Use of Pembrolizumab for Treatment of Progressive Multifocal Leukoencephalopathy in People Living with HIV.

Progressive Multifocal Leukoencephalopathy (PML) is a demyelinating disease occurring in advanced HIV infection, caused by the reactivation of poliomavirus JC (JCV). The use of pembrolizumab for treatment is based on the inhibition of programmed cell death protein 1 (PD-1), potentially improving the anti JCV-specific response. We used pembrolizumab with combined antiretroviral treatment (cART) on a compassionate-use basis. At each administration, clinical evaluation, MRI and laboratory testing, including CD3, CD4, CD8, PD-1 markers, HIV-RNA and JCV-DNA in cerebrospinal fluid (CSF)/plasma pairs, were performed. The JCV-specific T cell response was analysed by Elispot assay. This study included five HIV patients: four male, median age 43 years (29-52), median CD4 and CD8 count 150 (15-158) and 973 (354-1250) cell/mm3, respectively; median JCV-DNA and HIV-RNA in CSF/plasma pairs 9.540/1.503 cps/mL and 2.230/619 cp/mL, respectively. Overall, patients received between two and seven doses of pembrolizumab. After treatment, we observed JCV-DNA reduction and PD-1 down-regulation both in CSF and in plasma (high in circulating CD4 and CD8 at baseline), which remained stable at low levels in all patients. Three out of five patients showed stability of clinical picture and neuroimaging, while two others died. More data are needed in order to identify predictors of response to therapy.

Rearrangement in the Hypervariable Region of JC Polyomavirus Genomes Isolated from Patient Samples and Impact on Transcription Factor-Binding Sites and Disease Outcomes.

JC polyomavirus (JCPyV) is the causative agent of the fatal, incurable, neurological disease, progressive multifocal leukoencephalopathy (PML). The virus is present in most of the adult population as a persistent, asymptotic infection in the kidneys. During immunosuppression, JCPyV reactivates and invades the central nervous system. A main predictor of disease outcome is determined by mutations within the hypervariable region of the viral genome. In patients with PML, JCPyV undergoes genetic rearrangements in the noncoding control region (NCCR). The outcome of these rearrangements influences transcription factor binding to the NCCR, orchestrating viral gene transcription. This study examines 989 NCCR sequences from patient isolates deposited in GenBank to determine the frequency of mutations based on patient isolation site and disease status. The transcription factor binding sites (TFBS) were also analyzed to understand how these rearrangements could influence viral transcription. It was determined that the number of TFBS was significantly higher in PML samples compared to non-PML samples. Additionally, TFBS that could promote JCPyV infection were more prevalent in samples isolated from the cerebrospinal fluid compared to other locations. Collectively, this research describes the extent of mutations in the NCCR that alter TFBS and how they correlate with disease outcome.

Database and Statistical Analyses of Transcription Factor Binding Sites in the Non-Coding Control Region of JC Virus.

JC virus (JCV), as an archetype, establishes a lifelong latent or persistent infection in many healthy individuals. In immunocompromised patients, prototype JCV with variable mutations in the non-coding control region (NCCR) causes progressive multifocal leukoencephalopathy (PML), a severe demyelinating disease. This study was conducted to create a database of NCCR sequences annotated with transcription factor binding sites (TFBSs) and statistically analyze the mutational pattern of the JCV NCCR. JCV NCCRs were extracted from >1000 sequences registered in GenBank, and TFBSs within each NCCR were identified by computer simulation, followed by examination of their prevalence, multiplicity, and location by statistical analyses. In the NCCRs of the prototype JCV, the limited types of TFBSs, which are mainly present in regions D through F of archetype JCV, were significantly reduced. By contrast, modeling count data revealed that several TFBSs located in regions C and E tended to overlap in the prototype NCCRs. Based on data from the BioGPS database, genes encoding transcription factors that bind to these TFBSs were expressed not only in the brain but also in the peripheral sites. The database and NCCR patterns obtained in this study could be a suitable platform for analyzing JCV mutations and pathogenicity.

IFNα and ß Mediated JCPyV Suppression through C/EBPß-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 ß (IFNß) 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/EBPß). Treatment of glial cell line with interferons increases the endogenous level of C/EBPß-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/EBPß-LIP. Knockdown of C/EBPß-LIP by shRNA reverse the inhibitory effect on JCPyV viral replication. Therefore, IFNα and IFNß negatively regulate JCPyV through induction of C/EBPß-LIP, which together with other cellular transcriptional factors may control the balance between JCPyV latency and activation.

Teriflunomide Inhibits JCPyV Infection and Spread in Glial Cells and Choroid Plexus Epithelial Cells.

Several classes of immunomodulators are used for treating relapsing-remitting multiple sclerosis (RRMS). Most of these disease-modifying therapies, except teriflunomide, carry the risk of progressive multifocal leukoencephalopathy (PML), a severely debilitating, often fatal virus-induced demyelinating disease. Because teriflunomide has been shown to have antiviral activity against DNA viruses, we investigated whether treatment of cells with teriflunomide inhibits infection and spread of JC polyomavirus (JCPyV), the causative agent of PML. Treatment of choroid plexus epithelial cells and astrocytes with teriflunomide reduced JCPyV infection and spread. We also used droplet digital PCR to quantify JCPyV DNA associated with extracellular vesicles isolated from RRMS patients. We detected JCPyV DNA in all patients with confirmed PML diagnosis (n = 2), and in six natalizumab-treated (n = 12), two teriflunomide-treated (n = 7), and two nonimmunomodulated (n = 2) patients. Of the 21 patients, 12 (57%) had detectable JCPyV in either plasma or serum. CSF was uniformly negative for JCPyV. Isolation of extracellular vesicles did not increase the level of detection of JCPyV DNA versus bulk unprocessed biofluid. Overall, our study demonstrated an effect of teriflunomide inhibiting JCPyV infection and spread in glial and choroid plexus epithelial cells. Larger studies using patient samples are needed to correlate these in vitro findings with patient data.

Disease-modifying therapies and progressive multifocal leukoencephalopathy in multiple sclerosis: A systematic review and meta-analysis.

Background High efficacy disease modifying therapies (DMT) in the management of Multiple Sclerosis (MS) have a favorable effect on relapse rate and disability progression; however, they can expose patients to significant risks, such as progressive multifocal leukoencephalopathy (PML). Objective The study aims to investigate prognostic factors that can determine outcome in MS-related PML patients. Methods We conducted a literature review and meta-analysis of 194 patients from 62 articles in PubMed, SCOPUS and EMBASE. Results Out of 194 patients (66.5% women, 33.5% men), 81% had progression in their EDSS score by at least 1 point from the time of PML diagnosis (EDSS-P group). The remaining patients had either stable or improved EDSS (EDSS-S group). In univariate analysis, older age at the time of PML diagnosis was associated with higher probability of disability accumulation and worsening of EDSS by at least 1 point (mean age = 44.8, p = 0.046). After adjusting for other variables, age at time of PML diagnosis remained a significant predictive variable in the multivariable logistic model (OR = 0.93, 95% CI: 0.88-0.99, p = 0.037). Natalizumab is the most commonly associated DMT linked to PML, followed by fingolimod and others including dimethyl fumarate, ocrelizumab, alemtuzumab. Among the different treatments used, no therapeutic agent was found to be superior in improving post-PML EDSS. Conclusions Younger age and lower JCV viral load at the time of PML diagnosis were associated with better outcome in MS-associate PML, while none of the PML therapies was superior over the others or associated with favorable outcome.

JCPyV miR-J1-5p in Urine of Natalizumab-Treated Multiple Sclerosis Patients.

The use of Natalizumab in Multiple Sclerosis (MS) can cause the reactivation of the polyomavirus JC (JCPyV); this may result in the development of progressive multifocal leukoencephalopathy (PML), a rare and usually lethal disease. JCPyV infection is highly prevalent in worldwide population, but the detection of anti-JCPyV antibodies is not sufficient to identify JCPyV infection, as PML can develop even in patients with negative JCPyV serology. Better comprehension of the JCPyV biology could allow a better understanding of JCPyV infection and reactivation, possibly reducing the risk of developing PML. Here, we investigated whether JCPyV miR-J1-5p-a miRNA that down-regulates the early phase viral protein T-antigen and promotes viral latency-could be detected and quantified by digital droplet PCR (ddPCR) in urine of 25 Natalizumab-treated MS patients. A 24-month study was designed: baseline, before the first dose of Natalizumab, and after 1 (T1), 12 (T12) and 24 months (T24) of therapy. miR-J1-5p was detected in urine of 7/25 MS patients (28%); detection was possible in three cases at T24, in two cases at T12, in one case at T1 and T12, and in the last case at baseline and T1. Two of these patients were seronegative for JCPyV Ab, and viral DNA was never found in either urine or blood. To note, only in one case miR-J1-5p was detected before initiation of Natalizumab. These results suggest that the measurement of miR-J1-5p in urine, could be a biomarker to monitor JCPyV infection and to better identify the possible risk of developing PML in Natalizumab-treated MS patients.

Induction of Brain Tumors by the Archetype Strain of Human Neurotropic JCPyV in a Transgenic Mouse Model.

JC Virus (JCPyV), a member of the Polyomaviridiæ family, is a human neurotropic virus with world-wide distribution. JCPyV is the established opportunistic infectious agent of progressive multifocal leukoencephalopathy, a fatal demyelinating disease, which results from the cytolytic infection of oligodendrocytes. Mutations in the regulatory region of JCPyV determine the different viral strains. Mad-1 the strain associated with PML contains two 98 base pair repeats, whereas the archetype strain (CY), which is the transmissible form of JCPyV, contains only one 98 tandem with two insertions of 62 and 23 base pairs respectively. The oncogenicity of JCPyV has been suspected since direct inoculation into the brain of rodents and primates resulted in the development of brain tumors and has been attributed to the viral protein, T-Antigen. To further understand the oncogenicity of JCPyV, a transgenic mouse colony containing the early region of the archetype strain (CY), under the regulation of its own promoter was generated. These transgenic animals developed tumors of neural crest origin, including: primitive neuroectodermal tumors, medulloblastomas, adrenal neuroblastomas, pituitary tumors, malignant peripheral nerve sheath tumors, and glioblastomas. Neoplastic cells from all different phenotypes express T-Antigen. The close parallels between the tumors developed by these transgenic animals and human CNS tumors make this animal model an excellent tool for the study of viral oncogenesis.

Progressive multifocal leukoencephalopathy and the spectrum of JC virus-related disease.

Progressive multifocal leukoencephalopathy (PML) is a devastating CNS infection caused by JC virus (JCV), a polyomavirus that commonly establishes persistent, asymptomatic infection in the general population. Emerging evidence that PML can be ameliorated with novel immunotherapeutic approaches calls for reassessment of PML pathophysiology and clinical course. PML results from JCV reactivation in the setting of impaired cellular immunity, and no antiviral therapies are available, so survival depends on reversal of the underlying immunosuppression. Antiretroviral therapies greatly reduce the risk of HIV-related PML, but many modern treatments for cancers, organ transplantation and chronic inflammatory disease cause immunosuppression that can be difficult to reverse. These treatments - most notably natalizumab for multiple sclerosis - have led to a surge of iatrogenic PML. The spectrum of presentations of JCV-related disease has evolved over time and may challenge current diagnostic criteria. Immunotherapeutic interventions, such as use of checkpoint inhibitors and adoptive T cell transfer, have shown promise but caution is needed in the management of immune reconstitution inflammatory syndrome, an exuberant immune response that can contribute to morbidity and death. Many people who survive PML are left with neurological sequelae and some with persistent, low-level viral replication in the CNS. As the number of people who survive PML increases, this lack of viral clearance could create challenges in the subsequent management of some underlying diseases.

Characterization of JC Polyomavirus Derived from COS-IMRb Cells.

JC polyomavirus (JCPyV) causes progressive multifocal leukoencephalopathy (PML), a demyelinating disease of the central nervous system affecting immunocompromised patients. The study of PML-type JCPyV in vitro has been limited owing to the inefficient propagation of the virus in cultured cells. In this study, we carried out long-term culture of COS-7 cells (designated as COS-IMRb cells) transfected with PML-type M1-IMRb, an adapted viral DNA with a rearranged non-coding control region (NCCR). The JCPyV derived from COS-IMRb cells were characterized by analyzing the viral replication, amount of virus by hemagglutination (HA), production of viral protein 1 (VP1), and structure of the NCCR. HA assays indicated the presence of high amounts of PML-type JCPyV in COS-IMRb cells. Immunostaining showed only a small population of JCPyV carrying COS-IMRb cells to be VP1-positive. Sequencing analysis of the NCCR of JCPyV after long-term culture revealed that the NCCR of M1-IMRb was conserved in COS-IMRb cells without any point mutation. The JCPyV genomic DNA derived from a clone of COS-IMRb-3 cells was detected, via Southern blotting, as a single band of approximately 5.1 kbp without deletion. These findings suggest the potential of using COS-IMRb-3 cells as a useful tool for screening anti-JCPyV drugs.

Inadequate Immune Humoral Response against JC Virus in Progressive Multifocal Leukoencephalopathy Non-Survivors.

JC virus (JCV) causes progressive multifocal leukoencephalopathy (PML) in immunosuppressed patients. There is currently no effective specific antiviral treatment and PML management relies on immune restoration. Prognosis markers are crucially needed in this disease because of its high mortality rate. In this work, we investigated the compartmentalization of JCV strains as well as the humoral neutralizing response in various matrices to further understand the pathophysiology of PML and define markers of survival. Four patients were included, of which three died in the few months following PML onset. Cerebrospinal fluid (CSF) viral loads were the highest, with plasma samples having lower viral loads and urine samples being mostly negative. Whether at PML onset or during follow-up, neutralizing antibody (NAb) titers directed against the same autologous strain (genotype or mutant) were the highest in plasma, with CSF titers being on average 430-fold lower and urine titers 500-fold lower at the same timepoint. Plasma NAb titers against autologous genotype or mutant were lower in non-survivor patients, though no neutralization "blind spot" was observed. The surviving patient was followed up until nine months after PML onset and presented, at that time, an increase in neutralizing titers, from 38-fold against the autologous genotype to around 200-fold against PML mutants. Our results suggest that patients' humoral neutralizing response against their autologous strain may play a role in PML outcome, with survivors developing high NAb titers in both plasma and CSF.

Phosphoinositide 3'-Kinase γ Facilitates Polyomavirus Infection.

Polyomaviruses are small, non-enveloped DNA tumor viruses that cause serious disease in immunosuppressed people, including progressive multifocal leukoencephalopathy (PML) in patients infected with JC polyomavirus, but the molecular events mediating polyomavirus entry are poorly understood. Through genetic knockdown approaches, we identified phosphoinositide 3'-kinase γ (PI3Kγ) and its regulatory subunit PIK3R5 as cellular proteins that facilitate infection of human SVG-A glial cells by JCPyV. PI3Kα appears less important for polyomavirus infection than PI3Kγ. CRISPR/Cas9-mediated knockout of PIK3R5 or PI3Kγ inhibited infection by authentic JCPyV and by JC pseudovirus. PI3Kγ knockout also inhibited infection by BK and Merkel Cell pseudoviruses, other pathogenic human polyomaviruses, and SV40, an important model polyomavirus. Reintroduction of the wild-type PI3Kγ gene into the PI3Kγ knock-out SVG-A cells rescued the JCPyV infection defect. Disruption of the PI3Kγ pathway did not block binding of JCPyV to cells or virus internalization, implying that PI3Kγ facilitates some intracellular step(s) of infection. These results imply that agents that inhibit PI3Kγ signaling may have a role in managing polyomavirus infections.

JCPyV VP1 Mutations in Progressive MultifocalLeukoencephalopathy: Altering Tropismor Mediating Immune Evasion?

Polyomaviruses are ubiquitous human pathogens that cause lifelong, asymptomatic infections in healthy individuals. Although these viruses are restrained by an intact immune system, immunocompromised individuals are at risk for developing severe diseases driven by resurgent viral replication. In particular, loss of immune control over JC polyomavirus can lead to the development of the demyelinating brain disease progressive multifocal leukoencephalopathy (PML). Viral isolates from PML patients frequently carry point mutations in the major capsid protein, VP1, which mediates virion binding to cellular glycan receptors. Because polyomaviruses are non-enveloped, VP1 is also the target of the host's neutralizing antibody response. Thus, VP1 mutations could affect tropism and/or recognition by polyomavirus-specific antibodies. How these mutations predispose susceptible individuals to PML and other JCPyV-associated CNS diseases remains to be fully elucidated. Here, we review the current understanding of polyomavirus capsid mutations and their effects on viral tropism, immune evasion, and virulence.

Human iPS cell-derived astrocytes support efficient replication of progressive multifocal leukoencephalopathy-type JC polyomavirus.

JC polyomavirus (JCPyV) causes progressive multifocal leukoencephalopathy (PML), a demyelinating disease of the central nervous system, in immunocompromised patients. Although PML used to be rare, recently the incidence of PML has risen due to an increase in immunosuppressive therapy. An in vitro JCPyV infection system could be used for anti-drug screening and investigation of tropism changes, but study of JCPyV in vitro has been limited due to the difficulty of efficiently propagating the virus in cultured cells. PML-type JCPyV efficiently propagates in primary human fetal and progenitor cell-derived astrocytes, but the preparation of cells from human fetuses is associated with severe ethical problems. In this study, human iPS cell-derived astrocytes were exposed to PML-type JCPyV. Infection, replication, and VP1 and T antigens of JCPyV were detected and confirmed in this culture. The non-coding control region (NCCR) of M1-IMRb was conserved in infected cells without point mutations. In addition, PML-type JCPyV genomic DNA in infected cells was detected as a single band of approximately 5.1 kbp, with no deletions. This is the first demonstration that human iPS cell-derived astrocytes efficiently support replication of PML-type JCPyV without production of defective interfering particles. These findings indicated that a culture system using human iPS cell-derived astrocyte would be useful for studies of PML, especially for screening anti-JCPyV drugs.

COS-7 cells are a cellular model to monitor polyomavirus JC miR-J1-5p expression.

Polyomavirus JC (JCPyV) is a ubiquitous human neurotropic virus that can cause progressive multifocal leukoencephalopathy (PML), sometimes as a consequence of drug treatment for disabling diseases, including Multiple Sclerosis. JCPyV expresses microRNAs (miRNAs), and in particular miR-J1-5p, but at now we have limited knowledge regarding this aspect. In the present study the expression of JCPyV miR-J1-5p was measured in infected COS-7, to verify if and when this miRNA is expressed in a cell model of JCPyV-MAD-4 strain infection. Results showed that miR-J1-5p expression was relatively constant inside the cells from 11 days to 35 days after infection (mean: 4.13 × 105 copies/µg), and became measurable in supernatants 18 days after infection (mean: 7.20 × 104 copies/µl). miR-J1-5p expression in supernatants peaked (3.76 × 105 copies/µl) 25 days after infection and started to decrease 32 days after infection (7.20 × 104 copies/µl). These data show that COS-7 cells, already used as model for JCPyV replication cycle, can be also utilized to study JCPyV miRNAs expression, potentially opening new research avenues for diseases in which current therapeutic approaches could result in severe adverse effects (e.g. Natalizumab-associated JCPyV reactivation in Multiple Sclerosis patients). In these situations monitoring of miR-J1-5p may shed light on the mechanisms of virus reactivation and may help the clarification of the mechanisms responsible for such severe side effects.

Regulation of Polyomavirus Transcription by Viral and Cellular Factors.

Polyomavirus infection is widespread in the human population. This family of viruses normally maintains latent infection within the host cell but can cause a range of human pathologies, especially in immunocompromised individuals. Among several known pathogenic human polyomaviruses, JC polyomavirus (JCPyV) has the potential to cause the demyelinating disease progressive multifocal leukoencephalopathy (PML); BK polyomavirus (BKPyV) can cause nephropathy in kidney transplant recipients, and Merkel cell polyomavirus (MCPyV) is associated with a highly aggressive form of skin cancer, Merkel cell carcinoma (MCC). While the mechanisms by which these viruses give rise to the relevant diseases are not well understood, it is clear that the control of gene expression in each polyomavirus plays an important role in determining the infectious tropism of the virus as well as their potential to promote disease progression. In this review, we discuss the mechanisms governing the transcriptional regulation of these pathogenic human polyomaviruses in addition to the best-studied simian vacuolating virus 40 (SV40). We highlight the roles of viral cis-acting DNA elements, encoded proteins and miRNAs that control the viral gene expression. We will also underline the cellular transcription factors and epigenetic modifications that regulate the gene expression of these viruses.

Inhibition of JC polyomavirus infectivity by the retrograde transport inhibitor Retro-2.1.

JC polyomavirus (JCPyV) is a common human pathogen that results in a chronic asymptomatic infection in healthy adults. Under conditions of immunosuppression, JCPyV spreads to the central nervous system and can cause the fatal demyelinating disease progressive multifocal leukoencephalopathy (PML), a disease for which there are no vaccines or antiviral therapies. Retro-2 is a previously identified small molecule inhibitor that was originally shown to block retrograde transport of toxins such as ricin toxin from endosomes to the Golgi apparatus and endoplasmic reticulum (ER), and Retro-2.1 is a chemical analog of Retro-2 that has been shown to inhibit ricin intoxication of cells at low nanomolar concentrations. Retro-2 has previously been shown to prevent retrograde transport of JCPyV virions to the ER, but the effect of Retro-2.1 on JCPyV infectivity is unknown. Here it is shown that Retro-2.1 inhibits JCPyV with an EC50 of 3.9 µM. This molecule inhibits JCPyV infection at dosages that are not toxic to human tissue culture cells. Retro-2.1 was also tested against two other polyomaviruses, the human BK polyomavirus and simian virus 40, and was also shown to inhibit infection at similar concentrations. Viral uncoating studies demonstrate that Retro-2.1 inhibits BKPyV infectivity in a manner similar to Retro-2. These studies demonstrate that improved analogs of Retro-2 can inhibit infection at lower dosages than Retro-2 and further optimization of these compounds may lead to effective treatment options for those suffering from JCPyV infection and PML.

Progressive multifocal leukoencephalopathy associated with a lymphoproliferative disorder treated with pembrolizumab.

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease affecting the central nervous system as a result of reactivation of the John Cunningham (JC) polyomavirus and occurs almost exclusively in immunosuppressed individuals. The disease course of PML is variable but usually progressive and often fatal. Treatment is predominantly focused on immune restoration, although this is difficult to do outside of human immunodeficiency virus-associated PML. A recent case series demonstrated a potential role for programmed cell death protein 1 (PD-1) inhibitors, such as pembrolizumab, to contain and/or clear JC virus. Herein, we discuss the first reported Australian case of a 61-year-old female with PML secondary to chemoimmunotherapy demonstrating complete clearance of JC virus as well as clinical and radiological stabilisation following pembrolizumab treatment.

The Role of the JC Virus in Central Nervous System Tumorigenesis.

Cancer is the second leading cause of mortality worldwide. The study of DNA tumor-inducing viruses and their oncoproteins as a causative agent in cancer initiation and tumor progression has greatly enhanced our understanding of cancer cell biology. The initiation of oncogenesis is a complex process. Specific gene mutations cause functional changes in the cell that ultimately result in the inability to regulate cell differentiation and proliferation effectively. The human neurotropic Polyomavirus JC (JCV) belongs to the family Polyomaviridae and it is the causative agent of progressive multifocal leukoencephalopathy (PML), which is a fatal neurodegenerative disease in an immunosuppressed state. Sero-epidemiological studies have indicated JCV infection is prevalent in the population (85%) and that initial infection usually occurs during childhood. The JC virus has small circular, double-stranded DNA that includes coding sequences for viral early and late proteins. Persistence of the virus in the brain and other tissues, as well as its potential to transform cells, has made it a subject of study for its role in brain tumor development. Earlier observation of malignant astrocytes and oligodendrocytes in PML, as well as glioblastoma formation in non-human primates inoculated with JCV, led to the hypothesis that JCV plays a role in central nervous system (CNS) tumorigenesis. Some studies have reported the presence of both JC viral DNA and its proteins in several primary brain tumor specimens. The discovery of new Polyomaviruses such as the Merkel cell Polyomavirus, which is associated with Merkel cell carcinomas in humans, ignited our interest in the role of the JC virus in CNS tumors. The current evidence known about JCV and its effects, which are sufficient to produce tumors in animal models, suggest it can be a causative factor in central nervous system tumorigenesis. However, there is no clear association between JCV presence in CNS and its ability to initiate CNS cancer and tumor formation in humans. In this review, we will discuss the correlation between JCV and tumorigenesis of CNS in animal models, and we will give an overview of the current evidence for the JC virus's role in brain tumor formation.

Detection of Residual Tumor With 68Ga-Pentixafor PET/CT in a Patient With Waldenström Macroglobulinemia and Concurrent John Cunningham Virus-Related Progressive Multifocal Leukoencephalopathy.

A 75-year-old man diagnosed with Waldenström macroglobulinemia (WM) complained of neurological symptoms. Baseline F-FDG PET/CT showed diffusely increased radioactivity in the bone marrow and decreased FDG uptake in the right cerebellum. After rituximab-containing immunochemotherapy, the patient had clinically partial response of WM, but the cerebellar lesion was enlarged. Repeated F-FDG PET/CT was similar to the baseline. Ga-pentixafor PET/CT detected residual tumor of WM in occipital bone and cervical lymph nodes, but there was no uptake in the cerebellar lesion. Finally, John Cunningham virus-related progressive multifocal leukoencephalopathy was confirmed.