Neuromyelitis optica (NMO) is a chronic, mostly relapsing inflammatory demyelinating disease of the CNS characterized by serum anti-aquaporin 4 (AQP4) antibodies in the majority of patients. Anti-AQP4 antibodies derived from NMO patients target and deplete astrocytes in experimental models when co-injected with complement. However, the time course and mechanisms of oligodendrocyte loss and demyelination and the fate of oligodendrocyte precursor cells (OPC) have not been examined in detail. Also, no studies regarding astrocyte repopulation of experimental NMO lesions have been reported. We utilized two rat models using either systemic transfer or focal intracerebral injection of recombinant human anti-AQP4 antibodies to generate NMO-like lesions. Time-course experiments were performed to examine oligodendroglial and astroglial damage and repair. In addition, oligodendrocyte pathology was studied in early human NMO lesions. Apart from early complement-mediated astrocyte destruction, we observed a prominent, very early loss of oligodendrocytes and oligodendrocyte precursor cells (OPCs) as well as a delayed loss of myelin. Astrocyte repopulation of focal NMO lesions was already substantial after 1 week. Olig2-positive OPCs reappeared before NogoA-positive, mature oligodendrocytes. Thus, using two experimental models that closely mimic the human disease, our study demonstrates that oligodendrocyte and OPC loss is an extremely early feature in the formation of human and experimental NMO lesions and leads to subsequent, delayed demyelination, highlighting an important difference in the pathogenesis of MS and NMO.
Neuromyelitis optica; Demyelination; Oligodendrocyte death; Experimental autoimmune encephalomyelitis; Astrocyte
Several innovative disease-modifying treatments (DMTs) for relapsing remitting multiple sclerosis (RRMS) have been licensed recently, or are in late-stage development. The molecular targets of several of these DMTs are well defined. All affect at least one of four properties: (1) immune cell trafficking, (2) cell depletion, (3) immune cell function, or (4) cell replication. In contrast to β-interferons and glatiramer acetate, the first generation DMTs, several newer therapies are imbued with safety issues. In addition to efficacy, understanding the relationship between the mechanism of action (MOA) of the DMTs and their safety profile is essential for decision-making in patient care.
In this article, we relate safety issues of newer DMTs to their pharmacological characteristics, including molecular targets, MOA, chemical structure, and metabolism. Some newer DMTs also represent repurposing or modifications of previous treatments used in other diseases. Here, we describe how identification and understanding of adverse events (AEs) observed with these established drugs within the same class, provide clues regarding safety and toxicities of newer MS therapeutics.
Conclusions and relevance
While understanding mechanisms underlying DMT toxicities is incomplete, it is important to further develop this knowledge to minimize risk to patients, and to ensure future therapies have the most advantageous risk-benefit profiles. Recognizing the individual classes of DMTs described here may be beneficial when considering use of such agents sequentially and possibly in combination.
Multiple sclerosis; disease-modifying treatments; safety; mechanism of action; metabolism
To examine the potential role of 6-sulfo LacNAc+ (slan) dendritic cells (DCs) displaying pronounced proinflammatory properties in the pathogenesis of multiple sclerosis (MS).
We determined the presence of slanDCs in demyelinated brain lesions and CSF samples of patients with MS. In addition, we explored the impact of methylprednisolone, interferon-β, glatiramer acetate, or natalizumab on the frequency of blood-circulating slanDCs in patients with MS. We also evaluated whether interferon-β modulates important proinflammatory capabilities of slanDCs.
SlanDCs accumulate in highly inflammatory brain lesions and are present in the majority of CSF samples of patients with MS. Short-term methylprednisolone administration reduces the percentage of slanDCs in blood of patients with MS and the proportion of tumor necrosis factor-α– or CD150-expressing slanDCs. Long-term interferon-β treatment decreases the percentage of blood-circulating slanDCs in contrast to glatiramer acetate or natalizumab. Furthermore, interferon-β inhibits the secretion of proinflammatory cytokines by slanDCs and their capacity to promote proliferation and differentiation of T cells.
Accumulation of slanDCs in highly inflammatory brain lesions and their presence in CSF indicate that slanDCs may play an important role in the immunopathogenesis of MS. The reduction of blood-circulating slanDCs and the inhibition of their proinflammatory properties by methylprednisolone and interferon-β may contribute to the therapeutic efficiency of these drugs in patients with MS.
Multiple sclerosis (MS) is an inflammatory central nervous system (CNS) disorder, which typically occurs in early adulthood while it is rare in children. We tested in the MS-model, experimental autoimmune encephalomyelitis (EAE), whether functional maturation of innate immune cells may determine susceptibility to CNS autoimmune disease. 2 week-old mice were resistant to active EAE causing fulminant paralysis in adult mice, which was associated with an impaired development of Th1- and Th17 cells. Resistant, young mice contained a higher frequency of myeloid derived suppressor cells and plasmacytoid dendritic cells. Further, myeloid antigen-presenting cells (APC) as well as B-cells expressed lower levels of MHC class II and CD40, produced decreased amounts of pro-inflammatory cytokines, while release of anti-inflammatory IL-10 was enhanced. When used as APC, splenocytes from 2 week-old mice failed to differentiate naïve T-cells into Th1- and Th17 cells irrespective of the T-cell donor's age, and promoted development of regulatory T-cells and Th2 cells instead. Adoptive transfer of adult APC restored the ability of 2 week-old mice to generate encephalitogenic T-cells and to develop EAE. Collectively, these findings indicate that the innate immune cell compartment functionally matures during development which may be a prerequisite for development of T-cell-mediated CNS autoimmune disease.
multiple sclerosis; experimental autoimmune encephalomyelitis; age; susceptibility; antigen-presenting cells; MHC class II; co-stimulatory molecules; myeloid-derived suppressor cells; plasmacytoid dendritic cells; development; maturation
Clinical trials revealed that systemic administration of B-cell-depleting anti-CD20 antibodies can hold lesion formation in the early relapsing-remitting phase of multiple sclerosis (MS). Throughout the secondary-progressive (SP) course of MS, pathogenic B cells may, however, progressively replicate within the central nervous system (CNS) itself, which is largely inaccessible to systemic anti-CD20 treatment. Utilizing the murine MS model of experimental autoimmune encephalomyelitis, we show that intrathecal (i.t.) administration of anti-CD20 alone very efficiently depletes meningeal B cells from established CNS lesions. In SP-MS patients, adding i.t. administration of anti-CD20 to its systemic use may be a valuable strategy to target pathogenic B-cell function.
Laquinimod is an emerging oral medication for multiple sclerosis (MS) that reduces brain atrophy and progression of disability in two Phase III clinical trials. The mechanism of these effects is unclear. Persistent activation of microglia occurs in MS and contributes to injury. Thus, we investigated whether laquinimod alters properties of microglia in culture and in experimental autoimmune encephalomyelitis (EAE), and whether this reduces neurodegeneration.
Microglia were cultured from human brains. EAE was induced in mice.
The activation of human microglia increased levels of several pro- and anti-inflammatory cytokines and these elevations were attenuated by pretreatment with laquinimod. Laquinimod prevented the decline in activated microglia of miR124a, a microRNA implicated in maintaining microglia quiescence, and reduced the activity of several signaling pathways (Jun-N-terminal kinase, ribosomal S6 kinase, and AKT/protein kinase B) in activated microglia. In EAE, axonal injury correlated with accumulation of microglia/macrophages in the spinal cord. EAE mice treated with laquinimod before onset of clinical signs subsequently had reduced microglia/macrophage density and axonal injury. Remarkably, when laquinimod treatment was initiated well into the disease course, the progressive demyelination, and axonal loss was halted. Besides inflammatory molecules associated with microglia, the level of inducible nitric oxide (NO) synthase capable of producing free radical toxicity was attenuated by laquinimod in EAE mice. Finally, in coculture where microglia activation caused neuronal death, laquinimod decreased NO levels, and neurotoxicity.
Laquinimod is a novel inhibitor of microglial activation that lowers microglia-induced neuronal death in culture and axonal injury/loss in EAE.
IFN-γ produced by CD8+ cytotoxic T cells acts on neurons to induce Stat1-associated loss of dendrites and synapses in a mouse model of viral encephalitis.
Neurons are postmitotic and thus irreplaceable cells of the central nervous system (CNS). Accordingly, CNS inflammation with resulting neuronal damage can have devastating consequences. We investigated molecular mediators and structural consequences of CD8+ T lymphocyte (CTL) attack on neurons in vivo. In a viral encephalitis model in mice, disease depended on CTL-derived interferon-γ (IFN-γ) and neuronal IFN-γ signaling. Downstream STAT1 phosphorylation and nuclear translocation in neurons were associated with dendrite and synapse loss (deafferentation). Analogous molecular and structural alterations were also found in human Rasmussen encephalitis, a CTL-mediated human autoimmune disorder of the CNS. Importantly, therapeutic intervention by IFN-γ blocking antibody prevented neuronal deafferentation and clinical disease without reducing CTL responses or CNS infiltration. These findings identify neuronal IFN-γ signaling as a novel target for neuroprotective interventions in CTL-mediated CNS disease.
Cerebral cortex shows a high endogenous propensity for remyelination. Yet, widespread subpial cortical demyelination (SCD) is a common feature in progressive multiple sclerosis (MS) and can already be found in early MS. In the present study, we compared oligodendroglial loss in SCD in early and chronic MS. Furthermore, we addressed in an experimental model whether repeated episodes of inflammatory SCD could alter oligodendroglial repopulation and subsequently lead to persistently demyelinated cortical lesions. NogoA+ mature oligodendrocytes and Olig2+ oligodendrocyte precursor cells were examined in SCD in patients with early and chronic MS, normal-appearing MS cortex, and control cortex as well as in the rat model of repeated targeted cortical experimental autoimmune encephalomyelitis (EAE). NogoA+ and Olig2+ cells were significantly reduced in SCD in patients with chronic, but not early MS. Repeated induction of SCD in rats resulted only in a transient loss of NogoA+, but not Olig2+ cells during the demyelination phase. This phase was followed by complete oligodendroglial repopulation and remyelination, even after four episodes of demyelination. Our data indicate efficient oligodendroglial repopulation in subpial cortical lesions in rats after repeated SCD that was similar to early, but not chronic MS cases. Accordingly, four cycles of experimental de- and remyelination were not sufficient to induce sustained remyelination failure as found in chronic cortical MS lesions. This suggests that alternative mechanisms contribute to oligodendrocyte depletion in chronic cortical demyelination in MS.
Electronic supplementary material
The online version of this article (doi:10.1007/s00401-014-1260-8) contains supplementary material, which is available to authorized users.
Multiple sclerosis; Cortical demyelination; Oligodendrocytes; Oligodendrocyte precursors; Targeted cortical EAE
Multiple sclerosis is the most frequent demyelinating disease in the human CNS characterized by inflammation, demyelination, relative axonal loss and gliosis. Remyelination occurs, but is frequently absent or restricted to a small remyelinated rim at the lesion border. Impaired differentiation of oligodendroglial precursor cells is one factor contributing to limited remyelination, especially in chronic MS. TCF7L2 is an oligodendroglial transcription factor regulating myelin gene expression during developmental myelination as well as remyelination. TCF7L2 binds to co-effectors such as β-catenin or histone deacetylases and thereby activates or inhibits the transcription of downstream genes involved in oligodendroglial differentiation. To determine whether TCF7L2 can be used as a marker for differentiating or myelinating oligodendrocytes, we analyzed the expression patterns of TCF7L2 during myelination and remyelination in human and murine CNS tissue samples. Here, we demonstrate that marked expression of TCF7L2 in oligodendrocytes is restricted to a well defined time period during developmental myelination in human and mouse CNS tissue samples. In demyelinating diseases, such as multiple sclerosis, TCF7L2 is reexpressed in oligodendrocytes in a subset of MS patients, but is also present in tissue samples from patients with non-demyelinating, inflammatory diseases. Furthermore, TCF7L2 expression was also detected in astrocytes. HDAC2, a potential binding partner of TCF7L2 that promotes oligodendroglial differentiation and myelination, is expressed in the majority of oligodendrocytes in controls and MS tissue samples. In summary, our data demonstrate that the expression of TCF7L2 in oligodendrocytes is limited to a certain differentiation stage; however the expression of TCF7L2 is neither restricted to the oligodendroglial lineage nor to (re-)myelinating conditions.
Streptococcus pneumoniae (pneumococcal) meningitis is a common bacterial infection of the brain. The cholesterol-dependent cytolysin pneumolysin represents a key factor, determining the neuropathogenic potential of the pneumococci. Here, we demonstrate selective synaptic loss within the superficial layers of the frontal neocortex of post-mortem brain samples from individuals with pneumococcal meningitis. A similar effect was observed in mice with pneumococcal meningitis only when the bacteria expressed the pore-forming cholesterol-dependent cytolysin pneumolysin. Exposure of acute mouse brain slices to only pore-competent pneumolysin at disease-relevant, non-lytic concentrations caused permanent dendritic swelling, dendritic spine elimination and synaptic loss. The NMDA glutamate receptor antagonists MK801 and D-AP5 reduced this pathology. Pneumolysin increased glutamate levels within the mouse brain slices. In mouse astrocytes, pneumolysin initiated the release of glutamate in a calcium-dependent manner. We propose that pneumolysin plays a significant synapto- and dendritotoxic role in pneumococcal meningitis by initiating glutamate release from astrocytes, leading to subsequent glutamate-dependent synaptic damage. We outline for the first time the occurrence of synaptic pathology in pneumococcal meningitis and demonstrate that a bacterial cytolysin can dysregulate the control of glutamate in the brain, inducing excitotoxic damage.
Bacterial meningitis is one of the most devastating brain diseases. Among the bacteria that cause meningitis, Streptococcus pneumoniae is the most common. Meningitis predominantly affects children, especially in the Third World, and most of them do not survive. Those that do survive often suffer permanent brain damage and hearing problems. The exact morphological substrates of brain damage in Streptococcus pneumoniae meningitis remain largely unknown. In our experiments, we found that the brain cortex of patients with meningitis demonstrated a loss of synapses (the contact points among neurons, responsible for the processes of learning and memory), and we identified the major pneumococcal neurotoxin pneumolysin as a sufficient cause of this loss. The effect was not direct but was mediated by the brain neurotransmitter glutamate, which was released upon toxin binding by one of the non-neuronal cell types of the brain – the astrocytes. Pneumolysin initiated calcium influx in astrocytes and subsequent glutamate release. Glutamate damaged the synapses via NMDA-receptors – a mechanism similar to the damage occurring in brain ischemia. Thus, we show that synaptic loss is present in pneumococcal meningitis, and we identify the toxic bacterial protein pneumolysin as the major factor in this process. These findings alter our understanding of bacterial meningitis and establish new therapeutic strategies for this fatal disease.
Microglial nodules in the normal-appearing white matter have been suggested as the earliest stage(s) of multiple sclerosis (MS) lesion formation. Such nodules are characterized by an absence of leukocyte infiltration, astrogliosis or demyelination, and may develop into active demyelinating MS lesions. Although the etiology of MS is still not known, inflammation and autoimmunity are considered to be the central components of this disease. Previous studies provide evidence that Wallerian degeneration, occurring as a consequence of structural damage in MS lesions, might be responsible for observed pathological abnormalities in connected normal-appearing white matter. As innate immune cells, microglia/macrophages are the first to react to even minor pathological changes in the CNS. Biopsy tissue from 27 MS patients and autopsy and biopsy tissue from 22 normal and pathological controls were analyzed to determine the incidence of microglial nodules. We assessed MS periplaque white matter tissue from early disease stages to determine whether microglial nodules are associated with altered axons. With immunohistochemical methods, the spatial relation of the two phenomena was visualized using HLA-DR antibody for MHC II expression by activated microglia/macrophages and by applying antibodies against damaged axons, i.e., SMI32 (non-phosphorylated neurofilaments) and amyloid precursor protein as well as neuropeptide Y receptor Y1, which marks axons undergoing Wallerian degeneration. Our data demonstrate that the occurrence of microglial nodules is not specific to MS and is associated with degenerating as well as damaged axons in early MS. In addition, we show that early MS microglial nodules exhibit both pro- and antiinflammatory phenotypes.
Electronic supplementary material
The online version of this article (doi:10.1007/s00401-013-1082-0) contains supplementary material, which is available to authorized users.
Wallerian degeneration; Microglial nodules; Multiple sclerosis; Preactive lesions; Axonal damage; Microglia activation
Laquinimod (LAQ) is a new oral immunomodulatory compound that reduces relapse rate, brain atrophy and disability progression in multiple sclerosis (MS). LAQ has well-documented effects on inflammation in the periphery, but little is known about its direct activity within the central nervous system (CNS). To elucidate the impact of LAQ on CNS-intrinsic inflammation, we investigated the effects of LAQ on cuprizone-induced demyelination in mice in vivo and on primary CNS cells in vitro. Demyelination, inflammation, axonal damage and glial pathology were evaluated in LAQ-treated wild type and Rag-1-deficient mice after cuprizone challenge. Using primary cells we tested for effects of LAQ on oligodendroglial survival as well as on cytokine secretion and NF-κB activation in astrocytes and microglia. LAQ prevented cuprizone-induced demyelination, microglial activation, axonal transections, reactive gliosis and oligodendroglial apoptoses in wild type and Rag-1-deficient mice. LAQ significantly decreased pro-inflammatory factors in stimulated astrocytes, but not in microglia. Oligodendroglial survival was not affected by LAQ in vitro. Astrocytic, but not microglial, NF-κB activation was markedly reduced by LAQ as evidenced by NF-κB reporter assay. LAQ also significantly decreased astrocytic NF-κB activation in cuprizone-treated mice. Our data indicate that LAQ prevents cuprizone-induced demyelination by attenuating astrocytic NF-κB activation. These effects are CNS-intrinsic and not mediated by peripheral immune cells. Therefore, LAQ downregulation of the astrocytic pro-inflammatory response may be an important mechanism underlying its protective effects on myelin, oligodendrocytes and axons. Modulation of astrocyte activation may be an attractive therapeutic target to prevent tissue damage in MS.
Electronic supplementary material
The online version of this article (doi:10.1007/s00401-012-1009-1) contains supplementary material, which is available to authorized users.
Demyelination; Laquinimod; Cuprizone; Astrocytes; NF-κB; Multiple sclerosis
Cortical disease has emerged as a critical aspect of the pathogenesis of multiple sclerosis, being associated with disease progression and cognitive impairment. Most studies of cortical lesions have focused on autopsy findings in patients with long-standing, chronic, progressive multiple sclerosis, and the noninflammatory nature of these lesions has been emphasized. Magnetic resonance imaging studies indicate that cortical damage occurs early in the disease.
We evaluated the prevalence and character of demyelinating cortical lesions in patients with multiple sclerosis. Cortical tissues were obtained in passing during biopsy sampling of white-matter lesions. In most cases, biopsy was done with the use of stereotactic procedures to diagnose suspected tumors. Patients with sufficient cortex (138 of 563 patients screened) were evaluated for cortical demyelination. Using immunohistochemistry, we characterized cortical lesions with respect to demyelinating activity, inflammatory infiltrates, the presence of meningeal inflammation, and a topographic association between cortical demyelination and meningeal inflammation. Diagnoses were ascertained in a subgroup of 77 patients (56%) at the last follow-up visit (at a median of 3.5 years).
Cortical demyelination was present in 53 patients (38%) (104 lesions and 222 tissue blocks) and was absent in 85 patients (121 tissue blocks). Twenty-five patients with cortical demyelination had definite multiple sclerosis (81% of 31 patients who underwent long-term follow-up), as did 33 patients without cortical demyelination (72% of 46 patients who underwent long-term follow-up). In representative tissues, 58 of 71 lesions (82%) showed CD3+ T-cell infiltrates, and 32 of 78 lesions (41%) showed macrophage-associated demyelination. Meningeal inflammation was topographically associated with cortical demyelination in patients who had sufficient meningeal tissue for study.
In this cohort of patients with early-stage multiple sclerosis, cortical demyelinating lesions were frequent, inflammatory, and strongly associated with meningeal inflammation. (Funded by the National Multiple Sclerosis Society and the National Institutes of Health.)
We investigated the overlap shared between the immunoglobulin (Ig) proteome of the cerebrospinal fluid (CSF) and the B cell Ig-transcriptome of CSF and the central nervous system (CNS) tissue of three patients with multiple sclerosis. We determined the IgG-proteomes of CSF by mass spectrometry, and compared them to the IgG-transcriptomes from CSF and brain lesions, which were analyzed by cDNA cloning. Characteristic peptides that were identified in the CSF-proteome could also be detected in the transcriptomes of both, brain lesions and CSF, providing evidence for a strong overlap of the IgG repertoires in brain lesions and in the CSF.
multiple sclerosis; B cells; cerebrospinal fluid; central nervous system; oligoclonal bands
The IκB kinase complex induces nuclear factor kappa B activation and has recently been recognized as a key player of autoimmunity in the central nervous system. Notably, IκB kinase/nuclear factor kappa B signalling regulates peripheral myelin formation by Schwann cells, however, its role in myelin formation in the central nervous system during health and disease is largely unknown. Surprisingly, we found that brain-specific IκB kinase 2 expression is dispensable for proper myelin assembly and repair in the central nervous system, but instead plays a fundamental role for the loss of myelin in the cuprizone model. During toxic demyelination, inhibition of nuclear factor kappa B activation by conditional ablation of IκB kinase 2 resulted in strong preservation of central nervous system myelin, reduced expression of proinflammatory mediators and a significantly attenuated glial response. Importantly, IκB kinase 2 depletion in astrocytes, but not in oligodendrocytes, was sufficient to protect mice from myelin loss. Our results reveal a crucial role of glial cell-specific IκB kinase 2/nuclear factor kappa B signalling for oligodendrocyte damage during toxic demyelination. Thus, therapies targeting IκB kinase 2 function in non-neuronal cells may represent a promising strategy for the treatment of distinct demyelinating central nervous system diseases.
oligodendrocyte; demyelination; remyelination; NF-κB; glia; cuprizone; multiple sclerosis
There is mounting evidence that injury to one organ causes indirect damage to other organ systems with increased morbidity and mortality. The aim of this study was to determine the effects of acid aspiration pneumonitis (AAP) on extrapulmonary organs and to test the hypothesis that these could be due to circulatory depression or hypoxemia.
Mechanically ventilated anesthetized pigs were randomized to receive intrabronchial instillation of hydrochloric acid (n = 7) or no treatment (n = 7). Hydrochloric acid (0.1 N, pH 1.1, 2.5 ml/kg BW) was instilled into the lungs during the inspiratory phase of ventilation. Hemodynamics, respiratory function and computer tomography (CT) scans of lung and brain were followed over a four-hour period. Tissue samples of lung, heart, liver, kidney and hippocampus were collected at the end of the experiment.
Acid instillation caused pulmonary edema, measured as increased extravascular lung water index (ELWI), impaired gas exchange and increased mean pulmonary artery pressure. Gas exchange tended to improve during the course of the study, despite increasing ELWI. In AAP animals compared to controls we found: a) cardiac leukocyte infiltration and necrosis in the conduction system and myocardium; b) lymphocyte infiltration in the liver, spreading from the periportal zone with prominent areas of necrosis; c) renal inflammation with lymphocyte infiltration, edema and necrosis in the proximal and distal tubules; and d) a tendency towards more severe hippocampal damage (P > 0.05).
Acid aspiration pneumonitis induces extrapulmonary organ injury. Circulatory depression and hypoxemia are unlikely causative factors. ELWI is a sensitive bedside parameter of early lung damage.
Natalizumab is an approved medication for highly active multiple sclerosis (MS). Progressive multifocal leukoencephalopathy (PML) may occur as a severe side effect of this drug. Here, we describe pathological and radiological characteristics of immune reconstitution inflammatory syndrome (IRIS), which occurs in natalizumab-associated PML after the cessation of therapy, and we differentiate it from ongoing PML. Brain biopsy tissue and MRI scans from five MS patients with natalizumab-associated PML were analyzed and their histology compared with non-MS PML. Histology showed an extensive CD8-dominated T cell infiltrate and numerous macrophages within lesions, and in nondemyelinated white and grey matter, in four out of five cases. Few or no virally infected cells were found. This was indicative of IRIS as known from HIV patients with PML. Outstandingly high numbers of plasma cells were present as compared to non-MS PML and typical MS lesions. MRI was compatible with IRIS, revealing enlarging lesions with a band-like or speckled contrast enhancement either at the lesion edge or within lesions. Only the fifth patient showed typical PML pathology, with low inflammation and high numbers of virally infected cells. This patient showed a similar interval between drug withdrawal and biopsy (3.5 months) to the rest of the cohort (range 2.5–4 months). MRI could not differentiate between PML-associated IRIS and ongoing PML. We describe in detail the histopathology of IRIS in natalizumab-associated PML. PML–IRIS, ongoing PML infection, and MS exacerbation may be impossible to discern clinically alone. MRI may provide some clues for distinguishing different pathologies that can be differentiated histologically. In our individual cases, biopsy helped to clarify diagnoses in natalizumab-associated PML.
IRIS; Natalizumab; PML; MS; Pathology; MRI
To determine reciprocal and synergistic effects of acute intracranial hypertension and ARDS on neuronal and pulmonary damage and to define possible mechanisms.
Twenty-eight mechanically ventilated pigs were randomized to four groups of seven each: control; acute intracranial hypertension (AICH); acute respiratory distress syndrome (ARDS); acute respiratory distress syndrome in combination with acute intracranial hypertension (ARDS + AICH). AICH was induced with an intracranial balloon catheter and the inflation volume was adjusted to keep intracranial pressure (ICP) at 30–40 cmH2O. ARDS was induced by oleic acid infusion. Respiratory function, hemodynamics, extravascular lung water index (ELWI), lung and brain computed tomography (CT) scans, as well as inflammatory mediators, S100B, and neuronal serum enolase (NSE) were measured over a 4-h period. Lung and brain tissue were collected and examined at the end of the experiment.
In both healthy and injured lungs, AICH caused increases in NSE and TNF-alpha plasma concentrations, extravascular lung water, and lung density in CT, the extent of poorly aerated (dystelectatic) and atelectatic lung regions, and an increase in the brain tissue water content. ARDS and AICH in combination induced damage in the hippocampus and decreased density in brain CT.
AICH induces lung injury and also exacerbates pre-existing damage. Increased extravascular lung water is an early marker. ARDS has a detrimental effect on the brain and acts synergistically with intracranial hypertension to cause histological hippocampal damage.
Electronic supplementary material
The online version of this article (doi:10.1007/s00134-011-2232-2) contains supplementary material, which is available to authorized users.
ABI; ARDS; ELWI; CT scan; Organ dysfunction
We report a young woman with sudden and severe retroorbital headache, neck pain, and a large sellar mass extending to the suprasellar cistern. A presumptive diagnosis of non-secreting pituitary macroadenoma undergoing apoplexy was made and transphenoidal surgery performed. Histopathology revealed mononuclear infiltration and marked non-hemorrhagic necrosis of the anterior pituitary consistent with a diagnosis of necrotizing infundibulo-hypophysitis. The possible pathogenesis of this rare variant of hypophysitis is discussed.
Hypophysitis; Necrosis; Pituitary infarction
Impaired suppressive capacity of CD4+CD25+FOXP3+ regulatory T cells (Treg) from peripheral blood of patients with multiple sclerosis (MS) has been reported by multiple laboratories. It is, however, currently unresolved whether Treg dysfunction in MS patients is limited to reduced control of peripheral T cell activation since most studies analyzed peripheral blood samples only. Here, we assessed early active MS lesions in brain biopsies obtained from 16 patients with MS by FOXP3 immunohistochemistry. In addition, we used six-color flow cytometry to determine numbers of Treg by analysis of FOXP3/CD127 expression in peripheral blood and cerebrospinal fluid (CSF) of 17 treatment-naïve MS patients as well as quantities of apoptosis sensitive CD45ROhiCD95hi cells in circulating and CSF Treg subsets. Absolute numbers of FOXP3+ and CD4+ cells were rather low in MS brain lesions and Treg were not detectable in 30% of MS biopsies despite the presence of CD4+ cell infiltrates. In contrast, Treg were detectable in all CSF samples and Treg with a CD45ROhiCD95hi phenotype previously shown to be highly apoptosis sensitive were found to be enriched in the CSF compared to peripheral blood of MS patients. We suggest a hypothetical model of intracerebral elimination of Treg by CD95L-mediated apoptosis within the MS lesion.
Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system (CNS) that is thought to be caused by a combination of genetic and environmental factors. To date, considerable evidence has associated Epstein–Barr virus (EBV) infection with disease development. However, it remains controversial whether EBV infects multiple sclerosis brain and contributes directly to CNS immunopathology. To assess whether EBV infection is a characteristic feature of multiple sclerosis brain, a large cohort of multiple sclerosis specimens containing white matter lesions (nine adult and three paediatric cases) with a heterogeneous B cell infiltrate and a second cohort of multiple sclerosis specimens (12 cases) that included B cell infiltration within the meninges and parenchymal B cell aggregates, were examined for EBV infection using multiple methodologies including in situ hybridization, immunohistochemistry and two independent real-time polymerase chain reaction (PCR) methodologies that detect genomic EBV or the abundant EBV encoded RNA (EBER) 1, respectively. We report that EBV could not be detected in any of the multiple sclerosis specimens containing white matter lesions by any of the methods employed, yet EBV was readily detectable in multiple Epstein–Barr virus-positive control tissues including several CNS lymphomas. Furthermore, EBV was not detected in our second cohort of multiple sclerosis specimens by in situ hybridization. However, our real-time PCR methodologies, which were capable of detecting very few EBV infected cells, detected EBV at low levels in only 2 of the 12 multiple sclerosis meningeal specimens examined. Our finding that CNS EBV infection was rare in multiple sclerosis brain indicates that EBV infection is unlikely to contribute directly to multiple sclerosis brain pathology in the vast majority of cases.
B cells; Epstein–Barr virus; multiple sclerosis brain
The following review summarizes the progress in multiple sclerosis research published in the Journal of Neurology in 2009.
Multiple sclerosis; Neuromyelitis optica; Advances
Lassa virus (LASV), the causative agent of Lassa fever (LF), is endemic in West Africa, accounting for substantial morbidity and mortality. In spite of ongoing research efforts, LF pathogenesis and mechanisms of LASV immune control remain poorly understood. While normal laboratory mice are resistant to LASV, we report that mice expressing humanized instead of murine MHC class I (MHC-I) failed to control LASV infection and develop severe LF. Infection of MHC-I knockout mice confirmed a key role for MHC-I-restricted T cell responses in controlling LASV. Intriguingly we found that T cell depletion in LASV-infected HHD mice prevented disease, irrespective of high-level viremia. Widespread activation of monocyte/macrophage lineage cells, manifest through inducible NO synthase expression, and elevated IL-12p40 serum levels indicated a systemic inflammatory condition. The absence of extensive monocyte/macrophage activation in T cell-depleted mice suggested that T cell responses contribute to deleterious innate inflammatory reactions and LF pathogenesis. Our observations in mice indicate a dual role for T cells, not only protecting from LASV, but also enhancing LF pathogenesis. The possibility of T cell-driven enhancement and immunopathogenesis should be given consideration in future LF vaccine development.
Lassa virus (LASV) is the causative agent of Lassa fever (LF), accounting for substantial morbidity and mortality in West Africa. Yet the mechanisms leading to disease remain poorly understood. Here we propose a concept whereby the body's immune defense either defeats LASV rapidly or, if unsuccessful, becomes an essential facilitator of disease. This latter paradoxical postulate stems from observations in genetically engineered (HHD) mice, which we found to be susceptible to LF. HHD mice differ from resistant wild type mice in that they have a humanized repertoire of T cells, a main component of the mammalian immune system. Counterintuitively, we could protect HHD mice against LF by experimentally removing their T cells. We further found that LF correlated with widespread activation of macrophages, which again depended on T cells. Similar to T cells, macrophages are important players in our body's defense system, but their inflammatory products are also candidate mediators of LF. Taken together, these findings suggest that LF may represent an inappropriate host response to infection. Specifically, our study demonstrates a two-faced role of T cell responses against LASV. Such detrimental aspects of immune defense need to be given consideration in future LF vaccine development, to avoid enhancement of disease in vaccinated individuals.
Multiple sclerosis is the most frequent demyelinating disease in adults. It is characterized by demyelination, inflammation, gliosis and a variable loss of axons. Clinically and histologically, it shares features with other demyelinating and/or inflammatory CNS diseases. Diagnosis of an inflammatory demyelinating disease can be challenging, especially in small biopsy specimens. Here, we summarize the histological hallmarks and most important neuropathological differential diagnoses of early MS, and provide practical guidelines for the diagnosis of inflammatory demyelinating diseases.
Multiple sclerosis; Demyelination; Inflammation