Omar Malik

Innate Immunity in multiple sclerosis white matter lesions: expression of natural cytotoxicity triggering receptor 1 (NCR1)

BackgroundPathogenic or regulatory effects of natural killer (NK) cells are implicated in many autoimmune diseases, but evidence in multiple sclerosis (MS) and its murine models remains equivocal. In an effort to illuminate this, we have here analysed expression of the prototypic NK cell marker, NCR1 (natural cytotoxicity triggering receptor; NKp46; CD335), an activating receptor expressed by virtually all NK cells and therefore considered a pan-marker for NK cells. The only definitive ligand of NCR1 is influenza haemagglutinin, though there are believed to be others. In this study, we investigated whether there were differences in NCR1+ cells in the peripheral blood of MS patients and whether NCR1+ cells are present in white matter lesions.ResultsWe first investigated the expression of NCR1 on peripheral blood mononuclear cells and found no significant difference between healthy controls and MS patients. We then investigated mRNA levels in central nervous system (CNS) tissue from MS patients: NCR1 transcripts were increased more than 5 times in active disease lesions. However when we performed immunohistochemical staining of this tissue, few NCR1+ NK cells were identified. Rather, the major part of NCR1 expression was localised to astrocytes, and was considerably more pronounced in MS patients than controls. In order to further validate de novo expression of NCR1 in astrocytes, we used an in vitro staining of the human astrocytoma U251 cell line grown to model whether cell stress could be associated with expression of NCR1. We found up-regulation of NCR1 expression in U251 cells at both the mRNA and protein levels.ConclusionsThe data presented here show very limited expression of NCR1+ NK cells in MS lesions, the majority of NCR1 expression being accounted for by expression on astrocytes. This is compatible with a role of this cell-type and NCR1 ligand/receptor interactions in the innate immune response in the CNS in MS patients. This is the first report of NCR1 expression on astrocytes in MS tissue: it will now be important to unravel the nature of cellular interactions and signalling mediated through innate receptor expression on astrocytes.

Increased PK11195 PET binding in the cortex of patients with MS correlates with disability

Objective: Activated microglia are thought to play a major role in cortical gray matter (GM) demyelination in multiple sclerosis (MS). Our objective was to evaluate microglial activation in cortical GM of patients with MS in vivo and to explore its relationship to measures of disability. Methods: Using PET and optimized modeling and segmentation procedures, we investigated cortical 11C-PK11195 (PK11195) binding in patients with relapsing-remitting MS (RRMS), patients with secondary progressive MS (SPMS), and healthy controls. Disability was assessed with the Expanded Disability Status Scale (EDSS) and Multiple Sclerosis Impact Scale (MSIS-29). Results: Patients with MS showed increased cortical GM PK11195 binding relative to controls, which was multifocal and highest in the postcentral, middle frontal, anterior orbital, fusiform, and parahippocampal gyri. Patients with SPMS also showed additional increases in precentral, superior parietal, lingual and anterior superior, medial and inferior temporal gyri. Total cortical GM PK11195 binding correlated with EDSS scores, with a stronger correlation for the subgroup of patients with SPMS. In patients with SPMS, PK11195 binding also correlated with MSIS-29 scores. No correlation with disability measures was seen for PK11195 binding in white matter. Higher EDSS scores correlated with higher levels of GM PK11195 binding in the postcentral gyrus for patients with RRMS and in precentral gyrus for those with SPMS. Conclusions: Microglial activation in cortical GM of patients with MS can be assessed in vivo. The distribution is not uniform and shows a relationship to clinical disability. We speculate that the increased PK11195 binding corresponds to enhanced microglial activation described in postmortem SPMS cortical GM.

In Vivo Assessment of Brain White Matter Inflammation in Multiple Sclerosis with 18 F-PBR111 PET

PET radioligand binding to the 18-kD translocator protein (TSPO) in the brains of patients with multiple sclerosis (MS) primarily reflects activated microglia and macrophages. We previously developed genetic stratification for accurate quantitative estimation of TSPO using second-generation PET radioligands. In this study, we used 18F-PBR111 PET and MR imaging to measure relative binding in the lesional, perilesional, and surrounding normal-appearing white matter of MS patients, as an index of the innate immune response. Methods: 18F-PBR111 binding was quantified in 11 MS patients and 11 age-matched healthy volunteers, stratified according to the rs6971 TSPO gene polymorphism. Fluid-attenuated inversion recovery and magnetization transfer ratio (MTR) MR imaging were used to segment the white matter in MS patients as lesions, perilesional volumes, nonlesional white matter with reduced MTR, and nonlesional white matter with normal MTR. Results: 18F-PBR111 binding was higher in the white matter lesions and perilesional volumes of MS patients than in white matter of healthy controls (P < 0.05). Although there was substantial heterogeneity in binding between different lesions, a within-subject analysis showed higher 18F-PBR111 binding in MS lesions (P < 0.05) and in perilesional (P < 0.05) and nonlesional white matter with reduced MTR (P < 0.005) than in nonlesional white matter with a normal MTR. A positive correlation was observed between the mean 18F-PBR111 volume of distribution increase in lesions relative to nonlesional white matter with a normal MTR and the MS severity score (Spearman ρ = 0.62, P < 0.05). Conclusion: This study demonstrates that quantitative TSPO PET with a second-generation radioligand can be used to characterize innate immune responses in MS in vivo and provides further evidence supporting an association between the white matter TSPO PET signal in lesions and disease severity. Our approach is practical for extension to studies of the role of the innate immune response in MS for differentiation of antiinflammatory effects of new medicines and their longer term impact on clinical outcome.

Increased PK11195-PET binding in normal-appearing white matter in clinically isolated syndrome

The most accurate predictor of the subsequent development of multiple sclerosis in clinically isolated syndrome is the presence of lesions at magnetic resonance imaging. We used in vivo positron emission tomography with (11)C-(R)-PK11195, a biomarker of activated microglia, to investigate the normal-appearing white matter and grey matter of subjects with clinically isolated syndrome to explore its role in the development of multiple sclerosis. Eighteen clinically isolated syndrome and eight healthy control subjects were recruited. Baseline assessment included: history, neurological examination, expanded disability status scale, magnetic resonance imaging and PK11195-positron emission tomography scans. All assessments except the PK11195-positron emission tomography scan were repeated over 2 years. SUPERPK methodology was used to measure the binding potential relative to the non-specific volume, BPND. We show a global increase of normal-appearing white matter PK11195 BPND in clinically isolated syndrome subjects compared with healthy controls (P = 0.014). Clinically isolated syndrome subjects with T2 magnetic resonance imaging lesions had higher PK11195 BPND in normal-appearing white matter (P = 0.009) and their normal-appearing white matter PK11195 BPND correlated with the Expanded Disability Status Scale (P = 0.007; r = 0.672). At 2 years those who developed dissemination in space or multiple sclerosis, had higher PK11195 BPND in normal-appearing white matter at baseline (P = 0.007 and P = 0.048, respectively). Central grey matter PK11195 BPND was increased in subjects with clinically isolated syndrome compared to healthy controls but no difference was found in cortical grey matter PK11195 BPND. Microglial activation in clinically isolated syndrome normal-appearing white matter is diffusely increased compared with healthy control subjects and is further increased in those who have magnetic resonance imaging lesions. Furthermore microglial activation in clinically isolated syndrome normal-appearing white matter is also higher in those subjects who developed multiple sclerosis at 2 years. Our finding, if replicated in a larger study, could be of prognostic value and aid early treatment decisions in clinically isolated syndrome.

Hippocampal Neuroinflammation, Functional Connectivity, and Depressive Symptoms in Multiple Sclerosis

Background Depression, a condition commonly comorbid with multiple sclerosis (MS), is associated more generally with elevated inflammatory markers and hippocampal pathology. We hypothesized that neuroinflammation in the hippocampus is responsible for depression associated with MS. We characterized the relationship between depressive symptoms and hippocampal microglial activation in patients with MS using the 18-kDa translocator protein radioligand [18F]PBR111. To evaluate pathophysiologic mechanisms, we explored the relationships between hippocampal neuroinflammation, depressive symptoms, and hippocampal functional connectivities defined by resting-state functional magnetic resonance imaging. Methods The Beck Depression Inventory (BDI) was administered to 11 patients with MS and 22 healthy control subjects before scanning with positron emission tomography and functional magnetic resonance imaging. We tested for higher [18F]PBR111 uptake in the hippocampus of patients with MS relative to healthy control subjects and examined the correlations between [18F]PBR111 uptake, BDI scores, and hippocampal functional connectivities in the patients with MS. Results Patients with MS had an increased hippocampal [18F]PBR111 distribution volume ratio relative to healthy control subjects (p = .024), and the hippocampal distribution volume ratio was strongly correlated with the BDI score in patients with MS (r = .86, p = .006). Hippocampal functional connectivities to the subgenual cingulate and prefrontal and parietal regions correlated with BDI scores and [18F]PBR111 distribution volume ratio. Conclusions Our results provide evidence that hippocampal microglial activation in MS impairs the brain functional connectivities in regions contributing to maintenance of a normal affective state. Our results suggest a rationale for the responsiveness of depression in some patients with MS to effective control of brain neuroinflammation. Our findings also lend support to further investigation of the role of inflammatory processes in the pathogenesis of depression more generally.

Anti-JC virus antibody titres increase over time with natalizumab treatment.

Background: Anti-JC virus antibody status is a risk factor for progressive multifocal leukoencephalopathy after natalizumab treatment in multiple sclerosis. Previous studies have used a cross-sectional approach to conclude that the presence and duration of natalizumab treatment does not influence anti-JCV Ab seropositivity. Objectives: Using a longitudinal approach, we measured change in anti-JCV Ab results after natalizumab treatment. Methods: Anti-JCV Ab results (n = 1154) from the second-generation STRATIFY JCV™ DxSelect™ test were analysed from an observational cohort of MS patients on natalizumab (n = 485; n = 340 with repeat testing; n = 657 repeat tests on natalizumab). Results: Across sequential paired tests, seroconversion rate was greater than seroreversion rate (40/364 (11.0%) versus 18/293 (6.1%); p < 0.05). Moreover, anti-JCV Ab index increased across longitudinal paired tests (mA–B 0.102; paired t(656) = 5.0; p < 0.0001). This magnitude of Ab level increase far exceeds that expected due to increasing age alone. Conclusion: Our data suggest that natalizumab therapy is associated with a significant and substantial increase in anti-JCV Ab index over time. Further work should focus on the underlying mechanisms of this phenomenon, and the clinical relevance to risk stratification.

CADASIL with cord involvement associated with a novel and atypical NOTCH3 mutation

Background Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL) is a hereditary cause of cerebral small-vessel disease associated with one of many recognised mutations of the NOTCH3 gene. Spinal cord involvement is not a recognised feature. The authors describe a unique CADASIL pedigree that manifested a stereotypical pattern of cord lesions, in association with a novel and atypical NOTCH3 mutation. Methods Clinical, radiological, laboratory and genetic characterisation of three affected family members. The associated NOTCH3 mutation was further evaluated by site-directed mutagenesis, immunohistochemistry, CBF1-transcription reporter assay, and screened for in 100 unrelated pathologically confirmed multiple sclerosis (MS) patients. Results Three members of a family presented with CADASIL caused by a novel NOTCH3 missense mutation, C212Y. Two daughters of the proband also manifested a distinctive pattern of cord lesions confined to the posterocentral zone, cerebral lesions showing both a demyelinating and a typical CADASIL topography, positive antinuclear antibodies and intrathecally derived oligoclonal bands. The mutation occurred in exon 4—that is, outside the Notch3 ligand-binding domain—yet unusually for this location impaired Notch function as assessed by Jagged1 signal transduction. The C212Y mutation did not occur in 100 separate MS cases. Conclusions This is the first description of an inherited pattern of cord lesions in association with CADASIL. The fact that certain features of dysregulated immunity also occurred, in association with a novel and atypical loss-of-function NOTCH3 mutation, supports evidence for functional interactions of Notch3 with the immune system, in addition to its vascular support role.

Hematopoietic mobilization Potential biomarker of response to natalizumab in multiple sclerosis

Objective: To ascertain the mobilization from the bone marrow and the functional relevance of the increased number of circulating hematopoietic stem and progenitor cells (HSPC) induced by the anti-α-4 integrin antibody natalizumab in patients with multiple sclerosis (MS). Methods: We evaluated CD45lowCD34+ HSPC frequency by flow cytometry in blood from 45 natalizumab-treated patients (12 of whom were prospectively followed during the first year of treatment as part of a pilot cohort and 16 prospectively followed for validation), 10 untreated patients with MS, and 24 healthy donors. In the natalizumab-treated group, we also assessed sorted HSPC cell cycle status, T- and B-lymphocyte subpopulation frequencies (n = 29), and HSPC differentiation potential (n = 10). Results: Natalizumab-induced circulating HSPC were predominantly quiescent, suggesting recent mobilization from the bone marrow, and were capable of differentiating ex vivo. Circulating HSPC numbers were significantly increased during natalizumab, but heterogeneously, allowing the stratification of mobilizer and nonmobilizer subgroups. Nonmobilizer status was associated with persistence of disease activity during treatment. The frequency of B cells and CD103+CD8+ regulatory T cells persistently increased, more significantly in mobilizer patients, who also showed a specific naive/memory B-cell profile. Conclusions: The data suggest that natalizumab-induced circulating HSPC increase is the result of true mobilization from the bone marrow and has clinical and immunologic relevance. HSPC mobilization, associated with clinical remission and increased proportion of circulating B and regulatory T cells, may contribute to the treatments mode of action; thus, HSPC blood counts could represent an early biomarker of responsiveness to natalizumab.

A Comparison of Magnetization Transfer Methods to Assess Brain and Cervical Cord Microstructure in Multiple Sclerosis.

Demyelination is a core pathological feature of multiple sclerosis (MS) and spontaneous remyelination appears to be an important mechanism for repair in the disease. Magnetization transfer ratio imaging (MTR) has been used extensively to evaluate demyelination, although limitations to its specificity are recognized. MT saturation imaging (MTsat) removes some of the T1 dependence of MTR. We have performed a comparative evaluation of MTR and MTsat imaging in a mixed group of subjects with active MS, to explore their relative sensitivity to pathology relevant to explaining clinical outcomes.

Age independently affects myelin integrity as detected by magnetization transfer magnetic resonance imaging in multiple sclerosis.

Background Multiple sclerosis (MS) is a heterogeneous disorder with a progressive course that is difficult to predict on a case-by-case basis. Natural history studies of MS have demonstrated that age influences clinical progression independent of disease duration. Objective To determine whether age would be associated with greater CNS injury as detected by magnetization transfer MRI. Materials and methods Forty MS patients were recruited from out-patient clinics into two groups stratified by age but with similar clinical disease duration as well as thirteen controls age-matched to the older MS group. Images were segmented by automated programs and blinded readers into normal appearing white matter (NAWM), normal appearing gray matter (NAGM), and white matter lesions (WMLs) and gray matter lesions (GMLs) in the MS groups. WML and GML were delineated on T2-weighted 3D fluid-attenuated inversion recovery (FLAIR) and T1 weighted MRI volumes. Mean magnetization transfer ratio (MTR), region volume, as well as MTR histogram skew and kurtosis were calculated for each region. Results All MTR measures in NAGM and MTR histogram metrics in NAWM differed between MS subjects and controls, as expected and previously reported by several studies, but not between MS groups. However, MTR measures in the WML did significantly differ between the MS groups, in spite of no significant differences in lesion counts and volumes. Conclusions Despite matching for clinical disease duration and recording no significant WML volume difference, we demonstrated strong MTR differences in WMLs between younger and older MS patients. These data suggest that aging-related processes modify the tissue response to inflammatory injury and its clinical outcome correlates in MS.