TSPO PET imaging of natalizumab-associated progressive multifocal leukoencephalopathy.

Progressive multifocal leukoencephalopathy (PML) is a severe infection of the CNS caused by the polyomavirus JC that can occur in multiple sclerosis patients treated with natalizumab. Clinical management of patients with natalizumab-associated PML is challenging not least because current imaging tools for the early detection, longitudinal monitoring and differential diagnosis of PML lesions are limited. Here we evaluate whether translocator protein (TSPO) PET imaging can be applied to monitor the inflammatory activity of PML lesions over time and differentiate them from multiple sclerosis lesions. For this monocentre pilot study we followed eight patients with natalizumab-associated PML with PET imaging using the TSPO radioligand 18F-GE-180 combined with frequent 3 T MRI. In addition we compared TSPO PET signals in PML lesions with the signal pattern of multiple sclerosis lesions from 17 independent multiple sclerosis patients. We evaluated the standardized uptake value ratio as well as the morphometry of the TSPO uptake for putative PML and multiple sclerosis lesions areas compared to a radiologically unaffected pseudo-reference region in the cerebrum. Furthermore, TSPO expression in situ was immunohistochemically verified by determining the density and cellular identity of TSPO-expressing cells in brain sections from four patients with early natalizumab-associated PML as well as five patients with other forms of PML and six patients with inflammatory demyelinating CNS lesions (clinically isolated syndrome/multiple sclerosis). Histological analysis revealed a reticular accumulation of TSPO expressing phagocytes in PML lesions, while such phagocytes showed a more homogeneous distribution in putative multiple sclerosis lesions. TSPO PET imaging showed an enhanced tracer uptake in natalizumab-associated PML lesions that was present from the early to the chronic stages (up to 52 months after PML diagnosis). While gadolinium enhancement on MRI rapidly declined to baseline levels, TSPO tracer uptake followed a slow one phase decay curve. A TSPO-based 3D diagnostic matrix taking into account the uptake levels as well as the shape and texture of the TSPO signal differentiated >96% of PML and multiple sclerosis lesions. Indeed, treatment with rituximab after natalizumab-associated PML in three patients did not affect tracer uptake in the assigned PML lesions but reverted tracer uptake to baseline in the assigned active multiple sclerosis lesions. Taken together our study suggests that TSPO PET imaging can reveal CNS inflammation in natalizumab-associated PML. TSPO PET may facilitate longitudinal monitoring of disease activity and help to distinguish recurrent multiple sclerosis activity from PML progression.

Progressive multifocal leukoencephalopathy in multiple myeloma. A literature review and lessons to learn.

Progressive multifocal leukoencephalopathy (PML) is a rare opportunistic infection with high mortality rate usually seen in the context of immunosuppression. Although cases have been reported largely in patients with HIV/AIDS, following the use of monoclonal antibodies and occasionally in haematological malignancies, there is no review to date of patients with smouldering or treated myeloma who developed PML. Here, we conducted a literature search of PML cases in patients with multiple myeloma (MM), analyse patient and disease characteristics and describe the possible mechanisms that could lead to the development of PML. The lack of data and case reports until 2010 may indicate that PML in MM is underdiagnosed. Simultaneously, with an expanding field of new therapeutic options, patients with MM live longer, albeit continually immunosuppressed, and at risk of opportunistic infections. Emerging new treatments for PML in the horizon render the need to look out for this complication mandatory, and more case reports are needed to enrich our knowledge in this field.

JC Virus infected choroid plexus epithelial cells produce extracellular vesicles that infect glial cells independently of the virus attachment receptor.

The human polyomavirus, JCPyV, is the causative agent of progressive multifocal leukoencephalopathy (PML) in immunosuppressed and immunomodulated patients. Initial infection with JCPyV is common and the virus establishes a long-term persistent infection in the urogenital system of 50-70% of the human population worldwide. A major gap in the field is that we do not know how the virus traffics from the periphery to the brain to cause disease. Our recent discovery that human choroid plexus epithelial cells are fully susceptible to virus infection together with reports of JCPyV infection of choroid plexus in vivo has led us to hypothesize that the choroid plexus plays a fundamental role in this process. The choroid plexus is known to relay information between the blood and the brain by the release of extracellular vesicles. This is particularly important because human macroglia (oligodendrocytes and astrocytes), the major targets of virus infection in the central nervous system (CNS), do not express the known attachment receptors for the virus and do not bind virus in human tissue sections. In this report we show that JCPyV infected choroid plexus epithelial cells produce extracellular vesicles that contain JCPyV and readily transmit the infection to human glial cells. Transmission of the virus by extracellular vesicles is independent of the known virus attachment receptors and is not neutralized by antisera directed at the virus. We also show that extracellular vesicles containing virus are taken into target glial cells by both clathrin dependent endocytosis and macropinocytosis. Our data support the hypothesis that the choroid plexus plays a fundamental role in the dissemination of virus to brain parenchyma.

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

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

Progressive multifocal leukoencephalopathy and anti-CD20 monoclonal antibodies: What do we know after 20 years of rituximab.

In 1997, rituximab was the first monoclonal antibody clinically approved for the treatment of cancer. Ten years later, progressive multifocal leukoencephalopathy (PML), until that time a rare opportunistic infection mostly seen in AIDS patients, was added as a black box warning after retrospective case-control studies showed an increased incidence in both B-cell lymphoproliferative disorders and autoimmune diseases. Despite more than 5 million worldwide exposures to date (and about 500 000 new exposures per year), insufficient data collection has hampered identification of risk minimization strategies, and concerns have been raised about a class effect extending to the newer anti-CD20 monoclonal antibodies (ofatumumab, obinutuzumab, and ocrelizumab). Here, we report current PML case counts registered in the FAERS and EudraVigilance databases and comment on severe CD4+ T lymphopenia as a plausible common mechanism of action for anti-CD20 antibodies in causation of PML.

A controlled inflammation and a regulatory immune system are associated with more favorable prognosis of progressive multifocal leukoencephalopathy.

OBJECTIVE: In the present study, we analyzed the inflammatory profiles of brain tissues obtained from patients with progressive multifocal leukoencephalopathy (PML) due to John Cunningham (JC) virus infection to identify potential prognostic factors. METHODS: The study included seven patients (two men, five women) who had been pathologically diagnosed with PML, and all of whom were HIV negative. Fixed brain samples were analyzed via hematoxylin and eosin (HE) staining and Klüver-Barrera (KB) staining. We then performed immunohistochemistry (IHC) specific to JC virus capsid proteins (VP1 and VP2/3) and lymphocyte surface markers (CD4, CD8, CD138, and PD-1). RESULTS: The mean age at onset was 53.4, while the mean duration until biopsy/autopsy was 4.7 months. Four patients were included in the good prognosis (GP) group, while three were included in the poor prognosis (PP) group. Pathological analysis revealed a significantly larger number of CD4-positive T-cell infiltrations (P = .029) in the GP group, along with a preserved CD4:CD8 ratio. Larger numbers of CD138-positive plasma cells were also observed in the GP group (P = .029) than in the PP group. Linear regression analyses revealed a significant association between the numbers of CD138-positive plasma cells and PD-1-positive cells (R2 = 0.80). CONCLUSIONS: Viral loads in the cerebrospinal fluid, a controlled inflammatory response mediated by CD4- and CD8-positive T cells, and plasma cells are associated with PML prognosis. Our findings further indicate that regulatory plasma cells may regulate inflammatory T-cell activity via a PD-1/PD-L1 immuno-checkpoint pathway, thereby protecting the uninfected brain from excessive immune-mediated damage during an active JC virus infection.

Expression of Bone Morphogenetic Proteins in Multiple Sclerosis Lesions.

Bone morphogenetic proteins (BMPs) are secreted proteins that belong to the transforming growth factor-ß superfamily. In the adult brain, they modulate neurogenesis, favor astrogliogenesis, and inhibit oligodendrogenesis. Because BMPs may be involved in the failure of remyelination in multiple sclerosis (MS), we characterized the expression of BMP-2, BMP-4, BMP-5, and BMP-7; BMP type II receptor (BMPRII); and phosphorylated SMAD (pSMAD) 1/5/8 in lesions of MS and other demyelinating diseases. A total of 42 MS lesions, 12 acute ischemic lesions, 8 progressive multifocal leukoencephalopathy lesions, and 10 central nervous system areas from four nonneuropathological patients were included. Lesions were histologically classified according to the inflammatory activity. The expression of BMP-2, BMP-4, BMP-5, BMP-7, BMPRII, and pSMAD1/5/8 was quantified by immunostaining, and colocalization studies were performed. In MS lesions, astrocytes, microglia/macrophages, and neurons expressed BMP-2, BMP-4, BMP-5, and BMP-7; BMPRII; and pSMAD1/5/8. Oligodendrocytes expressed BMP-2 and BMP-7 and pSMAD1/5/8. The percentage of cells that expressed BMPs, BMPRII, and pSMAD1/5/8 correlated with the inflammatory activity of MS lesions, and changes in the percentage of positive cells were more relevant in MS than in other white matter-damaging diseases. These data indicate that BMPs are increased in active MS lesions, suggesting a possible role in MS pathogenesis.

Susceptibility of Primary Human Choroid Plexus Epithelial Cells and Meningeal Cells to Infection by JC Virus.

JC polyomavirus (JCPyV) establishes a lifelong persistence in roughly half the human population worldwide. The cells and tissues that harbor persistent virus in vivo are not known, but renal tubules and other urogenital epithelial cells are likely candidates as virus is shed in the urine of healthy individuals. In an immunosuppressed host, JCPyV can become reactivated and cause progressive multifocal leukoencephalopathy (PML), a fatal demyelinating disease of the central nervous system. Recent observations indicate that JCPyV may productively interact with cells in the choroid plexus and leptomeninges. To further study JCPyV infection in these cells, primary human choroid plexus epithelial cells and meningeal cells were challenged with virus, and their susceptibility to infection was compared to the human glial cell line, SVG-A. We found that JCPyV productively infects both choroid plexus epithelial cells and meningeal cells in vitro Competition with the soluble receptor fragment LSTc reduced virus infection in these cells. Treatment of cells with neuraminidase also inhibited both viral infection and binding. Treatment with the serotonin receptor antagonist, ritanserin, reduced infection in SVG-A and meningeal cells. We also compared the ability of wild-type and sialic acid-binding mutant pseudoviruses to transduce these cells. Wild-type pseudovirus readily transduced all three cell types, but pseudoviruses harboring mutations in the sialic acid-binding pocket of the virus failed to transduce the cells. These data establish a novel role for choroid plexus and meninges in harboring virus that likely contributes not only to meningoencephalopathies but also to PML.IMPORTANCE JCPyV infects greater than half the human population worldwide and causes central nervous system disease in patients with weakened immune systems. Several recent reports have found JCPyV in the choroid plexus and leptomeninges of patients with encephalitis. Due to their role in forming the blood-cerebrospinal fluid barrier, the choroid plexus and leptomeninges are also poised to play roles in virus invasion of brain parenchyma, where infection of macroglial cells leads to the development of progressive multifocal leukoencephalopathy, a severely debilitating and often fatal infection. In this paper we show for the first time that primary choroid plexus epithelial cells and meningeal cells are infected by JCPyV, lending support to the association of JCPyV with meningoencephalopathies. These data also suggest that JCPyV could use these cells as reservoirs for the subsequent invasion of brain parenchyma.

ERK Is a Critical Regulator of JC Polyomavirus Infection.

The human JC polyomavirus (JCPyV) infects the majority of the population worldwide and presents as an asymptomatic, persistent infection in the kidneys. In individuals who are immunocompromised, JCPyV can become reactivated and cause a lytic infection in the central nervous system resulting in the fatal, demyelinating disease progressive multifocal leukoencephalopathy (PML). Infection is initiated by interactions between the capsid protein viral protein 1 (VP1) and the α2,6-linked sialic acid on lactoseries tetrasaccharide c (LSTc), while JCPyV internalization is facilitated by 5-hydroxytryptamine 2 receptors (5-HT2Rs). The mechanisms by which the serotonin receptors mediate virus entry and the signaling cascades required to drive viral infection remain poorly understood. JCPyV was previously shown to induce phosphorylation of extracellular signal-regulated kinase (ERK), a downstream target of the mitogen-activated protein kinase (MAPK) pathway, upon virus entry. However, it remained unclear whether ERK activation was required for JCPyV infection. Both ERK-specific small interfering RNA (siRNA) and ERK inhibitor treatments resulted in significantly diminished JCPyV infection in both kidney and glial cells yet had no effect on the infectivity of the polyomavirus simian virus 40 (SV40). Experiments characterizing the role of ERK during steps in the viral life cycle indicate that ERK activation is required for viral transcription, as demonstrated by a significant reduction in production of large T antigen (TAg), a key viral protein associated with the initiation of viral transcription and viral replication. These findings delineate the role of the MAPK-ERK signaling pathway in JCPyV infection, elucidating how the virus reprograms the host cell to promote viral pathogenesis.IMPORTANCE Viral infection is dependent upon host cell factors, including the activation of cellular signaling pathways. These interactions between viruses and host cells are necessary for infection and play an important role in viral disease outcomes. The focus of this study was to determine how the human JC polyomavirus (JCPyV), a virus that resides in the kidney of the majority of the population and can cause the fatal, demyelinating disease progressive multifocal leukoencephalopathy (PML) in the brains of immunosuppressed individuals, usurps a cellular signaling pathway to promote its own infectious life cycle. We demonstrated that the activation of extracellular signal-regulated kinase (ERK), a component of the mitogen-activated protein kinase (MAPK) pathway, promotes JCPyV transcription, which is required for viral infection. Our findings demonstrate that the MAPK-ERK signaling pathway is a key determinant of JCPyV infection, elucidating new information regarding the signal reprogramming of host cells by a pathogenic virus.

Biomarkers identification for PML monitoring, during Natalizumab (Tysabri®) treatment in Relapsing-Remitting Multiple Sclerosis.

Natalizumab (NTZ, Tysabri®; Biogen-Idec, Cambridge, MA, USA) is a humanized anti-α4 integrin monoclonal antibody, largely used in the treatment of Relapsing-Remitting Multiple Sclerosis (RRMS). Although the drug has shown great efficacy in clinical trials (AFFIRM and SENTINEL) and in post-marketing observational studies (TYGRIS), by reducing clinical signs as disability status progression, brain lesions and annual relapse rate, there are numerous papers concerning the associated risk of progressive multifocal leukoencephalopathy (PML). PML is a brain infection caused by John Cunningham virus (JCV) and its incidence is related to intrinsic and extrinsic risk factors, such as long-term natalizumab therapy (more than 24 infusion doses), previous pharmacological immunosuppressive treatment and JVC antibody-positive status. The identification of risk factors provides an instrument to improve treatment decisions and to obtain an accurate benefit-risk evaluation. In order to evaluate the most appropriate natalizumab-MS therapy and to obtain minor incidence of PML, an accurate description of risk factors and a biological markers identification are needed. This article review aims to list some biomarkers that have been proposed to evaluate the safety of natalizumab therapy.

Monitoring CD49d Receptor Occupancy: A Method to Optimize and Personalize Natalizumab Therapy in Multiple Sclerosis Patients.

BACKGROUND: In natalizumab-treated relapsing-remitting MS (RRMS) patients, various extended interval dosing strategies are under evaluation to minimize severe treatment-associated side effects, mainly progressive multifocal leukoencephalopathy development. Up to now, it has not been presented any approach, even in form of assay design, to determine the optimal percentage of CD49d receptor occupancy (RO) associated with a favorable clinical, radiological, and immunological response. METHODS: A multiparametric quantitative flow cytometry method was settled to measure CD49d RO on peripheral blood lymphocytes. The analytical protocol was tested in a 6-month follow-up from 19 RRMS patients treated with the natalizumab standard dosing of every 4 weeks or an extended-interval dosing of every 6 weeks. RESULTS: Extended natalizumab dose schedule promoted an increase of CD49d molecules per cell surface and a reduction of CD49d RO levels. The reduction observed on CD49d RO was not only depending on dose schedule but also on individual parameters such as body mass. Interestingly, individual clinical outcome was apparently the same between the different dose schedules or even better with the extended interval dosing. CONCLUSIONS: Following up CD49d RO levels with a well-regulated monitoring work scheme is crucial to further identify over-/under-treated patients and to define a safe, personalized natalizumab regimen. © 2017 International Clinical Cytometry Society.

Infectious Entry and Neutralization of Pathogenic JC Polyomaviruses.

Progressive multifocal leukoencephalopathy (PML) is a lethal brain disease caused by uncontrolled replication of JC polyomavirus (JCV). JCV strains recovered from the brains of PML patients carry mutations that prevent the engagement of sialylated glycans, which are thought to serve as receptors for the infectious entry of wild-type JCV. In this report, we show that non-sialylated glycosaminoglycans (GAGs) can serve as alternative attachment receptors for the infectious entry of both wild-type and PML mutant JCV strains. After GAG-mediated attachment, PML mutant strains engage non-sialylated non-GAG co-receptor glycans, such as asialo-GM1. JCV-neutralizing monoclonal antibodies isolated from patients who recovered from PML appear to block infection by preventing the docking of post-attachment co-receptor glycans in an apical pocket of the JCV major capsid protein. Identification of the GAG-dependent/sialylated glycan-independent alternative entry pathway should facilitate the development of infection inhibitors, including recombinant neutralizing antibodies.

Anaplastic astrocytoma mimicking progressive multifocal leucoencephalopathy: a case report and review of the overlapping syndromes.

BACKGROUND: Co-occurrence of multiple sclerosis (MS) and glial tumours (GT) is uncommon although occasionally reported in medical literature. Interpreting the overlapping radiologic and clinical characteristics of glial tumours, MS lesions, and progressive multifocal leukoencephalopathy (PML) can be a significant diagnostic challenge. CASE PRESENTATION: We report a case of anaplastic astrocytoma mimicking PML in a 27-year-old patient with a 15-year history of MS. She was treated with interferon, natalizumab and finally fingolimod due to active MS. Follow-up MRI, blood and cerebrospinal fluid examinations, and biopsy were conducted, but only the latter was able to reveal the cause of progressive worsening of patient's disease. CONCLUSIONS: Anaplastic astrocytoma misdiagnosed as PML has not yet been described. We suppose that the astrocytoma could have evolved from a low grade glioma to anaplastic astrocytoma over time, as the tumour developed adjacent to typical MS plaques. The role of the immunomodulatory treatment as well as other immunological factors in the malignant transformation can only be hypothesised. We discuss clinical, laboratory and diagnostic aspects of a malignant GT, MS lesions and PML. The diagnosis of malignant GT must be kept in mind when an atypical lesion develops in a patient with MS.

Use of natalizumab in multiple sclerosis: current perspectives.

INTRODUCTION: Natalizumab is an efficacious monoclonal antibody approved for use in relapsing-remitting multiple sclerosis (RRMS). Multiple studies have demonstrated reduced relapse rate, decreased disability progression and prolonged disease-free intervals with natalizumab use. However, natalizumab is associated with an increased risk of progressive multifocal leukoencephalopathy (PML), thus restricting its widespread use with populations at high risk for developing PML. Recently, the effect of natalizumab in secondary-progressive (SPMS) population has been explored. AREAS COVERED: This review highlights the pathophysiology behind disease progression in MS and summarizes various attributes of natalizumab including: its pharmacological properties and global economic impact, results of clinical efficacy studies, its role in SPMS, pregnancy and its adverse events profile including PML and discontinuation protocols. EXPERT OPINION: Despite an established role in reducing RRMS disease activity, natalizumab has found limited use in SPMS due to insufficient evidence of efficacy. Current disease-modifying therapies exert modest overall benefit in SPMS owing to its complex pathophysiology, higher prevalence of comorbidities and increased PML risk with age and lack of reliable outcome measures. Finding more appropriate MRI and clinical outcome measures is quintessential for designing future randomized trials and possibly exploring primary neuroprotective agents for treating SPMS.

Expression of Signaling Molecules in Progressive Multifocal Leukoencephalopathy.

INTRODUCTION: Progressive multifocal leukoencephalopathy (PML) is a debilitating demyelinating disease of the CNS caused by the infection and destruction of glial cells by JC virus (JCV) and is an AIDS-defining disease. Infection with JCV is common and most people acquire antibodies early in life. After initial infection, JCV remains in an asymptomatic persistent state and can be detected by PCR in many tissues including brain. A major question in PML pathogenesis is how the virus reactivates from persistence in HIV-1/AIDS. Our studies with primary cultures of glial cells have implicated transcription factors NF-κB and NFAT4, which bind to a unique site in the JCV noncoding control region and stimulate viral gene expression. Furthermore, these transcription factors are controlled by pathways downstream of proinflammatory cytokines, e.g., TNF-α activates NF-κB and stimulates JCV transcription. OBJECTIVES: We hypothesize that HIV-1/PML initiation may involve reactivation of JCV by cytokine disturbances in the brain such as occur in HIV-1/AIDS. In this study, the objective was to evaluate HIV-1/PML clinical samples for expression of TNF-α and its receptors and subcellular localization of NF-κB p65 and NFAT4 compared to non-PML controls. METHODS: We evaluated HIV-1/PML clinical samples and non-PML controls for expression of TNF-α and its receptors and subcellular localization of NF-κB p65 and NFAT4 using Western blot and immunohistochemistry. RESULTS: Consistent with our hypothesis, compared to non-PML controls, HIV-1/PML tissue has high levels of TNF-α and TNFR1 expression and NF-κB and NFAT4 were preferentially localized to the nucleus. CONCLUSION: The involvement of TNF-α/NF-κB/NFAT4 signaling in JCV regulation that we reported from experiments in cultured human glial cells may be clinically relevant in PML.

Expression of semaphorin 3A, semaphorin 7A and their receptors in multiple sclerosis lesions.

BACKGROUND: Studies in multiple sclerosis (MS) and in experimental models point to a critical role of semaphorin (sema)3A and sema7A in MS pathogenesis. OBJECTIVE: The objective of this paper is to characterise the expression of sema3A, sema7A, and their receptors in MS lesions. METHODS: We included 44 demyelinating lesions from MS patients, 12 lesions with acute cerebral infarct, 11 lesions with progressive multifocal leucoencephalopathy and 10 non-neurological control patients. MS lesions were classified according to inflammatory activity and all samples were immunostained for sema3A, sema7A, neuropilin 1 (Np-1), α1-integrin, and ß1-integrin. RESULTS: In MS-damaged white matter sema3A and Np-1 were both detected in microglia/macrophages, whereas reactive astrocytes expressed only sema3A. Otherwise, sema7A, α1-integrin and ß1-integrin were observed in reactive astrocytes, and microglia/macrophages only expressed ß1-integrin. The expression of sema3A, sema7A and their receptors is more relevant in MS than in other demyelinating diseases. Sema3A and sema7A expression correlated with the inflammatory activity of the MS lesions, suggesting their involvement in the immunological process that takes place in MS. CONCLUSIONS: The expression pattern of sema3A, sema7A and their receptors in MS lesions suggests that both molecules contribute to create a negative environment for tissue regeneration, influencing the ability to regenerate the damaged tissue.

Usefulness of 11C-methionine-positron emission tomography for the diagnosis of progressive multifocal leukoencephalopathy.

Progressive multifocal leukoencephalopathy (PML) is a subacute demyelinating disease of the brain caused by the JC virus that occurs mainly in immunocompromised patients. The prognosis is very poor. As the lesion looks like non- specific leukoencephalopathy, making a diagnosis at the early stage is very difficult. We report three PML cases in which there was a mismatch between (11)C-methionine-positron emission tomography (MET-PET) uptake and (18)F-fluorodeoxyglucose-positron emission tomography (FDG-PET) uptake. All three cases demonstrated the hyper-uptake of MET around the white matter lesions and hypo-uptake of FDG inside the lesions. We speculate that the infection had ended inside the white matter lesions of these patients, while JC virus infection was ongoing around the lesions, resulting in the increase of methionine metabolism, and the glucose metabolism was reduced or intermediate because inflammatory cells infiltrate PML lesions rarely. Two patients who were diagnosed and treated with mefloquine while the JC virus was at a low level in the cerebrospinal fluid are still alive. We suggest the usefulness of MET-PET for the early diagnosis of PML and early treatment with mefloquine.

5-HT2 receptors facilitate JC polyomavirus entry.

The human JC polyomavirus (JCPyV) causes the rapidly progressing demyelinating disease progressive multifocal leukoencephalopathy (PML). The disease occurs most often in individuals with AIDS but also occurs in individuals receiving immunomodulatory therapies for immune-related diseases such as multiple sclerosis. JCPyV infection of host cells requires the pentasaccharide lactoseries tetrasaccharide c (LSTc) and the serotonin receptor 5-hydroxytryptamine (5-HT) receptor 5-HT2AR. While LSTc is involved in the initial attachment of virus to cells via interactions with VP1, the mechanism by which 5-HT2AR contributes to infection is not clear. To further define the roles of serotonin receptors in infection, HEK293A cells, which are poorly permissive to JCPyV, were transfected with 14 different isoforms of serotonin receptor. Only 5-HT2 receptors were found to support infection by JCPyV. None of the other 11 isoforms of serotonin receptor supported JCPyV infection. Expression of 5-HT2 receptors did not increase binding of JCPyV to cells, but this was not unexpected, given that the cells uniformly expressed the major attachment receptor, LSTc. Infection of these cells remained sensitive to inhibition with soluble LSTc, confirming that LSTc recognition is required for JCPyV infection. Virus internalization into HEK293A cells was significantly and specifically enhanced when 5HT2 receptors were expressed. Taken together, these data confirm that the carbohydrate LSTc is the attachment receptor for JCPyV and that the type 2 serotonin receptors contribute to JCPyV infection by facilitating entry.