Progressive multifocal leucoencephalopathy in the era of natalizumab: a review and discussion of the implications.

Progressive multifocal leucoencephalopathy (PML) is an opportunistic demyelinating infection of immunocompromised patients, caused by the human polyomavirus, JC virus. Prior to 2005, PML had not been described in patients with MS. In early 2005, however, two cases of PML were reported in patients with MS treated with the alpha-antegrin inhibitor, natalizumab. A third case was subsequently described in a patient with Crohn's disease who had also received the agent. These three cases resulted in withdrawal of natalizumab from the market and have had major implications for its reintroduction into clinical use. In this review, we discuss current knowledge concerning PML and its causative agent, the possible role of natalizumab in initiating PML in patients with MS, and the challenges posed by the risk of this infection as the drug returns to clinical use.

Antibody types and IgG subclasses in paraneoplastic neurological syndromes.

Three major patterns of antineuronal antibody response have been identified in patients with paraneoplastic neurological syndromes: Type I ('Anti-Yo'), associated with cerebellar degeneration in the setting of breast or gynecological cancer, Type IIa ('anti-Hu') associated with encephalomyeloneuritis in patients with small cell carcinoma of the lung, and Type IIb ('anti-Ri') associated with breast cancer. We have employed immunofluorescence methods to determine the antibody classes and the IgG subclasses which react with neurons in each of these patterns of paraneoplastic antibody response. In this study, IgG was the only antibody class identified; IgM and IgA antibodies were not found. IgG1 was the major subclass represented and was found in 9/9 patients with Type I antibody response, 26/27 patients with Type IIa antibody response, and 3/3 patients with Type IIb antibody response. Many patients also exhibited positive staining for IgG2 and IgG3. Trace amounts of IgG4 antineuronal antibodies were detected in a single patient with Type I antibody response; IgG4 antibodies were not found in other patients. Patients with paraneoplastic neurological syndromes exhibit an antibody response which is overwhelmingly IgG and is comprised predominantly of IgG subclasses capable of fixing complement. The role of these antibodies in the pathogenesis of paraneoplastic neurological disease remains uncertain.

Controversies in neurological infectious diseases.

The past several years have seen major advances in our understanding of neurological infectious diseases, their diagnosis, and their treatment. Along with these advances, however, new information about infectious agents and new therapeutic options have also introduced both uncertainty and controversy in the approach and management of patients with diseases of the central nervous system. Here, we discuss six such areas: the long-term efficacy of HAART therapy in treatment of HIV infection; the role of viral infection in chronic fatigue syndrome; Rasmussen's encephalitis as an infectious or autoimmune disease; the spectrum of neurological diseases caused by rickettsial infection; the role of Mycoplasma pneumoniae in human central nervous system disease; and the possible association of Chlamydia pneumoniae and human herpesvirus 6 with multiple sclerosis.

Bilateral hippocampal encephalitis caused by enteroviral infection.

Nonpolio enteroviral encephalitis usually presents as a diffuse, generalized encephalitis. Focal cerebral involvement by nonpolioviruses is uncommon, and neuroradiologic studies in these cases are usually normal. The authors present a case of a 5-year-old male with an acute encephalitic illness and bilateral lesions of the hippocampi on magnetic resonance imaging. Enteroviral nucleic acids were detected in the cerebrospinal fluid by the reverse transcription polymerase chain reaction. The findings suggest that enteroviral infection should be considered in the differential diagnosis of acute bilateral hippocampal encephalitis in patients in whom polymerase chain reaction fails to demonstrate the presence of herpes simplex virus.

Association of anti-Yo (type I) antibody with paraneoplastic cerebellar degeneration in the setting of transitional cell carcinoma of the bladder: detection of Yo antigen in tumor tissue and fall in antibody titers following tumor removal.

Anti-Yo (type I) autoantibodies reactive with Purkinje cell cytoplasmic antigens of 34 and 62 kd are found in the serum and cerebrospinal fluid of patients with paraneoplastic cerebellar degeneration associated with cancer of the ovary, uterus, adnexa, or breast. Anti-Yo antibody response is rarely associated with other tumors. Here, we present a patient who developed paraneoplastic cerebellar degeneration and anti-Yo antibody response in association with transitional cell carcinoma of the bladder. The presence of anti-Yo antibodies was confirmed by immunofluorescence assay and by Western blot analysis against both Purkinje cell lysates and the CDR62 fusion protein. Yo antigen was demonstrated in sections of the patient's tumor. Antibody titers fell after tumor removal. Transitional cell carcinoma should be considered in patients presenting with subacute cerebellar degeneration and anti-Yo antibody response in whom ovarian, adnexal, uterine, or breast cancer cannot be detected.

Autoantibodies to neuronal glutamate receptors in patients with paraneoplastic neurodegenerative syndrome enhance receptor activation.

BACKGROUND: Paraneoplastic syndromes are "remote" complications of cancer characterized clinically by neurological disease. The sera and cerebrospinal fluid (CSF) from patients with paraneoplastic neurological syndromes (PNS) frequently contain autoantibodies to ill-defined neuronal antigens. We report here that neuronal glutamate receptors are targets for autoantibodies found in the serum from some patients with well-characterized PNS. MATERIALS AND METHODS: We have analyzed the serum from seven patients with well-characterized PNS for the presence of autoreactive antibodies to non-NMDA glutamate receptor subunits. Autoantibodies were assessed using Western blot, immunohistochemistry, and immunocytochemistry. Whole-cell electrophysiological recordings were used to examine the effect of antibodies on glutamate receptors expressed by cortical neurons in culture. RESULTS: Six of seven patients' serum contained autoantibodies to the non-NMDA glutamate receptor (GluR) subunits GluR1, GluR4, and/or GluR5/6. No patient had autoantibodies to GluR2, and only one patient exhibited weak immunoreactivity to GluR3. Electrophysiological analysis demonstrated that the serum from four of the six GluR-antibody-positive patients enhanced glutamate-elicited currents on cultured cortical neurons but had no effect on receptor function alone. Enhancement of glutamate-elicited currents was also produced by affinity-purified antibody to GluR5. CONCLUSIONS: The occurrence of autoantibodies to specific neuronal neurotransmitter subunits in the sera of patients with PNS and the ability of these autoantibodies to modulate glutaminergic receptor function suggest that some paraneoplastic neurological injury could result from glutamate-mediated excitotoxicity.

Uptake of systemically administered human anticerebellar antibody by rat Purkinje cells following blood-brain barrier disruption.

Paraneoplastic cerebellar degeneration accompanying gynecological or breast malignancies is frequently associated with an autoantibody response, termed "type I" or "anti-Yo" directed against cytoplasmic antigens of cerebellar Purkinje cells. The role of this antibody response in the pathogenesis of paraneoplastic cerebellar degeneration is unknown; however, it is also not known whether anti-Purkinje cell antibodies from the systemic circulation bind to target Purkinje cell antigens under the conditions of brain inflammation and blood-brain barrier disruption, which are frequently present at the onset of cerebellar symptoms. Inbred Lewis rats received intraperitoneal injections of type I or normal IgG in the setting of blood-brain barrier disruption induced by adoptive transfer of experimental allergic encephalomyelitis (EAE) and were killed after 24, 48, and 96 h. Brains of these animals were studied histologically for evidence of EAE and immunohistochemically for binding of human or endogenous rat IgG to target neurons. Rat IgG was detected around vessels and in Purkinje cells of all animals studied. Human IgG was detected around vessels of all animals. In animals examined 96h after receiving type I human IgG, human IgG was identified within processes of Purkinje cells and within occasional Purkinje cell bodies. Uptake of type I IgG by other cell types was not observed, and neuronal uptake of IgG was not seen in brains of animals receiving normal human IgG. Our data demonstrate that circulating type I IgG is internalized by cerebellar Purkinje cells in the setting of blood-brain barrier disruption and suggest a mechanism by which an antibody response directed against cytoplasmic antigens of Purkinje cells may reach target antigens at the onset of paraneoplastic cerebellar degeneration.

Distribution of K-papovavirus in infected newborn mice.

Newborn mice were inoculated orally with 100 LD50 of K-papovavirus and the distribution of virus in fatally infected animals was studied by in-situ nuclei acid hybridization methods and immunoperoxidase staining for K virus capsid (V) antigen. Histopathologically, K virus produced extensive involvement of pulmonary endothelial cells, resulting in interstitial pneumonia, and widespread involvement of other endothelial cell populations throughout the systemic circulation. Endothelial cells in lungs, kidneys and other organs exhibited both specific hybridization for K virus nucleic acids and positive staining for K virus V antigen, indicative of productive infection. Scattered, apparently extravascular cells within brain parenchyma also exhibited both specific hybridization and immunohistological staining for K virus V antigen. In contrast, specific hybridization for K virus nuclei acids, in the absence of immunohistochemical labelling of K virus V antigen, suggesting transcription of viral DNA without expression of viral proteins, was detected in renal tubular epithelial cells and nonvascular, apparently lymphoid cells within the spleen and lymph nodes. The present study confirms the predominantly endotheliotropic nature of K virus infection in newborn mice and also demonstrates that the virus invades renal epithelial, lymphoid and possibly glial cells during primary infection.

Type IIa ('anti-Hu') antineuronal antibodies produce destruction of rat cerebellar granule neurons in vitro.

We reacted dispersed cultures of newborn rat cerebellar granule cells with serum, purified IgG, and CSF from patients with type IIa ("anti-Hu") antibody response accompanying paraneoplastic neurologic syndromes. All type IIa sera, IgGs, and CSFs, but not those of normal or cancer controls, produced bright nuclear immunofluorescence of cultured granule neurons. Type IIa serum and CSF labeled proteins of 35-42 kd in rat granule cell blots, identical in molecular weight to proteins labeled by type IIa antibodies in blots of human granule cells. IgGs eluted from the 35-42 kd band in blots of rat granule cells labeled proteins of similar molecular weights in blots of human granule cells and produced typical type IIa immunostaining of human cerebellar sections. Human IgG could be identified in nuclei and cytoplasm of neurons incubated for 72 hours with 2/4 type IIa sera tested, but not with normal sera. Type IIa sera or IgGs from 4/7 patients produced specific lysis of rat granule cells in the presence of complement, as compared with controls using normal serum or heat-inactivated complement. Prolonged (7-day) incubation of cultures with type IIa antibody without complement also resulted in specific lysis, whereas incubation with normal serum or serum from neurologically normal patients with small-cell carcinoma of the lung did not. Rat granule cell cultures provide a valuable in vitro system with which to study the interaction of type IIa antibody with neurons. The present study provides the first reported evidence that type IIa antibodies may cause cell injury directly, in the absence of lymphocyte-mediated immune response.

Analysis of autoantibody binding to 52-kd paraneoplastic cerebellar degeneration-associated antigen expressed in recombinant proteins.

A 52-kd neural antigen was reported to be recognized by anti-Purkinje cell antibodies in serum of a patient with paraneoplastic cerebellar degeneration associated with uterine carcinoma. In this study, we demonstrate that this neural antigen is recognized by antibodies known as anti-Purkinje cell antibody type I (PCAb Type I) and anti-YO. The latter's antigen is reported to be specific for the 62- to 64-kd antigen CDR62. Assuming that the 52-kd and 62- to 64-kd antigens share a common epitope(s) recognized by all of these antibodies, we examined the antigenic region on the 52-kd protein by immunoblots with deletion fragment proteins of the recombinant 52-kd protein. A major epitope was localized in the region of amino acid residues 94 to 133 of the 52-kd protein, which is the site of a leucine zipper motif. The potential pathogenicity of PCAb Type I is discussed.

The major site of murine K papovavirus persistence and reactivation is the renal tubular epithelium.

K virus, a murine papovavirus, produces a lethal pneumonia in newborn mice. Animals surviving acute illness develop a persistent infection which reactivates under conditions of immunosuppression. The present study was conducted to identify the cell populations which support persistent K virus infection and to determine the cell populations in which this persistent infection is reactivated during immunosuppression. Mice inoculated by the oral route with 100 50% newborn mouse lethal doses (LD50) of K virus at 14 days of age were followed over a period of 7 months. The distribution of infection was studied by virus assay, immunohistochemistry, and in situ nucleic acid hybridization methods. Viral replication during the acute phase of infection was confined to pulmonary and systemic vascular endothelial cells, as well as to scattered, apparently lymphoid cells within spleens. Beginning 2 months after inoculation, however, specific hybridization for K virus nucleic acids was detected in rare renal tubular epithelial cells, and by 6 months after inoculation renal tubular epithelial cells represented the major site of viral persistence. Positive cells were frequently present in groups of two or more, and a minority of positive cells also expressed viral capsid (V) antigen. Immunosuppression with cyclophosphamide resulted in reactivation of infection, with highest titers of virus being detected in kidneys and with increased numbers of renal tubular epithelial cells expressing viral capsid antigen. Capsid antigen was also detected in rare endothelial cells in kidneys, livers and lungs of these immunosuppressed mice. Although K virus behaves as an endotheliotrope during acute infection, the major site of K virus persistence and reactivation, the renal tubular epithelial cell, is similar to that involved during persistent infection by polyoma virus in mice, SV40 virus in monkeys, and BK and JC viruses in man. The observation that persistently infected renal tubular epithelial cells occur in groups of two or more and occasionally express capsid antigen suggests that virus may persist as a productive infection which is confined by antiviral antibody but maintains itself by cell-to-cell-spread. The present study represents the first instance in which the cell populations which support infection by a member of the polyomavirus subgroup in its natural host have been defined during acute, persistent, and reactivated infection.

Approach to diagnosis of meningitis. Cerebrospinal fluid evaluation.

CSF evaluation is the single most important aspect of the laboratory diagnosis of meningitis. Analysis of the CSF abnormalities produced by bacterial, mycobacterial, and fungal infections may greatly facilitate diagnosis and direct initial therapy. Basic studies of CSF that should be performed in all patients with meningitis include measurement of pressure, cell count and white cell differential; determination of glucose and protein levels; Gram's stain; and culture. In bacterial meningitis, Limulus lysate assay and tests to identify bacterial antigens may allow rapid diagnosis. Where there is strong suspicion of tuberculous or fungal meningitis, CSF should also be submitted for acid-fast stain, India ink preparation, and cryptococcal antigen; unless contraindicated by increased intracranial pressure, large volumes (up to 40-50 mL) should be obtained for culture. If a history of residence in the Southwest is elicited, complement-fixing antibodies to Coccidioides immitis should also be ordered. Newer tests based on immunologic methods or gene amplification techniques hold great promise for diagnosis of infections caused by organisms that are difficult to culture or present in small numbers. Despite the great value of lumbar puncture in the diagnosis of meningitis, injudicious use of the procedure may result in death from brain herniation. Lumbar puncture should be avoided if focal neurologic findings suggest concomitant mass lesion, as in brain abscess, and lumbar puncture should be approached with great caution if meningitis is accompanied by evidence of significant intracranial hypertension. Institution of antibiotic therapy for suspected meningitis should not be delayed while neuroradiologic studies are obtained to exclude abscess or while measures are instituted to reduce intracranial pressure.

Anticerebellar antibodies in neurologically normal patients with ovarian neoplasms.

Several groups of investigators have confirmed the occurrence of antibodies to Purkinje and other cerebellar neuronal populations in the serum and spinal fluid of patients with paraneoplastic cerebellar degeneration. Although this antibody response suggests that paraneoplastic cerebellar degeneration may have an autoimmune basis, it is not known what role anticerebellar antibodies play in the pathogenesis of this disorder or whether the presence of antibodies invariably results in cerebellar injury. We identified 3 patients with ovarian malignancies in whom high titers of circulating anticerebellar antibodies were present without clinical evidence of cerebellar disease. We followed these patients clinically and serologically until their deaths from their neoplasms. All 3 patients remained neurologically normal. In 2 of the patients, anticerebellar antibodies persisted at high titer. CSF obtained from 1 of these patients postmortem did not contain detectable levels of anticerebellar antibody, but histopathologic examination of her cerebellum revealed patchy loss of Purkinje cells. In the 3rd patient, antibody titers fell with removal of the primary tumor and chemotherapy but did not rise with tumor recurrence. Indirect immunofluorescence did not reveal anticerebellar antibodies in the serum or CSF of other patients with neoplasms, patients with other cerebellar disease, or normal controls. The present study demonstrates that patients with ovarian malignancies may occasionally develop antibodies that react with cerebellar neuronal antigens and can maintain this antibody response for protracted periods of time without clinically evident cerebellar injury. Tumor recurrence may not be accompanied by rise in titers of anticerebellar antibodies.

Immunoperoxidase labelling of rat brain sections with sera from patients with paraneoplastic cerebellar degeneration and systemic neoplasia.

Sera from patients with systemic cancer found by immunofluorescence staining to have antibodies to human cerebellar cell populations were reacted with vibratome sections of rat cerebellum and examined by peroxidase-antiperoxidase (PAP) methods. Seven patients with clinically or pathologically confirmed paraneoplastic cerebellar degeneration and two neurologically normal patients with high titers of anticerebellar antibodies were studied. Sera from all antibody-positive patients, but not from controls, produced intense staining of brain sections. Sera from patients with ovarian adenocarcinoma reacted predominantly with Purkinje cells and neurons within brainstem nuclei. Sera from patients with oat cell carcinoma and one patient with ductal carcinoma of the breast produced nuclear and cytoplasmic staining of neurons throughout the central nervous system. Serum from a patient with Hodgkin's disease labeled the peripheries of Purkinje cells and Golgi II cells. Serum from a patient with mixed mesodermal sarcoma of the ovary labeled Purkinje cells, basket cells, and scattered astrocytes. Staining of extraneural tissues was not observed. This study confirms the presence of antineural antibodies in patients with systemic neoplasia with and without paraneoplastic cerebellar degeneration and suggests that the antigens recognized by this antibody response may vary with the associated neoplasm.

Serial passage of murine K-papovavirus in primary cultures of mouse embryo cells. Brief report.

Murine K-papovavirus was serially passaged 10 times in primary cultures of mouse embryo cells, using cell suspensions and media from infected cultures to inoculate fresh flasks at each passage level. Titers of K virus infectivity in cell suspensions and media rose during serial passage, but viral hemagglutinating activity was not detected in cells or media before the 10th passage. Although the infectivity of K virus for mouse embryo cultures was enhanced by serial passage, lethality of the virus for suckling mice was lost. The present study represents the first successful serial transmission of K virus infection in vitro.