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

The role of high mobility group AT-hook 1 in viral infections: Implications for cancer pathogenesis

The crucial role of high mobility group AT-hook 1 (HMGA1) proteins in nuclear processes such as gene transcription, DNA replication, and chromatin remodeling is undeniable. Elevated levels of HMGA1 have been associated with unfavorable clinical outcomes and adverse differentiation status across various cancer types. HMGA1 regulates a diverse array of biological pathways, including tumor necrosis factor-alpha/nuclear factor-kappa B (TNF-α/NF-κB), epidermal growth factor receptor (EGFR), Hippo, Rat sarcoma/extracellular signal-regulated kinase (Ras/ERK), protein kinase B (Akt), wingless-related integration site/beta-catenin (Wnt/beta-catenin), and phosphoinositide 3-kinase/protein kinase B (PI3-K/Akt). While researchers have extensively investigated tumors in the reproductive, digestive, urinary, and hematopoietic systems, mounting evidence suggests that HMGA1 plays a critical role as a tumorigenic factor in tumors across all functional systems. Given its broad interaction network, HMGA1 is an attractive target for viral manipulation. Some viruses, including herpes simplex virus type 1, human herpesvirus 8, human papillomavirus, JC virus, hepatitis B virus, human immunodeficiency virus type 1, severe acute respiratory syndrome Coronavirus 2, and influenza viruses, utilize HMGA1 influence for infection. This interaction, particularly in oncogenesis, is crucial. Apart from the direct oncogenic effect of some of the mentioned viruses, the hit-and-run theory postulates that viruses can instigate cancer even before being completely eradicated from the host cell, implying a potentially greater impact of viruses on cancer development than previously assumed. This review explores the interplay between HMGA1, viruses, and host cellular machinery, aiming to contribute to a deeper understanding of viral-induced oncogenesis, paving the way for innovative strategies in cancer research and treatment.

Prevalence of JC Polyomavirus in Patients with Neuroinvasive Disease of Unknown Etiology in Croatia

Background and Objectives: John Cunningham polyomavirus (JCPyV) is a highly prevalent virus in the human population. The prevalence of JCPyV in patients with central nervous system disorders has not been examined extensively. The aim of this study was to analyze the prevalence of JCPyV DNA/antibodies in patients with neuroinvasive diseases (NID) of unknown etiology. Materials and Methods: The study included 132 patients with NID (febrile headache, meningitis, encephalitis) tested from January 2021 to December 2022. The control group consisted of 47 asymptomatic individuals. In patients with NID, serum and cerebrospinal fluid (CSF) samples were collected in the acute phase of the disease. CSF samples were tested for JCPyV DNA (PCR), while serum samples were tested for JCPyV IgG antibodies (ELISA). In controls, serum samples were tested for JCPyV IgG antibodies (ELISA). Results: JCPyV DNA was not detected in any of the CSF samples from patients with NID. JCPyV IgG antibodies were detected in 88.6% of patients and 74.5% of controls (p < 0.001). In the patients' group, a significant difference in the IgG prevalence was observed between males (94.6%) and females (81.0%). In addition, significant differences in the seropositivity between age groups were found. The lowest seroprevalence (28.6%) was in patients less than 20 years, followed by a sharp increase in the 20-29-year group (69.2%), after which the seroprevalence remained stable (90.0-94.1%) in patients up to 69 years. All patients older than 70 years were JCPyV IgG-seropositive. No significant difference in the seroprevalence was found in patients presenting with febrile headache (81.6%), meningitis (93.3%), or meningoencephalitis (91.3%). No difference in the seropositivity between genders was found in controls. Although the seropositivity steadily increased in older participants, these differences were not significant. Analyzing the JCPyV antibody levels in patients with NID, the median antibody titers differed significantly between groups, ranging from 248 AU/mL (younger age groups) to 400 AU/mL (older age groups). Conclusions: Higher seroprevalence in the patients' group highlights the need to further investigate the possible association of JCPyV and NID.

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.

Progressive multifocal leukoencephalopathy after durvalumab treatment for acute myeloid leukemia: A consequence of an immune reconstitution inflammatory syndrome?

Progressive multifocal leukoencephalopathy (PML) is a fatal demyelinating disease of the central nervous system resulting from the reactivation of the John Cunningham virus (JCV). PML occurs almost exclusively during profound immune suppression but it can also be observed in immunocompromised subjects as part of an inflammatory immune reconstitution syndrome (IRIS) in patients receiving antiviral therapy. We report a case of PML in a 61‐year‐old patient with acute myeloid leukemia who had developed after discontinuation of durvalumab (anti‐PD‐L1) therapy initiated after multiple treatments. Results suggest that PML may result from two nonexclusive mechanisms: (i) an inhibition of the protective response of JCV‐specific T cells as a consequence of the blockade of the PD1‐PDL1 pathway, associated with a lack of compensatory expression of other inhibitory receptors by T cells and (ii) a neuroinflammatory response (PML‐IRIS) that may have contributed to virus reactivation.

Progressive multifocal leukoencephalopathy in a patient with novel mutation in the RAC2 gene: a case report

Background

Progressive multifocal leukoencephalopathy is a rare demyelinating disease that is often secondary to lytic destruction of oligodendrocytes and, to a lesser extent, to astrocytes’ response to human neurotrophic John Cunningham polyomavirus. Any underlying congenital disorder of primary or secondary immunodeficiency may predispose to virus infection and possible invasion of the brain. We present the first reported case of progressive multifocal leukoencephalopathy due to a mutation in the RAC2 gene.

Case presentation

We describe the case of a 34-year-old Iranian man with recurrent infections from the age of 2 years, along with other disorders such as nephritic syndrome, factor XI deficiency, and hypogammaglobulinemia. He was treated regularly with intravenous immunoglobulin from the age of 10 years with a diagnosis of common variable immune deficiency. Genetic testing confirmed a novel homozygous mutation in the RAC2 gene in the patient. Owing to the onset of neurological symptoms a few months ago, the patient was completely avaluated, which confirmed the diagnosis of PML. Despite all efforts, the patient died shortly after progression of neurological symptoms.

Conclusions

According to previous studies, progressive multifocal leukoencephalopathy has been associated with 26 cases of primary immunodeficiency. Our patient presents a new case of primary immunodeficiency with progressive multifocal leukoencephalopathy. Accurate examination of these cases can help us to gain insight into the immune response to John Cunningham virus and better treat this potentially deadly disease.

Immune profile and radiological characteristics of progressive multifocal leukoencephalopathy

BACKGROUND AND PURPOSE

Progressive multifocal leukoencephalopathy (PML) constitutes a severe disease with increasing incidence, mostly in the context of immunosuppressive therapies. A detailed understanding of immune response in PML appears critical for the treatment strategy. The aim was a comprehensive immunoprofiling and radiological characterization of magnetic resonance imaging (MRI) defined PML variants.

METHODS

All biopsy-confirmed PML patients (n = 15) treated in our department between January 2004 and July 2019 were retrospectively analysed. Data from MRI, histology as well as detailed clinical and outcome data were collected. The MRI-defined variants of classical (cPML) and inflammatory (iPML) PML were discriminated based on the intensity of gadolinium enhancement. In these PML variants, intensity and localization (perivascular vs. parenchymal) of inflammation in MRI and histology as well as the cellular composition by immunohistochemistry were assessed. The size of the demyelinating lesions was correlated with immune cell infiltration.

RESULTS

Patients with MRI-defined iPML showed a stronger intensity of inflammation with an increased lymphocyte infiltration on histological level. Also, iPML was characterized by a predominantly perivascular inflammation. However, cPML patients also demonstrated certain inflammatory tissue alterations. Infiltration of CD163-positive microglia and macrophage (M/M) subtypes correlated with PML lesion size.

CONCLUSIONS

The non-invasive MRI-based discrimination of PML variants allows for an estimation of inflammatory tissue alterations, although exhibiting limitations in MRI-defined cPML. The association of a distinct phagocytic M/M subtype with the extent of demyelination might reflect disease progression.

JC Polyomavirus Infection Potentiated by Biologics

The risk of JC polyomavirus encephalopathy varies among biologic classes and among agents within the same class. Of currently used biologics, the highest risk is seen with natalizumab followed by rituximab. Multiple other agents have also been implicated. Drug-specific causality is difficult to establish because many patients receive multiple immunomodulatory medications concomitantly or sequentially, and have other immunocompromising factors related to their underlying disease. As use of biologic therapies continues to expand, further research is needed into pathogenesis, treatment, and prevention of JC polyomavirus encephalopathy such that risk for its development is better understood and mitigated, if not eliminated altogether.

AIDS-related progressive multifocal leukoencephalopathy

INTRODUCTION

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system caused by reactivation of JC virus (JCV).

METHODS

We described the profile of laboratory-confirmed PML cases among AIDS patients.

RESULTS

A total of 43 HIV patients with clinical conditions compatible with PML were obtained; 5 cases were confirmed by JCV testing. The main clinical finding was mental confusion. Median CD4 count was 54 cells/mm³.

CONCLUSIONS

Three of the five confirmed PML cases died; the time between diagnosis and death was 2, 5, and 6 months. It is important to consider JCV infection as a differential diagnosis.

John Cunningham Virus Status, Seroconversion Rate, and the Risk of Progressive Multifocal Leukoencephalopathy in Polish John Cunningham Virus-Seronegative Patients with Relapsing-Remitting Multiple Sclerosis

INTRODUCTION

Presence of anti-JC-virus antibodies (JCVAbs) is associated with the increased risk of natalizumab (NAT)-related progressive multifocal leukoencephalopathy (PML). Little is known about seroconversion rate and time to seroconversion in relapsing-remitting multiple sclerosis (RRMS) patients treated with NAT in Poland. The aim of the study was to assess the true risk of PML, seroconversion rate, and time to seroconversion in all JCVAb-negative RRMS patients treated with NAT in Poland.

METHODS

Demographic and clinical data of all Polish RRMS patients treated with NAT reimbursed by National Health Fund (NFZ) were prospectively collected in electronic files using the Therapeutic Programme Monitoring System provided by NFZ. The assessment of JCVAb presence (without collection of JCVAb index value) in serum (Unilabs, STRATIFY JCV: anti-JCV antibody ELISA) was done at the beginning of therapy and then repeated every 6 months. The maximum follow-up time was 4 years. In Poland, since 2013, according to the NFZ drug program guidance, only patients with negative JCVAb test have started treatment with NAT.

RESULTS

In all Polish multiple sclerosis centers, 210 negative JCVAb RRMS patients with at least 9 (±3) months of observation (146 females, 64 males, and the median age at baseline: 33 years) were included in the study. During the follow-up period, JCVAb status changed from negative to positive in 34 patients (16.2%). For half of the patients, the seroconversion was diagnosed 1 year after starting NAT treatment. In 4 patients (1.9%) during follow-up, JCVAb status changed again from positive to negative. In Poland, before establishment of NFZ drug program, 4 cases of PML in patients treated with NAT in clinical trials were diagnosed. In the NFZ drug program, since 2013, no patient treated with NAT has been diagnosed with PML.

CONCLUSIONS

NAT therapy in JCV-seronegative RRMS patients is safe and results in the absence of PML cases. In Poland, JCV seroconversion rate is similar to that observed in other European countries.

Progressive multifocal leukoencephalopathy in a patient with systemic sclerosis treated with methotrexate: A case report and literature review

Reactivation of viruses occurs in autoimmune disorders in the setting of certain immunosuppressive drugs. We describe a 54-year-old female with systemic sclerosis and extensive cutaneous calcinosis who had been treated with methotrexate for 18 months and presented with headache and neurological deficits. She was diagnosed with progressive multifocal leukoencephalopathy, a rare disease caused by JC virus. Methotrexate was discontinued and mirtazapine plus mefloquine were added. The patient showed a slow recovery and five years later she had complete resolution of progressive multifocal leukoencephalopathy clinical manifestations. Calcinosis had a limited response to various agents and severely affected daily activities of the patient. This case report, highlights the importance of clinical suspicion for progressive multifocal leukoencephalopathy in every patient with immune-mediated disease, even on weak immunosuppressant, who presents with central nervous system manifestations and also the unmet therapeutic need for systemic sclerosis-associated calcinosis.

Two susceptible HLA-DRB1 alleles for multiple sclerosis differentially regulate anti-JC virus antibody serostatus along with fingolimod

Background

Progressive multifocal leukoencephalopathy (PML) caused by JC virus (JCV) is a rare but serious complication of some disease-modifying drugs used to treat multiple sclerosis (MS). Japanese MS patients treated with fingolimod were reported to be 10 times more likely to develop PML than equivalent patients in other countries. The strongest susceptibility human leukocyte antigen (HLA) class II alleles for MS are distinct between races (DRB1*15:01 for Caucasians and DRB1*04:05 and DRB1*15:01 for Japanese); therefore, we investigated whether HLA class II alleles modulate anti-JCV antibody serostatus in Japanese MS patients with and without fingolimod.

Methods

We enrolled 128 Japanese patients with MS, in whom 64 (50%) were under fingolimod treatment at sampling, and examined the relationship between HLA class II alleles and anti-JCV antibody serostatus. Serum anti-JCV antibody positivity and index were measured using a second-generation two-step assay and HLA-DRB1 and -DPB1 alleles were genotyped.

Results

HLA-DRB1*15 carriers had a lower frequency of anti-JCV antibody positivity (57% vs 78%, p = 0.015), and lower antibody index (median 0.42 vs 1.97, p = 0.037) than non-carriers. Among patients without HLA-DRB1*15, DRB1*04 carriers had a higher seropositivity rate than non-carriers (84% vs 54%, p = 0.030), and DPB1*04:02 carriers had a higher anti-JCV antibody index than non-carriers (3.20 vs 1.34, p = 0.008) although anti-JCV antibody-positivity rates did not differ. Patients treated with fingolimod had a higher antibody index than other patients (1.46 vs 0.64, p = 0.039) and treatment period had a positive correlation with antibody index (p = 0.018). Multivariate logistic regression analysis revealed that age was positively associated, and HLA-DRB1*15 was negatively associated with anti-JCV antibody positivity (odds ratio [OR] = 1.06, p = 0.006, and OR = 0.37, p = 0.028, respectively). Excluding HLA-DRB1*15-carriers, DRB1*04 was an independent risk factor for the presence of anti-JCV antibody (OR = 5.50, p = 0.023).

Conclusions

HLA-DRB1*15 is associated with low anti-JCV antibody positive rate and low JCV antibody index, and in the absence of DRB1*15, DRB1*04 carriers are associated with a high antibody positive rate in Japanese, suggesting the effects of two susceptible HLA-DRB1 alleles on anti-JCV antibody serostatus differ.

Changes in Anti-JCV Antibody Status in a Large Population of Multiple Sclerosis Patients Treated with Natalizumab

INTRODUCTION

Natalizumab (NTZ) can be associated with an opportunistic infection, progressive multifocal leukoencephalopathy (PML), caused by John Cunningham virus (JCV). High titer of anti-JCV antibody (JCV index) in patients treated with NTZ for over 2 years limit it use, leading to treatment discontinuation.

OBJECTIVE

Aim of the study was to investigate the JCV index changes pre, during and post NTZ treatment and describe the trend after a long period of NTZ discontinuation.

METHODS

Patients with relapsing-remitting multiple sclerosis (RR-MS) treated with NTZ between 2010 and 2018 were enrolled in this retrospective-prospective observational study. Inclusion criteria were: (1) diagnosis of RR-MS according to the McDonald criteria 2010, (2) at least six NTZ administrations, (3) at least two determinations of JCV Index during the follow-up period, (4) NTZ discontinuation period for more than 6 months. JCV index was determined by STRATIFY II. There were three different timepoints: NTZ initiation (T0), NTZ discontinuation (T1) and time after NTZ suspension (T2). Seroconversion was defined as changing status of serum JCV antibody. Main outcomes were the JCV index changes and the rate of seroconversion.

RESULTS

At baseline we enrolled 285 patients (208 JCV negative, 67 JCV positive, and 10 not available). There was a statistically significant increase of JCV index during NTZ treatment period (T0 vs T1, p =0.0009) and during NTZ discontinuation period (T1 vs T2, p =0.04). Patients seroconverted to a positive status more frequently during NTZ treatment than after discontinuation (p =0.008). Moreover, patients who shifted to fingolimod (FTY) as exit strategy after NTZ discontinuation, showed a statistically significant increase of JCV index.

CONCLUSION

Our data confirmed that a high percentage of patients shift to or remain in a positive JCV status during NTZ treatment and after discontinuation. NTZ suspension seems not to be able to interfere on JCV status modification over an extended period. The choice of alternative treatment as exit strategy after NTZ discontinuation should be carefully considered because it could negatively influence the PML risk stratification of patients.

Investigation of Oligodendrocyte Precursor Cell Differentiation by Quantitative Proteomics

Oligodendrocytes, the myelinating cells of the central nervous system, are essential for correct brain function. They originate from oligodendrocyte precursor cells through a differentiation process which is only incompletely understood and impaired in a variety of demyelinating diseases. Better knowledge of this differentiation holds the promise to develop novel therapies for these disorders. The differentiation of rat oligodendrocyte precursor cells to oligodendrocytes in vitro is investigated. After confirmation of differentiation by immunohistochemical analysis using cell type-specific marker proteins, a quantitative proteomics study using tandem mass tags (TMT) is conducted. Four time points of differentiation covering early, intermediate, and late stages are investigated. Data analysis by Mascot and MaxQuant identified 5259 protein groups of which 471 are not described in the context of cells of the oligodendroglial lineage before. Quantitative analysis of the dataset revealed distinct regulation patterns for proteins of different functional categories including metabolic processes, regulation of the cell cycle, and transcriptional control of protein expression. The present data confirm a significant number of proteins known to play a role in oligodendrocytes and myelination. Furthermore, novel candidate proteins are identified which may play an important role in this differentiation process providing a valuable resource for oligodendrocyte research.

B Cell-based Therapies for Multiple Sclerosis

The traditional view of multiple sclerosis (MS) as a T cell mediated autoimmune disease of the central nervous system (CNS) has evolved into a concept of an immune-mediated disease where complex bi-directional interactions between T cells, B cells and myeloid cells underlie and shape CNS-directed autoimmunity. B cells are now recognized as major contributors to the pathogenesis of MS, largely due to increased understanding of their biology and the profound anti-inflammatory effects demonstrated by B cell depletion in MS. In this chapter we discuss the fundamental roles B cells play in the pathogenesis of MS and review current and future therapeutic strategies targeting B cells in MS, including B cell depletion with various monoclonal antibodies (mAbs) against the B cell surface markers CD20 and CD19, anti-B cell cytokine therapies, blocking Bruton's tyrosine kinase (BTK) in B cells, and various immunomodulatory and immunosuppressive effects exerted on B cells by virtually all other approved therapies for MS.

Serological profile of John Cunningham virus (JCV) in patients with multiple sclerosis

Treatment options for multiple sclerosis (MS) have changed over the last few years, bringing about a new category of drugs with more efficient profiles. However, these drugs have come with a whole new profile of potential adverse events that neurologists have to learn well and quickly. One of the most feared complications of these MS treatments is progressive multifocal leukoencephalopathy caused by the reactivation of the John Cunningham virus (JCV).

OBJECTIVE

To identify the serologic profile of JCV in patients with MS.

METHODS

Data on serum antibodies for JCV were obtained using the enzyme-linked immunosorbent assay provided by the STRATIFY-JCV program.

RESULTS

A total of 1,501 blood tests were obtained from 1,102 patients with MS. There were 633 patients (57.1%) who were positive for antibodies for JCV and 469 patients who were negative (42.9%). Twenty-three patients became positive after initially having negative JCV antibody status. The rate of seroconversion was 18.5% over 22 months.

CONCLUSION

The JCV serologic profile and seroconversion in Brazilian patients were similar to those described in other countries.

Favorable Response to Mirtazapine in John Cunningham Virus-related Gray Matter Lesion in a Patient with Human Immunodeficiency Virus

Mirtazapine has recently emerged as a promising agent for the treatment of progressive multifocal leukoencephalopathy (PML). While there is no Class I evidence for its use, numerous case reports have illustrated mirtazapine’s efficacy. True to its name, PML is known to occur mostly in the white matter of the brain as its causative agent, John Cunningham virus (JC virus), has a predilection for infecting glial cells. The virus replicates vigorously in oligodendrocytes and causes lysis of the glial cell culminating in demyelination. Therefore, gray matter involvement is rare. Mirtazapine’s 5HT2A receptor blocking capacity is presumed to hinder JC virus’ entry into glial cells. We report a case of a patient with human immunodeficiency virus (HIV) with predominantly gray matter lesions from JC virus reactivation. This case is the first reported case of gray matter PML in an Arabic patient who responded favorably to mirtazapine therapy.

A case of developing progressive multifocal leukoencephalopathy while using rituximab and mycophenolate mofetil in refractory systemic lupus erythematosus

Progressive multifocal leukoencephalopathy (PML) is a central nervous system infection caused by John Cunningham (JC) virus reactivation in an immunocompromised patient. PML has various neurologic symptoms and has very poor prognosis. A 36-year-old man developed transverse myelitis and had a psychiatric disorder at the age of 26. He was diagnosed with systemic lupus erythematosus (SLE) and neuropsychiatric SLE (NPSLE), on the basis of leukopenia and presence of anti-DNA and anti-nuclear antibodies. Treatment with glucocorticoid (GC) was started, and remission was introduced. Six months before PML onset, his condition was complicated with hemophagocytic lymphohistiocytosis (HLH) due to exacerbation of SLE. Remission re-induction therapy by GC, cyclosporine-A, intravenous cyclophosphamide, and rituximab (RTX) was initiated and HLH improved. However, interleukin-6 levels of the cerebrospinal fluid (CSF) continued to rise. We thought that the disease activity of NPSLE worsened; thus, we introduced mycophenolate mofetil (MMF) 4 months before the PML onset. He developed progressive dysarthria and right hemiplegia. He was diagnosed with PML via magnetic resonance imaging and JC virus polymerase chain reaction in CSF. Considering that immunosuppressants, including RTX and MMF, are precipitating factors of PML, we discussed the RTX removal using plasma exchange (PEx), but we did not introduce PEx, because it was expected that the concentration of RTX was already lowered when he was diagnosed with PML. Treatment for PML with mefloquine and mirtazapine saved his life, but severe residual disabilities remained. This is the first report of a patient who developed PML during combination therapy with RTX and MMF.

Systematic review of the published data on the worldwide prevalence of John Cunningham virus in patients with multiple sclerosis and neuromyelitis optica

OBJECTIVES

John Cunningham virus (JCV) is a polyoma virus that infects humans, mainly in childhood or adolescence, and presents no symptomatic manifestations. JCV can cause progressive multifocal leukoencephalopathy (PML) in immunosuppressed individuals, including those undergoing treatment for multiple sclerosis (MS) and neuromyelitis optica (NMO). PML is a severe and potentially fatal disease of the brain. The prevalence of JCV antibodies in human serum has been reported to be between 50.0 and 90.0%. The aim of the present study was to review worldwide data on populations of patients with MS and NMO in order to establish the rates of JCV seropositivity in these individuals.

METHODS

The present review followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines and used the following search terms: “JCV” OR “JC virus” AND “multiple sclerosis” OR “MS” OR “NMO” OR “neuromyelitis optica” AND “prevalence.” These terms were searched for both in smaller and in larger clusters of words. The databases searched included PubMed, MEDLINE, SciELO, LILACS, Google Scholar, and Embase.

RESULTS

After the initial selection, 18 papers were included in the review. These articles reported the prevalence of JCV antibodies in the serum of patients with MS or NMO living in 26 countries. The systematic review identified data on 29,319 patients with MS/NMO and found that 57.1% of them (16,730 individuals) were seropositive for the anti-JCV antibody (range, 40.0 to 69.0%).

CONCLUSIONS

The median worldwide prevalence of JCV among adults with MS or NMO was found to be 57.1%.

Progressive multifocal leukoencephalopathy in patients receiving rituximab and cyclophosphamide after haplo-identical T-cell replete transplantation and review of the literature

John Cunningham virus (JCV) reactivation, occurring mainly in immunocompromised patients, leads to progressive multifocal leukoencephalopathy, an uncommon but lethal disease. JCV reactivation after T-cell replete haploidentical stem cell transplantation, in the pre-cyclophosphamide era, is poorly represented in the literature. We therefore describe two cases of acute myeloid leukemia who developed JCV reactivation after receiving cyclophosphamide and rituximab post haploidentical stem cell transplantation, and review the literature, aiming to a better understanding of the disease course and its risk factors.

Replication of JC Virus DNA in the G144 Oligodendrocyte Cell Line Is Dependent Upon Akt

Progressive multifocal leukoencephalopathy (PML) is an often-fatal demyelinating disease of the central nervous system. PML results when oligodendrocytes within immunocompromised individuals are infected with the human JC virus (JCV). We have identified an oligodendrocyte precursor cell line, termed G144, that supports robust levels of JCV DNA replication, a central part of the JCV life cycle. In addition, we have determined that JC virus readily infects G144 cells. Furthermore, we have determined that JCV DNA replication in G144 cells is stimulated by myristoylated (i.e., constitutively active) Akt and reduced by the Akt-specific inhibitor MK2206. Thus, this oligodendrocyte-based model system will be useful for a number of purposes, such as studies of JCV infection, establishing key pathways needed for the regulation of JCV DNA replication, and identifying inhibitors of this process.IMPORTANCE The disease progressive multifocal leukoencephalopathy (PML) is caused by the infection of particular brain cells, termed oligodendrocytes, by the JC virus. Studies of PML, however, have been hampered by the lack of an immortalized human cell line derived from oligodendrocytes. Here, we report that the G144 oligodendrocyte cell line supports both infection by JC virus and robust levels of JCV DNA replication. Moreover, we have established that the Akt pathway regulates JCV DNA replication and that JCV DNA replication can be inhibited by MK2206, a compound that is specific for Akt. These and related findings suggest that we have established a powerful oligodendrocyte-based model system for studies of JCV-dependent PML.

Neurotherapeutic Strategies for Multiple Sclerosis

Multiple sclerosis (MS) is the most common disabling neurologic disease of young adults. There are now 16 US Food and Drug Administration (FDA)-approved disease-modifying therapies for MS as well as a cohort of other agents commonly used in practice when conventional therapies prove inadequate. This article discusses approved FDA therapies as well as commonly used practice-based therapies for MS, as well as those therapies that can be used in patients attempting to become pregnant, or in patients with an established pregnancy, who require concomitant treatment secondary to recalcitrant disease activity.

Late onset progressive multifocal leukoencephalopathy in Hodgkin lymphoma

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease resulting from infection of oligodendrocytes in the central nervous system with John Cunningham virus. Although PML is commonly diagnosed in immunocompromised patients with human immunodeficiency virus, it can also arise in other immunodeficient states. In this report, we present an unusual case of PML occurring 40years after chemoradiation therapy for Hodgkin lymphoma in a patient with normal total lymphocyte counts on annual surveillance. Although current guidelines recommend annual complete blood counts for patients in remission, this testing may be insufficient to monitor patients with chronic CD4+ lymphopenia.

Dimethyl Fumarate Selectively Reduces Memory T Cells and Shifts the Balance between Th1/Th17 and Th2 in Multiple Sclerosis Patients

Dimethyl fumarate (DMF; trade name Tecfidera) is an oral formulation of the fumaric acid ester that is Food and Drug Administration approved for treatment of relapsing-remitting multiple sclerosis. To better understand the therapeutic effects of Tecfidera and its rare side effect of progressive multifocal leukoencephalopathy, we conducted cross-sectional and longitudinal studies by immunophenotyping cells from peripheral blood (particularly T lymphocytes) derived from untreated and 4-6 and 18-26 mo Tecfidera-treated stable relapsing-remitting multiple sclerosis patients using multiparametric flow cytometry. The absolute numbers of CD4 and CD8 T cells were significantly decreased and the CD4/CD8 ratio was increased with DMF treatment. The proportions of both effector memory T cells and central memory T cells were reduced, whereas naive T cells increased in treated patients. T cell activation was reduced with DMF treatment, especially among effector memory T cells and effector memory RA T cells. Th subsets Th1 (CXCR3⁺), Th17 (CCR6⁺), and particularly those expressing both CXCR3 and CD161 were reduced most significantly, whereas the anti-inflammatory Th2 subset (CCR3⁺) was increased after DMF treatment. A corresponding increase in IL-4 and decrease in IFN-γ and IL-17-expressing CD4⁺ T cells were observed in DMF-treated patients. DMF in vitro treatment also led to increased T cell apoptosis and decreased activation, proliferation, reactive oxygen species, and CCR7 expression. Our results suggest that DMF acts on specific memory and effector T cell subsets by limiting their survival, proliferation, activation, and cytokine production. Monitoring these subsets could help to evaluate the efficacy and safety of DMF treatment.

Neurologic emergencies in HIV-negative immunosuppressed patients

HIV-negative immunosuppressed patients comprise a heterogeneous group including transplant patients, patients undergoing treatment with immunosuppressors, uremic patients, alcoholics, undernourished patients, diabetics, patients on dialysis, elderly patients, and those diagnosed with severe or neoplastic processes. Epileptic seizures, focal neurologic signs, and meningoencephalitis are neurologic syndromes that require urgent action. In most of these situations, neuroimaging tests are necessary, but the findings can be different from those observed in immunocompetent patients in function of the inflammatory response. Infectious disease is the first diagnostic suspicion, and the identification of an opportunistic pathogen should be oriented in function of the type and degree of immunosuppression. Other neurologic emergencies include ischemic stroke, cerebral hemorrhage, neoplastic processes, and pharmacological neurotoxicity. This article reviews the role of neuroimaging in HIV-negative immunodepressed patients with a neurologic complication that requires urgent management.

Polyomavirus and Naturally Occuring Neuroglial Tumors in Raccoons (Procyon Lotor)

Polyomavirus (PyV) infections are widespread in human populations and, although generally associated with silent persistence, rarely cause severe disease. Among diseases convincingly associated with natural PyV infections of humans, there are remarkably different tissue tropisms and outcomes, including progressive multifocal leukoencephalopathy, transient or progressive nephropathy, and cancer. The variable character and unpredictable outcomes of infection attest to large gaps in our basic understanding of PyV biology. In particular, the rich history of research demonstrating the oncogenic potential of PyVs in laboratory animals begs the question of why cancer is not more often associated with infection. Raccoon polyomavirus (RacPyV), discovered in 2010, is consistently identified in neuroglial tumors in free-ranging raccoons in the western United States. Exposure to RacPyV is widespread, and RacPyV is detected in tissues of raccoons without tumors. Studying the relationship of RacPyV with its natural host is a unique opportunity to uncover cogent cellular targets and protein interactions between the virus and its host. Our hypothesis is that RacPyV, as an intact episome, alters cellular pathways within neural progenitor cells and drives oncogenesis.

Predictors of severity and functional outcome in natalizumab-associated progressive multifocal leukoencephalopathy

Objective:

Progressive multifocal leukoencephalopathy (PML) is an emerging complication of immunosuppressive therapies, especially natalizumab in multiple sclerosis (MS). Factors associated with functional outcome of natalizumab-associated PML (natalizumab-PML) have not been sufficiently described.

Methods:

We retrospectively analyzed medical records of all patients with natalizumab-PML ( n = 32) treated in our hospital since 2009. Disability measured by Expanded Disability Status Scale (EDSS) at two different time points (highest available EDSS during PML and last available EDSS after PML diagnosis) served as functional outcome parameters. Clinical, laboratory, and imaging data were analyzed for association with functional outcome by applying Spearman’s rho and multivariate regression analysis.

Results:

In all, 31/32 patients survived PML. A poor functional outcome was associated with higher age, higher initial John Cunningham virus (JCV) copy number in cerebrospinal fluid (CSF), and more extensive PML lesions on initial magnetic resonance imaging (MRI). No association between functional outcome and the duration of natalizumab therapy or a delayed PML diagnosis was observed.

Conclusion:

This study will be useful for neurological practice to estimate functional outcome or disease severity of natalizumab-PML in primary care settings.

Drug-Induced Progressive Multifocal Leukoencephalopathy: A Comprehensive Analysis of the WHO Adverse Drug Reaction Database

OBJECTIVE

To identify safety signals concerning the association between the use of various drug classes and the onset of progressive multifocal leukoencephalopathy (PML).

METHODS

All reports containing suspected or interacting PML-related or leukoencephalopathy-related drugs, held in the World Health Organization spontaneous individual case safety reports database as at 1 September 2014, were retrieved. We identified safety signals by analysing the drug-reaction pairs, using the reporting odds ratio as a measure of disproportionality. A safety signal was defined if a drug was reported more than twice in PML cases with a reporting odds ratio >2 and a lower 95 % confidence limit >1.

RESULTS

We retrieved 2452 reports associated with PML (N = 1612), leukoencephalopathy (N = 835) or both (N = 5), corresponding to 343 different drugs. PML was reported similarly in male and female adults (18-64 years), and almost 30 % of the cases had a fatal outcome. The most frequent Anatomical Therapeutic Chemical (ATC) classification groups concerned antineoplastic agents (23.5 %), antivirals for systemic use (10.1 %) or immunostimulants (4.6 %). Significant disproportionality was found for 88 drugs in the overall analysis (of cases with 'progressive multifocal leukoencephalopathy' or 'leukoencephalopathy' as the Preferred Term), and a new safety signal was identified for 59 active substances (e.g. muromonab-CD3, basiliximab and antithymocyte Ig), as no information on a possible risk of PML was acknowledged in their Summary of Product Characteristics documents. Some safety signals were confirmed also after sensitivity analysis adjustment for several confounding factors (underlying diseases and considering only 'progressive multifocal leukoencephalopathy' as the Preferred Term).

CONCLUSION

We report a possible association between several drugs and PML that has not been previously described. In addition, we have confirmed previously reported signals in a number of drugs. We highlight the need for follow-up by regulatory agencies.

A dermatologist guide to immunogenicity

Dermatologists should be aware that autoantibody formation may occur after the initiation of biologic therapy. This phenomenon has been referred to as immunogenicity and biologic fatigue. Because of this, patients may experience loss of clinical efficacy to a particular drug. To combat this phenomenon, low-dose immunomodulators may be used in hopes of preventing autoantibodies. We review the current literature and provide a basic treatment algorithm for patients with moderate to severe psoriasis.

Increased Prevalence of Human Polyomavirus JC Viruria in Chronic Inflammatory Rheumatic Diseases Patients in Treatment with Anti-TNF α: A 18 Month Follow-Up Study

Chronic inflammatory rheumatic diseases (CIRDs) are immune-mediated pathologies involving joints. To date, TNFα-blocking agents administration is the most promising therapy, although these treatments are associated with an increased Polyomavirus JC (JCPyV) reactivation, the etiological agent of the Progressive Multifocal Leukoencephalopathy (PML). The aim of this study was the recruitment and the analysis of a CIRDs cohort in order to investigate a possible correlation between JCPyV presence and the influence of anti-TNF-α agents on viral loads. Blood and urine samples were collected from 34 CIRDs subjects prior the first anti-TNF-α infusion (T0) and after 3 (T3), 6 (T6), 12 (T12), and 18 (T18) months. Results showed persistent JC viruria significantly higher than JC viremia throughout the 18 month follow-up study (p = 0.002). In JCPyV positive samples, the non-coding control region (NCCR) was analyzed. Results evidenced archetypal structures (type II-S) in all isolates with the exception of a sequence isolated from a plasma sample, that corresponds to the type II-R found in PML subjects. Finally, the viral protein 1 (VP1) genotyping was performed and results showed the prevalence of the European genotypes 1A, 1B, and 4. Since only few studies have been carried out to understand whether there is a PML risk in CIRDs population infected by JCPyV, this study contributes to enrich literature insight on JCPyV biology in this cluster. Further investigations are necessary in order to recognize the real impact of biologics on JCPyV life cycle and to identify possible and specific viral variants related to increased virulence in CIRDs patients.

The neurobiology of HIV and its impact on cognitive reserve: A review of cognitive interventions for an aging population

The medications used to treat HIV have reduced the severity of cognitive deficits; yet, nearly half of adults with HIV still exhibit some degree of cognitive deficits, referred to as HIV-associated neurocognitive disorder or HAND. These cognitive deficits interfere with everyday functioning such as emotional regulation, medication adherence, instrumental activities of daily living, and even driving a vehicle. As adults are expected to live a normal lifespan, the process of aging in this clinical population may exacerbate such cognitive deficits. Therefore, it is important to understand the neurobiological mechanisms of HIV on cognitive reserve and develop interventions that are either neuroprotective or compensate for such cognitive deficits. Within the context of cognitive reserve, this article delivers a state of the science perspective on the causes of HAND and provides possible interventions for addressing such cognitive deficits. Suggestions for future research are also provided.

Treatment options for progressive multifocal leukoencephalopathy in HIV-infected persons: current status and future directions

Progressive multifocal encephalopathy (PML) caused by JC virus was frequently encountered in AIDS patients before combination antiretroviral therapy (cART). Incidence decreased and the outcome improved with cART. The immune reconstitution with cART is beneficial for HIV-infected patients and is an effective treatment for PML. However, when it is excessive an inflammatory response immune syndrome might occur with deterioration of PML. So far, no specific therapy has proven efficacious in small clinical trials in spite of some optimistic case reports. Combination of drugs targeted at different stages of JC virus life cycle seems to have a better effect. Passive and active immune therapies, immune competence "boosters" appear promising. New future approaches such as gene editing are not far away.

Structural Based Analyses of the JC Virus T-Antigen F258L Mutant Provides Evidence for DNA Dependent Conformational Changes in the C-Termini of Polyomavirus Origin Binding Domains

The replication of human polyomavirus JCV, which causes Progressive Multifocal Leukoencephalopathy, is initiated by the virally encoded T-antigen (T-ag). The structure of the JC virus T-ag origin-binding domain (OBD) was recently solved by X-ray crystallography. This structure revealed that the OBD contains a C-terminal pocket, and that residues from the multifunctional A1 and B2 motifs situated on a neighboring OBD molecule dock into the pocket. Related studies established that a mutation in a pocket residue (F258L) rendered JCV T-ag unable to support JCV DNA replication. To establish why this mutation inactivated JCV T-ag, we have solved the structure of the F258L JCV T-ag OBD mutant. Based on this structure, it is concluded that the structural consequences of the F258L mutation are limited to the pocket region. Further analyses, utilizing the available polyomavirus OBD structures, indicate that the F258 region is highly dynamic and that the relative positions of F258 are governed by DNA binding. The possible functional consequences of the DNA dependent rearrangements, including promotion of OBD cycling at the replication fork, are discussed.

Progressive multifocal leukoencephalopathy and immune reconstitution inflammatory syndrome (IRIS)

Progressive multifocal leukoencephalopathy is a viral encephalitis induced by the John Cunningham (JC) virus, an ubiquitous neurotropic papovavirus of the genus polyomavirus that in healthy people in latency resides in kidney and bone marrow cells. Activation and entry into the CNS were first seen in patients with malignancies of the hematopoietic system and an impaired immune system. During the 1980 and the 1990s with the appearance of human immunodeficiency virus infection in humans, PML was found to be the most important opportunistic infection of the central nervous system. As a result of highly efficient immunosuppressive and immunomodulatory treatments, in recent years, the number of PML cases again increased. PML is prevented by an intact cellular immune response and accordingly immune reconstitution can terminate established disease in the CNS. However, forced immune reconstitution can lead to massive destruction of virus-infected cells. This may result in clinical exacerbation associated with high morbidity and mortality and referred to as PML with immune reconstitution inflammatory syndrome (PML-IRIS). In the present review, we discuss virological properties and routes of infection in the CNS, but mostly focus on the pathology of PML and PML-IRIS and on the role of the immune system in these disorders. We show that PML and PML-IRIS result from predominant JC virus infection of oligodendrocytes and, to a lesser extent, of infected neurons. Inflammation in these encephalitides seems to be driven by a dominant cytotoxic T cell response which is massively exaggerated during IRIS.

Human polyomavirus JC replication and non-coding control region analysis in multiple sclerosis patients under natalizumab treatment

In the last years, the treatment of multiple sclerosis (MS) patients with natalizumab has been associated with the occurrence of progressive multifocal leukoencephalopathy (PML) caused by human polyomavirus JC (JCV). Here, we have shown a significant correlation between patients with JC viruria and positive JC-specific antibody response and patients without JCV-specific antibodies after 1 year of natalizumab (p = 0.0006). Furthermore, JCV-specific quantitative PCR on urine and plasma samples, collected at the enrollment (t0) and every 4 months (t1, t2, t3) in the first year and at two time points (t4 and t5) in the second year of natalizumab treatment, indicated the prevalence of JC viremia rather than JC viruria only in the second year of treatment (p = 0.04). Moreover, the analysis of JCV non-coding control region (NCCR) sequences in peripheral blood mononuclear cells of patients with JC-specific antibodies after 12 natalizumab infusions (t3) revealed the presence of rearranged sequences, whereas the prevalence of genotypes 1A, 1B, and 4 was detected in these patients by VP1 sequence analysis. In summary, JC viruria evaluation seems to be useful to identify early those patients who do not already develop a humoral immune response against JCV. It may also be interesting to study the JCV NCCR rearrangements since they could give us new insights on the onset of neuro-invasive viral variants.

Progressive multifocal leukoencephalopathy in common variable immunodeficiency: mitigated course under mirtazapine and mefloquine

Demonstration of survival and outcome of progressive multifocal leukoencephalopathy (PML) in a 56-year-old patient with common variable immunodeficiency, consisting of severe hypogammaglobulinemia and CD4+ T lymphocytopenia, during continuous treatment with mirtazapine (30 mg/day) and mefloquine (250 mg/week) over 23 months. Regular clinical examinations including Rankin scale and Barthel index, nine-hole peg and box and block tests, Berg balance, 10-m walking tests, and Montreal Cognitive Assessment (MoCA) were done. Laboratory diagnostics included complete blood count and JC virus (JCV) concentration in cerebrospinal fluid (CSF). The noncoding control region (NCCR) of JCV, important for neurotropism and neurovirulence, was sequenced. Repetitive MRI investigated the course of brain lesions. JCV was detected in increasing concentrations (peak 2568 copies/ml CSF), and its NCCR was genetically rearranged. Under treatment, the rearrangement changed toward the archetype sequence, and later JCV DNA became undetectable. Total brain lesion volume decreased (8.54 to 3.97 cm(3)) and atrophy increased. Barthel (60 to 100 to 80 points) and Rankin (4 to 2 to 3) scores, gait stability, and box and block (7, 35, 25 pieces) and nine-hole peg (300, 50, 300 s) test performances first improved but subsequently worsened. Cognition and walking speed remained stable. Despite initial rapid deterioration, the patient survived under continuous treatment with mirtazapine and mefloquine even though he belongs to a PML subgroup that is usually fatal within a few months. This course was paralleled by JCV clones with presumably lower replication capability before JCV became undetectable. Neurological deficits were due to PML lesions and progressive brain atrophy.

JC polyomavirus reactivation is common following allogeneic stem cell transplantation and its preemptive detection may prevent lethal complications

Extended application of allogeneic stem cell transplantation (alloSCT) is expected to increase the frequency of JC polyomavirus (JCPyV)-related progressive multifocal leukoencephalopathy (PML). The aim of this study was to assess frequency, risk factors and course of JCPyV reactivation in allografted hematology patients. This retrospective study included consecutive adult patients, treated with alloSCT between January 2008 and December 2011. Quantitative JCPyV-PCR analysis was performed on whole blood DNA samples, originally drawn for cytomegalovirus detection since transplant date. The study included 164 patients diagnosed with hematological malignancies. Patients received reduced-intensity conditioning (n=74) or myeloablative conditioning (n=90), followed by alloSCT. Twenty patients developed transient and 20 had persistent JCPyV reactivation. Two of the patients with persistent reactivation showed a gradual increase in JCPyV levels, preceding PML development by 96 and 127 days. Cessation of immunosuppression resulted in complete resolution of neurological symptoms in one patient, while the other died of PML. Seventy percent of the 'persistently reactivating' patients died. Multivariate analysis confirmed age to be the only significant predictive factor for JCPyV reactivation. In conclusion, JCPyV reactivation occurs in a quarter of allografted patients. Preemptive detection of JCPyV reactivation in high-risk subjects and early discontinuation of immunosuppressive therapy may prevent development of lethal PML.

CD49d antisense drug ATL1102 reduces disease activity in patients with relapsing-remitting MS

Objective:

This study evaluated the efficacy and safety of ATL1102, an antisense oligonucleotide that selectively targets the RNA for human CD49d, the α subunit of very late antigen 4, in patients with relapsing-remitting multiple sclerosis (RRMS).

Methods:

In a multicenter, double-blind, placebo-controlled randomized phase II trial, 77 patients with RRMS were treated with 200 mg of ATL1102 subcutaneously injected 3 times in the first week and twice weekly for 7 weeks or placebo and monitored for a further 8 weeks. MRI scans were taken at baseline and weeks 4, 8, 12, and 16. The primary endpoint was the cumulative number of new active lesions (either new gadolinium-enhancing T1 lesions or nonenhancing new or enlarging T2 lesions) at weeks 4, 8, and 12.

Results:

A total of 72 patients completed the study and 74 intention-to-treat patients were assessed. ATL1102 significantly reduced the cumulative number of new active lesions by 54.4% compared to placebo (mean 3.0 [SD 6.12] vs 6.2 [9.89], p = 0.01). The cumulative number of new gadolinium-enhancing T1 lesions was reduced by 67.9% compared to placebo (p = 0.002). Treatment-emergent adverse events included mild to moderate injection site erythema and decrease in platelet counts that returned to within the normal range after dosing.

Conclusions:

In patients with RRMS, ATL1102 significantly reduced disease activity after 8 weeks of treatment and was generally well-tolerated. This trial provides evidence for the first time that antisense oligonucleotides may be used as a therapeutic approach in neuroimmunologic disorders.

Classification:

This study provides Class I evidence that for patients with RRMS, the antisense oligonucleotide ATL1102 reduces the number of new active head MRI lesions.

Partial recovery after severe immune reconstitution inflammatory syndrome in a multiple sclerosis patient with progressive multifocal leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is a rare and severe complication of natalizumab therapy in patients with multiple sclerosis and it may be accompanied by immune reconstitution inflammatory syndrome (IRIS). Here, we describe a case of abnormally severe IRIS, which occurred 2 months after natalizumab-associated PML in a 38-year-old woman affected by multiple sclerosis. The patient was John Cunningham virus-positive and was treated for 21 months when she developed PML. The subsequent IRIS diffusely afflicted the brain, producing edema and signs of intracranial hypertension, with a clinically severe form compromising the state of consciousness, requiring intensive care and high-dosage steroid treatment. Nevertheless, she survived and partially recovered. There is still difficulty in differentiating PML progression from IRIS onset and there is not a clear description in the literature about different clinical forms of IRIS, prognostic factors and guidelines to properly treat this complication in order to reduce the residual disability of the patient surviving this treatment complication.

Analysis of JC virus DNA replication using a quantitative and high-throughput assay

Progressive Multifocal Leukoencephalopathy (PML) is caused by lytic replication of JC virus (JCV) in specific cells of the central nervous system. Like other polyomaviruses, JCV encodes a large T-antigen helicase needed for replication of the viral DNA. Here, we report the development of a luciferase-based, quantitative and high-throughput assay of JCV DNA replication in C33A cells, which, unlike the glial cell lines Hs 683 and U87, accumulate high levels of nuclear T-ag needed for robust replication. Using this assay, we investigated the requirement for different domains of T-ag, and for specific sequences within and flanking the viral origin, in JCV DNA replication. Beyond providing validation of the assay, these studies revealed an important stimulatory role of the transcription factor NF1 in JCV DNA replication. Finally, we show that the assay can be used for inhibitor testing, highlighting its value for the identification of antiviral drugs targeting JCV DNA replication.