of progressive multifocal encephalopathy (PML), an opportunistic infection with JV virus that may be prompted by diminished CNS immune surveillance. The initial host response to viral infections entails the synthesis of type I interferons (IFN) upon engagement of TLR3 receptors. We hypothesized that TLR3 agonism reestablishes CNS immune competence in the setting of α4-integrin deficiency.

METHOD

We generated the conditional knock out mouse strain Mx1.Cre+ α4-integrinfl/fl, in which the α4-integrin gene is ablated upon treatment with the TLR3 agonist poly I:C. Adoptive transfer of purified lymphocytes from poly I:C-treated Mx1.Cre+ α4-integrinfl/fl donors into naive recipients recapitulates immunosuppression under natalizumab. Active experimental autoimmune encephalomyelitis (EAE) in Mx1.Cre+ α4-integrinfl/fl mice treated with poly I:C represents immune-reconstitution.

RESULTS

Adoptive transfer of T cells from poly I:C treated Mx1.Cre+ α4-integrinfl/fl mice causes minimal EAE. The in vitro migratory capability of CD45+ splenocytes from these mice is reduced. In contrast, actively-induced EAE after poly I:C treatment results in full disease susceptibility of Mx1.Cre+ α4-integrinfl/fl mice, and the number and composition of CNS leukocytes is similar to controls. Extravasation of Evans Blue indicates a compromised blood-brain barrier. Poly I:C treatment results in a 2-fold increase in IFN β transcription in the spinal cord.

INTERPRETATION

Our data suggest that TLR3 agonism in the setting of relative α4-integrin deficiency can reestablish CNS immune surveillance in an experimental model. This pathway may present a feasible treatment strategy to treat and prevent PML under natalizumab therapy and should be considered for further experimental evaluation in a controlled setting.

JC Polyomavirus Infection of Primary Human Renal Epithelial Cells Is Controlled by a Type I IFN-Induced Response

The JC and BK human polyomaviruses (JCPyV and BKPyV, respectively) establish lifelong persistent infections in the kidney. In immunosuppressed individuals, JCPyV causes progressive multifocal leukoencephalopathy (PML), a fatal neurodegenerative disease, and BKPyV causes polyomavirus-associated nephropathy (PVN). In this study, we compared JCPyV and BKPyV infections in primary human renal proximal tubule epithelial (HRPTE) cells. JCPyV established a persistent infection, but BKPyV killed the cells in 15 days. To identify the cellular factors responsible for controlling JCPyV infection and promoting viral persistence, we profiled the transcriptomes of JCPyV- and BKPyV-infected cells at several time points postinfection. We found that infection with both viruses induced interferon production but that interferon-stimulated genes (ISGs) were only activated in the JCPyV-infected cells. Phosphorylated STAT1 and IRF9, which are responsible for inducing ISGs, translocated to the nucleus of JCPyV-infected cells but did not in BKPyV-infected cells. In BKPyV-infected cells, two critical suppressors of cytokine signaling, SOCS3 and SOCS1, were induced. Infection with BKPyV but not JCPyV caused reorganization of PML bodies that are associated with inactivating antiviral responses. Blockade of the interferon receptor and neutralization of soluble interferon alpha (IFN-α) and IFN-β partially alleviated the block to JCPyV infection, leading to enhanced infectivity. Our results show that a type I IFN response contributes to the establishment of persistent infection by JCPyV in HRPTE cells.

The human polyomaviruses JCPyV and BKPyV both establish lifelong persistent infection in the kidneys. In immunosuppressed patients, BKPyV causes significant pathology in the kidney, but JCPyV is only rarely associated with disease in this organ. The reasons behind this striking difference in kidney pathology are unknown. In this study, we show that infection of primary human renal tubule epithelial cells with JCPyV and BKPyV results in divergent innate immune responses that control JCPyV but fail to control BKPyV. This is the first study that directly compares JCPyV and BKPyV infection in vitro in the same cell type they naturally infect, and the significant differences that have been uncovered could in part explain the distinct disease outcomes.

Downregulation of MHC-I expression is prevalent but reversible in Merkel cell carcinoma

Merkel cell carcinoma (MCC) is an aggressive, polyomavirus-associated skin cancer. Robust cellular immune responses are associated with excellent outcomes in patients with MCC, but these responses are typically absent. We determined the prevalence and reversibility of major histocompatibility complex class I (MHC-I) downregulation in MCC, a potentially reversible immune-evasion mechanism. Cell-surface MHC-I expression was assessed on five MCC cell lines using flow cytometry as well as immunohistochemistry on tissue microarrays representing 114 patients. Three additional patients were included who had received intralesional IFN treatment and had evaluable specimens before and after treatment. mRNA expression analysis of antigen presentation pathway genes from 35 MCC tumors was used to examine the mechanisms of downregulation. Of note, 84% of MCCs (total n = 114) showed reduced MHC-I expression as compared with surrounding tissues, and 51% had poor or undetectable MHC-I expression. Expression of MHC-I was lower in polyomavirus-positive MCCs than in polyomavirus-negative MCCs (P < 0.01). The MHC-I downregulation mechanism was multifactorial and did not depend solely on HLA gene expression. Treatment of MCC cell lines with ionizing radiation, etoposide, or IFN resulted in MHC-I upregulation, with IFNs strongly upregulating MHC-I expression in vitro, and in 3 of 3 patients treated with intralesional IFNs. MCC tumors may be amenable to immunotherapy, but downregulation of MHC-I is frequently present in these tumors, particularly those that are positive for polyomavirus. This downregulation is reversible with any of several clinically available treatments that may thus promote the effectiveness of immune-stimulating therapies for MCC.

Central nervous system infections in cancer patients and hematopoietic stem cell transplant recipients

Central nervous system (CNS) infections in cancer patients present a diagnostic and therapeutic challenge for clinicians. While CNS infections are not frequent complications of cancer, its therapies, or hematopoietic stem cell transplantation, the importance of CNS infections lies in their propensity to result in profound morbidity and substantial mortality in this vulnerable patient population. With an expanding population of patients with malignant disease undergoing more potent and aggressive therapies and with the advent of newer immunomodulatory agents, the incidence of CNS infectious complications is likely to rise. This chapter will summarize the clinical and diagnostic evaluation of potential infections of the CNS in these patients and will discuss particular pathogens of interest with regard to this at-risk patient population.

The role of the immune response in merkel cell carcinoma

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine skin cancer. The Merkel cell polyomavirus (MCPyV) is implicated in its pathogenesis. Immune mechanisms are also implicated. Patients who are immunosuppressed have an increased risk. There is evidence that high intratumoral T-cell counts and immune transcripts are associated with favorable survival. Spontaneous regressions implicate immune effector mechanisms. Immunogenicity is also supported by observation of autoimmune paraneoplastic syndromes. Case reports suggest that immune modulation, including reduction of immune suppression, can result in tumor regression. The relationships between MCPyV infection, the immune response, and clinical outcome, however, remain poorly understood. Circulating antibodies against MCPyV antigens are present in most individuals. MCPyV-reactive T cells have been detected in both MCC patients and control subjects. High intratumoral T-cell counts are also associated with favorable survival in MCPyV-negative MCC. That the immune system plays a central role in preventing and controlling MCC is supported by several observations. MCCs often develop, however, despite the presence of humoral and cellular immune responses. A better understanding on how MCPyV and MCC evade the immune response will be necessary to develop effective immunotherapies.

Disease-modifying drugs for multiple sclerosis and JC virus expression

Natalizumab-associated progressive multifocal leukoencephalopathy in multiple sclerosis (MS) occurred in two individuals also treated with interferon β1a, raising concerns about the interaction of these disease-modifying agents and leading to the recommendation to avoid their concomitant administration. However, type I interferons are antiviral. Using a real-time quantitative polymerase chain reaction for the detection and quantification of the John Cunningham virus (JCV), DNA in peripheral blood mononuclear cells (PBMCs), and urine in MS patients, we tested the hypothesis that MS disease-modifying drugs (DMD) qualitatively and quantitatively alter JCV prevalence and viral copy numbers. Two hundred thirty-nine patients were enrolled in a cross-sectional study in which blood and urine specimens were collected at a single time and 37 newly diagnosed, treatment-naïve MS patients were enrolled in a longitudinal study in which specimens were obtained at diagnosis and 6 months after treatment initiation. JCV DNA was detected in PBMCs of only two patients (0.07 %), but was commonly detected in the urine (46.8 %) in this population. There was no effect of DMDs on blood or urinary JCV prevalence or viral copy numbers with either glatiramer acetate (Copaxone®) or interferon-β therapy (Avonex®, Betaseron®, or Rebif®). The small number of patients on other therapies precluded meaningful comment about their effects. No obvious effect of the platform DMDs on JCV prevalence was observed even for the interferon-βs.

Type I and II IFNs inhibit Merkel cell carcinoma via modulation of the Merkel cell polyomavirus T antigens

Merkel cell carcinoma (MCC) is a rare and highly aggressive skin cancer associated with the Merkel cell polyomavirus (MCV). As MCC cell lines show oncogene addiction to the MCV T antigens, pharmacologic interference of the large T antigen (LTA) may represent an effective therapeutic approach for this deadly cancer. In this study, we investigated the effects of IFNs on MCC cell lines, especially on MCV-positive (MCV(+)) lines. Type I IFNs (i.e., Multiferon, a mix of different IFN-α subtypes, and IFN-β) strongly inhibited the cellular viability. Cell-cycle analysis showed increased sub-G fractions for these cells upon IFN treatment indicating apoptotic cell death; these effects were less pronounced for IFN-γ. Notably, this inhibitory effect of type I IFNs on MCV(+) MCC cell lines was associated with a reduced expression of the MCV LTA as well as an increased expression of promyelocytic leukemia (PML) protein, which is known to interfere with the function of the LTA. In addition, the intratumoral application of Multiferon resulted in a regression of MCV(+) but not MCV(-) MCCs in vivo. Together, our findings show that type I IFNs have a strong antitumor effect, which is at least in part explained by modulation of the virally encoded LTA.

Progressive multifocal leukoencephalopathy: clinical and molecular aspects

The fatal CNS demyelinating disease, progressive multifocal leukoencephalopathy (PML), is rare and appears to occur almost always as a consequence of immune dysfunction. Thus, it is associated with HIV/AIDS and also as a side effect of certain immunomodulatory monoclonal antibody therapies. In contrast to the rarity of PML, the etiological agent of the disease, the polyomavirus JC (JCV), is widespread in populations worldwide. In the 40 years since JCV was first isolated, much has been learned about the virus and the disease from laboratory and clinical observations. However, there are many aspects of the viral life cycle and of the pathogenesis of the disease that remain unclear, and our understanding is constantly evolving. In this review, we will discuss our current understanding of the clinical features of PML and molecular characteristics of JCV and of how they relate to each other. Clinical observations can inform molecular studies of the virus, and likewise, molecular findings concerning the life cycle of the virus can guide the development of novel therapeutic strategies.

Hexadecyloxypropyl-cidofovir (CMX001) suppresses JC virus replication in human fetal brain SVG cell cultures

JC virus (JCV) is a polyomavirus that infects human oligodendrocytes, leading to development of progressive multifocal leukoencephalopathy (PML), an often fatal demyelinating disease occurring in immunocompromised individuals. Currently there are no effective therapies for the treatment of PML that result in clearance of JCV from the brain. Cidofovir (CDV) is an acyclic nucleoside phosphonate that inhibits DNA polymerases and has been used for the treatment of PML. However, CDV demonstrated little efficacy as a treatment for PML and causes substantial side effects to patients. To improve efficacy and reduce the toxicity of CDV, a lipid-ester derivative, CMX001, was generated by Chimerix and is currently in multicenter phase II clinical trials for the prevention or control of cytomegalovirus infection in hematopoietic stem cell transplant recipients and of BK virus in the urine of stem cell or renal allograft recipients. CMX001 caused minimal cytotoxic effects in human fetal brain SVG cells when used at concentrations between 0.01 μM and 0.1 μM. CMX001 resulted in a dose-dependent decrease in the number of JCV-infected cells during initial infection and nearly eliminated JCV-infected cells during an established infection. In addition, CMX001 treatment resulted in a 60% reduction in JCV DNA copy number during initial infection, which suggests that suppression of JCV infection by CMX001 is likely due to inhibition of virus DNA replication. This study demonstrates that CMX001 suppresses JCV infection at concentrations that have limited toxicity to human brain cells, indicating its potential use to limit JCV replication in infected patients.

Human polyomavirus JC (JCV) infection of human B lymphocytes: a possible mechanism for JCV transmigration across the blood-brain barrier

It has been suggested that JC virus (JCV) might travel to the central nervous system in infected B cells. Moreover, recent data suggest the presence of JCV in bone marrow plasma cells. However, the evidence for infection and replication of JCV in B cells is unclear. To address this question, we infected Epstein-Barr virus-transformed B cells with JCV and found that the viral genome decreased >1000-fold from days 0 to 20 after infection, which concurred with the absence of viral early and late messenger RNA transcripts and proteins. However, immunofluorescent images of B cells infected with fluorescein isothiocyanate-conjugated JCV demonstrated that JCV enters the B cells, and DNase protection assay confirmed the presence of intact JCV virions inside the B cells. Moreover, JCV-infected B cells were able to transmit infection to naive glial cells. These data confirm that JCV nonproductively infects B cells and possibly uses them as a vehicle for transmigration across the blood-brain barrier.

Phenotypic analysis of dengue virus isolates associated with dengue fever and dengue hemorrhagic fever for cellular attachment, replication and interferon signaling ability

Eighteen dengue viruses (DENVs) representing all four serotypes, isolated from pediatric patients at children's hospital, Queen Sirikit National Institute of Child Health, Bangkok, Thailand exhibiting a diverse spectrum of disease ranging from uncomplicated dengue fever (DF) to severe dengue hemorrhagic fever (DHF), were tested for their ability to attach to host cells, replicate and interfere with the IFNalpha signaling pathway by interfering with signal transducer and activator of transcription 1 (STAT-1) function. Although most isolates suppressed IFNalpha-induced STAT-1 phosphorylation, our results showed no difference between DENV strains associated with DF and those associated with DHF. However, the DHF isolates tended replicate to higher titers in dendritic cells (DCs) than the DF isolates, but this ability was independent of their cell-binding capability. Our results suggest that the emergence early in infection of viruses with a high degree of replication fitness may play an important role in DENV pathogenesis.

New take on comparative immunology: relevance to immunotherapy

It is becoming increasingly recognized that experimental animal models, while useful to address monothematic biological questions, bear unpredictable relevance to human disease. Several reasons have been proposed. However, the uncontrollable nature of human genetics and the heterogeneity of disease that can only be replicated with difficulty experimentally play a leading role. Comparative immunology is a term that generally refers to the analysis of shared or diverging facets of immunology among species; these comparisons are carried out according to the principle that evolutionarily conserved themes outline biologic functions universally relevant for survival. We propose that a similar strategy could be applied to searching for themes shared by distinct immune pathologies within our own species. Identification of common patterns may outline pathways necessary for a particular determinism to occur, such as tissue-specific rejection or tolerance. This approach is founded on the unproven but sensible presumption that nature does not require an infinite plethora of redundant mechanisms to reach its purposes. Thus, immune pathologies must follow, at least in part, common means that determine their onset and maintenance. Commonalities among diseases can, in turn, be segregated from disease-specific patterns uncovering essential mechanisms that may represent universal targets for immunotherapy.

Serotonin receptor 2A blocker (risperidone) has no effect on human polyomavirus JC infection of primary human fetal glial cells

A recent report demonstrated that JC virus (JCV) employs serotonin receptor 2A (5HT(2A)R) to infect the glial cells. To assess the ability of a potent 5HT(2A)R blocker, risperidone, to inhibit JCV infection, the authors treated primary human fetal glial (PHFG) cells in vitro with risperidone for 24 h and inoculated with JCV(Mad1). There was no significant difference in JCV genome copies or mRNA transcripts and protein expression in treatment-naive and risperidone-treated PHFG cells. These data indicate that risperidone does not inhibit JCV(Mad1) attachment, internalisation, and replication in PHFG cells, and 5HT(2A)R blockers may not be effective in treating progressive multifocal leukoencephalopathy (PML).

Update on PML: lessons from the HIV uninfected and new insights in pathogenesis and treatment

Significant advances in our understanding of progressive multifocal leukoencephalopathy (PML) and its causative agent, JC virus, have been made since PML was first described 50 years ago. However, immune reconstitution remains the only proven, effective therapy in this devastating central nervous system disorder. Early diagnosis and adjustments of immune suppressants and modulator agents are critical in managing PML in HIV-negative patients. This review summarizes recent advances in our understanding of PML in HIV-uninfected patients in oncology, rheumatology, organ transplantation, and idiopathic immune deficiency and in association with novel therapeutics. Brain MRI data from our case series of brain biopsy-proven HIV-negative PML patients indicate the presence of an inflammatory/immune reaction in brain tissues, which was confirmed by immunocytologic analysis. Future studies to better understand PML pathogenesis in HIV-negative individuals may help uncover new potential therapeutic targets and improve PML outcomes.

Interferon beta1-a and selective anti-5HT(2a) receptor antagonists inhibit infection of human glial cells by JC virus

JC virus (JCV) is the causative agent of progressive multifocal leukoenchaphalopathy (PML). The disease develops when JCV gains access to the central nervous system, infects and destroys oligodendrocytes. The disease is rapidly progressing, typically fatal and no effective therapies exist to treat or prevent PML. The recent occurrence of PML in multiple sclerosis patients being treated with Avonex (IFNbeta1-a) and Tysabri (Natalizumab) and the recent reports linking JCV infection to the 5HT(2a) serotonin receptor led us to evaluate the effects of IFNbeta1-a and a panel of 5HT(2a) receptor antagonists for their ability to modulate virus infection. IFNbeta1-a was found to be a potent inhibitor of both virus infection and viral early and late gene expression. In addition, several 5HT(2a) receptor antagonists inhibited initial infection of cells by JCV but were less effective at reducing viral loads in an already established infection.

In vitro effects of selenium deficiency on West Nile virus replication and cytopathogenicity

Background

Selenium (Se) deficiency plays an important role in viral pathogenesis. To understand the effects of Se deficiency on West Nile virus (WNV) infection, we analyzed cytopathogenicity, apoptosis and viral replication kinetics, using a newly developed Se-deficient cell culture system.

Results

Both Vero and SK-N-SH cells grown in Se-deficient media exhibited a gradual loss of glutathione peroxidase (GPx1) activity without any significant effect on cell growth and viability. In SK-N-SH cells, Se deficiency had no effect on the expression of key antioxidant enzymes, including manganese- and copper-zinc superoxide dismutase (MnSOD and CuZnSOD), catalase and inducible nitric oxide synthase, whereas Vero cells demonstrated a significant increase in the expression of MnSOD and an overall increase in oxidative stress (OS) at day 7 post-induction of Se deficiency. At 2 days after infection with WNV, CPE and cell death were significantly higher in WNV-infected Se-deficient Vero cells, compared to WNV-infected control cells. Furthermore, WNV-induced apoptosis was significantly heightened in Se-deficient cells and was contributed by loss of mitochondrial membrane potential and increased caspase activity. However, no significant difference was found in WNV copy numbers between control, Se-adequate and Se-deficient cell cultures.

Conclusion

Overall results demonstrate that the in vitro Se-deficient model can be used to study responses of WNV to this essential nutrient. Although Se deficiency has no in vitro effect on WNV replication kinetics, adequate Se is presumably critical to protect WNV-infected cells against virus-induced cell death.