Distribution of JC virus DNA in peripheral blood lymphocytes of hematological disease cases

JC virus nucleotides 376-396 are critical for VP1 capsid protein expression

JC virus (JCV) infection of the brain can cause progressive multifocal leukoencephalopathy, JCV granule cell neuronopathy, and JCV encephalopathy (JCVE). JCVCPN, isolated from the brain of a patient with JCVE, is a naturally occurring strain of JCV with a 143-base pair deletion in the agnogene. Cell culture studies of JCVCPN have shown that the loss of these nucleotides in the agnogene results in impaired expression of VP1 and infectious virion production. To better understand the role of this DNA sequence in JCV replication, we generated a series of deletions in the agnogene on the backbone of a virus which has a mutated agnoprotein start codon preventing agnoprotein expression. We found that deletion of nucleotides 376-396 results in decreased levels of viral DNA replication and a lack of VP1 expression. These results indicate that these nucleotides play a crucial role in JCV replication.

Agnogene deletion in a novel pathogenic JC virus isolate impairs VP1 expression and virion production

Infection of glial cells by the human polyomavirus JC (JCV) causes progressive multifocal leukoencephalopathy (PML). JCV Encephalopathy (JCVE) is a newly identified disease characterized by JCV infection of cortical pyramidal neurons. The virus JCV_CPN associated with JCVE contains a unique 143 base pair deletion in the agnogene. Contrary to most JCV brain isolates, JCV_CPN has an archetype-like regulatory region (RR) usually found in kidney strains. This provided us with the unique opportunity to determine for the first time how each of these regions contributed to the phenotype of JCV_CPN. We characterized the replication of JCV_CPN compared to the prototype virus JCV_Mad-1 in kidney, glial and neuronal cell lines. We found that JCV_CPN is capable of replicating viral DNA in all cell lines tested, but is unable to establish persistent infection seen with JCV_Mad-1. JCV_CPN does not have an increased ability to replicate in the neuronal cell line tested. To determine whether this phenotype results from the archetype-like RR or the agnogene deletion, we generated chimeric viruses between JCV_CPN of JCV_Mad-1. We found that the deletion in the agnogene is the predominant cause of the inability of the virus to maintain a persistent infection, with the introduction of a full length agnogene, either with or without agnoprotein expression, rescues the replication of JCV_CPN. Studying this naturally occurring pathogenic variant of JCV provides a valuable tool for understanding the functions of the agnogene and RR form in JCV replication.

JC virus granule cell neuronopathy is associated with VP1 C terminus mutants

The polyomavirus JC (JCV) infects glial cells and causes progressive multifocal leukoencephalopathy (PML). We described a novel JCV-variant with a 10 bp deletion in the C terminus of the VP1 capsid protein, JCV(GCN1). This mutant was associated with lytic infection of cerebellar granule cell neurons and cerebellar atrophy in an human immunodeficiency virus/PML patient. This condition, also observed independently from PML, was named JCV granule cell neuronopathy (JCV GCN). We characterized JCV mutations in cerebrospinal fluid (CSF) of four other JCV GCN patients, and reviewed the literature on 10 reported cases. The strain from one patient harboured the identical GCN1-deletion, while the other patients had novel mutations in the same area, named JCV(GCN2-4), causing variable changes in VP1 structure. One patient also had wild-type JCV in the CSF. To study the mechanisms leading to JCV GCN, we compared viral replication kinetics from JCV(GCN1) with the prototype JCV(Mad1), the PML isolate JCV(HWM) and the prototype JCV(Mad1D) engineered with the GCN1-deletion. While all strains replicated at low levels in the medulloblastoma cell line DAOY from a cerebellar neuronal tumour, JCV(Mad1) replicated better in astroglial SVG cells than JCV(Mad1D) or JCV(GCN1) and all strains replicated at higher levels in COS-7 kidney cells, suggesting that the GCN1-deletion confers a disadvantage for viral growth in central nervous system white matter. The GCN1-deletion remained stable after 100 days in culture and VP1 protein was produced in all cell lines, indicating that JCV(GCN1) is replication-competent in vitro. These data highlight an important and previously overlooked aspect of JCV-pathogenesis. Detection of GCN-type JCV strains in CSF may help clinicians diagnose JCV GCN.

A case report of progressive multifocal leukoencephalopathy in a human T-cell lymphotropic virus type 1-infected hemodialytic patient

We experienced a case manifesting progressive multifocal leukoencephalopathy (PML) in a hemodialytic patient with hepatitis C virus-induced liver cirrhosis and human T-cell lymphotropic virus type-1 (HTLV-1)-associated uveitis. A 57-year-old male patient had received chronic hemodialysis therapy for 10 years, during which he received multiple blood transfusions and HTLV-1-associated uveitis developed. He complained of visual disturbance and disorientation. Brain CT scan showed diffuse and multifocal low density areas in occipital and temporal lobes, with gray matter relatively spared. MRI imaging showed high intensity lesions in the same areas. Cerebrospinal fluid culture was negative, but using nested PCR, rearranged regulatory region of JC virus DNA was detected. His consciousness level gradually deteriorated and complete paraplegia developed. Seven months after admission, he died of pneumonia. An autopsy confirmed the diagnosis of PML. Notably, mononuclear cell infiltration, gliosis and demyelinating lesions but no nuclear inclusion bodies were observed in the thoracic cord, which suggested HTLV-1-associated myelopathy. Because JC virus is activated under immunocompromised conditions, precipitating factors in this case appear multifactorial; depressed immune system induced by chronic hemodialysis as well as blood-borne hepatitis C virus/HTLV-1 infection might contribute to the activation of dormant JC virus and the development of florid clinical manifestation of PML.

Transcriptional activation of JC virus by human T-lymphotropic virus type I Tax protein in human neuronal cell lines

Polyomavirus JC (JCV) causes the human demyelinating disease, progressive multifocal leukoencephalopathy (PML). The recent demonstration of cases of PML in association with human T-lymphotropic virus type I (HTLV-I) infection prompted us to examine whether the HTLV-I-encoded regulatory protein Tax activates JCV transcription. By employing a dual luciferase assay, we initially found that the expression of Tax activated the transcriptional potential of both early and late promoters of JCV in human neuronal but not in non-neuronal cells. We subsequently analyzed the mechanism of Tax-induced activation of the JCV promoter in neuronal cells with the following results: 1) the JCV promoter that lacks the NF-kappaB-binding motif could not be activated by Tax; 2) the overexpression of IkappaBalpha abolished Tax-induced transcriptional activation of the JCV promoter; 3) a Tax mutant (M22) lacking the potential for activation via the NF-kappaB pathway did not activate the JCV promoter. Furthermore, Tax enhances the gene expression of JCV T antigen and VP1. We examined mechanisms of the cell-specific activation of the JCV promoter by Tax. Electrophoretic mobility shift assay demonstrated the presence of Tax-bound protein(s) that were specifically present in non-neuronal cells. This study is the first demonstration of the activation of JCV promoter by HTLV-I Tax in an NF-kappaB-dependent manner.