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A small proportion of multiple sclerosis (MS) patients develop new disease activity soon after starting anti-CD20 therapy. This activity does not recur with further dosing, possibly reflecting deeper depletion of CD20-expressing cells with repeat infusions. We assessed cellular immune profiles and their association with transient disease activity following anti-CD20 initiation as a window into relapsing disease biology. Peripheral blood mononuclear cells from independent discovery and validation cohorts of MS patients initiating ocrelizumab were assessed for phenotypic and functional profiles using multiparametric flow cytometry. Pretreatment CD20-expressing T cells, especially CD20 dim CD8 + T cells with a highly inflammatory and central nervous system (CNS)-homing phenotype, were significantly inversely correlated with pretreatment MRI gadolinium-lesion counts, and also predictive of early disease activity observed after anti-CD20 initiation. Direct removal of pretreatment proinflammatory CD20 dim CD8 + T cells had a greater contribution to treatment-associated changes in the CD8 + T cell pool than was the case for CD4 + T cells. Early disease activity following anti-CD20 initiation was not associated with reconstituting CD20 dim CD8 + T cells, which were less proinflammatory compared with pretreatment. Similarly, this disease activity did not correlate with early reconstituting B cells, which were predominantly transitional CD19 + CD24 high CD38 high with a more anti-inflammatory profile. We provide insights into the mode-of-action of anti-CD20 and highlight a potential role for CD20 dim CD8 + T cells in MS relapse biology; their strong inverse correlation with both pretreatment and early posttreatment disease activity suggests that CD20-expressing CD8 + T cells leaving the circulation (possibly to the CNS) play a particularly early role in the immune cascades involved in relapse development.

SARS-CoV-2 messenger RNA vaccination in healthy individuals generates immune protection against COVID-19. However, little is known about SARS-CoV-2 mRNA vaccine-induced responses in immunosuppressed patients. We investigated induction of antigen-specific antibody, B cell and T cell responses longitudinally in patients with multiple sclerosis (MS) on anti-CD20 antibody monotherapy (n = 20) compared with healthy controls (n = 10) after BNT162b2 or mRNA-1273 mRNA vaccination. Treatment with anti-CD20 monoclonal antibody (aCD20) significantly reduced spike-specific and receptor-binding domain (RBD)-specific antibody and memory B cell responses in most patients, an effect ameliorated with longer duration from last aCD20 treatment and extent of B cell reconstitution. By contrast, all patients with MS treated with aCD20 generated antigen-specific CD4 and CD8 T cell responses after vaccination. Treatment with aCD20 skewed responses, compromising circulating follicular helper T (TFH) cell responses and augmenting CD8 T cell induction, while preserving type 1 helper T (TH1) cell priming. Patients with MS treated with aCD20 lacking anti-RBD IgG had the most severe defect in circulating TFH responses and more robust CD8 T cell responses. These data define the nature of the SARS-CoV-2 vaccine-induced immune landscape in aCD20-treated patients and provide insights into coordinated mRNA vaccine-induced immune responses in humans. Our findings have implications for clinical decision-making and public health policy for immunosuppressed patients including those treated with aCD20., SARS-CoV-2-specific antibodies and memory B cells are significantly reduced, but CD4+ and CD8+ T cells are robustly activated, in patients with multiple sclerosis on anti-CD20 monotherapy versus healthy controls after BNT162b2 or mRNA-1273 mRNA vaccination.

Total brain white matter lesion (WML) volume is the most widely established magnetic resonance imaging (MRI) outcome measure in studies of multiple sclerosis (MS). To estimate WML volume, there are a number of automatic segmentation methods available, yet manual delineation remains the gold standard approach. Automatic approaches often yield a probability map to which a threshold is applied to create lesion segmentation masks. Unfortunately, few approaches systematically determine the threshold employed; many methods use a manually selected threshold, thus introducing human error and bias into the automated procedure. In this study, we propose and validate an automatic thresholding algorithm, Thresholding Approach for Probability Map Automatic Segmentation in Multiple Sclerosis (TAPAS), to obtain subject-specific threshold estimates for probability map automatic segmentation of T2-weighted (T2) hyperintense WMLs. Using multimodal MRI, the proposed method applies an automatic segmentation algorithm to obtain probability maps. We obtain the true subject-specific threshold that maximizes the Sorensen-Dice similarity coefficient (DSC). Then the subject-specific thresholds are modeled on a naive estimate of volume using a generalized additive model. Applying this model, we predict a subject-specific threshold in data not used for training. We ran a Monte Carlo-resampled split-sample cross-validation (100 validation sets) using two data sets: the first obtained from the Johns Hopkins Hospital (JHH) on a Philips 3 Tesla (3T) scanner (n = 94) and a second collected at the Brigham and Women's Hospital (BWH) using a Siemens 3T scanner (n = 40). By means of the proposed automated technique, in the JHH data we found an average reduction in subject-level absolute error of 0.1 mL per one mL increase in manual volume. Using Bland-Altman analysis, we found that volumetric bias associated with group-level thresholding was mitigated when applying TAPAS. The BWH data showed similar absolute error estimates using group-level thresholding or TAPAS likely since Bland-Altman analyses indicated no systematic biases associated with group or TAPAS volume estimates. The current study presents the first validated fully automated method for subject-specific threshold prediction to segment brain lesions.

ObjectiveTo report 2 patients with anti–myelin oligodendrocyte glycoprotein (MOG)-associated encephalitis who were initially misdiagnosed with small vessel primary CNS vasculitis.MethodsReview of symptoms, MRI and neuropathologic features, and response to treatment. MOG antibodies were determined in serum and CSF using a cell-based assay.ResultsSymptoms included fever, headache, and progressive mental status changes and focal neurologic deficits. CSF studies revealed lymphocytic pleocytosis, and both patients had abnormal brain MRIs. Brain biopsy samples showed prominent lymphocytic infiltration of the wall of small vessels; these findings initially suggested small vessel CNS vasculitis, and both patients were treated accordingly. Although 1 patient had a relapsing-remitting course not responsive to cyclophosphamide, the other one (also treated with cyclophosphamide) did not relapse. Retrospective assessment of serum and CSF demonstrated MOG antibodies in both cases, and review of biopsy specimens showed absence of fibrinoid necrosis (a pathologic requirement for small vessel CNS vasculitis).ConclusionsAnti–MOG-associated encephalitis can be mistaken for small vessel CNS vasculitis. This is important because the diagnosis of anti–MOG-associated encephalitis does not require brain biopsy and can be established with a serologic test.

There is growing recognition that B cell contributions to normal immune responses extend well beyond their potential to become antibody-producing cells, including roles at the innate-adaptive interface and their potential to modulate the responses of other immune cells such as T cells and myeloid cells. These B cell functions can have both pathogenic and protective effects in the context of central nervous system (CNS) inflammation. Here, we review recent advances in the field of multiple sclerosis (MS), which has traditionally been viewed as primarily a T cell-mediated disease, and we consider antibody-dependent and, particularly, emerging antibody-independent functions of B cells that may be relevant in both the peripheral and CNS disease compartments.

To determine the pathogenic mechanisms of autoantibodies to the cell adhesion molecule Caspr2 in acquired neuromyotonia and autoimmune encephalitis.Caspr2-positive samples were confirmed using a cell-based assay, and their IgG subtypes were determined by enzyme-linked immunosorbent assay and cell-based assay. A solid phase binding assay quantified the binding of Caspr2 to contactin-2 in the presence of Caspr2 autoantibodies. Living cultures of primary rat hippocampal neurons were incubated with Caspr2-positive or control sera, and the distribution of Caspr2-positive immunofluorescent puncta and total surface Caspr2 was quantified. HEK cells transfected to express Caspr2 were incubated with Caspr2-positive or control samples, and cell-surface biotinylation and Western blot were used to assess total, internalized, and surface levels of Caspr2.We confirmed 6 samples with strong Caspr2 reactivity. IgG4 Caspr2 antibodies were present in all 6 cases. Caspr2 interacted with another cell adhesion molecule, contactin-2, with nanomolar affinity in the solid phase assay, and Caspr2 autoantibodies inhibited this interaction. Caspr2 autoantibodies did not affect the surface expression of Caspr2 in rat primary hippocampal neurons or transfected HEK cells.Caspr2 autoantibodies inhibit the interaction of Caspr2 with contactin-2 but do not cause internalization of Caspr2. Functional blocking of cell adhesion molecule interactions represents a potential mechanism with therapeutic implications for IgG4 autoantibodies to cell adhesion molecules in neurological diseases. Ann Neurol 2018;83:40-51.

Objective To measure the frequency, persistence, isoform specificity, and clinical correlates of neurofascin antibodies in patients with peripheral neuropathies. Methods We studied cohorts of patients with Guillain-Barre syndrome (GBS) or chronic inflammatory demyelinating polyneuropathy (CIDP) (n = 59), genetic neuropathy (n = 111), and idiopathic neuropathy (n = 43) for immunoglobulin (Ig) G and IgM responses to 3 neurofascin (NF) isoforms (NF140, NF155, and NF186) using cell-based assays. Results Neurofascin antibodies were more common in patients with GBS/CIDP (14%, 8 of 59) compared to genetic neuropathy controls (3%, 3 of 111, p = 0.01). Seven percent (3 of 43) of patients with idiopathic neuropathy also had neurofascin antibodies. NF155 IgG4 antibodies were associated with CIDP refractory to IV immunoglobulin but responsive to rituximab, and some of these patients had an acute onset resembling GBS. NF186 IgG and IgM to either isoform were less specific. A severe form of CIDP, approaching a locked-in state, was seen in a patient with antibodies recognizing all 3 neurofascin isoforms. Conclusions Neurofascin antibodies were 4 times more frequent in autoimmune neuropathy samples compared to genetic neuropathy controls. Persistent IgG4 responses to NF155 correlated with severe CIDP resistant to usual treatments but responsive to rituximab. IgG4 antibodies against the common domains shared by glial and axonal isoforms may portend a particularly severe but treatable neuropathy. The prognostic implications of neurofascin antibodies in a subset of idiopathic neuropathy patients and transient IgM responses in GBS require further investigation.

The work presented herein addresses a specific portion of the tau pathology, pre-fibrillar oligomers, now thought to be important pathological components in Alzheimer's disease and other neurodegenerative tauopathies. In previous work, we generated an antibody against purified recombinant cross-linked tau dimers, called Tau Oligomeric Complex 1 (TOC1). TOC1 recognizes tau oligomers and its immunoreactivity is elevated in Alzheimer's disease brains. In this report, we expand upon the previous study to show that TOC1 selectively labels tau oligomers over monomers or polymers, and that TOC1 is also reactive in other neurodegenerative tauopathies. Using a series of deletion mutants spanning the tau molecule, we further demonstrate that TOC1 has one continuous epitope located within amino acids 209-224, in the so-called proline rich region. Together with the previous study, our data indicates that TOC1 is a conformation-dependent antibody whose epitope is revealed upon dimerization and oligomerization, but concealed again as polymers form. This characterization of the TOC1 antibody further supports its potential as a powerful biochemical tool that can be used to better investigate the involvement of tau in neurodegenerative diseases.

Aggregated filamentous forms of hyperphosphorylated tau (a microtubule-associated protein) represent pathological hallmarks of Alzheimer's disease (AD) and other tauopathies. While axonal transport dysfunction is thought to represent a primary pathogenic factor in AD and other neurodegenerative diseases, the direct molecular link between pathogenic forms of tau and deficits in axonal transport remain unclear. Recently, we demonstrated that filamentous, but not soluble, forms of wild-type tau inhibit anterograde, kinesin-based fast axonal transport (FAT) by activating axonal protein phosphatase 1 (PP1) and glycogen synthase kinase 3 (GSK3), independent of microtubule binding. Here, we demonstrate that amino acids 2-18 of tau, comprising a phosphatase-activating domain (PAD), are necessary and sufficient for activation of this pathway in axoplasms isolated from squid giant axons. Various pathogenic forms of tau displaying increased exposure of PAD inhibited anterograde FAT in squid axoplasm. Importantly, immunohistochemical studies using a novel PAD-specific monoclonal antibody in human postmortem tissue indicated that increased PAD exposure represents an early pathogenic event in AD that closely associates in time with AT8 immunoreactivity, an early marker of pathological tau. We propose a model of pathogenesis in which disease-associated changes in tau conformation lead to increased exposure of PAD, activation of PP1-GSK3, and inhibition of FAT. Results from these studies reveal a novel role for tau in modulating axonal phosphotransferases and provide a molecular basis for a toxic gain-of-function associated with pathogenic forms of tau.

Neurofibrillary tangles, composed of insoluble aggregates of the microtubule-associated protein Tau, are a pathological hallmark of Alzheimer disease (AD) and other tauopathies. However, recent evidence indicates that neuronal dysfunction precedes the formation of these insoluble fibrillar deposits, suggesting that earlier prefibrillar Tau aggregates may be neurotoxic. To determine the composition of these aggregates, we have employed a photochemical cross-linking technique to examine intermolecular interactions of full-length Tau in vitro. Using this method, we demonstrate that dimerization is an early event in the Tau aggregation process and that these dimers self-associate to form larger oligomeric aggregates. Moreover, using these stabilized Tau aggregates as immunogens, we generated a monoclonal antibody that selectively recognizes Tau dimers and higher order oligomeric aggregates but shows little reactivity to Tau filaments in vitro. Immunostaining indicates that these dimers/oligomers are markedly elevated in AD, appearing in early pathological inclusions such as neuropil threads and pretangle neurons as well as colocalizing with other early markers of Tau pathogenesis. Taken as a whole, the work presented herein demonstrates the existence of alternative Tau aggregates that precede formation of fibrillar Tau pathologies and raises the possibility that these hierarchical oligomeric forms of Tau may contribute to neurodegeneration.

We report a 64-year-old man with a history of stage IV oropharyngeal squamous cell carcinoma treated with cisplatin and cetuximab followed by radiation therapy who developed a rapidly advancing rhombencephalomyelitis 11 months after the completion of radiation to the base of his tongue. His initial symptoms were left ear paresthesias, dysphagia, and progressive descending weakness. Routine cerebrospinal fluid (CSF) analysis was unremarkable. Initial MRI of the brain and cervical spinal cord revealed a demarcated symmetrical heterogeneously enhancing intramedullary lesion involving the cervicomedullary spinal cord. Progressive neurological worsening included increasing weakness of his limbs, facial weakness and ocular motility disorders and MRI revealed that the lesion was advancing into his pons and cervical spinal cord. Empiric treatment for radiation myelitis was initiated. Although CSF polymerase chain reaction was negative for varicella zoster virus (VZV), antibody studies revealed intrathecal synthesis of antibody to VZV and treatment for VZV was started as well. Improvement was slow and incomplete with subsequent worsening resulting in death in 5.5 weeks. The diagnosis of rhombencephalitis and myelitis following radiation therapy may be exquisitely challenging. The possibility of VZV, a treatable disorder, should be included in the differential diagnosis.

Alzheimer's disease (AD) is a progressive amnestic dementia that involves post-translational hyperphosphorylation, enzymatic cleavage, and conformational alterations of the microtubule-associated protein tau. The truncation state of tau influences many of its pathologic characteristics, including its ability to assume AD-related conformations and to assemble into filaments. Cleavage also appears to be an important marker in AD progression. Although C-terminal truncation of tau at D421 has recently been attributed to the apoptotic enzyme caspase-3, N-terminal processing of the protein remains mostly uncharacterized. Here, we report immunohistochemical staining in a cohort of 35 cases ranging from noncognitively impaired to early AD with a panel of three N-terminal anti-tau antibodies: Tau-12, 5A6, and 9G3-pY18. Of these three, the phosphorylation-independent epitope of 5A6 was the earliest to emerge in the pathological lesions of tau, followed by the appearance of the Tau-12 epitope. The unmasking of the Tau-12 epitope in more mature 5A6-positive tangles was not correlated with tau phosphorylation at tyrosine 18 (9G3-pY18). Still, later in the course of tangle evolution, the extreme N terminus of tau was lost, correlating temporally with the appearance of a C-terminal caspase-truncated epitope lacking residues 422-441. In addition, caspase-6 cleaved the N terminus of tauin vitro, preventing immunoreactivity with both Tau-12 and 5A6. Mass spectrometry confirmed that thein vitrocaspase-6 truncation site is D13, a semicanonical and hitherto undescribed caspase cleavage site in tau. Collectively, these results suggest a role for caspase-6 and N-terminal truncation of tau during neurofibrillary tangle evolution and the progression of Alzheimer's disease.

Tau is a microtubule-associated protein thought to help modulate the stability of neuronal microtubules. In tauopathies, including Alzheimer's disease and several frontotemporal dementias, tau is abnormally modified and misfolded resulting in its disassociation from microtubules and the generation of pathological lesions characteristic for each disease. A recent surge in the population of people with neurodegenerative tauopathies has highlighted the immense need for disease-modifying therapies for these conditions, and new attention has focused on tau as a potential target for intervention. In the current work we summarize evidence linking tau to disease pathogenesis and review recent therapeutic approaches aimed at ameliorating tau dysfunction. The primary therapeutic tactics considered include kinase inhibitors and phosphatase activators, immunotherapies, small molecule inhibitors of protein aggregation, and microtubule-stabilizing agents. Although the evidence for tau-based treatments is encouraging, additional work is undoubtedly needed to optimize each treatment strategy for the successful development of safe and effective therapeutics.

Tauopathies are characterized by abnormal aggregation of the microtubule associated protein tau. This aggregation is thought to occur when tau undergoes shifts from its native conformation to one that exposes hydrophobic areas on separate monomers, allowing contact and subsequent association into oligomers and filaments. Molecular chaperones normally function by binding to exposed hydrophobic stretches on proteins and assisting in their refolding. Chaperones of the heat shock protein 70 (Hsp70) family have been implicated in the prevention of abnormal tau aggregation in adult neurons. Tau exists as six alternatively spliced isoforms, and all six isoforms appear capable of forming the pathological aggregates seen in Alzheimer's disease. Because tau isoforms differ in primary sequence, we sought to determine whether Hsp70 would differentially affect the aggregation and microtubule assembly characteristics of the various tau isoforms. We found that Hsp70 inhibits tau aggregation directly, and not through inducer mediated effects. We also determined that Hsp70 inhibits the aggregation of each individual tau isoform and was more effective at inhibiting the three repeat isoforms. . Finally, all tau isoforms robustly induced microtubule formation while in the presence of Hsp70. The results presented herein indicate that Hsp70 affects tau isoform dysfunction while having very little impact on the normal function of tau to mediate microtubule assembly. This indicates that targeting Hsp70 to tau may provide a therapeutic approach for the treatment of tauopathies that avoids disruption of normal tau function.

Tau is a microtubule-associated protein predominantly expressed in axons where it is involved in the maintenance and stabilization of microtubules.1 Under physiological conditions, tau is a soluble protein with limited secondary structure.2 However, in Alzheimer's disease (AD), tau dissociates from microtubules and self-associates to form both fibrillar and prefibrillar oligomeric aggregates.3,4 Aggregated forms of tau are also found in various other tauopathies, including Pick's disease, corticobasal degeneration, and progressive supranuclear palsy.5 Importantly, the identification of mutations in the tau gene that cause hereditary tauopathies demonstrates that tau dysfunction is sufficient to cause neuronal degeneration. Neurofibrillary tangles (NFTs), a pathological hallmark of AD and other tauopathies, are composed of fibrillar tau aggregates and positively correlate with cognitive decline.6 However, recent evidence suggests that prefibrillar oligomeric tau aggregates may represent the main toxic species.7 For instance, neurodegeneration occurs in some tau overexpression animal models that lack overt neurofibrillary pathology.8,9 Another study demonstrated that levels of early multimeric tau aggregates that preceded neurofibrillary pathology correlated better with memory deficits.10 Moreover, suppression of tau expression improved memory function without affecting existing NFTs.11,12 The exact mechanisms underlying tau toxicity remain a matter of debate. However, recent experiments demonstrated that abnormal activation of kinase-based pathways and disruption of fast axonal transport (FAT) represent toxic gains of function associated with aggregated but not soluble tau species.13–15 Specifically, experiments in isolated squid axoplasm revealed that aggregated tau activates a protein phosphatase 1 (PP1) and glycogen synthase kinase 3 (GSK3)-dependent signaling pathway that results in the inhibition of conventional kinesin-dependent anterograde FAT.13 Given that aggregated tau pathology is a common denominator in several neurodegenerative diseases and that tau aggregates are demonstrably toxic, it follows that prevention of tau aggregation represents a reasonable therapeutic objective. Molecular chaperones make up a highly conserved family of related proteins that prevent protein misfolding and aggregation. Chaperone involvement has been implicated in several neurodegenerative diseases, including Parkinson's disease, Huntington's disease, and AD.16–20 In particular, molecular chaperones of the Hsp70 family are upregulated in AD and attenuate toxicity in a variety of neurodegenerative disease models.21 Hsp70 has been found to facilitate microtubule binding of tau and is associated with decreased levels of insoluble tau.22,23 In addition, Hsp70 facilitates the degradation of insoluble tau aggregates via a direct interaction with CHIP (carboxyl terminus of the Hsc70-interacting protein), a ubiquitin ligase,23 or BAG2 (BCL2-associated athanogene 2), a cochaperone.24 Taken together, the available data suggest that Hsp70 attenuates tau toxicity by maintaining tau in a soluble, nonaggregated state and by facilitating the degradation of aggregated tau species. However, the exact tau aggregate species targeted by Hsp70 chaperones remains unknown. Moreover, specific cellular processes protected by Hsp70 chaperones have not been identified, and thus data showing reduction of tau toxicity remain largely correlative. In this study, we demonstrate that Hsp70 directly inhibits tau aggregation by a mechanism involving preferential associations with soluble, monomeric and prefibrillar oligomeric tau species. In addition, Hsp70 prevents the toxic effect of preformed tau aggregates on anterograde FAT. When added to preformed tau aggregates in vitro, Hsp70 did not appreciably dissociate tau filaments. Interestingly, Hsp70 was found to associate preferentially with oligomeric versus fibrillar tau aggregates, suggesting that oligomeric aggregates may represent the main toxic species associated with aggregated tau.