Sex- and species-specific contribution of CD99 to T cell costimulation during multiple sclerosis.

BACKGROUND: Differences in immune responses between women and men are leading to a strong sex bias in the incidence of autoimmune diseases that predominantly affect women, such as multiple sclerosis (MS). MS manifests in more than twice as many women, making sex one of the most important risk factor. However, it is incompletely understood which genes contribute to sex differences in autoimmune incidence. To address that, we conducted a gene expression analysis in female and male human spleen and identified the transmembrane protein CD99 as one of the most significantly differentially expressed genes with marked increase in men. CD99 has been reported to participate in immune cell transmigration and T cell regulation, but sex-specific implications have not been comprehensively investigated. METHODS: In this study, we conducted a gene expression analysis in female and male human spleen using the Genotype-Tissue Expression (GTEx) project dataset to identify differentially expressed genes between women and men. After successful validation on protein level of human immune cell subsets, we assessed hormonal regulation of CD99 as well as its implication on T cell regulation in primary human T cells and Jurkat T cells. In addition, we performed in vivo assays in wildtype mice and in Cd99-deficient mice to further analyze functional consequences of differential CD99 expression. RESULTS: Here, we found higher CD99 gene expression in male human spleens compared to females and confirmed this expression difference on protein level on the surface of T cells and pDCs. Androgens are likely dispensable as the cause shown by in vitro assays and ex vivo analysis of trans men samples. In cerebrospinal fluid, CD99 was higher on T cells compared to blood. Of note, male MS patients had lower CD99 levels on CD4+ T cells in the CSF, unlike controls. By contrast, both sexes had similar CD99 expression in mice and Cd99-deficient mice showed equal susceptibility to experimental autoimmune encephalomyelitis compared to wildtypes. Functionally, CD99 increased upon human T cell activation and inhibited T cell proliferation after blockade. Accordingly, CD99-deficient Jurkat T cells showed decreased cell proliferation and cluster formation, rescued by CD99 reintroduction. CONCLUSIONS: Our results demonstrate that CD99 is sex-specifically regulated in healthy individuals and MS patients and that it is involved in T cell costimulation in humans but not in mice. CD99 could potentially contribute to MS incidence and susceptibility in a sex-specific manner.

The immune system protects us from bacterial and viral infections and impacts the outcome of many diseases. Thus, understanding immunological processes is crucial to unravel pathogenic mechanisms and to develop new therapeutic treatment options. Sex is a biological variable affecting immunity and it is known that females and males differ in their immunological responses. Women mount stronger immune responses leading to more rapid control of infections and greater vaccine efficacy compared to men. However, this enhanced immune responsiveness is accompanied by female preponderance and susceptibility to autoimmune diseases like systemic lupus erythematosus, rheumatoid arthritis and multiple sclerosis (MS). MS sex ratio varies around 2:1 to 3:1 with a steadily increasing incidence in female MS patients making sex one of the top risk factors for developing MS. However, the underlying biological mechanisms including sex hormones as well as genetic and epigenetic factors and their complex interplay remain largely unknown. Here, we discovered the gene and its encoded protein CD99 to be differentially expressed between women and men with men showing increased expression on many immune cell subsets including T cells. Since T cells are key contributors to MS pathogenesis, we examined the role of CD99 on T cells of healthy individuals and MS patients. We were able to identify CD99-mediated T cell regulation, which might contribute to sex differences in MS susceptibility and incidence indicating the importance to include sex as a biological variable. Of note, these differences were not reproduced in mice showing the necessity of functional research in humans.

Astrocytic uptake of posttranslationally modified amyloid-ß leads to endolysosomal system disruption and induction of pro-inflammatory signaling.

The disruption of astrocytic catabolic processes contributes to the impairment of amyloid-ß (Aß) clearance, neuroinflammatory signaling, and the loss of synaptic contacts in late-onset Alzheimer's disease (AD). While it is known that the posttranslational modifications of Aß have significant implications on biophysical properties of the peptides, their consequences for clearance impairment are not well understood. It was previously shown that N-terminally pyroglutamylated Aß3(pE)-42, a significant constituent of amyloid plaques, is efficiently taken up by astrocytes, leading to the release of pro-inflammatory cytokine tumor necrosis factor α and synapse loss. Here we report that Aß3(pE)-42, but not Aß1-42, gradually accumulates within the astrocytic endolysosomal system, disrupting this catabolic pathway and inducing the formation of heteromorphous vacuoles. This accumulation alters lysosomal kinetics, lysosome-dependent calcium signaling, and upregulates the lysosomal stress response. These changes correlate with the upregulation of glial fibrillary acidic protein (GFAP) and increased activity of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Treatment with a lysosomal protease inhibitor, E-64, rescues GFAP upregulation, NF-κB activation, and synapse loss, indicating that abnormal lysosomal protease activity is upstream of pro-inflammatory signaling and related synapse loss. Collectively, our data suggest that Aß3(pE)-42-induced disruption of the astrocytic endolysosomal system leads to cytoplasmic leakage of lysosomal proteases, promoting pro-inflammatory signaling and synapse loss, hallmarks of AD-pathology.

Comparison of immunoassay- with mass spectrometry-derived p-tau quantification for the detection of Alzheimer's disease pathology.

BACKGROUND: Antibody-based immunoassays have enabled quantification of very low concentrations of phosphorylated tau (p-tau) protein forms in cerebrospinal fluid (CSF), aiding in the diagnosis of AD. Mass spectrometry enables absolute quantification of multiple p-tau variants within a single run. The goal of this study was to compare the performance of mass spectrometry assessments of p-tau181, p-tau217 and p-tau231 with established immunoassay techniques. METHODS: We measured p-tau181, p-tau217 and p-tau231 concentrations in CSF from 173 participants from the TRIAD cohort and 394 participants from the BioFINDER-2 cohort using both mass spectrometry and immunoassay methods. All subjects were clinically evaluated by dementia specialists and had amyloid-PET and tau-PET assessments. Bland-Altman analyses evaluated the agreement between immunoassay and mass spectrometry p-tau181, p-tau217 and p-tau231. P-tau associations with amyloid-PET and tau-PET uptake were also compared. Receiver Operating Characteristic (ROC) analyses compared the performance of mass spectrometry and immunoassays p-tau concentrations to identify amyloid-PET positivity. RESULTS: Mass spectrometry and immunoassays of p-tau217 were highly comparable in terms of diagnostic performance, between-group effect sizes and associations with PET biomarkers. In contrast, p-tau181 and p-tau231 concentrations measured using antibody-free mass spectrometry had lower performance compared with immunoassays. CONCLUSIONS: Our results suggest that while similar overall, immunoassay-based p-tau biomarkers are slightly superior to antibody-free mass spectrometry-based p-tau biomarkers. Future work is needed to determine whether the potential to evaluate multiple biomarkers within a single run offsets the slightly lower performance of antibody-free mass spectrometry-based p-tau quantification.

Plasma pTau-217 and N-terminal tau (NTA) enhance sensitivity to identify tau PET positivity in amyloid-ß positive individuals.

INTRODUCTION: We set out to identify tau PET-positive (A+T+) individuals among amyloid-beta (Aß) positive participants using plasma biomarkers. METHODS: In this cross-sectional study we assessed 234 participants across the AD continuum who were evaluated by amyloid PET with [18 F]AZD4694 and tau-PET with [18 F]MK6240 and measured plasma levels of total tau, pTau-181, pTau-217, pTau-231, and N-terminal tau (NTA-tau). We evaluated the performances of plasma biomarkers to predict tau positivity in Aß+ individuals. RESULTS: Highest associations with tau positivity in Aß+ individuals were found for plasma pTau-217 (AUC [CI95% ] = 0.89 [0.82, 0.96]) and NTA-tau (AUC [CI95% ] = 0.88 [0.91, 0.95]). Combining pTau-217 and NTA-tau resulted in the strongest agreement (Cohen's Kappa = 0.74, CI95%  = 0.57/0.90, sensitivity = 92%, specificity = 81%) with PET for classifying tau positivity. DISCUSSION: The potential for identifying tau accumulation in later Braak stages will be useful for patient stratification and prognostication in treatment trials and in clinical practice. HIGHLIGHTS: We found that in a cohort without pre-selection pTau-181, pTau-217, and NTA-tau showed the highest association with tau PET positivity. We found that in Aß+ individuals pTau-217 and NTA-tau showed the highest association with tau PET positivity. Combining pTau-217 and NTA-tau resulted in the strongest agreement with the tau PET-based classification.

14-3-3 [Formula: see text]-reported early synaptic injury in Alzheimer's disease is independently mediated by sTREM2.

INTRODUCTION: Synaptic loss is closely associated with tau aggregation and microglia activation in later stages of Alzheimer's disease (AD). However, synaptic damage happens early in AD at the very early stages of tau accumulation. It remains unclear whether microglia activation independently causes synaptic cleavage before tau aggregation appears. METHODS: We investigated 104 participants across the AD continuum by measuring 14-3-3 zeta/delta ([Formula: see text]) as a cerebrospinal fluid biomarker for synaptic degradation, and fluid and imaging biomarkers of tau, amyloidosis, astrogliosis, neurodegeneration, and inflammation. We performed correlation analyses in cognitively unimpaired and impaired participants and used structural equation models to estimate the impact of microglia activation on synaptic injury in different disease stages. RESULTS: 14-3-3 [Formula: see text] was increased in participants with amyloid pathology at the early stages of tau aggregation before hippocampal volume loss was detectable. 14-3-3 [Formula: see text] correlated with amyloidosis and tau load in all participants but only with biomarkers of neurodegeneration and memory deficits in cognitively unimpaired participants. This early synaptic damage was independently mediated by sTREM2. At later disease stages, tau and astrogliosis additionally mediated synaptic loss. CONCLUSIONS: Our results advertise that sTREM2 is mediating synaptic injury at the early stages of tau accumulation, underlining the importance of microglia activation for AD disease propagation.

Comparative analysis of characteristics and outcomes in hospitalized COVID-19 patients infected with different SARS-CoV-2 variants between January 2020 and April 2022 - A retrospective single-center cohort study.

BACKGROUND: Since the beginning of the coronavirus disease 2019 (COVID-19) pandemic, the roll-out of vaccines and therapeutic agents, as well as the emergence of novel SARS-CoV-2 variants, have shown significant effects on disease severity. METHODS: Patients hospitalized at our center between January 2020 and April 2022 were attributed to subgroups depending on which SARS-CoV-2 variant was predominantly circulating in Germany: (i) Wild-type: January 1, 2020, to March 7, 2021, (ii) Alpha variant: August 3, 2021, to June 27, 2021, (iii) Delta variant: June 28, 2021, to December 26, 2021, and (iv) Omicron variant: December 27, 2021, to April 30, 2022. RESULTS: Between January 2020 and April 2022, 1500 patients with SARS-CoV-2 infections were admitted to the University Medical Center Hamburg-Eppendorf. The rate of patients who were admitted to the intensive care unit (ICU) decreased from 31.2% (n = 223) in the wild-type group, 28.5% (n = 72) in the Alpha variant group, 18.8% (n = 67) in the Delta variant group, and 13.4% (n = 135) in the Omicron variant group. Also, in-hospital mortality decreased from 20.6% (n = 111) in the wild-type group, 17.5% (n = 30) in the Alpha variant group, 16.8% (n = 33) in the Delta variant group, and 6.6% (n = 39) in the Omicron variant group. The median duration of hospitalization was similar in all subgroups and ranged between 11 and 15 days throughout the pandemic. CONCLUSIONS: In-hospital mortality and rate of ICU admission among hospitalized COVID-19 patients steadily decreased throughout the pandemic. However, the practically unchanged duration of hospitalization demonstrates the persistent burden of COVID-19 on the healthcare system.

Calcium channel ß3 subunit regulates ATP-dependent migration of dendritic cells.

Migratory dendritic cells (migDCs) continuously patrol tissues and are activated by injury and inflammation. Extracellular adenosine triphosphate (ATP) is released by damaged cells or actively secreted during inflammation and increases migDC motility. However, the underlying molecular mechanisms by which ATP accelerates migDC migration is not understood. Here, we show that migDCs can be distinguished from other DC subsets and immune cells by their expression of the voltage-gated calcium channel subunit ß3 (Cavß3; CACNB3), which exclusively facilitates ATP-dependent migration in vitro and during tissue damage in vivo. By contrast, CACNB3 does not regulate lipopolysaccharide-dependent migration. Mechanistically, CACNB3 regulates ATP-dependent inositol 1,4,5-trisphophate receptor-controlled calcium release from the endoplasmic reticulum. This, in turn, is required for ATP-mediated suppression of adhesion molecules, their detachment, and initiation of migDC migration. Thus, Cacnb3-deficient migDCs have an impaired migration after ATP exposure. In summary, we identified CACNB3 as a master regulator of ATP-dependent migDC migration that controls tissue-specific immunological responses during injury and inflammation.

Vagus nerve inflammation contributes to dysautonomia in COVID-19.

Dysautonomia has substantially impacted acute COVID-19 severity as well as symptom burden after recovery from COVID-19 (long COVID), yet the underlying causes remain unknown. Here, we hypothesized that vagus nerves are affected in COVID-19 which might contribute to autonomic dysfunction. We performed a histopathological characterization of postmortem vagus nerves from COVID-19 patients and controls, and detected SARS-CoV-2 RNA together with inflammatory cell infiltration composed primarily of monocytes. Furthermore, we performed RNA sequencing which revealed a strong inflammatory response of neurons, endothelial cells, and Schwann cells which correlated with SARS-CoV-2 RNA load. Lastly, we screened a clinical cohort of 323 patients to detect a clinical phenotype of vagus nerve affection and found a decreased respiratory rate in non-survivors of critical COVID-19. Our data suggest that SARS-CoV-2 induces vagus nerve inflammation followed by autonomic dysfunction which contributes to critical disease courses and might contribute to dysautonomia observed in long COVID.

History of cerebrovascular disease but not dementia increases the risk for secondary vascular events during SARS-CoV-2 infection with presumed Omicron variant: a retrospective observational study.

BACKGROUND AND PURPOSE: This study aimed to investigate if pre-existing neurological conditions, such as dementia and a history of cerebrovascular disease, increase the risk of severe outcomes including death, intensive care unit (ICU) admission and vascular events in patients hospitalized with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in 2022, when Omicron was the predominant variant. METHODS: A retrospective analysis was conducted of all patients with SARS-CoV-2 infection, confirmed by polymerase chain reaction test, admitted to the University Medical Center Hamburg-Eppendorf from 20 December 2021 until 15 August 2022. In all, 1249 patients were included in the study. In-hospital mortality was 3.8% and the ICU admission rate was 9.9%. Ninety-three patients with chronic cerebrovascular disease and 36 patients with pre-existing all-cause dementia were identified and propensity score matching by age, sex, comorbidities, vaccination status and dexamethasone treatment was performed in a 1:4 ratio with patients without the respective precondition using nearest neighbor matching. RESULTS: Analysis revealed that neither pre-existing cerebrovascular disease nor all-cause dementia increased mortality or the risk for ICU admission. All-cause dementia in the medical history also had no effect on vascular complications under investigation. In contrast, an increased odds ratio for both pulmonary artery embolism and secondary cerebrovascular events was observed in patients with pre-existing chronic cerebrovascular disease and myocardial infarction in the medical history. CONCLUSION: These findings suggest that patients with pre-existing cerebrovascular disease and myocardial infarction in their medical history may be particularly susceptible to vascular complications following SARS-CoV-2 infection with presumed Omicron variant.

Absence of self-reported neuropsychiatric and somatic symptoms after Omicron variant SARS-CoV-2 breakthrough infections.

Persistent somatic and neuropsychiatric symptoms have been frequently described in patients after infection with severe acute respiratory syndrome coronavirus 2 even after a benign clinical course of the acute infection during the early phases of the coronavirus severe acute respiratory syndrome coronavirus 2 pandemic and are part of Long COVID. The Omicron variant emerged in November 2021 and has rapidly become predominant due to its high infectivity and suboptimal vaccine cross-protection. The frequency of neuropsychiatric post-acute sequelae after infection with the severe acute respiratory syndrome coronavirus 2 Omicron and adequate vaccination status is not known. Here, we aimed to characterize post-acute symptoms in individuals with asymptomatic or mildly symptomatic breakthrough infection with severe acute respiratory syndrome coronavirus 2. These individuals had either proven infection with the Omicron variant (n = 157) or their infection occurred in 2022 where Omicron was the predominant variant of severe acute respiratory syndrome coronavirus 2 in Germany (n = 107). This monocentric cross-sectional study was conducted at the University Medical Center Hamburg-Eppendorf between 11 February 2022 and 11 April 2022. We employed questionnaires addressing self-reported somatic symptom burden (Somatic Symptom Scale 8) and neuropsychiatric symptoms including mood (Patient Health Questionnaire 2), anxiety (Generalized Anxiety Disorder 7), attention (Mindful Attention Awareness Scale) and fatigue (Fatigue Assessment Scale) in a cohort of hospital workers. Scores were compared between 175 individuals less than 4 weeks after positive testing for severe acute respiratory syndrome coronavirus 2, 88 individuals more than 4 weeks after positive testing and 87 severe acute respiratory syndrome coronavirus 2 uninfected controls. The majority (n = 313; 89.5%) of included individuals were vaccinated at least three times. After recovery from infection, no significant differences in scores assessing neuropsychiatric and somatic symptoms were detected between the three groups (severe acute respiratory syndrome coronavirus 2 uninfected controls, individuals less and more than 4 weeks after positive testing) independent of age, sex, preconditions and vaccination status. In addition, self-reported symptom burden did not significantly correlate with the number of vaccinations against severe acute respiratory syndrome coronavirus 2, time from recovery or the number of infections. Notably, in all three groups, the mean scores for each item of our questionnaire lay below the pathological threshold. Our data show that persistent neuropsychiatric and somatic symptoms after recovery from severe acute respiratory syndrome coronavirus 2 infection in fully vaccinated hospital workers do not occur more frequently than that in uninfected individuals. This will guide healthcare professionals in the clinical management of patients after recovery from breakthrough infections with severe acute respiratory syndrome coronavirus 2.

Jacob-induced transcriptional inactivation of CREB promotes Aß-induced synapse loss in Alzheimer's disease.

Synaptic dysfunction caused by soluble ß-amyloid peptide (Aß) is a hallmark of early-stage Alzheimer's disease (AD), and is tightly linked to cognitive decline. By yet unknown mechanisms, Aß suppresses the transcriptional activity of cAMP-responsive element-binding protein (CREB), a master regulator of cell survival and plasticity-related gene expression. Here, we report that Aß elicits nucleocytoplasmic trafficking of Jacob, a protein that connects a NMDA-receptor-derived signalosome to CREB, in AD patient brains and mouse hippocampal neurons. Aß-regulated trafficking of Jacob induces transcriptional inactivation of CREB leading to impairment and loss of synapses in mouse models of AD. The small chemical compound Nitarsone selectively hinders the assembly of a Jacob/LIM-only 4 (LMO4)/ Protein phosphatase 1 (PP1) signalosome and thereby restores CREB transcriptional activity. Nitarsone prevents impairment of synaptic plasticity as well as cognitive decline in mouse models of AD. Collectively, the data suggest targeting Jacob protein-induced CREB shutoff as a therapeutic avenue against early synaptic dysfunction in AD.

Sotrovimab in Hospitalized Patients with SARS-CoV-2 Omicron Variant Infection: a Propensity Score-Matched Retrospective Cohort Study.

In vitro data suggest the monoclonal antibody sotrovimab may have lost inhibitory capability against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant. We aimed to provide real-life data on clinical outcomes in hospitalized patients. We retrospectively analyzed patients who were treated at the University Medical Center Hamburg-Eppendorf, Germany, between December 2021 and June 2022. Out of all 1,254 patients, 185 were treated with sotrovimab: 147 patients received sotrovimab monotherapy, and 38 received combination treatment with sotrovimab and remdesivir. We compared in-hospital mortality for the different treatment regimens for patients treated on regular wards and the intensive care unit separately and performed propensity score matching by age, sex, comorbidities, immunosuppression, and additional dexamethasone treatment to select patients who did not receive antiviral treatment for comparison. No difference in in-hospital mortality was observed between any of the treatment groups and the respective control groups. These findings underline that sotrovimab adds no clinical benefit for hospitalized patients with SARS-CoV-2 Omicron variant infections. IMPORTANCE This study shows that among hospitalized patients with SARS-CoV-2 Omicron variant infection at risk of disease progression, treatment with sotrovimab alone or in combination with remdesivir did not decrease in-hospital mortality. These real-world clinical findings in combination with previous in vitro data about lacking neutralizing activity of sotrovimab against SARS-CoV-2 Omicron variant do not support sotrovimab as a treatment option in these patients.

Atraumatic spinal needle indicates correct CSF opening pressure.

The accurate assessment of cerebrospinal fluid opening pressure during spinal puncture provides important medical information in diagnosis, prognosis and therapy of several neurological conditions. However, purpose-specific spinal needle choice is debated. While atraumatic needles are associated with lower incidence of post-puncture headache and re-hospitalisation, some clinicians believe that they lack in accuracy of CSF opening pressure assessment. Our primary objective was to investigate different needle types on correctly assessing CSF opening pressure. We compared typical clinically utilised traumatic (0.9 mm outer diameter) and atraumatic (0.7 mm; 0.45 mm) spinal needles with regards to the assessment of the opening pressure in an experimental spinal puncture model testing experimental and cerebrospinal fluids in predefined pressures. Our goal was to measure the time until indicated pressure levels were correctly shown. Atraumatic needles of at least 0.7 mm diameter had a similar accuracy as traumatic needles without significant differences in time-to-equilibrium. These results were independent of protein and glucose concentration and the presence of haemoglobin. This study demonstrates that atraumatic needles can be used to accurately measure CSF opening pressure. This knowledge might guide clinicians in their choice of needle and help to reduce post-puncture headaches and re-hospitalisation.

G9a dictates neuronal vulnerability to inflammatory stress via transcriptional control of ferroptosis.

Neuroinflammation leads to neuronal stress responses that contribute to neuronal dysfunction and loss. However, treatments that stabilize neurons and prevent their destruction are still lacking. Here, we identify the histone methyltransferase G9a as a druggable epigenetic regulator of neuronal vulnerability to inflammation. In murine experimental autoimmune encephalomyelitis (EAE) and human multiple sclerosis (MS), we found that the G9a-catalyzed repressive epigenetic mark H3K9me2 was robustly induced by neuroinflammation. G9a activity repressed anti-ferroptotic genes, diminished intracellular glutathione levels, and triggered the iron-dependent programmed cell death pathway ferroptosis. Conversely, pharmacological treatment of EAE mice with a G9a inhibitor restored anti-ferroptotic gene expression, reduced inflammation-induced neuronal loss, and improved clinical outcome. Similarly, neuronal anti-ferroptotic gene expression was reduced in MS brain tissue and was boosted by G9a inhibition in human neuronal cultures. This study identifies G9a as a critical transcriptional enhancer of neuronal ferroptosis and potential therapeutic target to counteract inflammation-induced neurodegeneration.

The blood-brain barrier is dysregulated in COVID-19 and serves as a CNS entry route for SARS-CoV-2.

Neurological complications are common in COVID-19. Although SARS-CoV-2 has been detected in patients' brain tissues, its entry routes and resulting consequences are not well understood. Here, we show a pronounced upregulation of interferon signaling pathways of the neurovascular unit in fatal COVID-19. By investigating the susceptibility of human induced pluripotent stem cell (hiPSC)-derived brain capillary endothelial-like cells (BCECs) to SARS-CoV-2 infection, we found that BCECs were infected and recapitulated transcriptional changes detected in vivo. While BCECs were not compromised in their paracellular tightness, we found SARS-CoV-2 in the basolateral compartment in transwell assays after apical infection, suggesting active replication and transcellular transport of virus across the blood-brain barrier (BBB) in vitro. Moreover, entry of SARS-CoV-2 into BCECs could be reduced by anti-spike-, anti-angiotensin-converting enzyme 2 (ACE2)-, and anti-neuropilin-1 (NRP1)-specific antibodies or the transmembrane protease serine subtype 2 (TMPRSS2) inhibitor nafamostat. Together, our data provide strong support for SARS-CoV-2 brain entry across the BBB resulting in increased interferon signaling.

Multi-dimensional and longitudinal systems profiling reveals predictive pattern of severe COVID-19.

COVID-19 is a respiratory tract infection that can affect multiple organ systems. Predicting the severity and clinical outcome of individual patients is a major unmet clinical need that remains challenging due to intra- and inter-patient variability. Here, we longitudinally profiled and integrated more than 150 clinical, laboratory, and immunological parameters of 173 patients with mild to fatal COVID-19. Using systems biology, we detected progressive dysregulation of multiple parameters indicative of organ damage that correlated with disease severity, particularly affecting kidneys, hepatobiliary system, and immune landscape. By performing unsupervised clustering and trajectory analysis, we identified T and B cell depletion as early indicators of a complicated disease course. In addition, markers of hepatobiliary damage emerged as robust predictor of lethal outcome in critically ill patients. This allowed us to propose a novel clinical COVID-19 SeveriTy (COST) score that distinguishes complicated disease trajectories and predicts lethal outcome in critically ill patients.

Neuronal metabotropic glutamate receptor 8 protects against neurodegeneration in CNS inflammation.

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system with continuous neuronal loss. Treatment of clinical progression remains challenging due to lack of insights into inflammation-induced neurodegenerative pathways. Here, we show that an imbalance in the neuronal receptor interactome is driving glutamate excitotoxicity in neurons of MS patients and identify the MS risk-associated metabotropic glutamate receptor 8 (GRM8) as a decisive modulator. Mechanistically, GRM8 activation counteracted neuronal cAMP accumulation, thereby directly desensitizing the inositol 1,4,5-trisphosphate receptor (IP3R). This profoundly limited glutamate-induced calcium release from the endoplasmic reticulum and subsequent cell death. Notably, we found Grm8-deficient neurons to be more prone to glutamate excitotoxicity, whereas pharmacological activation of GRM8 augmented neuroprotection in mouse and human neurons as well as in a preclinical mouse model of MS. Thus, we demonstrate that GRM8 conveys neuronal resilience to CNS inflammation and is a promising neuroprotective target with broad therapeutic implications.

Frequent neurocognitive deficits after recovery from mild COVID-19.

Neuropsychiatric complications associated with coronavirus disease 2019 caused by the Coronavirus SARS-CoV-2 (COVID-19) are increasingly appreciated. While most studies have focussed on severely affected individuals during acute infection, it remains unclear whether mild COVID-19 results in neurocognitive deficits in young patients. Here, we established a screening approach to detect cognitive deficiencies in post-COVID-19 patients. In this cross-sectional study, we recruited 18 mostly young patients 20-105 days (median, 85 days) after recovery from mild to moderate disease who visited our outpatient clinic for post-COVID-19 care. Notably, 14 (78%) patients reported sustained mild cognitive deficits and performed worse in the Modified Telephone Interview for Cognitive Status screening test for mild cognitive impairment compared to 10 age-matched healthy controls. While short-term memory, attention and concentration were particularly affected by COVID-19, screening results did not correlate with hospitalization, treatment, viremia or acute inflammation. Additionally, Modified Telephone Interview for Cognitive Status scores did not correlate with depressed mood or fatigue. In two severely affected patients, we excluded structural or other inflammatory causes by magnetic resonance imaging, serum and cerebrospinal fluid analyses. Together, our results demonstrate that sustained sub-clinical cognitive impairments might be a common complication after recovery from COVID-19 in young adults, regardless of clinical course that were unmasked by our diagnostic approach.

Voltage-Gated Proton Channel Hv1 Controls TLR9 Activation in Plasmacytoid Dendritic Cells.

The voltage-gated proton channel Hv1 regulates proton fluxes across membranes, thereby influencing pH-dependent processes. Plasmacytoid dendritic cells (pDCs) require a particularly tight regulation of endosomal pH to ensure strong type I IFN secretion exclusively during infection, avoiding autoimmunity. However, whether Hv1 is important for pH control in pDCs is presently unknown. In this study, we show that mouse pDCs require Hv1 to achieve potent type I IFN responses after the recognition of foreign DNA by endosomal TLR9. Genetic disruption of Hvcn1, which encodes Hv1, impaired mouse pDC activation by CpG oligonucleotides in vitro and in vivo, reducing IFN-α secretion and the induction of IFN-stimulated genes. Mechanistically, Hvcn1 deficiency delayed endosomal acidification and enhanced intracellular reactive oxygen species production, consequently limiting protease activity and TLR9 signaling. Our study reveals a critical role of Hv1 during innate immune responses and places this channel as a key modulator of type I IFN production, the hallmark function of pDCs, commending Hv1 as an attractive target for modulating type I IFN-driven autoimmunity.