Progressive multifocal leukoencephalopathy in individuals with minimal or occult immunosuppression

Rituximab for the treatment of rheumatoid arthritis: an update

Rituximab is a chimeric monoclonal antibody that targets the CD20 molecule expressed on the surface of B cells. It was first used in the treatment of non-Hodgkin's lymphoma and later approved for the treatment of rheumatoid arthritis (RA) that does not respond adequately to disease-modifying antirheumatic drugs, including the anti-tumor-necrosis-factor (TNF) biologics. Sustained efficacy in RA can be achieved by repeated courses of rituximab. However, the optimal dose and retreatment schedule of rituximab in RA remains to be established. Seropositivity, complete B cell depletion shortly after treatment, and previous failure to no more than one anti-TNF agent are three factors associated with greater clinical benefits to rituximab. Infusion reaction to the first dose of rituximab occurs in approximately 25% of RA patients, and the incidence reduces with subsequent exposure. Immunogenicity to the chimeric compound occurs in 11% of RA patients, but this does not correlate with its efficacy in B cell depletion. Extended observation of randomized controlled trials in RA does not reveal a significant increase in the incidence of serious infections related to rituximab compared to placebo groups, and the infection rate remains static over time. Repeated treatment with rituximab is associated with hypogammaglobulinemia, which may increase the risk of serious, but rarely opportunistic, infections. Reactivation of occult hepatitis B infection has been reported in RA patients receiving rituximab, but no increase in the incidence of tuberculosis was observed. Screening for baseline serum immunoglobulin G level and hepatitis B status (including occult infection) is important, especially in Asian countries where hepatitis B infection is prevalent. The rare but fatal progressive multifocal leukoencephalopathy linked to the use of rituximab has to be noted. Postmarketing surveillance and registry data, particularly in Asia, are necessary to establish the long-term efficacy and safety of rituximab in the treatment of RA.

Immune surveillance and response to JC virus infection and PML

The ubiquitous human polyomavirus JC virus (JCV) is the established etiological agent of the debilitating and often fatal demyelinating disease, progressive multifocal leukoencephalopathy (PML). Most healthy individuals have been infected with JCV and generate an immune response to the virus, yet remain persistently infected at subclinical levels. The onset of PML is rare in the general population, but has become an increasing concern in immunocompromised patients, where reactivation of JCV leads to uncontrolled replication in the CNS. Understanding viral persistence and the normal immune response to JCV provides insight into the circumstances which could lead to viral resurgence. Further, clues on the potential mechanisms of reactivation may be gleaned from the crosstalk among JCV and HIV-1, as well as the impact of monoclonal antibody therapies used for the treatment of autoimmune disorders, including multiple sclerosis, on the development of PML. In this review, we will discuss what is known about viral persistence and the immune response to JCV replication in immunocompromised individuals to elucidate the deficiencies in viral containment that permit viral reactivation and spread.

Progressive multifocal leukoencephalopathy in an immunocompetent patient?

Background

Progressive multifocal leukoencephalopathy (PML) is a rapidly progressive, potentially fatal, demyelinating disease affecting immunosuppressed patients. PML is rarely reported in cases with no underlying disease or immunosuppression-associated condition.

Case Report

We present a 72-year-old previously healthy woman who developed a progressive neurological condition affecting the entire nervous system which led to her death within 5 months. PML was diagnosed at autopsy.

Conclusion

PML should be considered in patients with progressive neurological disorders involving the white matter, even in the absence of previous immunomodulatory treatment or immunosuppression.

Neurological complications of transplantation: part I: hematopoietic cell transplantation

Hematopoietic cell transplantation (HCT) is the preferred treatment for an expanding range of neoplastic and nonmalignant conditions. Increasing numbers of solid organ transplantations (SOTs) add an additional population of immunosuppressed patients with multiple potential neurological problems. While the spectrum of neurological complications varies with conditioning procedure and hematopoietic cell or solid organ source, major neurological complications occur with all transplantation procedures. This 2 part review emphasizes a practical consultative approach to central and peripheral nervous system problems related to HCT or SOT with clinical and neuroimaging examples from the authors' institutional experience with the following conditions: the diversity of manifestations of common infections such as varicella zoster virus, Aspergillus, and progressive multifocal leukoencephalopathy (PML), drug therapy-related complications, stroke mechanisms, the spectrum of graft versus host disease (GVHD), and neurologically important syndromes of immune reconstitution inflammatory syndrome (IRIS), posterior reversible encephalopathy syndrome (PRES), and posttransplantation lymphoproliferative disorder (PTLD). These complications preferentially occur at specific intervals after HCT and SOT, and neurological consultants must recognize an extensive spectrum of syndromes in order to effect timely diagnosis and expedite appropriate treatment.

Idiopathic CD4 Lymphocytopenia: Spectrum of opportunistic infections, malignancies, and autoimmune diseases

Idiopathic CD4 lymphocytopenia (ICL) was first defined in 1992 by the US Centers for Disease Control and Prevention (CDC) as the repeated presence of a CD4+ T lymphocyte count of fewer than 300 cells per cubic millimeter or of less than 20% of total T cells with no evidence of human immunodeficiency virus (HIV) infection and no condition that might cause depressed CD4 counts. Most of our knowledge about ICL comes from scattered case reports. The aim of this study was to collect comprehensive data from the previously published cases to understand the characteristics of this rare condition. We searched the PubMed database and Science Direct for case reports since 1989 for Idiopathic CD4 lymphocytopenia cases. We found 258 cases diagnosed with ICL in 143 published papers. We collected data about age, sex, pathogens, site of infections, CD4 count, CD8 count, CD4:CD8 ratio, presence of HIV risk factors, malignancies, autoimmune diseases and whether the patients survived or died. The mean age at diagnosis of first opportunistic infection (or ICL if no opportunistic infection reported) was 40.7 ± 19.2 years (standard deviation), with a range of 1 to 85. One-sixty (62%) patients were males, 91 (35.2%) were females, and 7 (2.7%) patients were not identified whether males or females. Risk factors for HIV were documented in 36 (13.9%) patients. The mean initial CD4 count was 142.6 ± 103.9/mm³ (standard deviation). The mean initial CD8 count was 295 ± 273.6/mm³ (standard deviation). The mean initial CD4:CD8 ratio was 0.6 ± 0.7 (standard deviation). The mean lowest CD4 count was 115.4 ± 87.1/mm³ (standard deviation). The majority of patients 226 (87.6%) had at least one infection. Cryptococcal infections were the most prevalent infections in ICL patients (26.6%), followed by mycobacterial infections (17%), candidal infections (16.2%), and VZV infections (13.1%). Malignancies were reported in 47 (18.1%) patients. Autoimmune diseases were reported in 37 (14.2%) patients.

The human JC polyomavirus (JCPyV): virological background and clinical implications

JC polyomavirus (JCPyV) was the first of now 12 PyVs detected in humans, when in 1964, PyV particles were revealed by electron microscopy in progressive multifocal leukoencephalopathy (PML) tissues. JCPyV infection is common in 35-70% of the general population, and the virus thereafter persists in the renourinary tract. One third of healthy adults asymptomatically shed JCPyV at approximately 50,000 copies/mL urine. PML is rare having an incidence of <0.3 per 100,000 person years in the general population. This increased to 2.4 per 1000 person years in HIV-AIDS patients without combination antiretroviral therapy (cART). Recently, PML emerged in multiple sclerosis patients treated with natalizumab to 2.13 cases per 1000 patients. Natalizumab blocks α4-integrin-dependent lymphocyte homing to the brain suggesting that not the overall cellular immunodeficiency but local failure of brain immune surveillance is a pivotal factor for PML. Recovering JCPyV-specific immune control, e.g., by starting cART or discontinuing natalizumab, significantly improves PML survival, but is challenged by the immune reconstitution inflammatory syndrome. Important steps of PML pathogenesis are undefined, and antiviral therapies are lacking. New clues might come from molecular and functional profiling of JCPyV and PML pathology and comparison with other replicative pathologies such as granule cell neuronopathy and (meningo-)encephalitis, and non-replicative JCPyV pathology possibly contributing to some malignancies. Given the increasing number of immunologically vulnerable patients, a critical reappraisal of JCPyV infection, replication and disease seems warranted.

Progressive multifocal leukoencephalopathy and idiopathic CD4 lymphocytopenia

Idiopathic CD4 lymphocytopenia (ICL) is a syndrome described in patients with low counts of CD4 cells and no other causes for immunosuppression. A few cases of progressive multifocal leukoencephalopathy (PML) have been described in association with this entity. There is no effective treatment for any of them, and the clinical course and outcome are unpredictable. We report on a case of ICL with PML and review the literature, trying to identify the clinical features and the prognosis clues associated to these entities together. A 72-year-old man presented with acute onset gait instability that progressed to a severe cerebellar syndrome with cognitive decline. A cranial MRI showed findings consistent with PML, this diagnosis being confirmed by CSF analyses. Absolute number of CD4+ was 242 cells/μL. An extensive work-up including HIV tests was negative. Ten cases of PML and ICL have previously been reported. Factors contributing to the different outcomes are unknown. Although an effective treatment does not exist for PML, it has been recently demonstrated in vitro that several 5HT2A-receptor antagonists block the JC virus infection. Our patient greatly improved and remains stable 34 months after onset; we describe the potential role of mirtazapine in the treatment of PML.

Progressive multifocal leukoencephalopathy in an immunocompetent patient

A 69-year old man presents with a subacute history of worsening confusion, anxiety and abnormal gait. Brain MRI revealed an extensive non-enhancing signal abnormality of parieto-occipito-temporal white matter. CSF PCR was positive for JC virus, suggestive of progressive multifocal leukoencephalopathy (PML). Extensive workup for occult immunosuppression was negative. Although PML in an immunocompetent patient is exceedingly rare, biopsy confirmed the diagnosis. Mirtazapine and mefloquine therapies were initiated and JCV DNA titre decreased by 100-fold at six months. One year later, his clinical course had stabilized and neuroimaging was improved. Our case suggests that PML can rarely afflict immunocompetent individuals and that serotonin receptor targeting pharmacological therapy may improve the outcome.

Failure of mefloquine therapy in progressive multifocal leukoencephalopathy: report of two Japanese patients without human immunodeficiency virus infection

Although progressive multifocal leukoencephalopathy (PML) cases showing responses to mefloquine therapy have been reported, the efficacy of mefloquine for PML remains unclear. We report on the failure of mefloquine therapy in two Japanese patients with PML unrelated to human immunodeficiency virus. One of the patients was a 47-year-old male who had been treated with chemotherapy for Waldenström macroglobulinemia, and the other was an 81-year-old male with idiopathic CD4(+) lymphocytopenia. Diagnosis of PML was established based on MRI findings and increased JC virus DNA in the cerebrospinal fluid in both patients. Mefloquine was initiated about 5 months and 2 months after the onset of PML, respectively. During mefloquine therapy, clinical and radiological progression was observed, and JC virus DNA in the cerebrospinal fluid was increased in both patients. Both patients died about 4 months and 2 months after initiation of mefloquine, respectively. Further studies are necessary to clarify the differences between mefloquine responders and non-responders in PML.

Molecular biology, epidemiology, and pathogenesis of progressive multifocal leukoencephalopathy, the JC virus-induced demyelinating disease of the human brain

Progressive multifocal leukoencephalopathy (PML) is a debilitating and frequently fatal central nervous system (CNS) demyelinating disease caused by JC virus (JCV), for which there is currently no effective treatment. Lytic infection of oligodendrocytes in the brain leads to their eventual destruction and progressive demyelination, resulting in multiple foci of lesions in the white matter of the brain. Before the mid-1980s, PML was a relatively rare disease, reported to occur primarily in those with underlying neoplastic conditions affecting immune function and, more rarely, in allograft recipients receiving immunosuppressive drugs. However, with the onset of the AIDS pandemic, the incidence of PML has increased dramatically. Approximately 3 to 5% of HIV-infected individuals will develop PML, which is classified as an AIDS-defining illness. In addition, the recent advent of humanized monoclonal antibody therapy for the treatment of autoimmune inflammatory diseases such as multiple sclerosis (MS) and Crohn's disease has also led to an increased risk of PML as a side effect of immunotherapy. Thus, the study of JCV and the elucidation of the underlying causes of PML are important and active areas of research that may lead to new insights into immune function and host antiviral defense, as well as to potential new therapies.

Progressive multifocal leukoencephalopathy: why gray and white matter

Since it was first described in 1958, progressive multifocal leukoencephalopathy (PML), a demyelinating disease of the brain caused by the polyomavirus JC (JCV), has evolved tremendously. It was once considered a noninflammatory disease that affected exclusively oligodendrocytes and astrocytes in the white matter of immunosuppressed individuals and was almost always fatal. Today, we understand that PML can present during the course of an immune reconstitution inflammatory syndrome and that it affects a broader range of individuals, including patients with minimal immunosuppression and those who are treated with novel immunomodulatory medications. Furthermore, JCV-infected glial cells are frequently located at the gray matter-white matter junction or within the gray matter, causing demyelinating lesions within cortical areas. Finally, JCV variants can also infect neurons, leading to the recognition of two distinct clinical entities: JCV granule cell neuronopathy and JCV encephalopathy.

Use of John Cunningham virus polymerase chain reaction in the diagnosis of progressive multifocal leucoencephalopathy - a rare presenting manifestation in an HIV-positive patient

John Cunningham virus infection is an important cause of progressive multifocal leucoencephalopathy (PML) in the context of advanced human immunodeficiency virus infection. Limited data are available regarding the true incidence of PML as a presenting manifestation of HIV. We report one such case and also highlight the effective use of polymerase chain reaction in confirming its diagnosis.

CNS infections in patients with cancer

PURPOSE OF REVIEW

This article provides a practical clinical approach to potential CNS infections in patients with cancer, discusses problematic presentations of posterior reversible encephalopathy syndrome and immune reconstitution inflammatory syndrome, and includes specific testing and treatment recommendations for bacterial meningitis, invasive fungal infections, and opportunistic viral infections.

RECENT FINDINGS

The major deficits predisposing patients with cancer to CNS infection are neutropenia, barrier disruption, B-lymphocyte or immunoglobulin deficiency, and impaired T lymphocyte-mediated immunity. Evolving patterns of drug resistance and prophylactic antimicrobial regimens have altered the timing and range of organisms causing infections. Increasingly intensive immunosuppression has made new groups of patients vulnerable to infections such as progressive multifocal leukoencephalopathy. New MRI sequences offer the potential to diagnose such infections earlier, at a stage when they are more treatable.

SUMMARY

Despite improved prophylactic and therapeutic antibiotic regimens, CNS infections remain an important source of morbidity and mortality among several cancer patient groups, particularly those patients undergoing craniotomy and those with hematologic malignancies receiving either hematopoietic cell transplantation or other intensive chemotherapy regimens.

Neurologic infectious disease emergencies

Nearly 70 years after the discovery of penicillin, neurologic infectious diseases (NIDs) remain an important worldwide source of morbidity and mortality. The clinician faced with a potential NID must urgently consider patient demographics, pace of illness and clinical syndrome, and laboratory data. In keeping with the topics of this issue, initial emergency diagnosis and management are emphasized, with appropriate references to relevant literature for subsequent longer-term interventions.

Progressive multifocal leukoencephalopathy in transplant recipients

OBJECTIVE

Transplant recipients are at risk of developing progressive multifocal leukoencephalopathy (PML), a rare demyelinating disorder caused by oligodendrocyte destruction by JC virus.

METHODS

Reports of PML following transplantation were found using PubMed Entrez (1958-July 2010). A multicenter, retrospective cohort study also identified all cases of PML among transplant recipients diagnosed at Mayo Clinic, Johns Hopkins University, Washington University, and Amsterdam Academic Medical Center. At 1 institution, the incidence of posttransplantation PML was calculated.

RESULTS

A total of 69 cases (44 solid organ, 25 bone marrow) of posttransplantation PML were found including 15 from the 4 medical centers and another 54 from the literature. The median time to development of first symptoms of PML following transplantation was longer in solid organ vs bone marrow recipients (27 vs 11 months, p = 0.0005, range of <1 to >240). Median survival following symptom onset was 6.4 months in solid organ vs 19.5 months in bone marrow recipients (p = 0.068). Case fatality was 84% (95% confidence interval [CI], 70.3-92.4%) and survival beyond 1 year was 55.7% (95% CI, 41.2-67.2%). The incidence of PML among heart and/or lung transplant recipients at 1 institution was 1.24 per 1,000 posttransplantation person-years (95% CI, 0.25-3.61). No clear association was found with any 1 immunosuppressant agent. No treatment provided demonstrable therapeutic benefit.

INTERPRETATION

The risk of PML exists throughout the posttransplantation period. Bone marrow recipients survive longer than solid organ recipients but may have a lower median time to first symptoms of PML. Posttransplantation PML has a higher case fatality and may have a higher incidence than reported in human immunodeficiency virus (HIV) patients on highly-active antiretroviral therapy (HAART) or multiple sclerosis patients treated with natalizumab.

Rituximab for management of refractory pregnancy-associated immune thrombocytopenic purpura

BACKGROUND

Rituximab is a novel therapy for immune thrombocytopenic purpura (ITP); however, information about its safety in pregnancy is limited. This case illustrates the successful use of rituximab to treat pregnancy-associated ITP.

CASE

A 34-year-old woman presented with severe ITP at 23 weeks' gestation. Standard treatment with corticosteroids, intravenous immune globulin, and splenectomy failed to raise the platelet count. Due to ongoing bleeding, rituximab was given in the 26th week of pregnancy. The platelet count rose to over 100 × 10(9)/L after four weeks. The neonatal B-lymphocyte count normalized at four months after delivery. There were no neonatal complications of rituximab therapy.

CONCLUSION

Rituximab may be safe for use in treating pregnancy-associated ITP. This case highlights the need to investigate further the safety and efficacy of rituximab in pregnancy.

Role of CD4+ and CD8+ T-cell responses against JC virus in the outcome of patients with progressive multifocal leukoencephalopathy (PML) and PML with immune reconstitution inflammatory syndrome

Progressive multifocal leukoencephalopathy (PML) is a severe demyelinating disease of the brain caused by JC virus (JCV). To assess the role of CD4(+) and CD8(+) T-cells against JCV in the clinical outcome of PML and PML in the setting of immune reconstitution inflammatory syndrome (IRIS), we tested gamma interferon (IFN-γ) response by enzyme-linked immunosorbent spot (ELISpot) and intracellular cytokine staining (ICS) in 117 subjects, including 66 PML patients with different clinical outcomes. Both assays were concordant and demonstrated that the cellular immune response against JCV is associated with better clinical outcome. PML survivors had an early CD8(+) T-cell response more frequently than PML progressors (100% versus 27.3%; P = 0.001), while only a trend was observed for the early CD4(+) T-cell response between these two groups (80% versus 45.5%; P = 0.18). Although IRIS itself was more frequent in the PML survivor group, there was no difference in IFN-γ-producing CD4(+) and CD8(+) T-cells between IRIS and non-IRIS PML patients, suggesting that T-cells expressing other cytokines likely have a role in the immunopathogenesis of IRIS. ELISpot and ICS assays are useful prognostic markers of PML evolution and may help in the clinical management of these patients.

Polyoma virus-associated progressive multifocal leukoencephalopathy after renal transplantation: regression following withdrawal of mycophenolate mofetil

The 2008-released FDA safety report described a potential association between use of MMF and progressive multifocal leukoencephalopathy. We here report the case of an 11-yr-old kidney transplanted boy suffering from PML who showed rapid improvement parallel to withdrawal of MMF. This case contributes to the increasing knowledge on side effects of MMF treatment in children.

Activities of different classes of acyclic nucleoside phosphonates against BK virus in primary human renal cells

BK virus (BKV), a virus belonging to the polyomavirus family, is a circular double-stranded DNA virus that causes nephropathies in immunocompromised patients after kidney or bone marrow transplantation. The occurrence of polyomavirus-associated nephropathy in kidney transplant patients may trigger graft loss, and guidelines for the management of BKV infection have not yet been clearly established. Treatment of BKV nephropathy with cidofovir (CDV) {(S)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine (HPMPC)}, an acyclic phosphonate analogue of dCMP with a broad antiviral activity against DNA virus infections, has been proposed. The benefit of this small-molecule-based treatment has been evaluated only with a limited number of cases. In this study, we report the evaluation of three different classes of acyclic nucleoside phosphonates for their activities against BKV replication in two different primary renal cells: renal proximal tubular epithelial cells (RPTECs) and human renal cortical epithelial (HRCE) cells. The data indicate that besides HPMPC and its cyclic form, (S)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]-5-azacytosine (HPMP-5-azaC), cyclic HPMP (cHPMP)-5-azaC, hexadecyloxyethyl (HDE)-cHPMP-5-azaC, and 9-[2-(phosphonomethoxy)ethyl]guanine (PMEG) are the most selective inhibitors of BKV replication. On the contrary, leflunomide, which has also been proposed for the management of BKV-associated diseases, is not able to inhibit BKV replication at nontoxic concentrations.

Activities of different classes of acyclic nucleoside phosphonates against BK virus in primary human renal cells

BK virus (BKV), a virus belonging to the polyomavirus family, is a circular double-stranded DNA virus that causes nephropathies in immunocompromised patients after kidney or bone marrow transplantation. The occurrence of polyomavirus-associated nephropathy in kidney transplant patients may trigger graft loss, and guidelines for the management of BKV infection have not yet been clearly established. Treatment of BKV nephropathy with cidofovir (CDV) {(S)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine (HPMPC)}, an acyclic phosphonate analogue of dCMP with a broad antiviral activity against DNA virus infections, has been proposed. The benefit of this small-molecule-based treatment has been evaluated only with a limited number of cases. In this study, we report the evaluation of three different classes of acyclic nucleoside phosphonates for their activities against BKV replication in two different primary renal cells: renal proximal tubular epithelial cells (RPTECs) and human renal cortical epithelial (HRCE) cells. The data indicate that besides HPMPC and its cyclic form, (S)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]-5-azacytosine (HPMP-5-azaC), cyclic HPMP (cHPMP)-5-azaC, hexadecyloxyethyl (HDE)-cHPMP-5-azaC, and 9-[2-(phosphonomethoxy)ethyl]guanine (PMEG) are the most selective inhibitors of BKV replication. On the contrary, leflunomide, which has also been proposed for the management of BKV-associated diseases, is not able to inhibit BKV replication at nontoxic concentrations.

JC virus infection of the brain

Since its initial description, there have been significant changes in the epidemiology, pathogenesis, and clinical and imaging manifestations of JCV infection of brain. The most common clinical manifestation is PML. Other recently described CNS manifestations are JCE, JCVGCN, and JCM. Although AIDS is the most common predisposing factor for JCV reactivation, there is increasing incidence of brain manifestations of JCV reactivation in non-HIV settings, including different rheumatologic, hematologic, and oncologic conditions; monoclonal antibody therapy; transplant recipients; primary immunodeficiency syndromes; and even in patients without any recognizable immune deficiency. IRIS may develop secondary to restoration of immunity in HIV-positive patients with PML receiving antiretroviral therapy. This is of profound clinical significance and needs to be diagnosed promptly. Imaging plays a crucial role in the diagnosis of the disease, monitoring of treatment response, identifying disease progression, and predicting prognosis. In this article, current understanding of the epidemiology, pathogenesis, clinical presentations, and all aspects of imaging of JCV infection of the brain have been comprehensively reviewed.

Imaging manifestations of progressive multifocal leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease caused by reactivation of JC virus in immunosuppressed patients. The diagnosis is usually suggested on imaging and confirmed by cerebrospinal fluid polymerase chain reaction (PCR) for JC virus DNA. In this article, we review the imaging manifestations of PML on computed tomography (CT), magnetic resonance imaging (MRI), diffusion-weighted imaging (DWI), diffusion tensor imaging (DTI), MR spectroscopy, single photon-emission computed tomography (SPECT) and positron-emission tomography (PET), and outline the role of imaging in follow-up and prognostication.

Progressive multifocal leukoencephalopathy in a patient without apparent immunosuppression

An 80-year-old man with no history of an immune-compromising disorder was diagnosed with progressive multifocal leukoencephalopathy (PML). He presented with dysphagia and left-sided weakness; magnetic resonance imaging demonstrated marked signal abnormality in the subcortical white matter of the left frontal lobe and in the posterior limb of the right internal capsule. Polymerase chain reaction (PCR) analysis of the cerebrospinal fluid (CSF) was negative for John Cunningham (JC) virus. On brain biopsy, foamy macrophages infiltrating the white matter were identified, staining positive for anti-simian virus 40 antibodies. Postoperatively, PCR for JC viral DNA in the CSF was positive, establishing the diagnosis of PML. Extensive investigation for an occult immunocompromising disorder was negative. The patient's neurologic deficits rapidly increased throughout his hospital stay, and he died 3.5 months after his diagnosis.

Demyelination as a complication of new immunomodulatory treatments

PURPOSE OF REVIEW

This review discusses demyelinating events of the nervous system that have been associated with new immunomodulatory treatments, in particular monoclonal antibodies (mAbs).

RECENT FINDINGS

Natalizumab, a mAb targeting the alpha-4 integrins, which is efficient in relapsing-remitting multiple sclerosis, has been associated with progressive multifocal leukoencephalopathy (PML). We will review the putative mechanisms linking natalizumab with JC virus, the agent of PML. Efalizumab, a mAb targeting a member of the integrin family, CD11a, was approved for the treatment of psoriasis, but had to be withdrawn in 2009 because of the occurrence of three cases of PML. Rituximab, an anti-CD20 mAb, is used in different neoplastic and autoimmune diseases and may soon enter the pharmacopeia of multiple sclerosis. It has been suggested that rituximab is a risk factor for PML; however, evidence of such a link is unclear. Antitumor necrosis factor-alpha agents are used in several autoimmune diseases. Several cases of demyelinating events of the nervous system have been reported, prompting a heightened surveillance of treated patients. Recent data are reassuring, suggesting that the incidence of such events is relatively low.

SUMMARY

Neurologists must become familiar with neurological complications of new immunomodulatory treatments, a field situated at the interface of neurology, immunology and infection.

JC virus latency in the brain and extraneural organs of patients with and without progressive multifocal leukoencephalopathy

JC virus (JCV) is latent in the kidneys and lymphoid organs of healthy individuals, and its reactivation in the context of immunosuppression may lead to progressive multifocal leukoencephalopathy (PML). Whether JCV is present in the brains or other organs of healthy people and in immunosuppressed patients without PML has been a matter of debate. We detected JCV large T DNA by quantitative PCR of archival brain samples of 9/24 (38%) HIV-positive PML patients, 5/18 (28%) HIV-positive individuals, and 5/19 (26%) HIV-negative individuals. In the same samples, we detected JCV regulatory region DNA by nested PCR in 6/19 (32%) HIV-positive PML patients, 2/11 (18%) HIV-positive individuals, and 3/17 (18%) HIV-negative individuals. In addition, JCV DNA was detected in some spleen, lymph node, bone, and kidney samples from the same groups. In situ hybridization data confirmed the presence of JCV DNA in the brains of patients without PML. However, JCV proteins (VP1 or T antigen) were detected mainly in the brains of 23/24 HIV-positive PML patients, in only a few kidney samples of HIV-positive patients, with or without PML, and rarely in the bones of HIV-positive patients with PML. JCV proteins were not detected in the spleen or lymph nodes in any study group. Furthermore, analysis of the JCV regulatory region sequences showed both rearranged and archetype forms in brain and extraneural organs in all three study groups. Regulatory regions contained increased variations of rearrangements correlating with immunosuppression. These results provide evidence of JCV latency in the brain prior to severe immunosuppression and suggest new paradigms in JCV latency, compartmentalization, and reactivation.

Progressive multifocal leukoencephalopathy and other disorders caused by JC virus: clinical features and pathogenesis

Progressive multifocal leukoencephalopathy (PML) is a rare but often fatal brain disease caused by reactivation of the polyomavirus JC. Knowledge of the characteristics of PML has substantially expanded since the introduction of combination antiretroviral therapy during the HIV epidemic and the development of immune reconstitution inflammatory syndrome (IRIS) in patients with PML. Recently, the monoclonal antibodies natalizumab, efalizumab, and rituximab--used for the treatment of multiple sclerosis, psoriasis, haematological malignancies, Crohn's disease, and rheumatic diseases--have been associated with PML. Additionally, the JC virus can also lead to novel neurological disorders such as JC virus granule cell neuronopathy and JC virus encephalopathy, and might also cause meningitis. The increasingly diverse populations at risk and the recent discovery of the presence of the JC virus in the grey matter invite us to reappraise the pathogenesis of this virus in the CNS.