Chloé Bost

Background/Objectives: This report is an assessment of the characteristics associated with cardiovascular dysautonomia (CVD) in the context of long Coronavirus disease (COVID), which is currently inadequately characterized. Material and Methods: A retrospective cross-sectional study was performed involving 106 patients with long COVID, including 34 individuals diagnosed with CVD, among whom eight met the criteria for Postural Tachycardia Syndrome (PoTS). The variables assessed encompassed individual characteristics (e.g., age, sex, comorbidities), immunization parameters (e.g., vaccination/viral status, timing, frequency), cellular and humoral anti-Spike and anti-Nucleocapsid (Nuc) immune responses, inflammatory and allergic biomarkers, as well as an extensive panel of common autoantibodies comprising anti-nuclear antibodies, anti-central nervous system antibodies (cerebellum, brain), and anti-peripheral nervous system antibodies (gangliosides). Results: An age < 45 years, body mass index, hyperventilation syndrome as well as a higher cumulative number of antigenic contacts (vaccinations plus infections ≥ 3) and an elevated basophil count (≥0.06 G/L) were independently associated with CVD. There was no association between CVD and inflammatory markers or common autoantibodies. Patients with PoTS criteria had a strong anti-Spike cellular immune response and increased IgG anti-Nuc humoral immunity when compared with CVD and non-CVD long COVID counterparts. Conclusions: Compared to other long COVID patients, patients with long COVID-associated CVD have distinctive clinical and immunovirological features. Our results suggest the potential role of the immune response against Spike and of allergic pathways rather than humoral autoimmunity against common autoantibodies in long COVID CVD.

Les encéphalites à anticorps (Ac) anti-récepteur NMDA (NMDAR) sont des pathologies auto-immunes nouvellement décrites ciblant un récepteur majeur du système nerveux central, le NMDAR. Les synapses glutamatergiques assurent la majeure partie de la transmission excitatrice du cerveau et les récepteurs ionotropiques au glutamate de type NMDA ont un rôle clé dans la plasticité synaptique, c'est-à-dire les modifications de la force de transmission synaptique constituant le corrélat cellulaire des processus d'apprentissage et de mémoire. Les études in vitro et in vivo de l'effet des Ac anti-NMDAR tendent à montrer une altération de la dynamique des NDMAR et une internalisation. Les Ac auraient un effet pathogénique pouvant expliquer des symptômes. Au cours de ma thèse, j'ai souhaité approfondir la compréhension de cette pathologie sur le plan clinique et mécanistique. Pour cela j'ai étudié les caractéristiques cliniques et histologiques des patients présentant une tumeur maligne associée, me permettant d'établir des recommandations de prise en charge au vu du taux de mortalité plus élevé chez ces patients et d'une fréquence plus importante de tératomes ovariens immatures que dans la population générale. En parallèle j'ai étudié l'effet des Ac anti-NMDAR sur la transmission et la plasticité synaptique dans un modèle murin d'administration chronique des anticorps. Ces études menées en électrophysiologie sur tranches aigües m'ont permis de mettre en évidence un effet des anticorps du LCR sur la plasticité synaptique significatif mais d'amplitude moindre que les études in vitro l'avaient suggéré. Nous avons également montré l'importance de la durée d'exposition aux anticorps

Background: Autoimmune encephalitis (AIE) is an increasingly broad nosological framework that may clinically mimic neurodegenerative diseases (NDDs). Cases Reported: We describe here the clinical, radiological, electrophysiological, and biological evolution of three patients. Two women aged 73 and 72 years and a 69-year-old man presented with complex cognitive and focal neurological symptoms and each had a predominant frontal dysexecutive involvement and an unexpectedly high titer of anti-MAG antibodies in the serum and cerebrospinal fluid (CSF). The question of an autoimmune cause was raised. After 2 years of follow-up and, for two of them, without improvement despite immunosuppressive treatments, diagnoses of NDD were eventually retained: post-radiation encephalopathy, progressive supranuclear palsy (PSP), and Alzheimer's disease. Conclusion: The presence of a high titer of anti-MAG antibodies may be found in NDD. It could reflect cerebral tissue damages, particularly in the case of significant frontal involvement. Atypical presentations may lead to a search for a paraneoplastic neurologic syndrome or AIE. However, the indirect immunofluorescence staining positivity on a monkey cerebellum section linked with anti-MAG antibodies should not lead to those diagnoses being retained.