Immune response in progressive multifocal leukoencephalopathy: an overview

JC polyomavirus: a short review of its biology, its association with progressive multifocal leukoencephalopathy, and the diagnostic value of different methods to manifest its activity or presence

INTRODUCTION

JC polyomavirus is the causative agent of progressive multifocal leukoencephalopathy (PML), a demyelinating disease resulting from the lytic infection of oligodendrocytes that may develop in immunosuppressed individuals: HIV1 infected or individuals under immunosuppressive therapies. Understanding the biology of JCPyV is necessary for a proper patient management, the development of diagnostic tests, and risk stratification.

AREAS COVERED

The review covers different areas of expertise including the genomic characterization of JCPyV strains detected in different body compartments (urine, plasma, and cerebrospinal fluid) of PML patients, viral mutations, molecular diagnostics, viral miRNAs, and disease.

EXPERT OPINION

The implementation of molecular biology techniques improved our understanding of JCPyV biology. Deep sequencing analysis of viral genomes revealed the presence of viral quasispecies in the cerebrospinal fluid of PML patients characterized by noncoding control region rearrangements and VP1 mutations. These neurotropic JCPyV variants present enhanced replication and an altered cell tropism that contribute to PML development. Monitoring these variants may be relevant for the identification of patients at risk of PML. Multiplex realtime PCR targeting both the LTAg and the archetype NCCR could be used to identify them. Failure to amplify NCCR should indicate the presence of a JCPyV prototype speeding up the diagnostic process.

Rapid cognitive decline in a patient with chronic lymphocytic leukaemia: a case report

Background

The use of monoclonal antibodies in various settings has been linked to the development of progressive multifocal leukoencephalopathy (PML). Whilst this association is well-described with agents such as rituximab and natalizumab, the literature describing the occurrence of PML with ofatumumab therapy (especially in a haematology setting) is sparse. This case aims to draw attention to the above association with a particular focus on the mechanisms by which B-cell-depleting therapy can precipitate PML during the treatment of haematological malignancy.

Case presentation

A 68-year-old Caucasian man presented with acute-on-subacute confusion and reduced mobility. He had a history of chronic lymphocytic leukaemia for which he had completed six cycles of ofatumumab and chlorambucil 2 months prior to presentation. Biochemistry, physical examination and imaging were unremarkable on admission. Subsequent neurological examination demonstrated diminished reflexes and an extensor right plantar, while magnetic resonance imaging (MRI) assessment revealed white matter hyperintensities in the frontal lobes with restricted diffusion surrounding these areas. Cerebrospinal fluid (CSF) analysis demonstrated normal cell counts and chemistry but detected John Cunningham virus (JCV) via polymerase chain reaction (PCR), with a quantitative value of 41,850 gEg/ml. CSF immunophenotyping excluded malignant processes. A diagnosis of PML was confirmed, and with the support of palliative care, the patient was discharged to a hospice for ongoing care with the family’s agreement.

Conclusion

PML remains a rare complication of ofatumumab treatment. Nevertheless, clinicians should maintain a certain level of suspicion for this risk, especially in the context of patients presenting with clinical syndromes of encephalopathy and focal neurologic deficits. Furthermore, research to better our understanding of the manifold links between B-cell function and JCV regulation could provide valuable information for use in the future prevention and treatment of PML.

Human Polyomavirus JCPyV and Its Role in Progressive Multifocal Leukoencephalopathy and Oncogenesis

The human neurotropic virus JCPyV, a member of the Polyomaviridiae family, is the opportunistic infectious agent of Progressive Multifocal Leukoencephalopathy (PML), a fatal disease seen in severe immunosuppressive conditions and, during the last decade, in patients undergoing immunotherapy. JCPyV is a ubiquitous pathogen with up to 85% of the adult population word-wide exhibiting antibodies against it. Early experiments demonstrated that direct inoculation of JCPyV into the brain of different species resulted in the development of brain tumors and other neuroectodermal-derived neoplasias. Later, several reports showed the detection of viral sequences in medulloblastomas and glial tumors, as well as expression of the viral protein T-Antigen. Few oncogenic viruses, however, have caused so much controversy regarding their role in the pathogenesis of brain tumors, but the discovery of new Polyomaviruses that cause Merkel cell carcinomas in humans and brain tumors in racoons, in addition to the role of JCPyV in colon cancer and multiple mechanistic studies have shed much needed light on the role of JCPyV in cancer. The pathways affected by the viral protein T-Antigen include cell cycle regulators, like p53 and pRb, and transcription factors that activate pro-proliferative genes, like c-Myc. In addition, infection with JCPyV causes chromosomal damage and T-Antigen inhibits homologous recombination, and activates anti-apoptotic proteins, such as Survivin. Here we review the different aspects of the biology and physiopathology of JCPyV.

Progressive multifocal leukoencephalopathy after allogeneic stem cell transplantation: Case report and review of the literature

Progressive multifocal leukoencephalopathy (PML) is a rare, yet typically fatal complication of allogeneic stem cell transplantation. It is caused by reactivation of the John Cunningham (JC) virus in an immunocompromised host. This report describes an unfortunate case of PML in a recipient of an allogeneic stem cell transplant for acute myelogenous leukemia. The JC virus was undetectable in the patient's cerebrospinal fluid by polymerase chain reaction (PCR); however, a positive diagnosis was made after a brain biopsy. This and other published cases demonstrate that recipients of allogeneic stem cells can develop PML. Moreover, early diagnosis of the disease is often difficult and, as demonstrated in this case, screening with PCR does not appear to have strong diagnostic significance. With no effective treatment presently available, restoration of immune function is the only intervention that can affect prognosis. Further prospective studies are needed to understand the pathophysiology and treatment of this disease.

B cells and progressive multifocal leukoencephalopathy: search for the missing link

Progressive multifocal leukoencephalopathy (PML) is a deadly demyelinating disease due to JC virus (JCV) replication in the brain. PML classically occurs in patients with severe immunodepression, and cases have recently been linked to therapeutic monoclonal antibodies such as natalizumab and also rituximab, which depletes B cells. B cells appear to play a complex role in the pathogenesis of PML. They may act as a viral reservoir and as a vector for viral dissemination in the central nervous system. Anti-JCV antibody responses appear to have a limited effect on JCV replication in the brain. However, accumulating evidence suggests that B cells may considerably influence T cell responses through their cytokine secretion. This immunomodulatory function of B cells may play an important role in the control of JCV infection and in the pathogenesis of PML, including rituximab-induced PML.

Treatment-related progressive multifocal leukoencephalopathy: current understanding and future steps

Progressive multifocal leukoencephalopathy (PML) is a rare demyelinating disorder of the brain caused by a ubiquitous polyomavirus, JC virus. PML is almost always associated with some underlying immunosuppression and acquired immune deficiency syndrome has been the most common predisposing disorder. Recently, different pharmacological agents have been demonstrated to increase the risk of PML. Therapies that predispose people to PML can be classified into three categories: therapies that uniquely increase the risk for the disorder, such as the monoclonal antibodies natalizumab and efalizumab; therapies that appear to increase the risk in individuals already at risk of PML due to pre-existing conditions, such as rituximab and mycophenolate mofetil; and therapies with a mechanism of action that might suggest a potential for increased PML risk and/or with which rare cases of PML have been observed. Unlike the latter two classes, therapeutic agents uniquely increasing the risk of PML are associated with a much greater prevalence of the disorder and a latent interval from the time of drug initiation to the development of PML. PML development with pharmacological agents has provided new insight into the pathogenesis of this devastating disorder. This review focuses on the risks of PML with multiple pharmacological agents, the proposed pathogenesis with these agents, and potential risk mitigation strategies.

JC virus antibody status underestimates infection rates

OBJECTIVE

JC virus (JCV) seropositivity is a risk factor for progressive multifocal leukoencephalopathy (PML) in patients on natalizumab. Accordingly, the JCV serological antibody test is of paramount importance in determining disease risk.

METHODS

We tested the accuracy of the JCV serum antibody test by comparing the results of JCV serology to JCV viruria and viremia in 67 patients enrolled in a single-center, retrospective cohort study. Bodily fluids (urine and blood) were assessed for JCV DNA by real time quantitative polymerase chain reaction 6 to 47 months (mean = 26.1 months) before JCV antibody testing. In 10 individuals, blood and urine samples were obtained on 2 separate occasions at 6-month intervals.

RESULTS

Forty (59.7%) of the 67 patients were JCV seropositive. Of 27 JCV seronegative patients, 10 (37%) had JCV viruria. Urine JCV DNA copy numbers were significantly higher in the seropositive group (mean log copy number = 5.93, range = 1.85-9.21) than the seronegative group (mean log copy number = 2.41, range = 1.85-5.43; p = 0.0026). Considering all body fluid test results, 50 (74.6%) of the 67 patients were previously infected with JCV.

INTERPRETATION

The false-negative rate of the JCV serology in this study was 37%; therefore, JCV serostatus does not appear to identify all patients infected with JCV. Thus, a negative JCV antibody result should not be conflated with absence of JCV infection. This discordance may be important in understanding JCV biology, risk for PML, and PML pathogenesis.

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 and newer biological agents

Progressive multifocal leukoencephalopathy (PML) is a rare demyelinating disease of the brain due to a polyoma virus, JC virus. Despite the ubiquity of this virus, PML is rare and almost always seen in association with an underlying immunosuppressive condition. In the last 30 years, AIDS has been the most common predisposing factor. The observation of PML attending the use of certain monoclonal antibody therapies and other pharmacological agents has raised concerns about the safety profile of these agents, but has also provided a window into the pathogenesis of PML. Certain agents, such as the monoclonal antibodies natalizumab, an α4β1 and α4β7 integrin inhibitor, and efalizumab, an antibody directed against CD11a, appear to uniquely predispose to PML. Prior to their introduction for multiple sclerosis and Crohn's disease with respect to natalizumab, and psoriasis with respect to efalizumab, PML had never been observed with these disorders. PML occurring with other agents that currently carry US FDA-mandated 'black-box' warnings, such as rituximab, an antibody directed to CD20, or mycophenolate mofetil, a drug that inhibits T- and B-cell proliferation, typically occur in the background of underlying disorders that have already been identified as risks for PML. This review will focus on the available data regarding the risk for PML with monoclonal antibodies and other drugs. A biologically plausible explanation for the increased risk of PML will be proposed, as well as potential strategies for mitigating disease risk.

Monoclonal antibodies and progressive multifocal leukoencephalopathy

Since their introduction, monoclonal antibodies have found an ever expanding role in the treatment of a wide number of disorders. However, the perturbation of the immune system that attends their use may also increase the risk for the development of disorders that arise in the setting of immunosuppressive conditions, such as, opportunistic infection and malignancy. In this paper, we address the association between some monoclonal antibodies and the development of a rare demyelinating disease of the brain, progressive multifocal leukoencephalopathy (PML). PML results from infection with a ubiquitous polyoma virus, JC virus, and typically occurs in the setting of impaired immunity, most commonly, AIDS. It was first recognized as a potential complication of monoclonal antibody therapy in patients with multiple sclerosis and Crohn disease being treated with natalizumab, an alpha 4 beta1 and alpha 4 beta 7 integrin inhibitor. Subsequently, efalizumab, a monoclonal antibody used in the treatment of psoriasis, was also demonstrated to be associated with PML. An increased risk has been suggested for rituximab, although most of the patients developing PML with that monoclonal antibody have been treated for B-cell disorders that predispose to the development of PML. Based on our current understanding of the biology of JC virus and the pathogenesis of PML, we propose an explanation for the increased risk for PML that is observed with natalizumab and certain other monoclonal antibodies.

Progressive Multifocal Leukoencephalopathy Complicating Waldenström's Macroglobulinaemia

Progressive multifocal leukoencephalopathy (PML) is a rare demyelinating neurological disorder caused by JC virus. Immunocompromised patients such as those with chronic lymphocytic leukemia, AIDS and following organ transplantation are at increased risk. We report a patient with PML complicating longstanding Waldenström's macroglobulinaemia. Although PML is a rare occurrence, the newer highly immunosuppressive treatment approaches for patients with lymphoproliferative disorders necessitate a high index of clinical suspicion. The diagnosis should be considered in patients with compatible clinical features who have received long-term immunosuppressive treatments recognized to impair cellular immunity.

Progressive multifocal leukoencephalopathy, a review and an extended report of five patients with different immune compromised states

Progressive multifocal leukoencephalopathy (PML) is an opportunistic infection of the brain caused by the JC-virus. Both a decreased cellular or humoral immune response can increase the susceptibility for JC-virus induced PML. Not only HIV infected people are at risk, a wide range of otherwise immune compromised patients are a potential target for this virus. This report of five PML patients shows the importance of a clinician's familiarity with this disease and it's presenting symptoms. The presenting symptoms of PML can sometimes mimic worsening of the underlying disease. Although different therapeutic strategies have been tried, the outcomes remain very poor. In this series, treatment with cidofovir appears not to be effective in treating PML, neither in HIV positive nor HIV negative patients. Experimental therapy with leflunomide, after tapering of the immunosuppressive medication, did change the natural course of PML in one patient.

Treatment options for AIDS patients with progressive multifocal leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is a demyelinating viral disease produced by the John Cunningham (JC) virus, which is ubiquitously distributed. Up to 80% of adults seroconvert to JC virus. Classically, PML is a life-threatening AIDS-defining disease of the CNS, usually occurring in severely immunocompromised individuals. Until now, and despite several therapeutic attempts, there is no specific treatment for PML. Soon after the widespread use of combination antiretroviral therapy (CART), several studies showed prolonged survival for patients with AIDS-associated PML who were treated with CART. The outcome of PML in patients receiving CART is unpredictable at disease onset. Prognostic markers are needed. The JC virus DNA detection in cerebrospinal fluid by nucleic acid amplification techniques and the CD4+ cell count are the most promising parameters. Higher levels of CD4+ cell counts were independently associated with an improved survival in different clinical observations. A summary of the main current knowledge about AIDS-related PML is presented. The most effective strategy is to optimize CART to completely suppress HIV-1 viral load and allow the best CD4+ T-cell immune recovery. Nowadays, AIDS-related PML is no longer an ultimately fatal disease. A substantial number of HIV-1-infected patients with this condition can improve with CART.

Progressive multifocal leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) was a rare disease until the advent of the HIV/AIDS pandemic. Recent interest in the disorder has been spurred by its appearance in patients treated with the monoclonal antibodies natalizumab and rituximab. Unless the accompanying underlying immune deficit can be reversed, PML typically progresses to death fairly rapidly. Treatment directed against the JC virus has been unhelpful, but an increased understanding of disease pathogenesis may result in effective therapeutic strategies.

No excess risk for colorectal cancer among subjects seropositive for the JC polyomavirus

The human polyomaviruses JC virus (JCV) and BK virus (BKV) are oncogenic in experimental systems and commonly infect humans. JCV DNA has been reported to be present in human colon mucosa and in colorectal cancers. To investigate whether the risk for colorectal cancer is associated with JCV or BKV infection, we performed a case-control study nested in the Janus biobank, a cohort of 330,000 healthy Norwegian subjects. A 30-year prospective follow-up using registry linkages identified 386 men with colorectal cancer who had baseline serum samples taken >3 months before diagnosis. Control subjects were matched for sex, age and date of blood sampling and county of residence. Seropositivity for JCV or BKV had high (97-100%) sensitivity for detection of viral DNA-positive subjects and discriminated the different polyomaviruses. Seropositivity was mostly stable over time in serial samples. The relative risk for colorectal cancer among JCV seropositive subjects was 0.9 (95% CI: 0.7-1.3) and the BKV-associated relative risk was 1.1 (95% CI: 0.8-1.5). Determining seropositivity using alternative cutoffs also found no evidence of excess risk. In summary, this prospective study found no association between JCV or BKV infections and excess risk for colorectal cancer.

Natalizumab treatment for multiple sclerosis: recommendations for patient selection and monitoring

Natalizumab is a new treatment option for patients with active relapsing-remitting multiple sclerosis. In phase III studies, natalizumab was highly effective and well tolerated; however, three cases of progressive multifocal leucoencephalopathy (PML) were identified (estimated incidence of one per 1000; 95% CI 0.2-2.8; mean treatment period 17.9 months). In this Review we summarise the current information on PML, the three confirmed cases of PML, and the results of an extensive safety assessment of all patients treated with natalizumab. On the basis of these reviews, we make recommendations for appropriate selection of candidates for natalizumab and pretreatment assessments. In addition, a three-step diagnostic and management algorithm was developed to monitor natalizumab-treated patients with multiple sclerosis for PML and other opportunistic infections. The algorithm includes strategies for clinical, MRI, and laboratory assessments. Maintaining clinical vigilance allows for early suspension of natalizumab in potential cases of PML, thereby increasing the opportunity for immune reconstitution, which may improve prognosis if PML is confirmed.

Frequency and phenotype of JC virus-specific CD8+ T lymphocytes in the peripheral blood of patients with progressive multifocal leukoencephalopathy

JC virus (JCV)-specific CD8+ cytotoxic T lymphocytes (CTL) are associated with a favorable outcome in patients with progressive multifocal leukoencephalopathy (PML) and cross-recognize the polyomavirus BK virus (BKV). We sought to determine the frequency and phenotype in fresh blood of CD8+ T cells specific for two A*0201-restricted JCV epitopes, VP1(p36) and VP1(p100), and assess their impact on JC and BK viremia and viruria in 15 healthy subjects, eight human immunodeficiency virus-positive (HIV+) individuals, and nine HIV+ patients with PML (HIV+ PML patients) classified as survivors. After magnetic pre-enrichment of CD8+ T cells, epitope-specific cells ranged from 0.001% to 0.022% [corrected] by tetramer staining, with no significant difference among the three study groups. By use of seven-color flow cytometry, there was no predominant differentiation phenotype subset among JCV-specific CD8+ T cells in healthy individuals, HIV+ subjects, or HIV+ PML patients. However, in one HIV+ PML patient studied in the acute phase, there was a majority of activated effector memory cells. BKV DNA was undetectable in all blood samples by quantitative PCR, while a low JC viral load was found in the blood of only one HIV+ and two HIV+ PML patients. JCV and BKV DNA were detected in 33.3% and 13.3% of all urine samples, respectively, independent of the presence of JCV-specific CTL. The detection of JCV DNA in the urine was associated with the presence of a JCV VP1(p100) CTL response. Immunotherapies aiming at increasing the cellular immune response against JCV may be valuable in the treatment of HIV+ individuals with PML.

Two cases of progressive multifocal leukoencephalopathy after allogeneic hematopoietic cell transplantation and a review of the literature

Progressive multifocal leukoencephalopathy (PML) is a rare subacute demyelinating disorder of the central nervous system (CNS) caused by the DNA JC human polyomavirus. In immunocompromised hosts, PML is caused by reactivation of a latent infection rather than de novo primary exposure. PML in the setting of hematopoietic cell transplantation (HCT) is exceedingly rare. PML should be considered in the differential diagnosis of HCT recipients, autologous or allogeneic, presenting with worsening of neurological symptoms, especially associated with post-transplant neurodegenerative findings. Although DNA polymerase chain reaction (PCR) of the cerebrospinal fluid (CSF) has emerged as a promising tool for detecting JC virus, a negative result does not rule out PML. Brain biopsy remains the most reliable and accurate method for diagnosing JC virus-associated PML. Presently, there is no universally effective antiviral therapy against JC virus and outcome is fatal in the majority of cases. We hereby describe two cases of PML developing after allogeneic HCT and provide a comprehensive review of the literature.

Natalizumab and progressive multifocal leucoencephalopathy

Current data suggest that as many as 1 in 1000 treated individuals may develop progressive multifocal leucoencephalopathy (PML) in concert with the use of natalizumab. Natalizumab was withdrawn in early 2005. The present paper provides a comprehensive description of PML and reviews the role of natalizumab in the pathogenesis of PML. It is likely that use of drugs which cause specific perturbations of the immune system will be accompanied by similar rare infections. Thus researchers should be on the alert when using such agents in clinical trials.

Paraneoplastic syndromes affecting the nervous system

The paraneoplastic neurologic disorders (PND) are a diverse group of diseases characterized by the presence of neurologic dysfunction in the setting of a remote cancer. PND can affect almost any part of the nervous system, and are most commonly associated with lung cancer (small cell) and gynecologic tumors. Laboratory studies have demonstrated that an autoimmune response links the neurologic disorder and the cancer, and established a model whereby the cancer is believed to initiate the syndrome by expressing a protein antigen normally expressed in the nervous system, leading to anti-tumor immune response followed by autoimmune neurologic symptoms. We review the currently known PND and their pathogenesis.

Progressive multifocal leukoencephalopathy: lessons from AIDS and natalizumab

The dramatic increase in the incidence of progressive multifocal leukoencephalopathy (PML) that occurred as a consequence of the AIDS pandemic and the recent association of PML with the administration of natalizumab, a monoclonal antibody to alpha4 integrin that blocks inflammatory cell entry into the brain, has stimulated a great deal of interest in this previously obscure viral demyelinating disease. The etiology of this disorder is JC virus (JCV), a polyoma virus, observed in 80% of the population worldwide. Seroepidemiological studies indicate that infection with this virus typically occurs before the age of 20 years. No primary illness owing to JCV infection has been recognized and the means of spread from person to person remains obscure. Following infection, the virus becomes latent in bone marrow, spleen, tonsils and other tissues. Periodically the virus reactivates during which time it can be demonstrated in circulating peripheral lymphocytes. The latter is significantly more commonly observed in immunosuppressed populations than that in normal subjects. Despite the large pool of people infected with JCV, PML remains a relatively rare disease. It is seldom observed in the absence of an underlying predisposing illness, typically one that results in impaired cellular immunity. A variety of factors are likely responsible for the unique increase in frequency of PML in HIV infection relative to other underling immunosuppressive disorders. Preliminary data suggests that natalizumab appears to distinctively predispose recipients to PML relative to other infectious complications. Studies in these populations will be invaluable in understanding the mechanisms of disease pathogenesis.

Rôle de l’immunité dans le développement de la leucoencéphalopathie multifocale progressive

INTRODUCTION

Progressive multifocal leukoencephalopathy (PML) caused by JC virus (JCV) mostly occurs in different conditions of impaired cellular immunity like acquired immunodeficiency syndrome (AIDS) and rarely when humoral immunity is involved. PML remains unusual although there is a high prevalence of JCV among the population and immunosuppression is not rare because of chemotherapies.

METHODS

We present two groups of patients: first, we studied reports of three patients suffering from lymphoma type B who developed a PML, proved by cerebral biopsy. The second group included six HIV-infected patients who developed a PML. No biopsy was made but MRI and the physical examination suggested strong arguments for the diagnosis.

RESULTS

In the first group, PML was furthered by humoral immunosuppression (rate of immunoglobulin G under 4 g/l). Average survival was five months. In the second group, HIV-infected patients had a survival range from 2 to 58 months after the first PML symptoms and one of them is still alive.

CONCLUSION

Humoral immunosuppression in lymphoma can contribute to the development of PML. PML prognosis is often severe but prolonged survivals were described. So it is necessary to restore a sufficient immunity level. But immunity failure may be insufficient to lead to PML. In the case of lymphomas, the role of malignant lymphocytes in multiplication and mutation of JCV might be an interesting pathophysiological hypothesis.

AIDS-associated progressive multifocal leukoencephalopathy : current management strategies

Progressive multifocal leukoencephalopathy (PML) is a rare, opportunistic infection of the CNS by the ubiquitous JC virus (JCV). PML is only seen in the context of severe and prolonged immunosuppression, a phenomenon now frequently encountered since the AIDS pandemic. PML is characterised by progressive lysis of oligodendrocytes with demyelination. A rapid clinical course ensues with focal neurological deficits and a median time to death of 3.5 months without treatment. Prior to highly active antiretroviral therapy (HAART), there was no effective therapy. Since the advent of HAART, the prognosis for PML has much improved; however, a significant number of patients appear unresponsive to antiretrovirals and some worsen because of the development of immune reconstitution disease. A better understanding of the biology of JCV and its interactions with host cells is leading to new anti-JCV-specific agents that await evaluation in randomised, controlled trials. Improved diagnostic tools and the possibility of immunotherapy and gene therapy are further advancing the field.

Progressive multifocal leukoencephalopathy in transplant recipients

Progressive multifocal leukoencephalopathy (PML) is a demyelinating infection caused by the JC virus. It is an emerging disease in transplant recipients; however, it remains poorly defined. Twenty-four cases of PML reported in the literature in transplant recipients were reviewed. Of the 24 cases, nine occurred in renal, six in bone marrow, four in liver, three in heart and two in lung transplant recipients. Median time to onset was 17 months; 71% occurred within 24 months of transplantation. PML tended to occur later in the kidney recipients (P=0.04). Seventy-five percent had subacute presentation; hemiparesis (50%), apathy (46%) and confusion (38%) were the most frequently presented features. Treatment included reduction of immunosuppression and chemotherapy, mainly cidofovir. Death occurred within 2.5 months of the onset of symptoms in 17 patients (71%). PML is a unique entity that should be considered in any transplant recipient with neurological symptoms. The outcome is usually fatal, although regression has been reported.

Kinetics of myeloid and lymphocyte recovery and infectious complications after unrelated umbilical cord blood versus HLA-matched unrelated donor allogeneic transplantation in adults

Sources for allogeneic stem cells for patients with haematological disorders lacking a histocompatible sibling donor include matched unrelated donor (MUD) and umbilical cord blood (UCB). A total of 51 patients with haematological disorders, treated with myeloablation and transplantation with either unrelated human leucocyte antigen (HLA) partially matched UCB (28 patients) or HLA-matched MUD grafts (23 patients) during 1997-2003, were evaluated for life-threatening infections, haematological reconstitution, graft versus host disease, relapse and event-free survival (EFS). The median duration of neutropenia after transplantation was longer (29 d vs. 14 d) in the UCB group. The probability of donor-derived neutrophil engraftment by day 42 was 0.86 [95% confidence interval (CI) 0.71-1.0] in UCB recipients versus 0.96 (95% CI 0.87-1.0) in MUD recipients surviving >28 d. Overall infection rates were higher in UCB recipients, particularly at the early time points (before day +50) after transplantation. Graft failure occurred in five UCB recipients and two MUD recipients and was associated with the occurrence of bacteraemia during neutropenia. The EFS at 3-year follow-up was 0.25 in UCB and 0.35 in MUD recipients. UCB transplantation in adults is associated with delayed neutrophil and lymphocyte recovery compared with MUD grafting, and higher rates of bacteraemia at early time points after transplantation.

Clinical epidemiology and survival of progressive multifocal leukoencephalopathy in the era of highly active antiretroviral therapy: data from the Italian Registry Investigative Neuro AIDS (IRINA)

Human immunodeficiency virus (HIV)-associated progressive multifocal leukoencephalopathy (PML) remains a relevant clinical problem even in the era of highly active antiretroviral therapy (HAART). Aims of the study were to analyze clinical and treatment-related features and the survival probability of PML patients observed within the Italian Registry Investigative Neuro AIDS (IRINA) during a 29-month period of HAART. Intravenous drug use, the presence of focal signs, and the involvement of white matter at neuroradiology increased the risk of having PML. A reduced probability of PML was observed when meningeal signs were reported. Patients starting HAART at PML diagnosis and previously naïve for antiretrovirals showed significantly higher 1-year probability of survival (.58), compared to those continuing HAART (.24), or never receiving HAART (.00). Higher CD4 cell count were associated with a higher survival probability (.45). At multivariate analysis, a younger age, higher CD4, starting HAART at PML diagnosis, the absence of previous acquired immunodeficiency syndrome (AIDS)-defining events, and the absence of a severe neurologic impairment were all associated with a reduced hazard of death. The use of cidofovir showed a trend towards a reduced risk of death.

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.