New trends in progressive multifocal leukoencephalopathy

Infection by Polyomavirus JC is a model of chronic active viral infection, closely controlled by the immune system. Progressive multifocal leucoencephalopathy (PML) is a deadly demyelinating disease of the central nervous system, consecutive to the lytic infection of oligodendrocytes by JC virus. Reactivation of JC virus occurs only in the setting of severe cellular immune deficiency. During the last 25 years, the incidence of PML has significantly increased related to the AIDS pandemic and, more recently, to the growing use of immunosuppressive drugs. There is no specific antiviral treatment for PML. Nevertheless, the availability of highly active antiretroviral therapy has changed the clinical course of PML in HIV-infected individuals. One-year mortality has decreased from 90 percent to approximately 50 percent as a result of reconstitution of the immune system. Recent advances in JC virus biology give new perspectives to the pathogenesis of PML. New trends in the understanding of the cellular immune response against the JC virus have direct implications for patient management and may lead to develop future strategy of immunotherapies for PML.     

Patient with progressive multifocal leukoencephalopathy by in situ hybridization: comparison of in situ hybridization using isotopic and biotinylated probes

Ward et al developed biotinylated probes to hasten virus nucleic acid detection. We used these probes to trace SV 40 and JC virus nucleic acids in PML brain. This procedure visualizes the hybridization of viral sequences by affinity cytochemistry with avidin-biotin peroxidase complexes and diaminobenzidine. In the PML frozen white matter numerous oligodendroglial nuclei hybridized with JC virus biotinylated and tritium labelled probes in areas adjacent to active demyelination. Although tritium labeled probes was most sensitive and gave lowest background this biotinylated method showed be useful as a rapid diagnostic test for the specific detection of viral nucleic acid sequences in brain tissues from patients with central nervous system (CNS) infectious diseases.     

Distribution of papovavirus, myelin-associated glycoprotein, and myelin basic protein in progressive multifocal leukoencephalopathy lesions

To study how viruses interact with oligodendroglia and produce demyelination, we immunostained paraffin and epon sections of lesions from patients with progressive multifocal leukoencephalopathy (PML) with antisera to papovaviruses, oligodendroglial myelin-associated glycoprotein (MAG), and myelin basic protein (MBP) according to the peroxidase-antiperoxidase method. In paraffin sections from a rapidly progressive case of PML, hyperimmune JC virus antiserum stained single oligodendroglia which were located in white matter that appeared normal histologically and stained normally with MAG and MBP antisera. In zones surrounding areas of demyelination, virus containing oligodendroglia were most numerous and MAG staining of periaxonal regions was decreased, but there was little change in MBP staining. In demyelinated regions, both MAG and MBP staining were severely altered; also there was much less JC virus staining. In tissue from three other chronic cases, viral antiserum stained fewer oligodendrocytes and the differences in MAG and MBP staining were much less striking. In epon sections from two biopsies of central nervous system tissue, we studied the electron microscopic appearance of oligodendroglia that also had been stained by JC virus antiserum. Virions were present in all nuclei and in some cytoplasmic regions. The results suggest that changes in MAG distribution are useful indicators of early oligodendroglial abnormalities which can cause myelin breakdown.     

Progressive multifocal leukoencephalopathy: Dot‐shaped inclusions and virus‐host interactions

Progressive multifocal leukoencephalopathy (PML) is a fatal demyelinating disease caused by reactivation of the asymptomatic persistent pathogen human polyomavirus JC (JC virus). The pathology of affected brain tissues demonstrates oligodendroglia‐like cells with viral inclusions in their enlarged nuclei, a diagnostic hallmark of this disease. Today, the pathological features of this disease are expanding, partly due to an unsteady balance between viral virulence and host immunity. Intranuclear viral inclusions were initially thought to be amphophilic materials comprising the entire enlarged nucleus, based on HE staining (full inclusions). Howevewr, recent immunohistochemical analyses detected the presence of intranuclear viral inclusions in dots (dot‐shaped inclusions). The dot‐shaped inclusions reflect clustered progeny virions at punctuated subnuclear domains called promyelocytic leukemia nuclear bodies, and are indicative of early‐stage viral infection or suppressed viral proliferation. Second, the JC virus is usually reactivated in patients with impaired immunity, and therefore the inflammatory reactions are poor. However, the causes of immunosuppression are divergent, as seen with the frequent use of immunosuppressive drugs, including natalizumab. Therefore, the degree of host immunity is variable; some patients show marked anti‐viral inflammatory reactions and a good prognosis, indicating that a strong resistance against viral infection remains. Recovery of the immune system may also induce paradoxical clinical worsening, known as immune reconstitution inflammatory syndrome, the mechanism of which has not been clarified. The virus‐host interactions have increased in complexity, and the pathology of PML is diverging. In this review, the pathology of PML will be described, with a focus on the intranuclear target of JC virus infection and host inflammatory reactions.     

Progressive multifocal leukoencephalopathy (PML) associated with HIV Clade C—is not uncommon

Progressive multifocal leukoencephalopathy (PML) is a rare, subacute, demyelinating disease of the central nervous system caused by JC virus. Studies of PML from HIV Clade C prevalent countries are scarce. We sought to study the clinical, neuroimaging, and pathological features of PML in HIV Clade C patients from India. This is a prospective cum retrospective study, conducted in a tertiary care Neurological referral center in India from Jan 2001 to May 2012. Diagnosis was considered “definite” (confirmed by histopathology or JCV PCR in CSF) or “probable” (confirmed by MRI brain). Fifty-five patients of PML were diagnosed between January 2001 and May 2012. Complete data was available in 38 patients [mean age 39?±?8.9 years; duration of illness—82.1?±?74.7 days). PML was prevalent in 2.8 % of the HIV cohort seen in our Institute. Hemiparesis was the commonest symptom (44.7 %), followed by ataxia (36.8 %). Definitive diagnosis was possible in 20 cases. Eighteen remained “probable” wherein MRI revealed multifocal, symmetric lesions, hypointense on T1, and hyperintense on T2/FLAIR. Stereotactic biopsy (n?=?11) revealed demyelination, enlarged oligodendrocytes with intranuclear inclusions and astrocytosis. Immunohistochemistry revelaed the presence of JC viral antigen within oligodendroglial nuclei and astrocytic cytoplasm. No differences in clinical, radiological, or pathological features were evident from PML associated with HIV Clade B. Clinical suspicion of PML was entertained in only half of the patients. Hence, a high index of suspicion is essential for diagnosis. There are no significant differences between clinical, radiological, and pathological picture of PML between Indian and Western countries.     

Update on Progressive Multifocal Leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is a severe, often fatal, opportunistic viral infection of the central nervous system that is mainly seen in the context of AIDS and certain monoclonal immune-suppressive therapies. The causative agent, a polyoma virus, named JC virus infects only humans and there is no animal model for PML. This update focuses on information gathered in recent years on the pathogenesis of the disorder, on several clinical aspects associated with diagnosis and therapy, and on the immune reconstitution inflammatory syndrome (IRIS), a complication associated with removal of immunosuppressive therapy in PML.     

Progressive multifocal leukoencephalopathy developed in incomplete Heerfordt syndrome,a rare manifestation of sarcoidosis,without steroid therapy responding to cidofovir

Progressive multifocal leukoencephalopathy (PML) is a severe demyelinating disease of the central nervous system caused by the JC virus; the mortality rate is high and it is usually refractory to treatment. In non-HIV patients, PML occurs as a late consequence of hematologic malignancies or during prolonged immunosuppression for transplantation or autoimmune disease. We describe a 34-year-old PML patient with incomplete Heerfordt syndrome, a rare type of sarcoidosis, who had not received any immunosuppressants, including steroids, at the onset and who was clinically and radiologically responsive to the antiviral drug cidofovir.     

Progressive multifocal leukoencephalopathy in a lymphoma patient with complete remission after treatment with cytostatics and rituximab: case report and review of the literature

A 44-year-old woman presented with dysarthria, visual disturbances, ataxia and cognitive impairment. There was a rapid progression of her neurological disease, and she died 8 months later. She was previously treated for a low-grade follicular B-cell lymphoma; complete remission was achieved by conventional radiotherapy and chemotherapy, including rituximab. Two years later, the neurological symptoms and signs started. MRI revealed a cerebral demyelinating process. Serology was negative. Autopsy disclosed areas in cerebral white matter with grey discoloration. Microscopy revealed demyelination, oligodendroglial viral inclusions and gliosis with bizarre astrocytes. Polymerase chain reaction (PCR) was positive for JC virus. These findings were consistent with progressive multifocal leukoencephalopathy (PML). This is one of recent reports on PML occurring in a patient treated with the anti-20 monoclonal antibody rituximab.     

Virus demyelination

A number of viruses can initiate central nervous system (CNS) diseases that include demyelination as a major feature of neuropathology. In humans, the most prominent demyelinating diseases are progressive multifocal leukoencephalopathy, caused by JC papovirus destruction of oligodendrocytes, and subacute sclerosing panencephalitis, an invariably fatal childhood disease caused by persistent measles virus. The most common neurological disease of young adults in the developed world, multiple sclerosis, is also characterized by lesions of inflammatory demyelination; however, the etiology of this disease remains an enigma. A viral etiology is possible, because most demyelinating diseases of known etiology in both man and animals are viral. Understanding of the pathogenesis of virus-induced demyelination derives for the most part from the study of animal models. Studies with neurotropic strains of mouse hepatitis virus, Theiler's virus, and Semliki Forest virus have been at the forefront of this research. These models demonstrate how viruses enter the brain, spread, persist, and interact with immune responses. Common features are an ability to infect and persist in glial cells, generation of predominantly CD8(+) responses, which control and clear the early phase of virus replication but which fail to eradicate the infection, and lesions of inflammatory demyelination. In most cases demyelination is to a limited extent the result of direct virus destruction of oligodendrocytes, but for the most part is the consequence of immune and inflammatory responses. These models illustrate the roles of age and genetic susceptibility and establish the concept that persistent CNS infection can lead to the generation of CNS autoimmune responses.     

Progressive multifocal leukoencephalopathy (PML) in chronic lymphatic leukemia (CLL). Review of the literature and case report

Progressive multifocal leukoencephalopathy (PML) is an infectious disease of the central nervous system caused by the JC virus. Progressive multifocal leukoencephalopathy represents a reactivation of the JC virus after long-standing immunosuppression. Also, PML plays an important role as an opportunistic infection in patients with AIDS. The average time of survival in patients with PML in combination with chronic lymphatic leukemia (CLL) (n = 17 in the literature) is 4.3 months, and therapeutic options are not established. We report the case of a patient with CLL and PML. Clinical symptoms are slight hemiparesis of the right side, mainly appearing as a disturbance of motor function. In MRI, a typical subcortical lesion was shown, and JC virus DNA was positive in the CSF by PCR. Because of first positive results in treatment of PML in patients with AIDS, therapy with cidofovir was started. After treatment for 16 months, symptoms are stable, the PML-induced lesions in MRI are in regression, and JC virus DNA is not detectable in the CSF.     

Persistence and pathogenesis of the neurotropic polyomavirus JC

Many neurological diseases of the central nervous system (CNS) are underpinned by malfunctions of the immune system, including disorders involving opportunistic infections. Progressive multifocal leukoencephalopathy (PML) is a lethal CNS demyelinating disease caused by the human neurotropic polyomavirus JC (JCV) and is found almost exclusively in individuals with immune disruption, including patients with human immunodeficiency virus/acquired immunodeficiency syndrome, patients receiving therapeutic immunomodulatory monoclonal antibodies to treat conditions such as multiple sclerosis, and transplant recipients. Thus, the public health significance of this disease is high, because of the number of individuals constituting the at‐risk population. The incidence of PML is very low, whereas seroprevalence for the virus is high, suggesting infection by the virus is very common, and so it is thought that the virus is restrained but it persists in an asymptomatic state that can only occasionally be disrupted to lead to viral reactivation and PML. When JCV actively replicates in oligodendrocytes and astrocytes of the CNS, it produces cytolysis, leading to formation of demyelinated lesions with devastating consequences. Defining the molecular nature of persistence and events leading to reactivation of the virus to cause PML has proved to be elusive. In this review, we examine the current state of knowledge of the JCV life cycle and mechanisms of pathogenesis. We will discuss the normal course of the JCV life cycle including transmission, primary infection, viremia, and establishment of asymptomatic persistence as well as pathogenic events including migration of the virus to the brain, reactivation from persistence, viral infection, and replication in the glial cells of the CNS and escape from immunosurveillance. Ann Neurol 2015;77:560–570     

Human demyelinating disease and the polyomavirus JCV

Many human neurological diseases involve demyelination of the central and/or peripheral nervous systems. These include the hereditary leukodystrophies--which have a genetic basis; multiple sclerosis (MS)--where the underlying cause of demyelination remains unknown; and progressive multifocal leukoencephalopathy (PML)--where the etiology is well-established as being viral. The human neurotropic polyomavirus--JC virus (JCV)--is the etiologic agent of PML, a fatal demyelinating disease of the central nervous system that occurs mainly in immunosuppressed patients, especially those with HIV/AIDS. JCV belongs to the polyomavirus family of tumor viruses that are characterized by non-enveloped icosahedral capsids containing small, circular, double-stranded DNA genomes. Serological studies have shown that JCV is widespread throughout the human population, but infections are usually restricted by the immune system, particularly cell-mediated immunity, causing the virus to enter a latent phase. An important corollary of this is that situations of severe immunosuppression may permit JCV to replicate and are thus a risk factor for PML.     

Progressive multifocal leukoencephalopathy in an HIV patient was diagnosed by 3 times lumbar punctures and 2 times brain biopsies

Journal of NeuroVirology - Progressive multifocal leukoencephalopathy (PML) is a rare demyelinating disease of the central nervous system caused by JC virus (JCV) and is difficult to diagnose. We...     

A case of progressive multifocal leukoencephalopathy with hypogammaglobulinemia and a TCF3 mutation

Journal of NeuroVirology - Progressive multifocal leukoencephalopathy (PML) is a rare and potentially fatal demyelinating disease of the central nervous system (CNS) caused by JC virus; it was...     

Progressive multifocal leukoencephalopathy: a review of the neuroimaging features and differential diagnosis

Progressive multifocal leukoencephalopathy (PML) is an uncommon and often fatal demyelinating disease of human central nervous system, which is caused by reactivation of the polyomavirus JC (JCV). PML generally occurs in patients with profound immunosuppression such as AIDS patients. Recently, a number of PML cases have been associated with administration of natalizumab for treatment of multiple sclerosis (MS) patients. Diagnosis and management of PML became a major concern after its occurrence in multiple sclerosis patients treated with natalizumab. Diagnosis of PML usually rests on neuroimaging in the appropriate clinical context and is further confirmed by cerebrospinal fluid polymerase chain reaction (PCR) for JCV DNA. Treatment with antiretroviral therapies in HIV-seropositive patients or discontinuing natalizumab in MS patients with PML may lead to the development of immune reconstitution inflammatory syndrome (IRIS) which presents with deterioration of the previous symptoms and may lead to death. In patients under treatment with monoclonal antibodies in routine practice, or new ones in ongoing clinical trials, differentiating PML from new MS lesions on brain MRI is critical for both the neurologists and neuroradiologists. In this review, we discuss the clinical features, neuroimaging manifestations of PML, IRIS and neuroimaging clues to differentiate new MS lesions from PML. In addition, various neuroimaging features of PML on the non-conventional MR techniques such as diffusion-weighted imaging (DWI), diffusion tensor imaging (DTI), and MR spectroscopy (MRS) are discussed.     

Progressive multifocal leukoencephalopathy--epidemiology, clinical pictures, diagnosis and therapy]

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system caused by the reactivation of a ubiquitous polyomavirus JC (JCV). PML was for many years a rare disease occurring only in patients with underlying severe impaired immunity. Over the past three decades, the incidence of PML has significantly increased related to the AIDS (acquired immunodeficiency syndrome) pandemic and, more recently, to the growing use of immunosuppressive drugs. The clinical presentation of PML is variable with neurological symptoms corresponding to affected cerebral areas. Usually, the clinical outcome of patients with PML is poor with an inexorable progression to death within 6 months of symptom onset. Although PML usually requires a brain biopsy or autopsy for confirmation, radiological imaging and a demonstration of JCV-DNA in the CSF (cerebrospinal fluid) provide supportive evidence for the diagnosis. Although there is no proven effective therapy for PML, patients with HIV (human immunodeficeincy virus)-related PML may benefit significantly from HAART (highly active antiretroviral therapy). In this article the author reviews the epidemiology, especially in Japan, current challenges in the diagnosis and the treatment guidelines of patients with PML based on recent advances in the understanding of the JC virus biology.     

Progressive multifocal leukoencephalopathy and other forms of JC virus disease

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the brain caused by the JC virus (JCV). PML usually occurs via reactivation of JCV when an immune system becomes compromised. A diagnosis of PML is normally made on the basis of distinguishing neurological features at presentation, characteristic brain MRI changes and the presence of JCV DNA in cerebrospinal fluid. PML has a 3 month mortality rate of 20-50%, so prompt intervention is essential. Currently, reconstitution of the immune system affords the best prognosis for this condition. When PML is first suspected, and where possible, immunosuppressant or immunomodulatory therapy should be suspended or reduced. If PML is associated with a protein therapy that has a long half-life the use of plasma exchange to accelerate the removal of the drug from the circulation may aid the restoration of immune system function. Rapid improvements in immune function, however, might lead to transient worsening of the disease. In this Review, we critically appraise the controversies surrounding JCV infection, and provide practical management guidelines for PML.     

Early T cell response in the central nervous system in canine distemper virus infection

The initial demyelinating lesions in canine distemper virus (CDV) infection develop during a period of severe immunosuppression in the absence of inflammation. In vitro and in vivo studies suggest that early demyelination is due to directly virus-induced oligodendroglial changes. In the present spatiotemporal study in experimentally CDV-infected dogs we observed diffuse up-regulation of T cells throughout the central nervous system (CNS) and T cell invasion in early demyelinating lesions. Invasion of T cells in the CNS occurred despite severe immunosuppression and without any perivascular cuffing. However, the major fraction of invading T cells correlated with sites of viral replication and coincided with the demonstration of an early immune response against the nucleocapsid protein of CDV. Activation of microglial cells was thought to have elicited the migration of T cells to the CNS by secretion of chemokines: marked IL-8 activity was found in the CSF of dogs with acute lesions. In areas of early demyelination, large numbers of CD3⁺ cells accumulated in the tissue in the absence of any morphological sign of inflammation. Whether the T cells at lesion sites contribute to the development of acute demyelination remains uncertain at this stage. Antiviral cytotoxicity was not apparent since viral clearance in demyelinating lesions is only effective when B cells and concurring antiviral antibody production appeared in the subacute and chronic inflammatory stage of the disease. CD3⁺ cells appear to persist for several weeks after infection since they were also found in recovered dogs that did not develop demyelination. Accumulation of immune cells, including a significant proportion of resting T cells (CD45RA⁺) in the CNS in the early stages of the disease may facilitate the later development of the intrathecal immune response and associated immunopathological complications. Received: 16 March 1998 / Revised, accepted: 6 July 1998     

Oligodendroglial degeneration in distemper: apoptosis or necrosis?

Canine distemper virus (CDV) causes a multifocal demyelinating disease in dogs. It was previously shown that the initial demyelinating lesions are directly virus induced since a correlation between the occurrence of demyelination and CDV replication in white matter cells was observed. During the course of infection oligodendrocytes undergo distinct morphological alterations, partly due to a restricted CDV infection of these cells, and eventually disappear from the lesions. This phenomenon has been described in vivo as well as in vitro. However, the reason for the morphological alterations and the following oligodendroglial depletion remained unclear. Since virus infection can induce cell death, it was investigated whether apoptosis or necrosis plays a role in the pathogenesis of demyelination in canine distemper. In brain tissue sections from dogs with acute distemper apoptotic cells were not detected within the demyelinating lesions using morphological and biochemical cell death criteria. In chronic distemper, apoptotic cells – presumably inflammatory cells – were seen within the perivascular cuffs. These in vivo findings were correlated to the in vitro situation using CDV-infected primary dog brain cell cultures as well as Vero cells. Infection with culture-adapted CDV lead to massive necrosis but not to apoptosis. After infection with virulent CDV neither apoptosis nor necrosis was a predominant feature in either culture system. These findings suggest that virus-induced demyelination in canine distemper is not the direct consequence of apoptosis or necrosis. It is speculated that another mechanism must be responsible for the observed morphological alterations of oligodendrocytes, ultimately leading to demyelination. Received: 29 April 1998 / Revised, accepted: 27 August 1998