Validating a minipig model of reversible cerebral demyelination using human diagnostic modalities and electron microscopy.

BACKGROUND: Inflammatory demyelinating diseases of the central nervous system, such as multiple sclerosis, are significant sources of morbidity in young adults despite therapeutic advances. Current murine models of remyelination have limited applicability due to the low white matter content of their brains, which restricts the spatial resolution of diagnostic imaging. Large animal models might be more suitable but pose significant technological, ethical and logistical challenges. METHODS: We induced targeted cerebral demyelinating lesions by serially repeated injections of lysophosphatidylcholine in the minipig brain. Lesions were amenable to follow-up using the same clinical imaging modalities (3T magnetic resonance imaging, 11C-PIB positron emission tomography) and standard histopathology protocols as for human diagnostics (myelin, glia and neuronal cell markers), as well as electron microscopy (EM), to compare against biopsy data from two patients. FINDINGS: We demonstrate controlled, clinically unapparent, reversible and multimodally trackable brain white matter demyelination in a large animal model. De-/remyelination dynamics were slower than reported for rodent models and paralleled by a degree of secondary axonal pathology. Regression modelling of ultrastructural parameters (g-ratio, axon thickness) predicted EM features of cerebral de- and remyelination in human data. INTERPRETATION: We validated our minipig model of demyelinating brain diseases by employing human diagnostic tools and comparing it with biopsy data from patients with cerebral demyelination. FUNDING: This work was supported by the DFG under Germany's Excellence Strategy within the framework of the Munich Cluster for Systems Neurology (EXC 2145 SyNergy, ID 390857198) and TRR 274/1 2020, 408885537 (projects B03 and Z01).

Case Series: Acute Hemorrhagic Encephalomyelitis After SARS-CoV-2 Vaccination.

We present three cases fulfilling diagnostic criteria of hemorrhagic variants of acute disseminated encephalomyelitis (acute hemorrhagic encephalomyelitis, AHEM) occurring within 9 days after the first shot of ChAdOx1 nCoV-19. AHEM was diagnosed using magnetic resonance imaging, cerebrospinal fluid analysis and brain biopsy in one case. The close temporal association with the vaccination, the immune-related nature of the disease as well as the lack of other canonical precipitating factors suggested that AHEM was a vaccine-related adverse effect. We believe that AHEM might reflect a novel COVID-19 vaccine-related adverse event for which physicians should be vigilant and sensitized.

CD20 monoclonal antibodies for the treatment of multiple sclerosis: up-to-date.

INTRODUCTION: Featuring demyelination and axonal degeneration, multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system representing a prominent cause of disability in young adults. The recently established therapeutic targeting of B cells in MS patients using CD20 monoclonal antibodies (CD20-mAbs) not only profoundly suppresses inflammatory disease activity but also materializes as the first treatment approach against disability accumulation in a subset of patients with primary progressive MS. AREAS COVERED: We will review current concepts regarding the immunopathology of B cells as well as results of clinical trials with CD20-mAbs in MS, from the murine-human chimeras rituximab and ublituximab to their increasingly humanized counterparts ocrelizumab and ofatumumab. We conducted a literature search using PubMed, clinicaltrials.gov, and clinicaltrialsregister.eu. We will focus on studies emphasizing the effectiveness of these mAbs in reducing MS disease activity and progression, long-term safety, optimal dosage and maintenance regimens. Lastly, we will turn to outstanding questions regarding anti-CD20 therapy in MS. EXPERT OPINION: CD20-mAbs could become first-line drugs in selected patients with highly active MS and already constitute an option for PPMS. Future studies could evaluate whether administration regimens currently in use can be optimized, while registry data could shed light on risk versus benefits on the long run, considering immunosenescence and a potentially increased risk of malignancies and infections in an aging population.