Jar Chi Lee

Control of microglial neurotoxicity by the fractalkine receptor

Microglia, the resident inflammatory cells of the CNS, are the only CNS cells that express the fractalkine receptor (CX3CR1). Using three different in vivo models, we show that CX3CR1 deficiency dysregulates microglial responses, resulting in neurotoxicity. Following peripheral lipopolysaccharide injections, Cx3cr1−/− mice showed cell-autonomous microglial neurotoxicity. In a toxic model of Parkinson disease and a transgenic model of amyotrophic lateral sclerosis, Cx3cr1−/− mice showed more extensive neuronal cell loss than Cx3cr1+ littermate controls. Augmenting CX3CR1 signaling may protect against microglial neurotoxicity, whereas CNS penetration by pharmaceutical CX3CR1 antagonists could increase neuronal vulnerability.

Differential roles of microglia and monocytes in the inflamed central nervous system

Phagocytic monocyte-derived macrophages associate with the nodes of Ranvier and initiate demyelination while microglia clear debris and display a suppressed metabolic gene signature in EAE.

Defining interferon β response Status in Multiple Sclerosis patients

IFN‐β is effective in reducing relapses and magnetic resonance imaging (MRI) lesions in multiple sclerosis (MS). It is assumed that individual therapeutic responses vary, but methods to identify IFN‐β responsiveness have not been validated. Our objective was to evaluate methods to classify IFN‐β responder status using relapses and MRI lesions. Data was analyzed from 172 patients who were followed up in a placebo‐controlled clinical trial of IFN‐β1a for 2 years. Patients were classified as responders or nonresponders using (1) the number of relapses during the 2‐year trial; (2) the number of new T2 lesions after 2 years; and (3) the number of gadolinium‐enhancing lesions at year 1 and year 2 on study. Outcomes included 2‐year change in the Expanded Disability Status Scale, Multiple Sclerosis Functional Composite, and brain parenchymal fraction. We found that subgroups with high on‐study relapse numbers had more disease progression, differences between responder subgroups were similar in the IFN‐β1a and placebo arms. In contrast, subgroups with high numbers of new MRI lesions had significantly more disease progression only in the IFN‐β1a arm. Baseline characteristics failed to account for differential outcome. New MRI lesion activity during IFN‐β1a treatment correlates with poor response to IFN‐β1a. MRI classification may facilitate rational therapeutic decisions, better clinical trial designs, and studies correlating biomarkers with therapeutic response. Ann Neurol 2004

Quantification of Self-Recognition in Multiple Sclerosis by Single-Cell Analysis of Cytokine Production

Identifying and quantifying autoaggressive responses in multiple sclerosis (MS) has been difficult in the past due to the low frequency of autoantigen-specific T cells, the high number of putative determinants on the autoantigens, and the different cytokine signatures of the autoreactive T cells. We used single-cell resolution enzyme-linked immunospot (ELISPOT) assays to study, directly ex vivo, proteolipid protein (PLP)-specific memory cell reactivity from MS patients and controls. Overlapping 9-aa-long peptides, spanning the entire PLP molecule in single amino acid steps, were used to determine the frequency and fine specificity of PLP-specific lymphocytes as measured by their IFN-γ and IL-5 production. MS patients (n = 22) responded to 4 times as many PLP peptides as did healthy controls (n = 22). The epitopes recognized in individual patients, up to 22 peptides, were scattered throughout the PLP molecule, showing considerable heterogeneity among MS patients. Frequency measurements showed that the number of PLP peptide-specific IFN-γ-producing cells averaged 11 times higher in MS patients than in controls. PLP peptide-induced IL-5-producing T cells occurred in very low frequencies in both MS patients and controls. This first comprehensive assessment of the anti-PLP-Th1/Th2 response in MS shows a greatly increased Th1 effector cell mass in MS patients. Moreover, the highly IFN-γ-polarized, IL-5-negative cytokine profile of the PLP-reactive T cells suggests that these cells are committed Th1 cells. The essential absence of uncommitted Th0 cells producing both cytokines may explain why therapeutic strategies that aim at the induction of immune deviation show little efficacy in the established disease.

Gray matter atrophy correlates with MS disability progression measured with MSFC but not EDSS

BACKGROUNDnGray matter (GM) pathology is an important component of the multiple sclerosis (MS) disease process. Accelerated gray matter atrophy has been observed in MS patients, but its relationship to neurological disability is not defined. This study was done to determine the relationship between whole brain, GM, and white matter (WM) atrophy and MS disability progression.nnnMETHODSnPatients with MS and Clinically Isolated Syndromes (CIS), and age- and gender-matched healthy controls were entered into an observational protocol. Baseline brain parenchymal fraction (BPF), GM fraction, and WM fraction, and change over 4 years were correlated with sustained disability progression over the entire study duration. Disability progression was measured using the Multiple Sclerosis Functional Composite (MSFC) and the Expanded Disability Status Scale (EDSS).nnnRESULTSnSeventy MS and CIS patients and 17 HCs were studied for an average of 6.6 years (range, 3.6-7.8 years). At the final visit, 7 patients were classified as CIS, 36 as relapsing-remitting MS (RRMS), and 27 as secondary progressive MS (SPMS). Baseline whole brain, GM, and WM atrophy predicted EDSS >6.0 at the last study visit. Twenty-one (33%) patients worsened using the EDSS to define disability progression; 29 (46%) worsened using MSFC to define disability progression. Patients with MSFC progression had significantly higher GM atrophy rates compared with patients who were stable on MSFC. White matter atrophy was similar in patients with and without disability progression. Atrophy rates were not different in patients with or without disability progression defined using EDSS.nnnCONCLUSIONSnWhole brain, GM, and WM atrophy predicted MS disability progression observed over the next 6.6 years. Gray matter atrophy rates over 4 years correlated with disability progression measured with the MSFC, but not EDSS. This indicates that MSFC defined disability progression is more closely linked to brain atrophy than EDSS defined disability progression, and provides important new insight into the poor correlation between MRI and clinical disability in MS. The findings confirm the clinical relevance of gray matter atrophy in MS.

Significance of T2 lesions in multiple sclerosis: A 13-year longitudinal study

To evaluate the relation between T2 lesions and disease severity in relapsing‐remitting multiple sclerosis (MS).

Association of fatigue and brain atrophy in multiple sclerosis

Functional imaging studies have demonstrated a relationship between fatigue and altered cerebral activation patterns in multiple sclerosis patients, but no relationship between fatigue and brain atrophy has been demonstrated. We hypothesized that the subjective complaint of fatigue would predict the severity of destructive brain pathology. We assessed the relationship between fatigue and brain atrophy longitudinally in a cohort of 134 patients previously enrolled in a 2-year clinical trial of interferon beta-1a and re-evaluated 8 years after randomization into the trial. Brain atrophy was measured using the brain parenchymal fraction (BPF), and disability was measured using the Multiple Sclerosis Functional Composite at baseline, year 2 and year 8. Fatigue was measured using the Sickness Impact Profiles Sleep and Rest Scale (SIPSR) at baseline, year 2 and year 8. Linear regression analyses were used to assess the relationship between changes in fatigue and atrophy progression. Worsening fatigue on the SIPSR during the initial 2 years was significantly associated with progressive brain atrophy over the subsequent 6 years. The relationships between fatigue and brain atrophy were independent of changes in disability, mood, or other MRI characteristics. This suggests that the subjective complaint of fatigue is linked to destructive pathologic processes in RRMS patients.

Immunomodulatory effects of interferon beta-1a in multiple sclerosis

Several studies have established a role for interferon beta (IFNbeta) as a treatment for relapsing-remitting multiple sclerosis (MS). IFNbeta has been reported to decrease the relapse rate, relapse severity, progression of disability and development of new brain lesions. Its mechanisms of action, however, remain unclear. We hypothesize that immunomodulatory effects of IFNbeta may underlie its clinical efficacy. We used intracellular cytokine flow cytometry to analyze the effects of IFNbeta-1a on expression of the anti-inflammatory cytokine, IL-10, and its effects on major co-stimulatory molecules in MS patients. We found that peripheral blood mononuclear cells (PBMC) produced more IL-10 following in vitro or in vivo treatment with IFNbeta-1a. The primary cellular sources of IL-10 were monocytes and CD4(+) T lymphocytes. IL-10 production in response to IFNbeta-1a was increased in unseparated PBMC compared to purified lymphocyte cultures, indicating that interaction between monocytes and lymphocytes may influence IL-10 production in response to IFNbeta-1a. Using flow cytometry, we monitored the ex vivo expression of two major co-stimulatory pairs-B7/CD28 and CD40/CD40L-before and after intramuscular IFNbeta-1a treatment of MS patients. IFNbeta-1a lowered the expression of B7.1 on circulating B cells and increased B7.2 expression on monocytes. CD40 expression on B cells was down-regulated, but CD40 on monocytes was up-regulated by IFNbeta-1a treatment. These data suggest that co-stimulatory molecules are modulated by IFNbeta, providing a possible mechanism for its in vivo immune regulatory effects.

Sex differences in cytokine responses to myelin peptides in multiple sclerosis

Many autoimmune diseases preferentially affect women; however, the underlying mechanisms for the sex differences are poorly understood. We examined sex-dependent differences in the immunologic response to myelin proteins in 22 multiple sclerosis (MS) patients and 22 healthy controls. Using ELISA spot assay (ELISPOT) methodology, interferon (IFN) gamma and IL-5 secretions were examined at the single cell level in response to overlapping proteolipid protein (PLP) peptides. As previously reported, we observed an overall disease effect in the IFNgamma response, such that MS patients were significantly higher than controls. With respect to PLP-induced IFNgamma secretion, both MS and control females responded higher than their corresponding males. Female MS patients demonstrated the highest responses compared to MS males or healthy controls of either sex. Although MS females had high IFNgamma responses to PLP, they had no IL-5 responses at all, suggesting strong Th1 skewing. In contrast, MS males had more IL-5 than control males, who lacked IL-5 responses. These IL-5 responses suggested that disease and gender are not independent, but rather interact to influence the cytokine response to myelin. The data suggest a gender bias towards Th1 responses in MS, which may contribute to the female predominance in this disease.

Disability progression in a clinical trial of relapsing-remitting multiple sclerosis eight-year follow-up

OBJECTIVEnTo investigate the value of Expanded Disability Status Scale (EDSS) worsening sustained for at least 6 months and other parameters as predictors for disability status.nnnDESIGNnRetrospective analysis of the Multiple Sclerosis Collaborative Research Group study data.nnnSETTINGnThe intramuscular interferon beta-1a pivotal trial was a double-blind, placebo-controlled phase 3 study.nnnPARTICIPANTSnPatients with relapsing-remitting multiple sclerosis who received at least 2 years of treatment and completed an EDSS evaluation 8 years postrandomization.nnnINTERVENTIONnThirty micrograms of intramuscular interferon beta-1a or placebo once weekly during the 2-year clinical trial.nnnMAIN OUTCOME MEASURESnPositive predictive values for 6-month sustained progression during 2 years were calculated to determine the ability to predict disability status at 8 years. A multivariate logistic regression model was used to assess the relationship between predictors and EDSS milestones at follow-up.nnnRESULTSnForty-five patients had sustained 6-month EDSS progression during the clinical trial and 115 did not. Progression during the trial was the strongest predictor of reaching EDSS milestones at the follow-up visit, 8 years after randomization. Other independent predictors were treatment arm assignment and baseline EDSS score.nnnCONCLUSIONnIn this phase 3 clinical trial of intramuscular interferon beta-1a, compared with effects of treatment, baseline EDSS score, and number of relapses during the study, worsening of 1 point or more on EDSS from baseline lasting 6 months was the strongest predictor of clinically significant disability 8 years after randomization into the clinical trial.