David N. Irani

Multiple sclerosis risk after optic neuritis: Final optic neuritis treatment trial follow-up

OBJECTIVE To assess the risk of developing multiple sclerosis (MS) after optic neuritis and the factors predictive of high and low risk. DESIGN Subjects in the Optic Neuritis Treatment Trial, who were enrolled between July 1, 1988, and June 30, 1991, were followed up prospectively for 15 years, with the final examination in 2006. SETTING Neurologic and ophthalmologic examinations at 13 clinical sites. PARTICIPANTS Three hundred eighty-nine subjects with acute optic neuritis. MAIN OUTCOME MEASURES Development of MS and neurologic disability assessment. RESULTS The cumulative probability of developing MS by 15 years after onset of optic neuritis was 50% (95% confidence interval, 44%-56%) and strongly related to presence of lesions on a baseline non-contrast-enhanced magnetic resonance imaging (MRI) of the brain. Twenty-five percent of patients with no lesions on baseline brain MRI developed MS during follow-up compared with 72% of patients with 1 or more lesions. After 10 years, the risk of developing MS was very low for patients without baseline lesions but remained substantial for those with lesions. Among patients without lesions on MRI, baseline factors associated with a substantially lower risk for MS included male sex, optic disc swelling, and certain atypical features of optic neuritis. CONCLUSIONS The presence of brain MRI abnormalities at the time of an optic neuritis attack is a strong predictor of the 15-year risk of MS. In the absence of MRI-detected lesions, male sex, optic disc swelling, and atypical clinical features of optic neuritis are associated with a low likelihood of developing MS. This natural history information is important when considering prophylactic treatment for MS at the time of a first acute onset of optic neuritis.

Cerebrospinal fluid levels of MMP-2, 7, and 9 are elevated in association with human immunodeficiency virus dementia.

Pathological evidence suggests that alterations of the blood–brain barrier (BBB) may occur in association with human immunodeficiency virus (HIV) dementia (HIVD). Increased BBB permeability could contribute to the development of dementia by facilitating the entry of activated and infected monocytes, as well as potentially toxic serum proteins, into the central nervous system. One mechanism by which BBB permeability may be altered is through increased activity of select matrix metalloproteinases (MMPs). In the present study, we examined the possibility that MMPs that target critical BBB proteins, including laminin, entactin, and collagen type IV, are elevated in the cerebrospinal fluid (CSF) of patients with HIVD. We also examined the possibility that such MMPs could be produced by brain‐derived cells, and that MMP production by these cells might be increased by tumor necrosis factor‐α, an inflammatory cytokine that is produced by HIV‐infected monocytes/microglia and is elevated in HIVD. By using western blot and enzyme‐linked immunosorbent assay, we observed that CSF levels of pro–MMP‐2 and pro–MMP‐7 were increased in association with HIVD. In addition, through the use of gelatin substrate zymography, a sensitive functional assay for MMP‐2 and MMP‐9, we observed that MMP‐2 or pro–MMP‐9 activity was more frequently detectable in the CSF of individuals with HIV dementia (9/16) than in the CSF from either nondemented seropositive (2/11) or seronegative (0/11) controls. Although the presence of MMPs in the serum could contribute to elevated levels in the CSF, we also show that brain‐derived cells release MMP‐2, 7, and 9, and that such release is increased after their stimulation with tumor necrosis factor‐α. Together, these results suggest that elevated CSF levels of select MMPs may reflect immune activation within the central nervous system. They also suggest that further studies may be warranted to determine whether these proteins may play a role in the development of symptomatic neurological disease.

Immune reconstitution inflammatory syndrome in the CNS of HIV-infected patients

Objective: To describe challenges in diagnosis and management of patients with clinical syndromes of immune reconstitution inflammatory syndrome (IRIS) involving the CNS. Methods: The authors describe three patients with clinically distinct neurologic manifestations of IRIS with HIV infection who presented as diagnostic and therapeutic challenges. Results: One patient with cryptococcal meningitis developed acute cerebellitis with mass effect and brainstem compression. Corticosteroid therapy was associated with complete resolution of the cerebellar lesion but the patient developed VZV encephalitis. Another patient with progressive multifocal leukoencephalopathy developed subacute progression of focal neurologic deficits associated with contrast enhancing lesions on brain MRI. This patient had spontaneous resolution of the lesion but was left with residual deficits. One patient developed a progressive dementing syndrome and deterioration over several months resulting in coma during combination antiretroviral therapy. A brain biopsy in this latter patient showed massive infiltration of T lymphocytes predominantly of the CD8 subtype. This patient had a significant improvement with corticosteroids and change in antiretroviral regimen although she was left with residual cognitive impairment. Conclusions: Immune reconstitution inflammatory syndrome should be suspected in patients who show clinical or radiologic deterioration following initiation of antiretroviral therapy accompanied with improvement in CD4 cell count and viral load. Some patients may respond to a brief course of treatment with corticosteroids.

Interferon β in multiple sclerosis: is IL-12 suppression the key?

Abstract Recently, much has been learned about the immunology of multiple sclerosis (MS). However, a mechanistic understanding of currently employed immunomodulatory therapies has lagged behind, hindering both the search for more effective agents and clearer insight into the immunopathogenesis of MS. Christopher Karp and colleagues explore a unifying hypothesis for the mechanism of action of interferon β in MS: suppression of interleukin 12 production.

Cleavage of Cystatin C in the Cerebrospinal Fluid of Patients with Multiple Sclerosis

The diagnosis of multiple sclerosis (MS) can be challenging because of the lack of a specific diagnostic test. Recent advances in proteomics, however, offer new opportunities for biomarker discovery and the study of disease pathogenesis.

Viral-Induced Spinal Motor Neuron Death Is Non-Cell-Autonomous and Involves Glutamate Excitotoxicity

Neuroadapted Sindbis virus (NSV) is a neurotropic virus capable of inducing the death of spinal motor neurons in mice and rats. In this study we investigated the mechanisms that underlie NSV-induced motor neuron death. We found that many degenerating spinal motor neurons were not infected directly with NSV, suggesting that bystander cell death occurs. An excitotoxic mechanism was confirmed when blockade of calcium-permeable AMPA receptors attenuated motor neuron death both in vitro and in vivo. Blockade of astroglial glutamate reuptake potentiated NSV-induced motor neuron loss in vivo, suggesting that astrocyte-mediated removal of perisynaptic glutamate is important in limiting NSV-induced excitotoxic injury. Astroglial glutamate transport was reduced markedly in the spinal cord during NSV infection, in advance of motor neuron injury in susceptible mice. In contrast, we found 5.6-fold elevated glutamate uptake in the spinal cords of mice resistant to NSV-induced paralysis. Likewise, minocycline markedly increased spinal cord glutamate transport and protected mice from NSV-induced motor neuron death. These studies suggest that NSV infection triggers a cascade of events in the spinal cord resulting in impaired astrocytic glutamate transport and excitotoxic injury of motor neurons mediated via calciumpermeable AMPA receptors. Similar changes may occur in other motor neuron disorders such as amyotrophic lateral sclerosis or West Nile Virus-induced poliomyelitis, suggesting a common tissue injury pathway.

Relapse in Guillain‐Barré syndrome after treatment with human immune globulin

Seven adult patients received human immune globulin intravenously as initial therapy for Guillain-Barré syndrome. Although all patients initially stabilized or improved, five patients deteriorated 1 to 16 days after completion of treatment. In all five patients, clinical worsening included loss of at least one functional grade together with a decreased forced vital capacity. We subsequently treated each patient with a course of plasma exchange, which led to varying degrees of clinical improvement in four. In contrast to previously reported relapse rates for Guillain-Barré syndrome, our experience suggests that clinically significant relapses may occur in patients more often following human immune globulin therapy than after either plasma exchange or no therapy.

The Inflammatory Cytokine, Interleukin-1 Beta, Mediates Loss of Astroglial Glutamate Transport and Drives Excitotoxic Motor Neuron Injury in the Spinal Cord During Acute Viral Encephalomyelitis

Astrocytes remove glutamate from the synaptic cleft via specific transporters, and impaired glutamate reuptake may promote excitotoxic neuronal injury. In a model of viral encephalomyelitis caused by neuroadapted Sindbis virus (NSV), mice develop acute paralysis and spinal motor neuron degeneration inhibited by the AMPA receptor antagonist, NBQX. To investigate disrupted glutamate homeostasis in the spinal cord, expression of the main astroglial glutamate transporter, GLT‐1, was examined. GLT‐1 levels declined in the spinal cord during acute infection while GFAP expression was preserved. There was simultaneous production of inflammatory cytokines at this site, and susceptible animals treated with drugs that blocked IL‐1β release also limited paralysis and prevented the loss of GLT‐1 expression. Conversely, infection of resistant mice that develop mild paralysis following NSV challenge showed higher baseline GLT‐1 levels as well as lower production of IL‐1β and relatively preserved GLT‐1 expression in the spinal cord compared to susceptible hosts. Finally, spinal cord GLT‐1 expression was largely maintained following infection of IL‐1β‐deficient animals. Together, these data show that IL‐1β inhibits astrocyte glutamate transport in the spinal cord during viral encephalomyelitis. They provide one of the strongest in vivo links between innate immune responses and the development of excitotoxicity demonstrated to date.

Aseptic Meningitis and Viral Myelitis

Meningitis and myelitis represent common and very infrequent viral infections of the central nervous system, respectively. The number of cases of viral meningitis that occurs annually exceeds the total number of meningitis cases caused by all other etiologies combined. Focal central nervous system infections, such as occur in the spinal cord with viral myelitis, are much less common and may be confused with noninfectious disorders that cause acute flaccid paralysis. This article reviews some of the important clinical features, epidemiology, diagnostic approaches, and management strategies for patients with aseptic meningitis and viral myelitis. Particular focus is placed on the diseases caused by enteroviruses, which as a group account for most aseptic meningitis cases and many focal infections of the spinal cord.

Isolation of brain parenchymal lymphocytes for flow cytometric analysis: Application to acute viral encephalitis

A strategy for the isolation of mononuclear cells from the brain parenchyma of mice with ongoing central nervous system (CNS) inflammation has been developed in order to permit flow cytometric (FCM) analysis of these cell populations. Sindbis virus (SV) encephalitis in mice is characterized morphologically by an infiltration of mononuclear cells into both brain parenchyma and cerebrospinal fluid (CSF). Perfused brain tissue from infected animals is collected, homogenized, and subjected to a mild enzymatic digestion. A sedimentation at unit gravity is performed to remove any large particulate debris, and the remaining tissue is then centrifuged over a modified density gradient which separates intact cells from smaller tissue fragments. Cells collected directly from these gradients can be stained with monoclonal antibodies and analyzed by FCM without further manipulation. Data generated by this method correlates with previous studies of SV encephalitis using immunohistochemical analysis of brain tissue sections to quantify mononuclear cell types. This suggests that representative samples of the cellular infiltrate are obtained using this technique. The approach however, offers the possibility of more sophisticated and quantitative analyses of CNS inflammatory cells which is unobtainable by tissue section staining.