Roberta Magliozzi

Detection of Ectopic B‐cell Follicles with Germinal Centers in the Meninges of Patients with Secondary Progressive Multiple Sclerosis

Multiple sclerosis (MS) is characterized by synthesis of oligoclonal immunoglobulins and the presence of B‐cell clonal expansions in the central nervous system (CNS). Because ectopic lymphoid tissue generated at sites of chronic inflammation is thought to be important in sustaining immunopathological processes, we have investigated whether structures resembling lymphoid follicles could be identified in the CNS of MS patients. Sections from post‐mortem MS brains and spinal cords were screened using immunohistochemistry for the presence of CD20+ B‐cells, CD3+ T‐cells, CD 138+ plasma cells and CD21+, CD35+ follicular dendritic cells, and for the expression of lymphoid chemokines (CXCL13, CCL21) and peripheral node addressin (PNAd). Lymphoid follicle‐like structures containing B‐cells, T‐cells and plasma cells, and a network of follicular dendritic cells producing CXCL13 were observed in the cerebral meninges of 2 out of 3 patients with secondary progressive MS, but not in relapsing remitting and primary progressive MS. We also show that proliferating B‐cells are present in intrameningeal follicles, a finding which is suggestive of germinal center formation. No follicle‐like structures were detected in parenchymal lesions. The formation of ectopic lymphoid follicles in the meninges of patients with MS could represent a critical step in maintaining humoral autoimmunity and in disease exacerbation.

Meningeal inflammation is widespread and linked to cortical pathology in multiple sclerosis

Meningeal inflammation in the form of ectopic lymphoid-like structures has been suggested to play a prominent role in the development of cerebral cortical grey matter pathology in multiple sclerosis. The aim of this study was to analyse the incidence and distribution of B cell follicle-like structures in an extensive collection of cases with secondary progressive multiple sclerosis with a wide age range and to determine their relationship to diffuse meningeal inflammation, white matter perivascular infiltrates and microglial activation. One hundred and twenty three cases with secondary progressive multiple sclerosis were examined for the presence of meningeal and perivascular immune cell infiltrates in tissue blocks and/or whole coronal macrosections encompassing a wide array of brain areas. Large, dense, B cell-rich lymphocytic aggregates were screened for the presence of follicular dendritic cells, proliferating B cells and plasma cells. Ectopic B cell follicle-like structures were found, with variable frequency, in 49 cases (40%) and were distributed throughout the forebrain, where they were most frequently located in the deep sulci of the temporal, cingulate, insula and frontal cortex. Subpial grey matter demyelinated lesions were located both adjacent to, and some distance from such structures. The presence of B cell follicle-like structures was associated with an accompanying quantitative increase in diffuse meningeal inflammation that correlated with the degree of microglial activation and grey matter cortical demyelination. The median age of disease onset, time to disease progression, time to wheelchair dependence and age at death all differed significantly in these cases when compared with those without B cell follicle-like structures. Our findings suggest that meningeal infiltrates may play a contributory role in the underlying subpial grey matter pathology and accelerated clinical course, which is exacerbated in a significant proportion of cases by the presence of B cell follicle-like structures.

A Gradient of neuronal loss and meningeal inflammation in multiple sclerosis

Prominent inflammation with formation of ectopic B‐cell follicle‐like structures in the meninges in secondary progressive multiple sclerosis (MS) (SPMS) is associated with extensive cortical pathology and an exacerbated disease course. Our objective was to evaluate the cellular substrates of the cortical damage to understand the role of meningeal inflammation in MS pathology.

Intracerebral expression of CXCL13 and BAFF is accompanied by formation of lymphoid follicle-like structures in the meninges of mice with relapsing experimental autoimmune encephalomyelitis

Given the abnormalities in B-cell activity occurring in the central nervous system (CNS) of patients with multiple sclerosis (MS), we have explored the possibility that CNS inflammation induced in mouse models of experimental autoimmune encephalomyelitis (EAE) triggers expression of molecules that control the development and functional organization of lymphoid follicles, the sites where B-cell responses are initiated. By reverse transcription-polymerase chain reaction (RT-PCR), we find that gene expression of CXCL13, a chemokine involved in B-cell recruitment into lymphoid follicles, and BAFF, a key regulator of B-cell survival, is markedly and persistently upregulated in the CNS of mice with relapsing-remitting and chronic-relapsing EAE. Using immunohistochemical techniques, we also show the presence of lymphoid follicle-like structures containing B cells and a reticulum of CXCL13+ and FDC-M1+ follicular dendritic cells within the meninges of several mice undergoing progressive relapsing EAE. These observations indicate that, under chronic inflammatory conditions, the less immunoprivileged meningeal compartment is the site where ectopic lymphoid follicles preferentially develop and where pathogenic B-cell responses could be sustained in autoimmune disorders of the CNS.

Meningeal inflammation plays a role in the pathology of primary progressive multiple sclerosis

The primary progressive form of multiple sclerosis is characterized by accrual of neurological dysfunction from disease onset without remission and it is still a matter of debate whether this disease course results from different pathogenetic mechanisms compared with secondary progressive multiple sclerosis. Inflammation in the leptomeninges has been identified as a key feature of secondary progressive multiple sclerosis and may contribute to the extensive cortical pathology that accompanies progressive disease. Our aim was to investigate the extent of perivascular and meningeal inflammation in primary progressive multiple sclerosis in order to understand their contribution to the pathogenetic mechanisms associated with cortical pathology. A comprehensive immunohistochemical analysis was performed on post-mortem brain tissue from 26 cases with primary progressive multiple sclerosis. A variable extent of meningeal immune cell infiltration was detected and more extensive demyelination and neurite loss in the cortical grey matter was found in cases exhibiting an increased level of meningeal inflammation. However, no tertiary lymphoid-like structures were found. Profound microglial activation and reduction in neuronal density was observed in both the lesions and normal appearing grey matter compared with control cortex. Furthermore, cases with primary progressive multiple sclerosis with extensive meningeal immune cell infiltration exhibited a more severe clinical course, including a shorter disease duration and younger age at death. Our data suggest that generalized diffuse meningeal inflammation and the associated inflammatory milieu in the subarachnoid compartment plays a role in the pathogenesis of cortical grey matter lesions and an increased rate of clinical progression in primary progressive multiple sclerosis.

Exploring the origins of grey matter damage in multiple sclerosis

Multiple sclerosis is characterized at the gross pathological level by the presence of widespread focal demyelinating lesions of the myelin-rich white matter. However, it is becoming clear that grey matter is not spared, even during the earliest phases of the disease. Furthermore, grey matter damage may have an important role both in physical and cognitive disability. Grey matter pathology involves both inflammatory and neurodegenerative mechanisms, but the relationship between the two is unclear. Histological, immunological and neuroimaging studies have provided new insight in this rapidly expanding field, and form the basis of the most recent hypotheses on the pathogenesis of grey matter damage.

Epstein-Barr virus latent infection and BAFF expression in B cells in the multiple sclerosis brain: implications for viral persistence and intrathecal B-cell activation.

A cardinal feature of multiple sclerosis (MS) is the persistent intrathecal synthesis of antibodies. Our previous finding that a large fraction of B cells infiltrating the MS brain are infected with Epstein-Barr virus (EBV) raises the possibility that this virus, because of its ability to establish a latent infection in B cells and interfere with their differentiation, contributes to B-cell dysregulation in MS. The aim of this study was to gain further insight into EBV latency programs and their relationship to B-cell activation in the MS brain. Immunohistochemical analysis of postmortem MS brain samples harboring large EBV deposits revealed that most B cells in white matter lesions, meninges, and ectopic B-cell follicles are CD27+ antigen-experienced cells and coexpress latent membrane protein 1and latent membrane protein 2A, 2 EBV-encoded proteins that provide survival and maturation signals to B cells. By combining laser-capture microdissection with preamplification reverse transcription-polymerase chain reaction techniques, EBV latency transcripts (latent membrane protein 2A, EBV nuclear antigen 1) were detected in all MS brain samples analyzed. We also found that B cell-activating factor of the tumor necrosis factor family is expressed in EBV-infected B cells in acute MS lesions and ectopic B-cell follicles. These findings support a role for EBV infection in B-cell activation in the MS brain and suggest that B cell-activating factor of the tumor necrosis factor family produced by EBV-infected B cells may contribute to this process resulting in viral persistence and, possibly, disruption of B-cell tolerance.

Inhibition of soluble tumour necrosis factor is therapeutic in experimental autoimmune encephalomyelitis and promotes axon preservation and remyelination.

Tumour necrosis factor is linked to the pathophysiology of various neurodegenerative disorders including multiple sclerosis. Tumour necrosis factor exists in two biologically active forms, soluble and transmembrane. Here we show that selective inhibition of soluble tumour necrosis factor is therapeutic in experimental autoimmune encephalomyelitis. Treatment with XPro1595, a selective soluble tumour necrosis factor blocker, improves the clinical outcome, whereas non-selective inhibition of both forms of tumour necrosis factor with etanercept does not result in protection. The therapeutic effect of XPro1595 is associated with axon preservation and improved myelin compaction, paralleled by increased expression of axon-specific molecules (e.g. neurofilament-H) and reduced expression of non-phosphorylated neurofilament-H which is associated with axon damage. XPro1595-treated mice show significant remyelination accompanied by elevated expression of myelin-specific genes and increased numbers of oligodendrocyte precursors. Immunohistochemical characterization of tumour necrosis factor receptors in the spinal cord following experimental autoimmune encephalomyelitis shows tumour necrosis factor receptor 1 expression in neurons, oligodendrocytes and astrocytes, while tumour necrosis factor receptor 2 is localized in oligodendrocytes, oligodendrocyte precursors, astrocytes and macrophages/microglia. Importantly, a similar pattern of expression is found in post-mortem spinal cord of patients affected by progressive multiple sclerosis, suggesting that pharmacological modulation of tumour necrosis factor receptor signalling may represent an important target in affecting not only the course of mouse experimental autoimmune encephalomyelitis but human multiple sclerosis as well. Collectively, our data demonstrate that selective inhibition of soluble tumour necrosis factor improves recovery following experimental autoimmune encephalomyelitis, and that signalling mediated by transmembrane tumour necrosis factor is essential for axon and myelin preservation as well as remyelination, opening the possibility of a new avenue of treatment for multiple sclerosis.

Selection of novel reference genes for use in the human central nervous system: A BrainNet Europe Study

The use of an appropriate reference gene to ensure accurate normalisation is crucial for the correct quantification of gene expression using qPCR assays and RNA arrays. The main criterion for a gene to qualify as a reference gene is a stable expression across various cell types and experimental settings. Several reference genes are commonly in use but more and more evidence reveals variations in their expression due to the presence of on-going neuropathological disease processes, raising doubts concerning their use. We conducted an analysis of genome-wide changes of gene expression in the human central nervous system (CNS) covering several neurological disorders and regions, including the spinal cord, and were able to identify a number of novel stable reference genes. We tested the stability of expression of eight novel (ATP5E, AARS, GAPVD1, CSNK2B, XPNPEP1, OSBP, NAT5 and DCTN2) and four more commonly used (BECN1, GAPDH, QARS and TUBB) reference genes in a smaller cohort using RT-qPCR. The most stable genes out of the 12 reference genes were tested as normaliser to validate increased levels of a target gene in CNS disease. We found that in human post-mortem tissue the novel reference genes, XPNPEP1 and AARS, were efficient in replicating microarray target gene expression levels and that XPNPEP1 was more efficient as a normaliser than BECN1, which has been shown to change in expression as a consequence of neuronal cell loss. We provide herein one more suitable novel reference gene, XPNPEP1, with no current neuroinflammatory or neurodegenerative associations that can be used for gene quantitative gene expression studies with human CNS post-mortem tissue and also suggest a list of potential other candidates. These data also emphasise the importance of organ/tissue-specific stably expressed genes as reference genes for RNA studies.

Cortical grey matter demyelination can be induced by elevated pro-inflammatory cytokines in the subarachnoid space of MOG-immunized rats

A substantial proportion of cases with secondary progressive multiple sclerosis have extensive inflammation in the leptomeninges that is associated with increased subpial demyelination, neuronal loss and an exacerbated disease course. However, the mechanisms underlying this extensive subpial pathology are poorly understood. We hypothesize that pro-inflammatory cytokine production within the meninges may be a key to this process. Post-mortem cerebrospinal fluid and dissected cerebral leptomeningeal tissue from patients with multiple sclerosis were used to study the presence of tumour necrosis factor and interferon gamma protein and messenger RNA levels. A novel model of subpial cortical grey matter demyelination was set up in Dark Agouti rats and analysed using quantitative immunohistochemistry. Increased expression of the pro-inflammatory cytokines tumour necrosis factor and interferon gamma was found in the meninges of cases with secondary progressive multiple sclerosis exhibiting tertiary lymphoid-like structures. Injection of tumour necrosis factor and interferon gamma into the subarachnoid space of female Dark Agouti rats pre-immunized with a subclinical dose of myelin oligodendrocyte glycoprotein mimicked the pathology seen in multiple sclerosis, including infiltration of lymphocytes (CD4+ and CD8+ T cells and CD79+ B cells) into the meninges and extensive subpial demyelination. Extensive microglial/macrophage activation was present in a gradient from the pial surface to deeper cortical layers. Demyelination did not occur in control animals immunized with incomplete Freunds adjuvant and injected with cytokines. These results support the hypothesis that pro-inflammatory molecules produced in the meninges play a major role in cortical demyelination in multiple sclerosis, but also emphasize the involvement of an anti-myelin immune response.