Chen S. Tan

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

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

Asymptomatic Reactivation of JC Virus in Patients Treated with Natalizumab

BACKGROUND Progressive multifocal leukoencephalopathy (PML) occurs in a fraction of patients with multiple sclerosis who were treated with natalizumab. Most adults who are infected with the JC virus, the etiologic agent in PML, do not have symptoms. We sought to determine whether exposure to natalizumab causes subclinical reactivation and neurotropic transformation of JC virus. METHODS We followed 19 consecutive patients with multiple sclerosis who were treated with natalizumab over an 18-month period, performing quantitative polymerase-chain-reaction assays in blood and urine for JC virus reactivation; BK virus, a JC virus-related polyomavirus, was used as a control. We determined JC virus-specific T-cell responses by means of an enzyme-linked immunospot assay and antibody responses by means of an enzyme-linked immunosorbent assay and analyzed JC virus regulatory-region sequences. RESULTS After 12 months of natalizumab therapy, the prevalence of JC virus in the urine of the 19 patients increased from a baseline value of 19% to 63% (P=0.02). After 18 months of treatment, JC virus was detectable in 3 of 15 available plasma samples (20%) and in 9 of 15 available samples of peripheral-blood mononuclear cells (60%) (P=0.02). JC virus regulatory-region sequences in blood samples and in most of the urine samples were similar to those usually found in PML. Conversely, BK virus remained stable in urine and was undetectable in blood. The JC virus-specific cellular immune response dropped significantly between 6 and 12 months of treatment, and variations in the cellular immune response over time tended to be greater in patients in whom JC viremia developed. None of the patients had clinical or radiologic signs of PML. CONCLUSIONS Subclinical reactivation of JC virus occurs frequently in natalizumab-treated patients with multiple sclerosis. Viral shedding is associated with a transient drop in the JC virus-specific cellular immune response.

Detection of JC Virus DNA and Proteins in the Bone Marrow of HIV-Positive and HIV-Negative Patients: Implications for Viral Latency and Neurotropic Transformation

BACKGROUND We sought to determine the prevalence of JC virus (JCV) in bone marrow samples from human immunodeficiency virus (HIV)-positive and HIV-negative patients and to determine whether bone marrow is a site of latency and neurotropic transformation of JCV, the agent of progressive multifocal leukoencephalopathy (PML). METHODS We collected bone marrow aspirates, archival bone marrow samples, and blood and urine samples from 75 HIV-negative and 47 HIV-positive patients without PML as well as bone marrow and urine or kidney samples from 8 HIV-negative and 15 HIV-positive patients with PML. Samples were tested for JCV DNA by quantitative polymerase chain reaction and for JCV protein expression by immunohistochemical analysis. JCV regulatory regions (RRs) were characterized by sequencing. RESULTS JCV DNA was detected in bone marrow samples from 10 (13%) of 75 and 22 (47%) of 47 of the HIV-negative and HIV-positive patients without PML, respectively, compared with 3 (38%) of 8 and 4 (27%) of 15 of the HIV-negative and HIV-positive patients with PML. JCV DNA (range, 2-1081 copies/microg of cellular DNA) was detected in multiple leukocyte subpopulations of blood and bone marrow samples. JCV large T antigen, but not VP1 capsid protein, was expressed in bone marrow plasma cells. Bone marrow JCV RR sequences were similar to those usually found in the brains of patients with PML. CONCLUSIONS Bone marrow is an important reservoir and a possible site of neurotropic transformation for JCV.

JC Virus Latency in the Brain and Extraneural Organs of Patients with and without Progressive Multifocal Leukoencephalopathy

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

JC Virus Antibody and Viremia as Predictors of Progressive Multifocal Leukoencephalopathy in Human Immunodeficiency Virus-1–Infected Individuals

We examined whether prediagnostic John Cunningham virus (JCV) antibodies and viremia are predictors of progressive multifocal leukoencephalopathy (PML) in 83 PML cases and 240 human immunodeficiency virus (HIV) disease-matched controls. JCV viremia was not predictive of PML, but some patients showed higher anti-JCV immunoglobulin G (IgG) responses 6 months prior to diagnosis.

Rearrangement of the JC virus regulatory region sequence in the bone marrow of a patient with rheumatoid arthritis and progressive multifocal leukoencephalopathy

The polyomavirus JC (JCV) is the etiologic agent of progressive multifocal leukoencephalopathy (PML). JCV remains quiescent in kidneys, where it displays a stable archetypal regulatory region (RR). Conversely, rearranged JCV RR, including tandem repeat patterns found in the central nervous system (CNS) of PML patients, have been associated with neurovirulence. The precise site and mechanism of JCV RR transformation is unknown. We present herein a patient with rheumatoid arthritis treated with methotrexate, who developed PML and had a rapid fatal outcome. JCV DNA polymerase chain reaction (PCR) was positive in cerebrospinal fluid (CSF), bone marrow, blood, and urine. Double-immunohistochemical staining demonstrated that 9% of bone marrow CD138+ plasma cells sustained productive infection by JCV, accounting for 94% of JCV-infected cells. JCV RR analysis revealed archetype and rearranged RR forms in bone marrow, whereas RR with tandem repeat was predominant in blood. These results suggest that the bone marrow may be a potential site of JCV pathogenic transformation. Further studies will be needed to determine the prevalence of JCV in bone marrow of immunosuppressed individuals at risk of PML and characterize the RR and phenotype of these JCV isolates.

DAS181 treatment of hematopoietic stem cell transplant patients with parainfluenza virus lung disease requiring mechanical ventilation

Parainfluenza infection is a cause of significant morbidity and mortality in allogeneic hematopoietic stem cell transplant (HSCT) patients. DAS181 is a novel antiviral agent with activity against influenza and parainfluenza. We report the first 2 cases, to our knowledge, of successful DAS181 use in ventilated HSCT patients with severe parainfluenza lung disease.

Detection of JC Virus-Specific Immune Responses in a Novel Humanized Mouse Model

Progressive Multifocal Leukoencephalopathy (PML) is an often fatal disease caused by the reactivation of the JC virus (JCV). Better understanding of viral-host interactions has been hampered by the lack of an animal model. Engrafting NOD/SCID/IL-2-Rg (null) mice with human lymphocytes and thymus, we generated a novel animal model for JCV infection. Mice were inoculated with either a PML isolate, JCV Mad-4, or with JCV CY, found in the kidney and urine of healthy individuals. While mice remained asymptomatic following inoculation, JCV DNA was occasionally detected in both the blood and the urine compartments. Mice generated both humoral and cellular immune responses against JCV. Expressions of immune exhaustion marker, PD-1, on lymphocytes were consistent with response to infection. Using this model we present the first in vivo demonstration of virological and immunological differences between JCV Mad-4 and CY. This model may prove valuable for studying JCV host immune responses.

Increased program cell death-1 expression on T lymphocytes of patients with progressive multifocal leukoencephalopathy.

Abstract:The cellullar immune response is important in the containment of progressive multifocal leukoencephalopathy (PML). We examined program cell death-1 (PD-1) expression, a marker of cellular immune exhaustion, on T lymphocytes in PML. PD-1 expression was elevated on total CD4+ and CD8+ T cells (medians 36% and 24%) in PML patients compared with healthy control subjects (medians 14% and 18%; P = 0.0015 and P = 0.033). In PML patients, JC virus (JCV)-specific CD8+ cytotoxic T lymphocytes expressed PD-1 more frequently than total CD8+ T lymphocytes (means 39% and 78%, P = 0.0004). Blocking the PD-1 receptor increased JCV-specific T-cell immune response in a subgroup of PML patients.

Infrequent Detection of KI, WU and MC Polyomaviruses in Immunosuppressed Individuals with or without Progressive Multifocal Leukoencephalopathy

Conflicting prevalence of newly identified KI(KIPyV), WU(WUPyV) and Merkel Cell Carcinoma(MCPyV) polyomaviruses have been reported in progressive multifocal leukoencephalopathy(PML) patient samples, ranging from 0 to 14.3%. We analyzed the prevalence of these polyomaviruses in cerebrospinal fluid(CSF), peripheral blood mononuclear cells(PBMC), and bone marrow samples from PML patients, immunosuppressed individuals with or without HIV, and multiple sclerosis(MS) patients. Distinct PCR tests for KIPyV, WUPyV and MCPyV DNA performed in two independent laboratories detected low levels of MCPyV DNA only in 1/269 samples. The infrequent detections of these viruses in multiple samples from immunosuppressed individuals including those with PML suggest that their reactivation mechanisms may be different from that of JC polyomavirus (JCPyV) and that they do not play a role in the pathogenesis of PML.