Infection with JC virus and possible dysplastic ganglion-like transformation of the cerebral cortical neurons in a case of progressive multifocal leukoencephalopathy

JC virus small tumor antigen promotes S phase entry and cell cycle progression

The early coding region of JC virus (JCV) encodes several regulatory proteins including large T antigen (LT-Ag), small t antigen (Sm t-Ag) and T' proteins because of the alternative splicing of the pre-mRNA. LT-Ag plays a critical role in cell transformation by targeting the key cell cycle regulatory proteins including p53 and pRb, however, the role of Sm t-Ag in this process remains elusive. Here, we investigated the effect of Sm t-Ag on the cell cycle progression and demonstrated that it facilitates S phase entry and exit when cells are released from G0/G1 growth arrest. Examination of the cell cycle stage specific expression profiles of the selected cyclins and cyclin-dependent kinases, including those active at the G1/S and G2/M transition state, demonstrated a higher level of early expression of these regulators such as cyclin B, cycling E, and Cdk2. In addition, analysis of the effect of Sm t-Ag on the growth promoting pathways including those active in the PI3K/Akt/mTOR axis showed substantially higher levels of the phosphorylated-Akt, -Gsk3-β and -S6K1 in Sm t-Ag-positive cells. Collectively, our results demonstrate that Sm t-Ag promotes cell cycle progression by activating the growth promoting pathways through which it may contribute to LT-Ag-mediated cell transformation.

The Role of the JC Virus in Central Nervous System Tumorigenesis

Cancer is the second leading cause of mortality worldwide. The study of DNA tumor-inducing viruses and their oncoproteins as a causative agent in cancer initiation and tumor progression has greatly enhanced our understanding of cancer cell biology. The initiation of oncogenesis is a complex process. Specific gene mutations cause functional changes in the cell that ultimately result in the inability to regulate cell differentiation and proliferation effectively. The human neurotropic Polyomavirus JC (JCV) belongs to the family Polyomaviridae and it is the causative agent of progressive multifocal leukoencephalopathy (PML), which is a fatal neurodegenerative disease in an immunosuppressed state. Sero-epidemiological studies have indicated JCV infection is prevalent in the population (85%) and that initial infection usually occurs during childhood. The JC virus has small circular, double-stranded DNA that includes coding sequences for viral early and late proteins. Persistence of the virus in the brain and other tissues, as well as its potential to transform cells, has made it a subject of study for its role in brain tumor development. Earlier observation of malignant astrocytes and oligodendrocytes in PML, as well as glioblastoma formation in non-human primates inoculated with JCV, led to the hypothesis that JCV plays a role in central nervous system (CNS) tumorigenesis. Some studies have reported the presence of both JC viral DNA and its proteins in several primary brain tumor specimens. The discovery of new Polyomaviruses such as the Merkel cell Polyomavirus, which is associated with Merkel cell carcinomas in humans, ignited our interest in the role of the JC virus in CNS tumors. The current evidence known about JCV and its effects, which are sufficient to produce tumors in animal models, suggest it can be a causative factor in central nervous system tumorigenesis. However, there is no clear association between JCV presence in CNS and its ability to initiate CNS cancer and tumor formation in humans. In this review, we will discuss the correlation between JCV and tumorigenesis of CNS in animal models, and we will give an overview of the current evidence for the JC virus’s role in brain tumor formation.

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.

An autopsy case of progressive multifocal leukoencephalopathy after rituximab therapy for malignant lymphoma

Progressive multifocal leukoencephalopathy (PML) is a rare fatal demyelinating disease of the central nervous system caused by reactivation of the JC virus (JCV), which is named after the initials of the patient from whom the virus was first isolated. JCV is highly prevalent worldwide, infects humans in early childhood, and the infection persists throughout the course of life in latent form. The present paper deals with the second autopsy case report of rituximab-associated PML in Japan. A 63-year-old woman who had undergone chemotherapy for non-Hodgkin lymphoma developed progressive dysarthria and cerebellar ataxia. Head magnetic resonance imaging (MRI) revealed small, scattered, hyperintense areas in the midbrain, pons and thalamus, and the patient was first diagnosed as having cerebral infarction. Follow-up MRI showed tendency toward cerebellar atrophy and multiple system atrophy cerebellar type was suggested, which we concluded must have coincidentally occurred. It was challenging to perform biopsy due to the location of the foci and the patient's condition. Twelve months later she died of aspiration pneumonia caused by the bulbar lesion. At autopsy, the histological examination suggested the presence of demyelinating foci with numerous foamy macrophages. In the foci, oligodendrocytes with enlarged ground-glass like nuclei were found in a scattered manner and astrocytes with bizarre nuclei were also detected. These findings verified the case as PML. The first diagnosis of cerebral infarction was later withdrawn, although appropriate disorders were not recalled even after testing with various antibodies. The rate of PML development tends to increase after treatment with molecular-targeted therapies, which directly or indirectly attenuate the cellular-mediated immune system. Various novel molecular-targeted and immunosuppressive drugs have been released on the market; the cases of PML have consequently increased. Accordingly, pathologists should keep this disease in mind in the differential diagnosis when neural symptoms newly emerge in patients who are treated with these drugs.

Viral tumor antigen expression is no longer required in radiation-resistant subpopulation of JCV induced mouse medulloblastoma cells

The human neurotropic polyomavirus JC, JC virus (JCV), infects the majority of human population during early childhood and establishes a latent/persistent infection for the rest of the life. JCV is the etiologic agent of the fatal demyelinating disease of the central nervous system, progressive multifocal leukoencephalopathy (PML) that is seen primarily in immunocompromised individuals. In addition to the PML, JCV has also been shown to transform cells in culture systems and cause a variety of tumors in experimental animals. Moreover, JCV genomic DNA and tumor antigen expression have been shown in a variety of human tumors with CNS origin. Similar to all polyomaviruses, JCV encodes for several tumor antigens from a single transcript of early coding region via alternative splicing. There is little known regarding the characteristics of JCV induced tumors and impact of DNA damage induced by radiation on viral tumor antigen expression and growth of these cells. Here we analyzed the possible impact of ionizing radiation on transformed phenotype and tumor antigen expression by utilizing a mouse medulloblastoma cell line (BSB8) obtained from a mouse transgenic for JCV tumor antigens. Our results suggest that a small subset of BSB8 cells survives and shows radiation resistance. Further analysis of the transformed phenotype of radiation resistant BSB8 cells (BSB8-RR) have revealed that they are capable of forming significantly higher numbers and sizes of colonies under anchorage dependent and independent conditions with reduced viral tumor antigen expression. Moreover, BSB8-RR cells show an increased rate of double-strand DNA break repair by homologous recombination (HR). More interestingly, knockout studies of JCV tumor antigens by utilizing CRISPR/Cas9 gene editing reveal that unlike parental BSB8 cells, BSB8-RR cells are no longer required the expression of viral tumor antigens in order to maintain transformed phenotype.

BK virus encephalopathy and sclerosing vasculopathy in a patient with hypohidrotic ectodermal dysplasia and immunodeficiency

Human BK polyomavirus (BKV) is reactivated under conditions of immunosuppression leading most commonly to nephropathy or cystitis; its tropism for the brain is rare and poorly understood. We present a unique case of BKV-associated encephalopathy in a man with hypohidrotic ectodermal dysplasia and immunodeficiency (HED-ID) due to IKK-gamma (NEMO) mutation, who developed progressive neurological symptoms. Brain biopsy demonstrated polyomavirus infection of gray and white matter, with predominant involvement of cortex and distinct neuronal tropism, in addition to limited demyelination and oligodendroglial inclusions. Immunohistochemistry demonstrated polyoma T-antigen in neurons and glia, but expression of VP1 capsid protein only in glia. PCR analysis on both brain biopsy tissue and cerebrospinal fluid detected high levels of BKV DNA. Sequencing studies further identified novel BKV variant and disclosed unique rearrangements in the noncoding control region of the viral DNA (BKVN NCCR). Neuropathological analysis also demonstrated an unusual form of obliterative fibrosing vasculopathy in the subcortical white matter with abnormal lysosomal accumulations, possibly related to the patient's underlying ectodermal dysplasia. Our report provides the first neuropathological description of HED-ID due to NEMO mutation, and expands the diversity of neurological presentations of BKV infection in brain, underscoring the importance of its consideration in immunodeficient patients with unexplained encephalopathy. We also document novel BKVN NCCR rearrangements that may be associated with the unique neuronal tropism in this patient.

Novel syndromes associated with JC virus infection of neurons and meningeal cells: no longer a gray area

PURPOSE OF REVIEW

The availability of a growing number of immunomodulatory medications over the past few years has been associated with various JC virus (JCV)-associated brain syndromes in patients with autoimmune diseases, including multiple sclerosis, Crohn's disease, and psoriasis that had not been previously recognized as predisposing factors for progressive multifocal leukoencephalopathy. This review covers the three novel syndromes discovered in the last decade that are caused by JCV infection of neurons and meningeal cells.

RECENT FINDINGS

For more than 30 years, JCV was thought to exclusively infect oligodendrocytes and astrocytes in the white matter of the brain of immunosuppressed individuals. We now recognize that JCV-infected glial cells are frequently located at the gray-white matter junction or exclusively within the gray matter causing demyelination in the cortex. Mutations in JCV can trigger a change in tropism leading to involvement of other cell types, such as neurons and meningeal cells, causing clinically distinct entities. These new features of JCV infection provide challenges for clinicians taking care of affected patients and investigators studying the biology of this polyomavirus, its pathogenesis, and tropism.

SUMMARY

We hope that increasing awareness of these syndromes will lead to early diagnosis, and pave the way for new avenues of research to better understand all aspects of JCV pathogenesis and develop efficient therapies for our patients. However, we need to remain vigilant and open to the possibility that additional JC variants or yet unknown polyomaviruses may also be associated with neurological diseases.

Simian Virus 40 Infection in the Spinal Cord of Simian Immunodeficiency Virus-Immunosuppressed Rhesus Macaques

Progressive multifocal leukoencephalopathy (PML) is an often-fatal demyelinating disease of the CNS that usually develops in immunocompromised individuals because of reactivation of quiescent JC virus (JCV). There are only a few reports of JCV infection in the human spinal cord. Progressive multifocal leukoencephalopathy-like demyelinating lesions have been documented in the brains of simian immunodeficiency virus-infected macaques. To determine whether simian virus 40 (SV40) can infect and cause PML lesions in spinal cords of immunosuppressed macaques, we examined archival spinal cord samples from 15 simian immunodeficiency virus-infected rhesus monkeys with acquired immunodeficiency syndrome and SV40 infection of the brain. Among those, 6 (40%) had SV40-infected cells in the spinal cord, including 1 with PML-like lesions, 1 with PML-like lesions and meningoencephalitis, 2 with meningoencephalitis, 1 with gray matter gliosis, and 1 with no lesions. One animal with a large PML-like lesion had extensive demyelination and SV40 infection of astrocytes, oligodendrocytes, and meningeal cells. None of the 6 animals had SV40-infected spinal cord neurons. These observations indicate that, like JCV in immunosuppressed humans, SV40 can infect glial cells and cause PML-like lesions in the spinal cord of immunosuppressed rhesus macaques. Rhesus macaques could serve as an animal model to study polyomavirus infection and pathogenesis in the spinal cord.

Acute disseminated encephalomyelitis

Acute disseminated encephalomyelitis (ADEM) is an acute multifocal demyelinating disease of the central nervous system that typically follows an infectious illness. Its clinical course in most cases is monophasic; however, relapsing ADEM is rarely seen, which poses a diagnostic challenge for distinguishing this disease from multiple sclerosis (MS). Although typically encountered in children, it also occurs in adults with disease characteristics slightly different from the pediatric cases. Formerly, ADEM occurred particularly often in children with measles. However, the illness most often follows a non-descript viral or even bacterial infectious illness. ADEM occurs throughout the world, and may even be more common in less-developed countries, where MS is rare, than in developed ones, where MS is common. Children seldom get MS as opposed to adults, indicating that ADEM constitutes a distinct entity from MS. The prognosis of ADEM is generally good, but severe neurologic sequelae after ADEM are occasionally seen. In this chapter, the etiology, clinical/laboratory/radiologic characteristics, treatment options, and prognosis of ADEM are discussed.

Fatal encephalitis due to BK virus in a patient with common variable immunodeficiency: a case report

Encephalitis due to BK virus is a rare condition. Here, we describe a young male patient with common variable immunodeficiency who developed fatal encephalitis due to BK virus. The patient presented initially with ocular symptoms that were followed by behavioral changes and spastic quadriparesis. Diagnosis was made by the compatible clinical findings and detection of viral DNA by polymerase chain reaction in the cerebrospinal fluid. To the best of our knowledge, this is the first report of BK virus encephalitis in a patient with common variable immunodeficiency. We suggest that BK virus should be suspected in cases of encephalitis; particularly in patients with immunodeficiency.

Progressive multifocal leukoencephalopathy: why gray and white matter

Since it was first described in 1958, progressive multifocal leukoencephalopathy (PML), a demyelinating disease of the brain caused by the polyomavirus JC (JCV), has evolved tremendously. It was once considered a noninflammatory disease that affected exclusively oligodendrocytes and astrocytes in the white matter of immunosuppressed individuals and was almost always fatal. Today, we understand that PML can present during the course of an immune reconstitution inflammatory syndrome and that it affects a broader range of individuals, including patients with minimal immunosuppression and those who are treated with novel immunomodulatory medications. Furthermore, JCV-infected glial cells are frequently located at the gray matter-white matter junction or within the gray matter, causing demyelinating lesions within cortical areas. Finally, JCV variants can also infect neurons, leading to the recognition of two distinct clinical entities: JCV granule cell neuronopathy and JCV encephalopathy.

Frequent infection of cortical neurons by JC virus in patients with progressive multifocal leukoencephalopathy

The human polyomavirus JC (JCV) infects glial cells and causes progressive multifocal leukoencephalopathy (PML), a demyelinating disease of the brain, in immunosuppressed individuals. The extent of JCV infection of neurons is unclear. We determined the prevalence and pattern of JCV infection in gray matter (GM) by immunostaining in archival brain samples of 49 PML patients and 109 control subjects. Among PML patients, 96% had demyelinating lesions in white matter and at the gray-white junction (GWJ); 57% had them in the GM. Most JCV-infected cells in GWJ and GM were glia, but JCV also infected neurons in PML lesions at the GWJ of 54% and GM of 50% patients and in GM outside areas of demyelination in 11% of patients. The JCV regulatory T antigen (Ag) was expressed more frequently in cortical neurons than the VP1 capsid protein. None of the control subjects without PML had any cells expressing JCV proteins. Thus, the cerebral cortex often harbors demyelinating lesions of PML, and JCV infection of cortical neurons is frequent in PML patients. The predominance of T Ag over VP1 expression suggests a restrictive infection in neurons. These results indicate that JCV infection of cerebral cortical neurons is a previously under appreciated component of PML pathogenesis.

Progressive multifocal leukoencephalopathy and promyelocytic leukemia nuclear bodies: a review of clinical, neuropathological, and virological aspects of JC virus-induced demyelinating disease

Progressive multifocal leukoencephalopathy is a fatal viral-induced demyelinating disease that was once rare but has become more prevalent today. Over the past decades, much has been learned about the disease from molecular study of the etiological agent of the disease, JC virus. Recently, promyelocytic leukemia nuclear bodies (PML-NBs), punctuate structures for important nuclear functions in eukaryotic cells, were identified as an intranuclear target of JC virus infection. Neuropathologically, JC virus-infected glial cells display diffuse amphophilic viral inclusions by hematoxylin–eosin staining (full inclusions), a diagnostic hallmark of this disease. Recent results using immunohistochemistry, however, revealed the presence of punctate viral inclusions preferentially located along the inner nuclear periphery (dot-shaped inclusions). Dot-shaped inclusions reflect the accumulation of viral progeny at PML-NBs, which may be disrupted after viral replication. Structural changes to PML-NBs have been reported for a variety of human diseases, including cancers and neurodegenerative disorders. Thus, PML-NBs may provide clues to the further pathogenesis of JC virus-induced demyelinating disease. Here, we review what we have learned since the disease entity establishment, including a look at recent progress in understanding the relationship between JC virus, etiology and PML-NBs.

Progressive Multifocal Leukoencephalopathy in a Patient with X-linked Agammaglobulinemia

To our knowledge, this is the first case report describing progressive multifocal leukoencephalopathy (PML) associated with X-linked agammaglobulinemia. The JC virus was confirmed at autopsy and PML was diagnosed. Humoral immunodeficiency with normal cellular immunity could be infected with JCV.

Fulminant JC virus encephalopathy with productive infection of cortical pyramidal neurons

The polyomavirus JC (JCV) is the causative agent of progressive multifocal leukoencephalopathy and of JCV granule cell neuronopathy. We present a human immunodeficiency virus-negative patient who experienced development of multiple cortical lesions, aphasia, and progressive cognitive decline after chemotherapy for non-small-cell lung cancer. Brain biopsy and cerebrospinal fluid polymerase chain reaction demonstrated JCV, and she had a rapidly fatal outcome. Postmortem analysis showed diffuse cortical lesions and areas of necrosis at the gray-white junction. Immunostaining showed a productive JCV infection of cortical pyramidal neurons, confirmed by electron microscopy, with limited demyelination. This novel gray matter syndrome expands the scope of JCV clinical presentation and pathogenesis.

Clinicopathological study of early progressive multifocal leukoencephalopathy incidentally found in a schizophrenia patient

A 58-year-old Japanese man developed psychomotor excitement and hallucinatory paranoia at age 53, which gradually developed to residual schizophrenia. He was administered various common tranquilizers until death. Myelodysplastic syndrome was noted 10 months before death. A routine autopsy was performed. The brain weighed 1365 g, and macroscopic observation revealed no remarkable findings. However, microscopic examination disclosed cells with enlarged and basophilic nuclei, and unusual astrocytes in the demyelinated foci, especially at the corticomedullary junctions in the temporal and occipital lobes. On the other hand, the white matter was relatively intact. Immunohistochemical analysis using anti-JC virus protein, VP-1 antibody, demonstrated JC virus-infected cells in not only abnormal glial cells and neurons but also normal-looking cells, which are suggestive of progressive multifocal leukoencephalopathy (PML). Immunostaining for GFAP revealed severe gliosis and some scattered abnormal enlarged nuclear cells in the lesions. Some clusters of CD8-positive lymphocytes were seen, which kill infected cells. PML could be considered a short-term disease preceding death, as "incidental PML" in this case. This is a rare autopsy case of early PML occurring in a schizophrenia patient with PML.

Progressive multifocal leukoencephalopathy showing extensive spinal cord involvement in a patient with lymphocytopenia

A 64-year-old Japanese man who was diagnosed as having cerebral infarcts at an early clinical stage was found to have progressive multifocal leukoencephalopathy (PML). A decrease of leukocytes and lymphocytes had been detected in the previous year. During a total clinical course of 11 months, he showed marked depletion of lymphocytes ranging from 264/microL to 459/microL. Autopsy disclosed no underlying diseases such as malignancies or tuberculosis. Extensive PML lesions were seen in the cerebral white matter. Small perivascular cuffs comprising many CD8+ T lymphocytes and a few CD4+ T cells were scattered in the PML lesions. CD20+ B cells were rarely evident. The subsets of the infiltrating lymphocytes differed from those of primary or spontaneous PML. Similar extensive PML lesions were observed not only in the cerebellum and brainstem but also in the spinal cord. All 26 segments of the spinal cord, especially the cervical, lumbar and sacral cord, showed extensive lesions involving the lateral and anterior columns. To our knowledge, only three cases of PML with such extensive spinal cord lesions have been reported previously. These three cases, and the present one, may represent a group of PML that shows extensive lesions in the spinal cord as well as the cerebrum, cerebellum and brainstem. The underlying disease in the present case was unclear. Because lymphocytopenia is not observed in primary or spontaneous PML, and the immunohistochemical findings of the infiltrating lymphocytes in the present case are different from primary or spontaneous PML, the decrease in his total blood lymphocytes may have played a significant role in his immunosuppressed condition as the underlying disease.

Spinal cord lesions of progressive multifocal leukoencephalopathy in an acquired immunodeficiency syndrome patient

Progressive multifocal leukoencephalopathy (PML) is a deadly demyelinating disease of the central nervous system, which occurs in immunosuppressed individuals. This disease is caused by a reactivation of the polyomavirus JC (JCV). Clinical presentation can be variable from patient to patient as lesions can occur anywhere in the CNS white matter; however, they appear to spare the optic nerves and the spinal cord. The authors present a case of PML in the setting of acquired immunodeficiency syndrome (AIDS) who developed PML lesions in the spinal cord, discovered during the postmortem examination. This finding is significant because PML has recently been diagnosed in patients with multiple sclerosis (MS) treated with the novel immunomodulatory medication natalizumab. Indeed, spinal cord lesions are frequent in MS. Therefore clinicians should be aware that in addition to the brain, PML may also affect the spinal cord white matter.

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.

Progressive multifocal leukoencephalopathy in a patient with common variable immunodeficiency and abnormal CD8+ T-cell subset distribution

BACKGROUND

Patients with primary hypogammaglobulinemia have been reported to have encephalopathy, but progressive multifocal leukoencephalopathy (PML) due to JC virus reactivation is a rare cause.

OBJECTIVE

To provide the clinical details and case discussion of a patient diagnosed as having common variable immunodeficiency (CVID) who has progressive neurodegenerative symptoms and was found to have PML and an abnormal CD8+ T-cell subset distribution.

METHODS

A detailed case report providing the patient's immunodeficiency history, diagnostic evaluation, and medical management and a review of related literature.

RESULTS

Before his neurodegenerative illness, the patient was found to have hypogammaglobulinemia, poor specific antibody responses, low circulating B-cell levels, and abnormal delayed-type hypersensitivity responses; there was no Bruton tyrosine kinase (BTK) mutation. The PML was diagnosed using brain biopsy and was confirmed using a DNA probe specific for JC virus. Peripheral blood flow cytometry at the time of PML diagnosis revealed an accumulation of naive CD8+ T cells (CD3+CD8+CD45RA+) and a deficiency of memory CD8+ T-cell subsets (CD3+CD8+CD45RA- or CD3+CD8+CD45RO+). Despite aggressive treatment with interleukin 2, interferon-gamma, and intravenous cidofovir, the patient died.

CONCLUSIONS

JC virus infection should be considered in the differential diagnosis of the patient with CVID and signs and symptoms of encephalopathy. The role of this patient's abnormal CD8' T-cell subset distribution in the development or control of this rare infection is worthy of consideration and has encouraged us to enumerate naive and memory CD4+ and CD8+ T-cell subsets in patients diagnosed as having CVID, even in the absence of neurodegenerative symptoms.

JC virus granule cell neuronopathy: A novel clinical syndrome distinct from progressive multifocal leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) typically affects the CNS white matter of the central nervous system. We present an human immunodeficiency virus-infected patient with polyomavirus JC infection restricted to granule cell neurons of the cerebellum and with corresponding neurological symptomatology. Magnetic resonance imaging demonstrated cerebellar atrophy without white matter lesions and stereotactic biopsy showed selective infection of the cerebellar granular cell layer, with preservation of Purkinje cells and absence of classic progressive multifocal leukoencephalopathy histopathology in underlying white matter. Evolution over 8 years was marked by symptomatic improvement corresponding to highly active antiretroviral therapy (HAART), with modest increase in CD4(+) T-cell counts. We propose to call this novel syndrome JCV granule cell neuronopathy (JCV GCN).

JC virus early protein detection by immunohistochemistry in progressive multifocal leukoencephalopathy: a comparative study with in situ hybridization and polymerase chain reaction

In situ hybridization (ISH) for JC virus (JCV) is generally applied for the diagnosis of progressive multifocal leukoencephalopathy (PML). To explore the usefulness of immunohistochemistry (IHC) for JCV early proteins, 14 paraffin-embedded postmortem brain specimens with histologic features compatible with PML were tested for the presence of JCV by means of DNA-DNA ISH with a biotinylated probe corresponding to the entire JCV genome, for JCV early proteins IHC with both PAb 2003 and anti-SV40 large T antigen monoclonal antibodies, and polymerase chain reaction (PCR) amplification of JCV virion protein 3 (VP3) and transcriptional control region (TCR) sequences. ISH was positive in 13 cases and IHC in all 14 cases, the number of IHC-positive cells generally being far in excess of ISH-positive cells. Of the 2 monoclonal antibodies used, PAb 2003 proved to be more sensitive than anti-SV40 large T antigen. Occasional neuronal nuclei were positive for JCV early proteins in 5 cases. As for PCR, VP3 was amplified in all 14 cases and TCR in 9 cases. Consequently, PAb 2003 IHC for JCV early proteins seems to be a powerful tool for viral demonstration in PML and may well become the diagnostic recourse of choice in this setting.

Differential distribution of the JC virus receptor-type sialic acid in normal human tissues

JC virus (JCV), a member of the polyomavirus family, causes a demyelinating disease of the central nervous system (CNS) in humans known as progressive multifocal leukoencephalopathy. Although glial cells are the principal target of JCV productive infection in progressive multifocal leukoencephalopathy patients, little is known regarding the site of JCV persistence and the mechanisms by which the virus spreads to the CNS to cause disease. Previous work has demonstrated the presence of replicating JCV DNA in B lymphocytes from peripheral blood, tonsil, and spleen and it has been hypothesized that lymphocytes may be one site of JCV persistence. Detection of viral gene products in renal tubules and excretion of JC virions in the urine suggests JCV persistence in the kidney. A respiratory route of viral transmission has also been hypothesized implicating the lung as another possible site of persistent JCV infection. Earlier studies from our laboratory have shown that terminal alpha 2,6-linked sialic acid is a critical component of the JCV receptor. In this report we examined the tissue distribution of this JCV receptor-type sialic acid in a panel of normal human tissues. Our results demonstrate that in normal brain JCV receptor-type sialic acids are expressed on oligodendrocytes and astrocytes, but not on cortical neurons. The receptor-type sialic acid is also more highly expressed on B lymphocytes than on T lymphocytes in normal human spleen and tonsil. In addition, both the kidney and lung express abundant levels of alpha 2-6-linked sialic acids. Our data show a striking correlation between the expression of the JCV receptor-type sialic acid on cells and their susceptibility to infection by the virus. These findings also support the hypothesis of JCV persistence in lymphoid tissue and B-cell-facilitated viral dissemination to the CNS.

Viruses and cancer: lessons from the human polyomavirus, JCV

The possible role of eucaryotic viruses in the development of cancer has been the subject of intense investigation during the past 50 years. Thus far, a strong link between some RNA and DNA viruses and various cancers in humans has been established and the transforming activity of several of the viruses in cell culture and their oncogenecity in experimental animals has been well documented. Perhaps, one of the most common themes among the oncogenic viruses rests in the ability of one or more of the viral proteins to deregulate pathways involved in the control of cell proliferation. For example, inactivation of tumor suppressors through their association with viral transforming proteins, and/or impairment of signal transduction pathways upon viral infection and expression of viral proteins are among the key biological events that can either trigger and/or contribute to the process of cancer. In recent years, more attention has been paid to human polyomaviruses, particularly JC virus (JCV), which infects greater than 80% of the human population, due to the ability of this virus to induce a fatal demyelinating disease in the brain, its presence in various tumors of central nervous system (CNS) and non-CNS origin, and the oncogenic potential of this virus in several laboratory animal models. Here, we will focus our attention on JCV and describe several pathways employed by the virus to contribute to and/or accelerate cancer development.

p53 in nonneoplastic central nervous system lesions: an immunohistochemical and genetic sequencing study

OBJECTIVE

Immunostaining for p53 commonly is considered a marker of neoplasia. Previous studies of nonneoplastic processes have yielded conflicting results.

METHODS

To test the assumption that p53 immunoreactivity indicates neoplasia, we examined 60 formalin-fixed, paraffin-embedded biopsies of nonneoplastic central nervous system lesions, including gliosis (n = 12), infarction (n = 9), demyelinating disease (n = 23), progressive multifocal leukoencephalopathy (n = 11), and herpes simplex virus encephalitis (n = 5). Diffuse astrocytomas (n = 50) of World Health Organization Grades 2 to 4 also were studied, as were six control autopsy brains. The avidin-biotin-peroxidase complex method was used with commercially available monoclonal antisera to both p53 (clone DO7; Dako, Carpinteria, CA) and mdm2 (Dako), a protein known to stabilize p53. Two samples of each nonneoplastic lesion also were subjected to deoxyribonucleic acid isolation, amplification, and sequencing of exons 5 to 8 of TP53.

RESULTS

Although it was low level in most instances, p53 immunoreactivity was noted in all but normal control samples. In reactive lesions, staining was largely observed in astrocytes and histiocytes. Scant oligodendroglia also were labeled in demyelinating disease. The progressive multifocal leukoencephalopathy samples revealed exceptionally strong staining in astrocytes and infected oligodendrocytes. Staining also was noted in occasional endothelial cells and neurons, and in rare lymphocytes. Immunoreactivity for mdm2, studied only in nonneoplastic lesions, was moderate to strong in all cases and limited to reactive astrocytes and histiocytes. No TP53 mutations were noted in the nonneoplastic lesions studied. To some extent, all astrocytomas exhibited p53 immunopositivity, particularly high-grade lesions.

CONCLUSION

p53 immunoreactivity is not limited to astrocytomas, but it can be observed in lesions that often are mistaken for glioma. No TP53 mutations accompany p53 expression in nonneoplastic lesions, and mdm2 may be responsible for persistence of p53 expression in these processes.

Broad distribution of the JC virus receptor contrasts with a marked cellular restriction of virus replication

To investigate the early events of JC virus (JCV) infection, including attachment, penetration, transport to the nuclei, and replication of the virus, we analyzed the susceptibility of 15 different cell lines to infection using a semiquantitative polymerase chain reaction (PCR) assay, in situ hybridization, laser scanning confocal microscopy, and a viral replication assay. The cell lines examined were human permissive and nonpermissive cells as well as cells of monkey and mouse origin. JCV entry into the nuclei of the all cell lines was observed within 10 min after inoculation, demonstrating that the virus receptor is widely distributed among mammalian cells. Inhibition of viral entry by an anti-JCV VP1 antibody and sialidase treatment to remove sialic acid residues, which are considered a candidate for the JCV receptor, suggested that VP1 may interact with the cellular surface sialic acid. In addition, chlorpromazine, a clathrin-dependent pathway inhibitor, significantly suppressed entry of JCV into nuclei. In spite of the broad spectrum of cells susceptible to JCV entry, replication of the virus occurred exclusively in human neuroblastoma cell lines. These results suggest that whereas JCV can enter a wide variety of cell types and localize to the nuclei, cell-specific intranuclear mechanisms are required for virus replication.

JC virus large T protein transforms rodent cells but is not involved in human medulloblastoma

JC virus (JCV) together with Simian virus 40 (SV40) and BK virus (BKV), belong to the polyomavirus group and these viruses are neuro-oncogenic to rodents by expression of large T antigen (LT), which binds to cellular p53 and pRB thus reducing the anticancer potential of the cell. The function of LT has not been clarified because small t antigen (st) is transcribed from the same start codon as the overlapping reading frame of LT, and is translated as a different protein with the same N-terminal residues (1-81 amino acids) by a splice-site variant of mRNA. To elucidate the function of LT without st, we constructed plasmids that express LT only by deleting the splicing region including the C-terminus of st, and consequently stable cell lines were established that express only JCLT, SV40LT and BKLT. The growth rates of these cells were examined in colonies on soft agar and it was found that LT alone has a transforming capacity; the order of efficiency being SV40LT, BKLT and JCLT. In addition, to verify the involvement of JCV in human medulloblastoma, eight cases of medulloblastoma, six cases of frozen material and five cases of paraffin-embedded tissues which included three cases of frozen tissues, were examined. PCR assay, genomic Southern blotting, and in situ hybridization were applied to detect the JCV genome, and LT and st were examined by immunohistochemistry; the results were compared with JCV-infected tissues as a positive control. All methods failed to detect not only JCV genome but also LT protein in medulloblastoma and it was concluded that JCV LT has transforming activities in rodent cells, but is not related to human medulloblastoma.