An siRNA against JC virus (JCV) agnoprotein inhibits JCV infection in JCV-producing cells inoculated in nude mice

Revisiting JC virus and progressive multifocal leukoencephalopathy

Since its definition 65 years ago, progressive multifocal leukoencephalopathy (PML) has continued to devastate a growing population of immunosuppressed patients despite major advances in our understanding of the causative JC virus (JCV). Unless contained by the immune system, JCV lyses host oligodendrocytes collateral to its life cycle, leading to demyelination, neurodegeneration, and death. Novel treatments have stagnated in the absence of an animal model while current antiviral agents fail to address the now ubiquitous polyomavirus. In this review, we highlight the established pathogenesis by which JCV infection progresses to PML, highlighting major challenges that must be overcome to eliminate the underlying virus and, therefore, the debilitating disease.

In vitro toxicity and efficacy of verdinexor, an exportin 1 inhibitor, on opportunistic viruses affecting immunocompromised individuals

Infection of immunocompromised individuals with normally benign opportunistic viruses is a major health burden globally. Infections with viruses such as Epstein-Barr virus (EBV), human cytomegalovirus (HCMV), Kaposi's sarcoma virus (KSHV), adenoviruses (AdV), BK virus (BKPyV), John Cunningham virus (JCPyV), and human papillomavirus (HPV) are significant concerns for the immunocompromised, including when these viruses exist as a co-infection with human immunodeficiency virus (HIV). These viral infections are more complicated in patients with a weakened immune system, and often manifest as malignancies resulting in significant morbidity and mortality. Vaccination is not an attractive option for these immune compromised individuals due to defects in their adaptive immune response. Verdinexor is part of a novel class of small molecules known as SINE (Selective Inhibitor of Nuclear Export) compounds. These small molecules demonstrate specificity for the nuclear export protein XPO1, to which they bind and block function, resulting in sequestration of XPO1-dependent proteins in the nucleus of the cell. In antiviral screening, verdinexor demonstrated varying levels of efficacy against all of the aforementioned viruses including previously with HIV. Studies by other labs have discussed likely mechanisms of action for verdinexor (ie. XPO1-dependence) against each virus. GLP toxicology studies suggest that anti-viral activity can be achieved at a tolerable dose range, based on the safety profile of a previous phase 1 clinical trial of verdinexor in healthy human volunteers. Taken together, these results indicate verdinexor has the potential to be a broad spectrum antiviral for immunocompromised subjects for which vaccination is a poor option.

A review on current status of antiviral siRNA

Viral diseases like influenza, AIDS, hepatitis, and Ebola cause severe epidemics worldwide. Along with their resistant strains, new pathogenic viruses continue to be discovered so creating an ongoing need for new antiviral treatments. RNA interference is a cellular gene‐silencing phenomenon in which sequence‐specific degradation of target mRNA is achieved by means of complementary short interfering RNA (siRNA) molecules. Short interfering RNA technology affords a potential tractable strategy to combat viral pathogenesis because siRNAs are specific, easy to design, and can be directed against multiple strains of a virus by targeting their conserved gene regions. In this review, we briefly summarize the current status of siRNA therapy for representative examples from different virus families. In addition, other aspects like their design, delivery, medical significance, bioinformatics resources, and limitations are also discussed.

Emerging From the Unknown: Structural and Functional Features of Agnoprotein of Polyomaviruses

Agnoprotein is an important regulatory protein of polyomaviruses, including JCV, BKV, and SV40. In the absence of its expression, these viruses are unable to sustain their productive life cycle. It is a highly basic phosphoprotein that localizes mostly to the perinuclear area of infected cells, although a small amount of the protein is also found in nucleus. Much has been learned about the structure and function of this important regulatory protein in recent years. It forms highly stable dimers/oligomers in vitro and in vivo through its Leu/Ile/Phe-rich domain. Structural NMR studies revealed that this domain adopts an alpha-helix conformation and plays a critical role in the stability of the protein. It associates with cellular proteins, including YB-1, p53, Ku70, FEZ1, HP1α, PP2A, AP-3, PCNA, and α-SNAP; and viral proteins, including small t antigen, large T antigen, HIV-1 Tat, and JCV VP1; and significantly contributes the viral transcription and replication. This review summarizes the recent advances in the structural and functional properties of this important regulatory protein. J. Cell. Physiol. 231: 2115-2127, 2016. © 2016 Wiley Periodicals, Inc.

Animal Models for Progressive Multifocal Leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is a severe demyelinating disease of the CNS caused by the human polyomavirus JC (JCV). JCV replication occurs only in human cells and investigation of PML has been severely hampered by the lack of an animal model. The common feature of PML is impairment of the immune system. The key to understanding PML is working out the complex mechanisms that underlie viral entry and replication within the CNS and the immunosurveillance that suppresses the virus or allows it to reactivate. Early models involved the simple inoculation of JCV into animals such as monkeys, hamsters, and mice. More recently, mouse models transgenic for the gene encoding the JCV early protein, T-antigen, a protein thought to be involved in the disruption of myelin seen in PML, have been employed. These animal models resulted in tumorigenesis rather than demyelination. Another approach is to use animal polyomaviruses that are closely related to JCV but able to replicate in the animal such as mouse polyomavirus and SV40. More recently, novel models have been developed that involve the engraftment of human cells into the animal. Here, we review progress that has been made to establish an animal model for PML, the advances and limitations of different models and weigh future prospects.

Progressive multifocal leukoencephalopathy: current treatment options and future perspectives

Progressive multifocal leukoencephalopathy (PML) is a rare but debilitating and frequently fatal viral disease of the central nervous system, primarily affecting individuals with chronically and severely suppressed immune systems. The disease was relatively obscure until the outbreak of HIV/AIDS, when it presented as one of the more frequent opportunistic infections in this immune deficiency syndrome. It attracted additional attention from the medical and scientific community following the discovery of significant PML risk associated with natalizumab, a monoclonal antibody used for treatment of relapsing-remitting multiple sclerosis. This was followed by association of PML with other immunosuppressive or immunomodulating drugs. PML is currently untreatable disease with poor outcomes, so it is a significant concern when developing new immunotherapies. Current prophylaxis and treatment of PML are focused on immune reconstitution, restoration of immune responses to JC virus infection, and eventual suppression of immune reconstitution inflammatory syndrome. This approach was successful in reducing the incidence of PML and improved survival of PML patients with HIV infection. However, the outcome for the majority of PML patients, regardless of their medical history, is still relatively poor. There is a high unmet need for both prophylaxis and treatment of PML. The aim of this review is to discuss potential drug candidates for prophylaxis and treatment of PML with a critical review of previously conducted and completed PML treatment studies as well as to provide perspectives for future therapies.

Emerging Roles of Viroporins Encoded by DNA Viruses: Novel Targets for Antivirals?

Studies have highlighted the essential nature of a group of small, highly hydrophobic, membrane embedded, channel-forming proteins in the life cycles of a growing number of RNA viruses. These viroporins mediate the flow of ions and a range of solutes across cellular membranes and are necessary for manipulating a myriad of host processes. As such they contribute to all stages of the virus life cycle. Recent discoveries have identified proteins encoded by the small DNA tumor viruses that display a number of viroporin like properties. This review article summarizes the recent developments in our understanding of these novel viroporins; describes their roles in the virus life cycles and in pathogenesis and speculates on their potential as targets for anti-viral therapeutic intervention.

Oligomerization of neutral peptides derived from the JC virus agnoprotein through a cysteine residue

The JC virus is the causative agent of progressive multifocal leukoencephalopathy. The viral genome encodes a multifunctional protein known as agnoprotein which is essential for viral proliferation and reported to possess the oligomerization sequence. However, the structural relationship with the oligomerization is unclear. We synthesized 23 amino acid residue neutral peptides derived from the JC virus agnoprotein, Lys22 to Asp44. The secondary structures of these peptides were β-sheet in aqueous buffer that converted to a helical structure in a hydrophobic environment. These peptides interestingly formed dimers and oligomers under oxidizing conditions. The oligomerization was facilitated by addition of bismaleimides and the derivative without thiol group did not form such oligomers. These results suggest that Agno(22-44) could be transmembrane and one disulfide bond between Cys40 triggers the oligomerization.

Human glial chimeric mice reveal astrocytic dependence of JC virus infection

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease triggered by infection with the human gliotropic JC virus (JCV). Due to the human-selective nature of the virus, there are no animal models available to investigate JCV pathogenesis. To address this issue, we developed mice with humanized white matter by engrafting human glial progenitor cells (GPCs) into neonatal immunodeficient and myelin-deficient mice. Intracerebral delivery of JCV resulted in infection and subsequent demyelination of these chimeric mice. Human GPCs and astrocytes were infected more readily than oligodendrocytes, and viral replication was noted primarily in human astrocytes and GPCs rather than oligodendrocytes, which instead expressed early viral T antigens and exhibited apoptotic death. Engraftment of human GPCs in normally myelinated and immunodeficient mice resulted in humanized white matter that was chimeric for human astrocytes and GPCs. JCV effectively propagated in these mice, which indicates that astroglial infection is sufficient for JCV spread. Sequencing revealed progressive mutation of the JCV capsid protein VP1 after infection, suggesting that PML may evolve with active infection. These results indicate that the principal CNS targets for JCV infection are astrocytes and GPCs and that infection is associated with progressive mutation, while demyelination is a secondary occurrence, following T antigen-triggered oligodendroglial apoptosis. More broadly, this study provides a model by which to further assess the biology and treatment of human-specific gliotropic viruses.

The rapidly expanding family of human polyomaviruses: recent developments in understanding their life cycle and role in human pathology

Since their discovery in 1971, the polyomaviruses JC (JCPyV) and BK (BKPyV), isolated from patients with progressive multifocal leukoencephalopathy and polyomavirus-associated nephropathy, respectively, remained for decades as the only known members of the Polyomaviridae family of viruses of human origin. Over the past five years, the application of new genomic amplification technologies has facilitated the discovery of several novel human polyomaviruses (HPyVs), bringing the present number to 10. These HPyVs share many fundamental features in common such as genome size and organization. Infection by all HPyVs is widespread in the human population, but they show important differences in their tissue tropism and association with disease. Much remains unknown about these new viruses. In this review, we discuss the problems associated with studying HPyVs, such as the lack of culture systems for the new viruses and the gaps in our basic understanding of their biology. We summarize what is known so far about their distribution, life cycle, tissue tropism, their associated pathologies (if any), and future research directions in the field.

Polycation-based nanoparticle delivery of RNAi therapeutics: adverse effects and solutions

Small interfering RNA (siRNA) that silence genes by the process of RNA interference offers a new therapeutic modality for disease treatment. Polycation-based nanoparticles termed polyplexes have been developed to maximise extracellular and intracellular siRNA delivery, a key requirement for enabling the clinical translation of RNAi-based drugs. Medical applications are dependent on safety; therefore, detailed investigation into potential toxicity to the cell or organism is required. This review addresses potential adverse effects arising from cellular and tissue interactions, immune stimulation and altered gene expression that can be associated with the assembled polyplex or the polycation and siRNA component parts. A greater understanding of the cellular mechanisms involved allows design-based solutions for rationale development of safe, effective and clinically relevant polyplex-based RNAi drugs.

[Progressive multifocal leukoencephalopathy (PML)]

Progressive multifocal leukoencephalopathy (PML) is caused by reactivation of latently infected JCV when hosts' immune system is impaired by HIV infection, hematologic diseases, collagen diseases, immunemodulatory therapy and so on. PML was rare but HIV infection and Natalizumab have made it much more common while the prognosis is much better than other PML. PML patients present with various signs and symptoms including hemiparesis, dementia, aphasia, visual disturbance, cranial nerve paresis, cerebellar signs and bladder bowel disturbance. Brain MRI reveals characteristic demyelinating lesions in the CNS white matter and CSF mild increase of protein with or without mild mononuclear pleocytosis. Detection of JCV genome from CSF is crucial for the clinical diagnosis of PML. PML was once thought to be fatal but some HIV infected PML patients showed halting progression or even recovery after introduction of HAART. In addition, anti-malarial drug mefloquine was found to be effective. Recovery of immunity may provoke some inflammatory responses known as immune reconstruction inflammatory syndrome (IRIS) which requires high dose corticosteroid. In Japan, we are providing free test of CSF-JCV genome and organized a unique system for surveillance and clinical research of PML. Using this system we hope to improve diagnosis and therapy of PML in Japan.

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.

Progressive multifocal leukoencephalopathy: what's new?

Progressive multifocal leukoencephalopathy (PML), a severe demyelinating disease that is caused by human JC polyomavirus, was first described as a complication of immune suppression 50 years ago and emerged as a major complication of HIV infection in the 1980s. The prognosis has remained dismal since then, with discouraging results from clinical trials of various therapeutic approaches, including immunomodulation and/or inhibition of viral replication. PML is caused by reactivation of latent JC virus, and serotonergic 5-HT(2a) receptors have been identified as being critical for viral infection of glial cells. In recent years, immunosuppressive therapeutic antibodies have been associated with an increased incidence rate of PML. Here, the authors review findings on the pathogenesis of PML and the encouraging case reports of novel treatments.

Efficient gene transfer using the human JC virus-like particle that inhibits human colon adenocarcinoma growth in a nude mouse model

The JC virus (JCV) may infect human oligodendrocytes and consequently cause progressive multifocal leukoencephalopathy (PML) in patients with immune deficiency. In addition, the virus has also been detected in other human tissues, including kidney, B lymphocytes, and gastrointestinal tissue. The recombinant major structural protein, VP1, of JCV is able to self-assemble to form a virus-like particle (VLP). It has been shown that the VLP is capable of packaging and delivering exogenous DNA into human cells for gene expression. However, gene transfer is not efficient when using in vitro DNA packaging methods with VLPs. In this study, a novel in vivo DNA packaging method using the JCV VLP was used to obtain high efficiency gene transfer. A reporter gene, the green fluorescence protein, and a suicide gene, the herpes simplex virus thymidine kinase (tk), were encapsidated into VLPs in Escherichia coli. The VLP was used to specifically target human colon carcinoma (COLO-320 HSR) cells in a nude mouse model. Intraperitoneal administration of ganciclovir in the tk-VLP-treated mice greatly reduced tumor volume. These findings suggest that it will be possible to develop the JCV VLP as a gene delivery vector for human colon cancer therapy in the future.

The human polyoma JC virus agnoprotein acts as a viroporin

Virus infections can result in a range of cellular injuries and commonly this involves both the plasma and intracellular membranes, resulting in enhanced permeability. Viroporins are a group of proteins that interact with plasma membranes modifying permeability and can promote the release of viral particles. While these proteins are not essential for virus replication, their activity certainly promotes virus growth. Progressive multifocal leukoencephalopathy (PML) is a fatal demyelinating disease resulting from lytic infection of oligodendrocytes by the polyomavirus JC virus (JCV). The genome of JCV encodes six major proteins including a small auxiliary protein known as agnoprotein. Studies on other polyomavirus agnoproteins have suggested that the protein may contribute to viral propagation at various stages in the replication cycle, including transcription, translation, processing of late viral proteins, assembly of virions, and viral propagation. Previous studies from our and other laboratories have indicated that JCV agnoprotein plays an important, although as yet incompletely understood role in the propagation of JCV. Here, we demonstrate that agnoprotein possesses properties commonly associated with viroporins. Our findings demonstrate that: (i) A deletion mutant of agnoprotein is defective in virion release and viral propagation; (ii) Agnoprotein localizes to the ER early in infection, but is also found at the plasma membrane late in infection; (iii) Agnoprotein is an integral membrane protein and forms homo-oligomers; (iv) Agnoprotein enhances permeability of cells to the translation inhibitor hygromycin B; (v) Agnoprotein induces the influx of extracellular Ca(2+); (vi) The basic residues at amino acid positions 8 and 9 of agnoprotein key are determinants of the viroporin activity. The viroporin-like properties of agnoprotein result in increased membrane permeability and alterations in intracellular Ca(2+) homeostasis leading to membrane dysfunction and enhancement of virus release.

Inhibitory effect of serotonin antagonists on JC virus propagation in a carrier culture of human neuroblastoma cells

Human polyomavirus, JCV, causes fatal demyelinating disease, progressive multifocal leukoencephalopathy (PML). It has been shown that 5HT(2A)R acts as a cellular receptor for JCV on human glial cells. In the current study, we examined the inhibitory effects of 5HT(2A)R antagonists, ketanserin and ritanserin, both on JCV infection and on propagation by using human neuroblastoma cells IMR-32 and JCI, which continuously produce JCV. Transcriptional analysis revealed that 5HT(2A)R was constitutively expressed in JCI cells. Treatments with 5HT(2A)R antagonists led to a significant reduction in the titers of progeny viruses and the population of infected JCI cells. In addition, the amount of JCV genomic DNA was decreased in JCI cells in the presence of 5HT(2A)R antagonists. These results indicate that 5HT(2A)R antagonists have an inhibitory effect on JCV infection and reproduction, and JCI cells are applicable to an experimental model for pharmacological evaluation of antiviral agents against JCV.

Delivery of RNA interference therapeutics using polycation-based nanoparticles

RNAi-based therapies are dependent on extracellular and intracellular delivery of RNA molecules for enabling target interaction. Polycation-based nanoparticles (or polyplexes) formed by self-assembly with RNA can be used to modulate pharmacokinetics and intracellular trafficking to improve the therapeutic efficacy of RNAi-based therapeutics. This review describes the application of polyplexes for extracellular and intracellular delivery of synthetic RNA molecules. Focus is given to routes of administration and silencing effects in animal disease models. The inclusion of functional components into the nanoparticle for controlling cellular trafficking and RNA release is discussed. This work highlights the versatile nature of polycation-based nanoparticles to fulfil the delivery requirements for RNA molecules with flexibility in design to evolve alongside an expanding repertoire of RNAi-based drugs.

Generation and characterization of JCV permissive hybrid cell lines

JC virus (JCV) is a human neurotropic polyomavirus whose replication in the central nervous system induces the fatal demyelinating disease, progressive multifocal leukoencephalopathy (PML). JCV particles have been detected primarily in oligodendrocytes and astrocytes of the brains of patients with PML and in the laboratory its propagation is limited to primary cultures of human fetal glial cells. In this short communication, the development of a new cell culture system is described through the fusion of primary human fetal astrocytes with the human glioblastoma cell line, U-87MG. The new hybrid cell line obtained from this fusion has the capacity to support efficiently expression of JCV and replication of viral DNA in vitro up to 16 passages. This cell line can serve as a reliable culture system to study the biology of JCV host-cell interaction, determine the mechanisms involved in cell type specific replication of JCV, and provide a convenient cell culture system for high throughput screening of anti-viral agents.