Paul S. Giacomini

Interferon-γ secretion by peripheral blood T-cell subsets in multiple sclerosis: Correlation with disease phase and interferon-β therapy

Interferon‐γ (IFN‐γ) is implicated as a participant in the immune effector and regulatory mechanisms considered to mediate the pathogenesis of multiple sclerosis (MS). We have used an intracellular cytokine staining technique to demonstrate that the proportion of ex vivo peripheral blood CD4 and CD8 T‐cell subsets expressing IFN‐γ is increased in secondary progressing (SP) MS patients, whereas the values in untreated relapsing‐remitting (RR) MS patients are reduced compared with those of controls. Patients treated with interferon‐β (IFN‐β) have an even more significant reduction in the percentage of IFN‐γ–secreting cells. The finding that the number of IFN‐γ–expressing CD8 cells is increased in SPMS patients, a group with reduced functional suppressor activity, and is most significantly reduced by IFN‐β therapy, which increases suppressor activity, indicates that IFN‐γ secretion by CD8 T cells and functional suppressor defects attributed to this cell subset in MS can be dissociated. Ann Neurol 1999;45:247–250

Maraviroc and JC Virus–Associated Immune Reconstitution Inflammatory Syndrome

The immune reconstitution inflammatory syndrome can be a serious complication of immune reversal in the treatment of progressive multifocal leukoencephalopathy. A new potential treatment for IRIS is described in this letter.

Evaluation of automated techniques for the quantification of grey matter atrophy in patients with multiple sclerosis

Several methods exist and are frequently used to quantify grey matter (GM) atrophy in multiple sclerosis (MS). Fundamental to all available techniques is the accurate segmentation of GM in the brain, a difficult task confounded even further by the pathology present in the brains of MS patients. In this paper, we examine the segmentations of six different automated techniques and compare them to a manually defined reference standard. Results demonstrate that, although the algorithms perform similarly to manual segmentations of cortical GM, severe shortcomings are present in the segmentation of deep GM structures. This deficiency is particularly relevant given the current interest in the role of GM in MS and the numerous reports of atrophy in deep GM structures.

Quantitative magnetization transfer and myelin water imaging of the evolution of acute multiple sclerosis lesions.

Quantitative magnetization transfer imaging provides in vivo estimates of liquid and semisolid constituents of tissue, while estimates of the liquid subpopulations, including myelin water, can be obtained from multicomponent T2 analysis. Both methods have been suggested to provide improved myelin specificity compared to conventional MRI. The goal of this study was to investigate the sensitivity of each technique to the progression of acute, gadolinium‐enhancing regions of multiple sclerosis. Magnetization transfer and T2 relaxometry data were acquired longitudinally over the course of 1 year in five relapsing‐remitting multiple sclerosis patients and in five healthy controls. Parametric maps were analyzed in enhancing lesions and normal‐appearing white matter regions. Quantitative magnetization transfer parameters in lesions were most abnormal at the time of enhancement and followed a pattern of recovery over subsequent months. Lesion myelin water fraction was abnormal but did not show a significant trend over time. Quantitative magnetization transfer was able to track the degree and timing of the partial recovery in enhancing multiple sclerosis lesions in a small group of patients, while the recovery was not detected in myelin water estimates, possibly due to their large variability. Our data suggest the recovery is characterized by quick resolution of inflammation and a slower remyelination process. Magn Reson Med, 2010.

Dimethyl Fumarate Treatment Mediates an Anti-Inflammatory Shift in B Cell Subsets of Patients with Multiple Sclerosis

The therapeutic mode of action of dimethyl fumarate (DMF), approved for treating patients with relapsing-remitting multiple sclerosis, is not fully understood. Recently, we and others demonstrated that Ab-independent functions of distinct B cell subsets are important in mediating multiple sclerosis (MS) relapsing disease activity. Our objective was to test whether and how DMF influences both the phenotype and functional responses of disease-implicated B cell subsets in patients with MS. High-quality PBMC were obtained from relapsing-remitting MS patients prior to and serially after initiation of DMF treatment. Multiparametric flow cytometry was used to monitor the phenotype and functional response-profiles of distinct B cell subsets. Total B cell counts decreased following DMF treatment, largely reflecting losses of circulating mature/differentiated (but not of immature transitional) B cells. Within the mature B cell pool, DMF had a greater impact on memory than naive B cells. In keeping with these in vivo effects, DMF treatment in vitro remarkably diminished mature (but not transitional B cell) survival, mediated by inducing apoptotic cell death. Although DMF treatment (both in vivo and in vitro) minimally impacted B cell IL-10 expression, it strongly reduced B cell expression of GM-CSF, IL-6, and TNF-α, resulting in a significant anti-inflammatory shift of B cell response profiles. The DMF-mediated decrease in B cell proinflammatory cytokine responses was further associated with reduced phosphorylation of STAT5/6 and NF-κB in surviving B cells. Together, these data implicate novel mechanisms by which DMF may modulate MS disease activity through shifting the balance between pro- and anti-inflammatory B cell responses.

Reproducibility of quantitative magnetization-transfer imaging parameters from repeated measurements.

Quantitative magnetization‐transfer imaging methods provide in vivo estimates of parameters of the two‐pool model for magnetization‐transfer in tissue. The goal of this study was to evaluate the reproducibility of quantitative magnetization‐transfer imaging parameter estimates in healthy subjects. Magnetization‐transfer–weighted and T1 relaxometry data were acquired in five healthy subjects at multiple time points, and the variability of the resulting fitted magnetization‐transfer parameters was evaluated. The impact of subsampling the magnetization‐transfer data and correcting field inhomogeneities was also evaluated. The key parameters measured in this study had an average variability, across time points, of 4.7% for the relative size of the restricted pool (F), 7.3% for the forward exchange constant (kf), 1.9% for the free pool spin‐lattice relaxation constant (R1f), 4.5% for the T2 of the free pool (T2f), and 2.3% for the T2 of the restricted pool (T2r). Our findings show that serial quantitative magnetization‐transfer imaging experiments can be performed reliably, with good reproducibility of the model parameter estimates, and demonstrate the reproducibility of acquisition schemes with fewer magnetization‐transfer contrasts. This establishes the feasibility of this technique for monitoring patients affected by degenerative white matter diseases while providing critical data to estimate the statistical power of such studies. Magn Reson Med, 2010.

Emerging multiple sclerosis disease-modifying therapies

Purpose of reviewWe focus on emerging therapies for the treatment of multiple sclerosis (MS) whose progress through late-phase clinical trials has furthered our understanding of MS pathophysiology. Recent findingsA promising array of potential new therapies for MS is targeting a broadening range of pathophysiologic mechanisms. Essentially all emerging therapies in late-phase clinical trials continue to focus on peripheral immune mechanisms that predominate early in the illness. The success of some of these, with varying mechanisms of action, has contributed to an evolution in our conceptual framework of MS. SummarySeveral of the emerging therapies focusing on immune-mediated disease mechanisms seem to offer stronger efficacy than the currently approved immune modulators for MS, although with potential for serious adverse effects. These therapies have also broadened our understanding of MS pathophysiology by demonstrating that significant decreases in new disease activity can be achieved through targeting of distinct cell types and mechanisms.

Non-conventional MRI techniques for measuring neuroprotection, repair and plasticity in multiple sclerosis.

Purpose of reviewTo summarize recent developments using non-conventional MRI techniques to measure neuroprotection, repair and plasticity in multiple sclerosis. Recent findingsRecent advances in our understanding of the pathogenesis of multiple sclerosis, particularly as it relates to the development of chronic disability, have led away from a ‘lesion-centric’ view of multiple sclerosis towards investigating neurodegeneration and pathology in normal appearing brain tissue. Advanced image processing techniques that measure atrophy globally and regionally also have provided insight into the putative mechanisms that contribute to neurodegeneration. In addition, novel quantitative imaging techniques that are more specific than conventional MRI for myelin and axonal pathology have been instrumental in revealing the dynamic nature of injury and repair of myelin and axons in lesions. Novel imaging techniques that are sensitive to the pathology of myelin and axons that happens in multiple sclerosis also provide a method by which we can measure neuroprotection and test the efficacy of putative therapeutic agents in multiple sclerosis. SummaryNon-conventional MRI techniques have contributed to a greater understanding of the complex pathogenesis of neurodegenerative phenomena that occur in multiple sclerosis. The pathological specificity of these novel imaging methods enables the evaluation of the neuroprotective effects of novel therapeutic strategies.

Effects of fumarates on circulating and CNS myeloid cells in multiple sclerosis

Dimethyl fumarate (DMF), a therapy for relapsing‐remitting multiple sclerosis (RRMS), is implicated as acting on inflammatory and antioxidant responses within both systemic immune and/or central nervous system (CNS) compartments. Orally administered DMF is rapidly metabolized to monomethyl fumarate (MMF). Our aim was to analyze the impact of fumarates on antiinflammatory and antioxidant profiles of human myeloid cells found in the systemic compartment (monocytes) and in the inflamed CNS (blood‐derived macrophages and brain‐derived microglia).

Dimethyl fumarate–induced lymphopenia in MS due to differential T-cell subset apoptosis

Objective: To examine the mechanism underlying the preferential CD8+ vs CD4+ T-cell lymphopenia induced by dimethyl fumarate (DMF) treatment of MS. Methods: Total lymphocyte counts and comprehensive T-cell subset analyses were performed in high-quality samples obtained from patients with MS prior to and serially following DMF treatment initiation. Random coefficient mixed-effects analysis was used to model the trajectory of T-cell subset losses in vivo. Survival and apoptosis of distinct T-cell subsets were assessed following in vitro exposure to DMF. Results: Best-fit modeling indicated that the DMF-induced preferential reductions in CD8+ vs CD4+ T-cell counts nonetheless followed similar depletion kinetics, suggesting a similar rather than distinct mechanism involved in losses of both the CD8+ and CD4+ T cells. In vitro, DMF exposure resulted in dose-dependent reductions in T-cell survival, which were found to reflect apoptotic cell death. This DMF-induced apoptosis was greater for CD8+ vs CD4+, as well as for memory vs naive, and conventional vs regulatory T-cell subsets, a pattern which mirrored preferential T-cell subset losses that we observed during in vivo treatment of patients. Conclusions: Differential apoptosis mediated by DMF may underlie the preferential lymphopenia of distinct T-cell subsets, including CD8+ and memory T-cell subsets, seen in treated patients with MS. This differential susceptibility of distinct T-cell subsets to DMF-induced apoptosis may contribute to both the safety and efficacy profiles of DMF in patients with MS.