Development Of Progressive Multifocal Leukoencephalopathy Research Articles

Association Between BKPyV Serotype I Antibody Level and Natalizumab-Associated Progressive Multifocal Leukoencephalopathy.

To determine the association between BK polyomavirus (BKPyV) types 1 and 4 capsid antibody and natalizumab-associated progressive multifocal leukoencephalopathy (PML) in patients with multiple sclerosis (MS), serum samples were obtained from 10 natalizumab-associated PML cases and 130 control MS patients treated with natalizumab, and 82 control MS patients never exposed to natalizumab. In a sex- and age-adjusted regression model, BKPyV serotype 1 antibody levels were significantly higher in natalizumab-treated controls (p = 0.009) compared with cases, and were higher in controls never treated with natalizumab compared with cases, but the difference did not reach statistical significance (p = 0.158). There was no association between BKPyV serotype 4 antibody and PML. We hypothesize that a robust immune response to BKPyV may be protective against the development of PML.

John Cunningham virus conversion in relation to natalizumab concentration in multiple sclerosis patients.

Infection with the John Cunningham virus (JCV) is required for the development of progressive multifocal leukoencephalopathy, the feared complication of natalizumab treatment in multiple sclerosis patients. The JCV seroconversion rate seems higher in natalizumab treated patients than in the normal population, with an unknown cause. Natalizumab concentration was correlated to JCV antibody status and seroconversion in a large cohort of multiple sclerosis patients. One hundred and thirty-five patients were included. No correlation was found between natalizumab concentration and JCV status, JCV seroconversion or JCV index. Higher natalizumab concentrations do not explain the increased JCV seroconversion rate in natalizumab treated patients.

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

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

Progressive multifocal leukoencephalopathy and rheumatoid arthritis treatments

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system due to reactivation of the JC virus (JCV). PML is extremely uncommon despite the high prevalence of the virus in the general population. No specific treatment is available, and the prognosis is bleak. The diagnosis is based on brain imaging findings, detection of the JCV genome in cerebrospinal fluid samples and, in some cases, histological studies of the brain lesions. The pathophysiological mechanisms that drive the development of PML are incompletely understood. However, a consistent feature is the presence of a predisposing factor, most notably immunosuppression. The risk of developing PML varies with the underlying disease (e.g., HIV infection or autoimmune disease) and with the drugs used to treat them. Biologics have been ranked according to the risk of PML during their use. Natalizumab, a monoclonal antibody given to treat multiple sclerosis, is among the drugs associated with a high risk of PML. Patients given natalizumab are now closely monitored based on anti-JCV antibody titers and index values. In rheumatology, the expanding use of biologics has led to an increase in cases of PML, with rituximab being associated with the highest risk. Given the absence of specific recommendations, exhaustive registries and postmarketing observational studies are urgently needed to gauge the risk of PML according to the underlying disease and drug treatments, with the goal of defining optimal monitoring protocols.

Natalizumab treatment of multiple sclerosis: new insights.

Natalizumab is a monoclonal antibody directed against the α4 chain of the very late activating antigen 4 and α4β7 integrins, present on the leukocytes surface, used as monotherapy for the treatment of relapsing-remitting multiple sclerosis. It substantially reduces relapse rate and the accumulation of disability, but its use is associated with a very adverse event, that is the development of progressive multifocal leukoencephalopathy, a fatal demyelinating disease of the CNS, due to the lytic replication of the human polyomavirus JC. The main focus of the review is to describe the newest insights on natalizumab, its current use in the clinical practice, the natalizumab-treated patients' management and the risk stratification related to the progressive multifocal leukoencephalopathy development.

Drug-induced progressive multifocal leukoencephalopathy: a case/noncase study in the French pharmacovigilance database.

Progressive multifocal leukoencephalopathy (PML) is an often fatal demyelinating disease of the central nervous system. As effective treatment is unavailable, identification of all drugs that could be associated with PML is essential. The objective of this study was to investigate the putative association of reports of PML and drugs. We used the case/noncase method in the French PharmacoVigilance database (FPVD). Cases were reports of PML in the FPVD between January 2008 and December 2015. Noncases were all other reports during the same period. To assess the association between PML and drug intake, we calculated an adverse drug report odds ratio (ROR) with its 95% confidence interval. We have studied the delay of onset of PML for each drug concerned. Among the 101 cases of PML, 39 drugs were mentioned as suspect. The main therapeutic classes suspected with significant ROR were antineoplastic agents (n = 85), immunosuppressants (n = 67), and corticosteroids. A latent interval from the time of drug initiation to the development of PML is established: the median time to onset was 365 days (123-1095 days). The onset of PML is highly variable and differs among drug classes [from 1 to 96 months (IQR: 39.0-126)]. An association between PML and some immunosuppressant drugs was found as expected, but also with antineoplastic agents and glucocorticoids. An important delay of PML onset after stopping treatment is suspected and should alert prescribers. Prescribers but also patients should be informed about the potential associations with all these drugs. Monitoring could be necessary for many drugs to early detect PML.

Predictors of Response to Multiple Sclerosis Therapeutics in Individual Patients.

Multiple sclerosis (MS) is a chronic inflammatory disorder of the central nervous system. Several disease-modifying therapies have been shown to ameliorate the disease course; however, the individual treatment response and the occurrence of adverse events remain highly unpredictable. In the last 2 decades, a multitude of studies have aimed to identify biomarkers that enable treatment allocation in the individual patient or subgroup of patients with regard to treatment efficacy and safety profile. Following a PubMed database search, we provide an overview on what is presently known about body fluid markers for the prediction of response to the currently approved MS therapeutics. We also discuss the potential use of biomarkers with regard to drug-induced adverse events. To date, only a few molecules have been introduced in clinical routine: anti-drug antibodies against interferon (IFN)-β and natalizumab that are associated with abolished drug levels and treatment failure; anti-JC virus (JCV) antibody index that allows risk stratification for the development of progressive multifocal leukoencephalopathy (PML), a rare but severe adverse event during natalizumab treatment; and serostatus of varicella zoster virus as screening examination prior to fingolimod therapy to prevent the infection. A few candidate biomarkers still need closer examination, such as type I IFN signature and T-helper cell (Th)-17 reactivity for prediction of IFN-β treatment response, L-selectin expression for prediction of natalizumab-associated PML, interleukin (IL)-21 levels for prediction of secondary autoimmunity after exposure to alemtuzumab, lymphocyte count with regard to PML risk while receiving dimethyl fumarate or N-terminal-pro-B-type natriuretic peptide (NT-proBNP) for monitoring of cardiac side effects during mitoxantrone therapy.

Polyomaviruses.

Over the last 10 years, the number of identified polyomaviruses has grown to more than 35 subtypes, including 13 in humans. The polyomaviruses have similar genetic makeup, including genes that encode viral capsid proteins VP1, 2, and 3 and large and small T region proteins. The T proteins play a role in viral replication and have been implicated in viral chromosomal integration and possible dysregulation of growth factor genes. In humans, the Merkel cell polyomavirus has been shown to be highly associated with integration and the development of Merkel cell cancers. The first two human polyomaviruses discovered, BKPyV and JCPyV, are the causative agents for transplant-related kidney disease, BK commonly and JC rarely. JC has also been strongly associated with the development of progressive multifocal leukoencephalopathy (PML), a rare but serious infection in untreated HIV-1-infected individuals and in other immunosuppressed patients including those treated with monoclonal antibody therapies for autoimmune diseases systemic lupus erythematosus, rheumatoid arthritis, or multiple sclerosis. The trichodysplasia spinulosa-associated polyomavirus (TSAPyV) may be the causative agent of the rare skin disease trichodysplasia spinulosa. The remaining nine polyomaviruses have not been strongly associated with clinical disease to date. Antiviral therapies for these infections are under development. Antibodies specific for each of the 13 human polyomaviruses have been identified in a high percentage of normal individuals, indicating a high rate of exposure to each of the polyomaviruses in the human population. PCR methods are now available for detection of these viruses in a variety of clinical samples.

Host cell virus entry mechanisms enhance anti-JCV-antibody switch in natalizumab-treated multiple sclerosis patients.

Estimating the individual risk for the development of progressive multifocal leukoencephalopathy (PML) in anti-John Cunningham virus (JCV) antibody-negative patients with multiple sclerosis (MS) treated with natalizumab is a major challenge. A serological conversion occurring under treatment from anti-JCV antibody-negative to positive status may significantly increase this risk. We investigated changes in peripheral blood cells' gene expression induced by natalizumab treatment in anti-JCV antibody-negative MS patients and tested blood transcriptional profile that characterizes patients predisposed to antibody switch under natalizumab treatment. After 3years of natalizumab treatment, 24.6% of anti-JCV antibody-negative MS patients switched to become anti-JCV antibody-positive (JCV switchers). Natalizumab induced 946 and 1186 significantly differentiating genes in JCV switchers and non-switchers, respectively. In JCV switchers, the signature was enriched by over-expression of genes associated with the first stages of viral entry to host cells including macropinocytosis (p = 1.82E-06), virus entry via endocytosis (p = 1.60E-06), clathrin-mediated endocytosis (p = 1.13E-04), and caveolar-mediated endocytosis (p = 4.50E-04) pathways. Further analysis to identify pre-existing transcriptional differences that characterize future JCV switchers prior to treatment initiation also demonstrated a transcriptional signature enriched by similar viral entry mechanisms. These findings, verified in an additional independent cohort of natalizumab-treated patients, could lead to future identification of patients that remain anti-JCV antibody-negative thus allowing safe continuation of treatment, as well as the development of future targeted therapeutic interventions to reduce the risk of PML.

The TOUCH program and natalizumab: Fundamental flaw in patient protection.

Many drugs have been approved by the Food and Drug Administration (FDA) since 1993 for treatment of relapsing forms of multiple sclerosis (MS). One such drug is natalizumab (Tysabri, Biogen Idec and Elan pharmaceuticals) which has enjoyed great success in the management of MS since its re-introduction in 2006. One of the complications of using natalizumab is the risk of development of progressive multifocal leukoencephalopathy (PML). To mitigate the risk of PML development, Biogen Idec initiated the TOUCH program - this strategy helps monitor the disease. Clinical vigilance remains key in the early diagnosis of PML but serological testing for the John Cunningham Virus Antibody (JCV) helps with risk stratification of PML. However, some physicians do not test for the JCV Ab and since they are not required to send such data to the company or inform the patient, one red flag for suspicion of PML is lost particularly if the patient is asymptomatic. This undercuts the premise of the TOUCH program. In an ideal world, reporting JCV Ab status should be made mandatory since that ensures a basic tenet of the program is met - to identify patients at increased risk of developing PML and make appropriate recommendations based on that finding. Lack of requirement of reporting of this vital finding opens the door for uncertainty in assessment of risk PML development and everyone remains in the dark till it may be too late. This is unacceptable when the company created the TOUCH program specifically with intent to track PML risk in patients on natalizumab. It makes no scientific sense to let the drug be used without setting stringent criteria given the possibility of PML development.

Natalizumab-induced POU2AF1/Spi-B upregulation: A possible route for PML development.

Objectives:To assess messenger RNA (mRNA) expression of POU2AF1 and Spi-B and their potential regulatory microRNAs (miRNAs) in natalizumab-treated patients with multiple sclerosis and in therapy-associated progressive multifocal leukoencephalopathy (PML).Methods:Expression of POU2AF1/Spi-B was analyzed by using real-time reverse transcription PCR assays on isolated B/CD8+ T lymphocytes and peripheral blood mononuclear cells (PBMCs) from cohorts of untreated and natalizumab-treated patients with and without PML. Longitudinal expression analysis was performed on CD4+, CD8+ T and B cells from 14 patients who interrupted natalizumab therapy for 8 weeks. The miRNA profiling was conducted in PBMCs from 5 untreated and 5 natalizumab-treated patients using low-density arrays followed by validation with single miRNAs assays in untreated and natalizumab-treated patients.Results:POU2AF1 and Spi-B mRNAs were upregulated in B and CD8+ T cells from natalizumab-treated patients, which was validated in PBMCs from different cohorts of natalizumab-treated patients with and without PML, with a noteworthy higher expression of Spi-B in patients with PML. In contrast, downregulation of POU2AF1/Spi-B expression was measured in B and CD8+ T cells after natalizumab discontinuation. Seventeen differentially expressed miRNAs including miR-10b, a regulator of POU2AF1 mRNA, were identified in long-term natalizumab-treated patients compared with untreated ones.Conclusions:Upregulation of POU2AF1 and Spi-B, known transactivators of the JC virus, the causative agent for PML, and its association with occurrence of PML in natalizumab-treated patients, corroborates POU2AF1/Spi-B as potential biomarkers for PML risk, which merits further evaluation.

The TOUCH program and natalizumab: Fundamental flaw in patient protection

Many drugs have been approved by the Food and Drug Administration (FDA) since 1993 for treatment of relapsing forms of multiple sclerosis (MS). One such drug is natalizumab (Tysabri, Biogen Idec and Elan pharmaceuticals) which has enjoyed great success in the management of MS since its re-introduction in 2006. One of the complications of using natalizumab is the risk of development of progressive multifocal leukoencephalopathy (PML). To mitigate the risk of PML development, Biogen Idec initiated the TOUCH program – this strategy helps monitor the disease. Clinical vigilance remains key in the early diagnosis of PML but serological testing for the John Cunningham Virus Antibody (JCV) helps with risk stratification of PML. However, some physicians do not test for the JCV Ab and since they are not required to send such data to the company or inform the patient, one red flag for suspicion of PML is lost particularly if the patient is asymptomatic. This undercuts the premise of the TOUCH program. In an ideal world, reporting JCV Ab status should be made mandatory since that ensures a basic tenet of the program is met – to identify patients at increased risk of developing PML and make appropriate recommendations based on that finding. Lack of requirement of reporting of this vital finding opens the door for uncertainty in assessment of risk PML development and everyone remains in the dark till it may be too late. This is unacceptable when the company created the TOUCH program specifically with intent to track PML risk in patients on natalizumab. It makes no scientific sense to let the drug be used without setting stringent criteria given the possibility of PML development.

The TOUCH program and natalizumab: Fundamental flaw in patient protection

Many drugs have been approved by the Food and Drug Administration (FDA) since 1993 for treatment of relapsing forms of multiple sclerosis (MS). One such drug is natalizumab (Tysabri, Biogen Idec and Elan pharmaceuticals) which has enjoyed great success in the management of MS since its re-introduction in 2006. One of the complications of using natalizumab is the risk of development of progressive multifocal leukoencephalopathy (PML). To mitigate the risk of PML development, Biogen Idec initiated the TOUCH program – this strategy helps monitor the disease. Clinical vigilance remains key in the early diagnosis of PML but serological testing for the John Cunningham Virus Antibody (JCV) helps with risk stratification of PML. However, some physicians do not test for the JCV Ab and since they are not required to send such data to the company or inform the patient, one red flag for suspicion of PML is lost particularly if the patient is asymptomatic. This undercuts the premise of the TOUCH program. In an ideal world, reporting JCV Ab status should be made mandatory since that ensures a basic tenet of the program is met – to identify patients at increased risk of developing PML and make appropriate recommendations based on that finding. Lack of requirement of reporting of this vital finding opens the door for uncertainty in assessment of risk PML development and everyone remains in the dark till it may be too late. This is unacceptable when the company created the TOUCH program specifically with intent to track PML risk in patients on natalizumab. It makes no scientific sense to let the drug be used without setting stringent criteria given the possibility of PML development.

The TOUCH program and natalizumab: Fundamental flaw in patient protection

Many drugs have been approved by the Food and Drug Administration (FDA) since 1993 for treatment of relapsing forms of multiple sclerosis (MS). One such drug is natalizumab (Tysabri, Biogen Idec and Elan pharmaceuticals) which has enjoyed great success in the management of MS since its re-introduction in 2006. One of the complications of using natalizumab is the risk of development of progressive multifocal leukoencephalopathy (PML). To mitigate the risk of PML development, Biogen Idec initiated the TOUCH program - this strategy helps monitor the disease. Clinical vigilance is remains key in the early diagnosis of PML but serological testing for the John Cunningham Virus Antibody (JCV) helps with risk stratification of PML. However, some physicians do not test for the JCV Ab and since they are not required to send such data to the company or inform the patient, one red flag for suspicion of PML is lost particularly if the patient is asymptomatic. This undercuts the premise of the TOUCH program. In an ideal world, reporting JCV Ab status should be made mandatory since that ensures a basic tenet of the program is met - to identify patients at increased risk of developing PML and make appropriate recommendations based on that finding. Lack of requirement of reporting of this vital finding opens the door for uncertainty in assessment of risk PML development and everyone remains in the dark till it may be too late. This is unacceptable when the company created the TOUCH program specifically with intent to track PML risk in patients on natalizumab. It makes no scientific sense to let the drug be used without setting stringent criteria given the possibility of PML development.

Monitoring the John Cunningham virus throughout natalizumab treatment in multiple sclerosis patients.

Progressive multifocal leukoencephalopathy (PML) cases have arisen amongst multiple sclerosis patients treated with natalizumab. Our objective was to gain a better understanding of the mechanisms that underlie the John Cunningham virus (JCV) infection which causes PML. A study was made of (i) the quarterly JCV DNA levels in peripheral blood mononuclear cells (PBMCs), serum and urine samples in 100 multiple sclerosis patients during their natalizumab treatment (3-39 months), (ii) the association between human leukocyte antigen (HLA) class II and the previous viral detection and (iii) the identification of the JCV variants in those patients suspected of having PML. (i) JCV DNA in PBMCs and/or serum was detected in 23% of our cohort. Patients with an intermittent JCV excretion in urine had a significant increase of the viral load and prevalence in this compartment during natalizumab treatment. (ii) The frequency of the DRB1*07/DQA1*02:01/DQB1*02:02 haplotype tended to be higher in patients with detectable versus undetectable JCV DNA in PBMCs (P(corrected) = 0.108). (iii) The variants in PBMCs and serum of the non-PML patient matched the archetype. In the patient with non-fatal PML, the archetype and the same neurotropic variant in PBMCs, serum and cerebrospinal fluid was identified at the time PML was diagnosed, whereas in the patient with a worse PML prognosis, four neurotropic variants in the three previous compartments were found by the PML diagnosis. The detection of the neurotropic variant in blood during natalizumab treatment could be critical in the prevention of the development of severe PML, since this variant appears simultaneously with the clinical symptoms of PML and mutates quickly.

BK virus capsid antibodies are associated with protection against subsequent development of PML in HIV-infected patients

Progressive multifocal leukoencephalopathy (PML) is caused by JC polyomavirus (JCPyV). Because a reciprocal relationship has been described between antibody levels to JCPyV and BK polyomavirus (BKPyV), we performed a nested case control study with pre-diagnostic serum samples from HIV infected subjects to examine the relationship between BKPyV capsid antibodies and the risk of PML. Serum samples collected 0.5–2 years before PML diagnosis from 25 cases (66 samples) and 80 matched controls (204 samples) were tested in ELISA for JCPyV, BKPyV type 1 and type 4 capsid antibodies. High levels of BKPyV 1 and 4 antibodies were associated with a lower risk of PML (BKPyV 1 OR, 0.56, 95% CI, 0.35–0.89; BKPyV 4 OR, 0.40, 95% CI, 0.24–0.0.67). Our study demonstrates that antibodies to BKPyV capsids are an immunological marker of protection against development of PML. Further studies are needed to define the mechanism.

Neuropathology of Natalizumab-Associated Progressive Multifocal Leukoencephalopathy

The pathological findings of natalizumab-associated progressive multifocal leukoencephalopathy (PML) are reviewed. In addition to the classical pathology of PML including the presence of enlarged abnormal astrocytes, intranuclear inclusions mainly found within large swollen oligodendrocytes and abundant myelin-laden macrophages/microglia, massive perivascular and parenchymal mononuclear cell infiltration was observed. The latter pathologic picture is that of immune reconstitution inflammatory syndrome (IRIS), and most of these infiltrating cells are CD8-positive T cells. Because IRIS inevitably occurs after the cessation of natalizumab therapy due to the development of PML and subsequent plasma exchange, most of the published pathologic pictures of natalizumab-associated PML patients were a mixture of PML and PML-IRIS. PML-IRIS is also characterized by fewer oligodendroglial viral inclusions and fewer cells that are immunoreactive against anti-JCV antibodies. These findings suggest the effective removal of JCV after the return of normal immune-surveillance in the central nervous system, but clinicians should be aware that JCV elimination is not complete under the IRIS condition, and the immunosuppressive therapy against IRIS should be carefully performed. Mononuclear cell infiltration in natalizumab-associated PML-IRIS patients was much more prominent than that in HIV-associated PML-IRIS patients, reflecting the retained, even enhanced, systemic immunities in patients treated by natalizumab.

The JCPYV DNA load inversely correlates with the viral microrna expression in blood and cerebrospinal fluid of patients at risk of PML

BackgroundIn light of their regulatory role, changes in the expression of Polyomavirus JC (JCPyV) microRNAs may be relevant for virus reactivation and the development of progressive multifocal leukoencephalopathy (PML). ObjectivesTo investigate the presence of JCPyV-DNA and JCPyV microRNA expression in clinical specimens of patients at risk for PML. Study designThe JCPyV-DNA and microRNA status was assessed in peripheral blood mononuclear cells (PBMCs) and plasma from 100 HIV patients, in serum and cerebrospinal fluid (CSF) from 14 HIV PML patients and in PBMCs and plasma from 50 healthy controls using Multiplex real-time PCR and JCPyV miRNA-J1-3p and −5p stem-loop RT-PCR. The JCPyV-DNA microRNA-expressing region was also sequenced. ResultsA positive JCPyV-DNA status was more prevalent in HIV patients (67%, 67/100) compared to healthy controls (18%, 9/50). Among these, 46% and 42% of the HIV patients and 18% and 0% of the healthy controls were positive based on PBMC and plasma determinations, respectively. PBMC JCPyV microRNA positivity was observed in 22 out of 46 (48%) JCPyV+ HIV patients and in 3 out of 9 (33%) JCPyV+ healthy controls. Moreover, JCPyV microRNAs in exosomes were found in 6 out of 100 (6%) HIV plasma samples, in 12 out of 50 (24%) healthy samples, in 6 out of 14 (43%) serum samples, and in 3 out of 5 (60%) HIV PML CSF samples. Of note, the JCPyV-DNA load was inversely correlated with expression of the viral microRNA. The JCPyV microRNA genomic expression region showed a different combination of three mutations. ConclusionsThe low levels of JCPyV microRNA expression in HIV patients with high JCPyV-DNA prevalence observed in this study highlight the potential clinical relevance of JCPyV microRNAs in PML risk assessment.

Is there a (host) genetic predisposition to progressive multifocal leukoencephalopathy?

Progressive multifocal leukoencephalopathy (PML) has been described in association with a variety of predisposing risk factors, including HIV/AIDS, lymphoproliferative disorders and, most recently, treatment with a range of biologics, most notably natalizumab in multiple sclerosis (MS) (1). However, while these underlying disorders appear to be (usually) necessary, they are not sufficient to predict the development of PML, since only a small fraction of such individuals will succumb, raising the question of whether host genetic factors must also play a role. Evidence is mounting that this is, indeed, the case but more work needs to be done to fully delineate these underlying genetic factors. Finally, while it is possible that an underlying genetic susceptibility for PML in general will be uncovered in the future, the current evidence argues for a collection of multiple, individually rare underlying susceptibilities (with one predominant single genetic susceptibility in each individual), as described in this review.

JC polyomavirus reactivation is common following allogeneic stem cell transplantation and its preemptive detection may prevent lethal complications.

Extended application of allogeneic stem cell transplantation (alloSCT) is expected to increase the frequency of JC polyomavirus (JCPyV)-related progressive multifocal leukoencephalopathy (PML). The aim of this study was to assess frequency, risk factors and course of JCPyV reactivation in allografted hematology patients. This retrospective study included consecutive adult patients, treated with alloSCT between January 2008 and December 2011. Quantitative JCPyV-PCR analysis was performed on whole blood DNA samples, originally drawn for cytomegalovirus detection since transplant date. The study included 164 patients diagnosed with hematological malignancies. Patients received reduced-intensity conditioning (n=74) or myeloablative conditioning (n=90), followed by alloSCT. Twenty patients developed transient and 20 had persistent JCPyV reactivation. Two of the patients with persistent reactivation showed a gradual increase in JCPyV levels, preceding PML development by 96 and 127 days. Cessation of immunosuppression resulted in complete resolution of neurological symptoms in one patient, while the other died of PML. Seventy percent of the 'persistently reactivating' patients died. Multivariate analysis confirmed age to be the only significant predictive factor for JCPyV reactivation. In conclusion, JCPyV reactivation occurs in a quarter of allografted patients. Preemptive detection of JCPyV reactivation in high-risk subjects and early discontinuation of immunosuppressive therapy may prevent development of lethal PML.