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Noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonists can produce positive and negative symptomatology as well as impairment of cognitive function that closely resemble those present in schizophrenia. In rats, these drugs induce a behavioral syndrome (characterized by hyperlocomotion and stereotypies), an enhanced glutamatergic transmission in the medial prefrontal cortex, and damage to retrosplenial cortical neurons in adult rats, which was measured as the induction of the stress protein 72/73 kDa heat shock protein (Hsp72/73). In the present work we have examined the existence of possible differences among different antipsychotic drugs in their capacity to block immunolabeling of Hsp72/73 in the retrosplenial cortex of the rat induced by the potent NMDA receptor antagonist, MK-801. In addition, the effects of selective monoaminergic agents were also studied to delineate the particular receptors responsible for the actions of antipsychotic drugs. Pretreatment with clozapine, chlorpromazine, olanzapine, ziprasidone -and to a lesser extent haloperidol- reduced the formation of Hsp72/73 protein in the rat retrosplenial cortex after the administration of MK-801. In addition, antagonism at dopamine D2 (raclopride), 5-HT2A (M100907) and α1-adrenoceptors (prazosin) as well as agonism at 5-HT1A receptors (BAY x 3702) also diminished the MK-801-induced number of cells labeled with Hsp72/73. Each of these effects may contribute to antipsychotic action. The results suggest that the efficacy of atypical antipsychotic drugs in the clinic may result from a combined effect on 5-HT2A, 5-HT1A and α1-adrenergic receptors added to the classical dopamine D2 receptor antagonism. ; This work was supported by the Instituto de Salud Carlos III, Subdirección General de Evaluación y Fomento de la Investigación (FIS Grants PI070111 and PI1001103), Centro de Investigación Biomédica en Red de Salud Mental, CIBERSAM, and by the Innovative Medicine Initiative Joint Undertaking under grant agreement no. 115008, of which resources are composed of EFPIA in-kind contribution and financial contribution from the European Union's Seventh Framework Programme (FP7/2007-2013). Funding by the Generalitat de Catalunya (2009SGR220) and co-funding by the European Regional Development Fund (a way to build Europe) is also acknowledged ; Peer reviewed

© 2015 Pereira, Medina, Baena, Planas and Pozas. The adult subventricular zone (SVZ) is the main neurogenic niche in normal adult brains of mice and rats. Interferon gamma (IFNγ) has somewhat controversially been associated with SVZ progenitor proliferation and neurogenesis. The in vivo involvement of IFNγ in the physiology of the adult SVZ niche is not fully understood and its intracellular mediators are unknown. Here we show that IFNγ, through activation of its canonical signal transducer and activator of transcription 1 (STAT1) pathway, acts specifically on Nestin+ progenitors by decreasing both progenitor proliferation and the number of cycling cells. In addition, IFNγ increases the number of neuroblasts generated without shifting glial fate determination. The final result is deficient recruitment of newborn neurons to the olfactory bulb (OB), indicating that IFNγ-induced stimulation of neuronal differentiation does not compensate for its antiproliferative effect. We conclude that IFNγ signaling via STAT1 in the SVZ acts dually as an antiproliferative and proneurogenic factor, and thereby regulates neurogenesis in normal adult brains. ; This work was supported by the Marató TV3, and a Mapfre foundation award to EP, and Spanish Ministry of Economy MINECO (SAF2014-56279-R) to AMP. Also EP was a researcher in the Spanish government's Ramón y Cajal program (MICINN-Spain) ; Peer Reviewed

This is an open access article distributed under the Creative Commons Attribution License.-- et al. ; Ischemic stroke is an acute vascular event that obstructs blood supply to the brain, producing irreversible damage that affects neurons but also glial and brain vessel cells. Immediately after the stroke, the ischemic tissue produces nitric oxide (NO) to recover blood perfusion but also produces superoxide anion. These compounds interact, producing peroxynitrite, which irreversibly nitrates protein tyrosines. The present study measured NO production in a human neuroblastoma (SH-SY5Y), a murine glial (BV2), a human endothelial cell line (HUVEC), and in primary cultures of human cerebral myocytes (HC-VSMCs) after experimental ischemia in vitro. Neuronal, endothelial, and inducible NO synthase (NOS) expression was also studied up to 24 h after ischemia, showing a different time course depending on the NOS type and the cells studied. Finally, we carried out cell viability experiments on SH-SY5Y cells with H2O2, a prooxidant agent, and with a NO donor to mimic ischemic conditions. We found that both compounds were highly toxic when they interacted, producing peroxynitrite. We obtained similar results when all cells were challenged with peroxynitrite. Our data suggest that peroxynitrite induces cell death and is a very harmful agent in brain ischemia. © 2013 Marta Tajes et al. ; This work was supported by the Spanish Ministry of Science and Innovation (SAF2012-38140; SAF 2009-10365); Fondo de Investigación Sanitaria (PI10/00587; FIS CP04-00112, FIS PS09/00664 and Red HERACLES RD12/0042/0014, RD12/0042/0016 and RD12/0042/0020); FEDER Funds; Generalitat de Catalunya (SGR05-266); and Fundació la Marató de TV3 (100310). Miguel A. Valverde is the recipient of an ICREA Academia Award. Dr. Ana M. Galán belongs to the Miguel Servet stabilization program of the Spanish Government's ISCIII research institute and "Direcció d'Estratègia i Coordinació del Departament de Salut" of the Generalitat de Catalunya. ; Peer Reviewed

El pdf del artículo es la versión pre-print.-- et al. ; Alzheimer's disease (AD) is a devastating age-related neurodegenerative disease. Age is the main risk factor for sporadic AD, which is the most prevalent type. Amyloid-β peptide (Aβ) neurotoxicity is the proposed first step in a cascade of deleterious events leading to AD pathology and dementia. Glial cells play an important role in these changes. Astrocytes provide vital support to neurons and modulate functional synapses. Therefore, the toxic effects of Aβ on astrocytes might promote neurodegenerative changes that lead to AD. Aging reduces astrocyte antioxidant defenses and induces oxidative stress. We studied the effects of Aβ {42} on cultures of human astrocytes in the presence or absence of the following pro-oxidant agents: buthionine sulfoximine (BSO), a glutathione synthesis inhibitor, and FeSO{4}, which liberates redox active iron. Pro-oxidant conditions potentiated Aβ toxicity, as shown by the generation of free radicals, inflammatory changes, and apoptosis. Similar treatments were assessed in rats in vivo. A combination of Aβ {40} and Aβ {42} or Aβ {42} alone was infused intracerebroventricularly for 4 weeks. Other animal groups were also infused with BSO and FeSO{4}. A long-term analysis that ended 4 months later showed greater cognitive impairment in the Morris water maze task, which was induced by Aβ plus pro-oxidant agent treatments. Pro-oxidant agents also potentiated brain tissue pathology. This was demonstrated in histological studies that showed highly increased astrocyte reactivity in AD-vulnerable areas, Aβ deposits, and oxidative damage of AD-sensitive hippocampal neurons. To increase our understanding of AD, experimental models should be used that mimic age-related brain changes, in which age-related oxidative stress potentiates the effects of Aβ. © 2010 - IOS Press and the authors. ; This study was supported by grants SAF200613092-C02-02 from the Spanish Ministerio de Ciencia e Innovación, RD06/0013/1004 (RETICEF) from the Instituto de Salud Carlos III, 062931 from Fundació La Marató de TV3 and by the European Network of Excellence DiMI (LSHB-CT-2005-512146). S. García-Matas received a Generalitat (Autonomous Government of Catalonia) fellowship. ; Peer Reviewed

In this study, the second harmonic generation (SHG) response to polarization and subsequent data analysis is used to discriminate, in the same image, different SHG source architectures with pixel resolution. This is demonstrated in a mammalian tissue containing both skeletal muscle and fibrilar collagen. The SHG intensity variation with the input polarization (PSHG) is fitted pixel by pixel in the image using an algorithm based on a generalized biophysical model. The analysis provides the effective orientation, θe, of the different SHG active structures (harmonophores) at every pixel. This results in a new image in which collagen and muscle are clearly differentiated. In order to quantify the SHG response, the distribution of θe for every harmonophore is obtained. We found that for collagen, the distribution was centered at θe = 42.7° with a full width at half maximum of ∆θ = 5.9° while for muscle θe = 65.3°, with ∆θ = 7.7°. By comparing these distributions, a quantitative measurement of the discrimination procedure is provided. ; This work is supported by the Generalitat de Catalunya and by the Spanish government grant TEC2006-12654 SICO. Authors also acknowledge The Centre for Innovacio i Desenvolupament Empresarial-CIDEM (RDITSCON07-1-0006), Grupo Ferrer and the European Regional Development Fund. This research has been partially supported by Fundació Cellex Barcelona. ; Peer reviewed

Neuronal death can be preceded by progressive dysfunction of axons. Several pathological conditions such as ischemia can disrupt the neuronal cytoskeleton. Microtubules are basic structural components of the neuronal cytoskeleton that regulate axonal transport and neuronal function. Up-to-date, high-resolution observation of microtubules in living neuronal cells is usually accomplished using fluorescent-based microscopy techniques. However, this needs exogenous fluorescence markers to produce the required contrast. This is an invasive procedure that may interfere with the microtubule dynamics. In this work, we show, for the first time to our knowledge, that by using the endogenous (label-free) contrast provided by second harmonic generation (SHG) microscopy, it is possible to identify early molecular changes occurring in the microtubules of living neurons under ischemic conditions. This is done by measuring the intensity modulation of the SHG signal as a function of the angular rotation of the incident linearly polarized excitation light (technique referred to as PSHG). Our experiments were performed in microtubules from healthy control cultured cortical neurons and were compared to those upon application of several periods of oxygen and glucose deprivation (up to 120 min) causing ischemia. After 120-min oxygen and glucose deprivation, a change in the SHG response to the polarization was measured. Then, by using a three-dimensional PSHG biophysical model, we correlated this finding with the structural changes occurring in the microtubules under oxygen and glucose deprivation. To our knowledge, this is the first study performed in living neuronal cells that is based on direct imaging of axons and that provides the means of identifying the early symptoms of ischemia. Live observation of this process might bring new insights into understanding the dynamics and the mechanisms underlying neuronal degeneration or mechanisms of protection or regeneration. ; This work is supported by the Spanish government through the Ministry of Economy and Competitiveness, grants No. TEC2009-09698 and No. FIS2009-09928; the Ministerio de Sanidad, grant No. FIS PI081932; the Laserlab-Europe Cont. grant No. JRA4:Optobio 212025; and the Photonics for Life Networks of Excellence. This research has also been partially supported by Fundació Cellex Barcelona and partially conducted at the Institute of Photonic Sciences' Super-Resolution Light Nanoscopy Facility. ; Peer reviewed

In this paper we provide, for the first time to our knowledge, the effective orientation of the SHG source in cultured cortical neuronal processes in vitro. This is done by the use of the polarization sensitive second harmonic generation (PSHG) imaging microscopy technique. By performing a pixel-level resolution analysis we found that the SHG dipole source has a distribution of angles centered at θe =33.96°, with a bandwidth of ∆θe = 12.85°. This orientation can be related with the molecular geometry of the tubulin heterodimmer contained in microtubules. ; This work is supported by the Generalitat de Catalunya and by the Spanish government grant TEC2006-12654. Authors also acknowledge The Centre for Innovacio i Desenvolupament Empresarial - CIDEM (RDITSCON07-1-0006), Grupo Ferrer and the European Regional Development Fund. This research has been partially supported by Fundació Cellex Barcelona. ; Peer reviewed

In this study, polarization second harmonic generation (SHG) imaging is used and data analysis is developed to gain contrast and to discriminate with pixel resolution, in the same image, SHG source architectures. We use mammalian tissue in which both skeletal muscle and fibrilar collagen can be found. The images are fitted point by point using an algorithm based on a biophysical model, where the coefficient of determination is utilized as a filtering mechanism. For the whole image we retrieve for every pixel, the effective orientation, θe, of the SHG active structures. As a result a new image is formed which its contrast depends on the values of θe. Collagen presented in the forward direction for a predefined region of interest (ROI), peak distribution of angles θe centered in the region of ∼45°, while muscle in the region of ∼65°. Consequently, collagen and muscle are represented in different colors in the same image. Thus, here we show that it is possible to gain contrast and to discriminate between collagen and muscle without the use of any exogenous labeling or any co-localization with fluorescence imaging. © 2009 SPIE-OSA. ; This work is supported by the Generalitat de Catalunya and by the Spanish government grant TEC2006-12654 SICO. Authors also acknowledge The Centre Innovacio i Desenvolupament Empresarial-CIDEM (RDITSCON07-1-0006), Grupo Ferrer and the European Regional Development Fund. This research has been partially supported by Fundació Cellex Barcelona. ; Peer Reviewed

Central nervous system (CNS)-border associated macrophages (BAMs) maintain their steady-state population during adulthood and are not replaced by circulating monocytes under physiological conditions. Their roles in CNS integrity and functions under pathological conditions remain largely unknown. Until recently, BAMs and microglia could not be unequivocally distinguished due to expression of common macrophage markers. We investigated the transcriptional profiles of immunosorted BAMs from rat sham-operated and ischemic brains using RNA sequencing. We found that BAMs express the distinct transcriptional signature than microglia and infiltrating macrophages. The enrichment of functional groups associated with the cell cycle in CD163 cells isolated 3 days after the ischemic injury indicates the proliferative capacity of these cells. The increased number of CD163 cells 3 days post-ischemia was corroborated by flow cytometry and detecting the increased number of CD163 cells positive for a proliferation marker Ki67 at perivascular spaces. CD163 cells in the ischemic brains up-regulated many inflammatory genes and parenchymal CD163+ cells expressed iNOS, which indicates acquisition of a pro-inflammatory phenotype. In mice, BAMs typically express CD206 and we found a subset of these cells expressing CD169. Chimeric mice generated by transplanting bone marrow of donor Cx3cr1CCR2 mice to wild type hosts showed an increased number of CX3CR1CD169 perivascular macrophages 3 days post-ischemia. Furthermore, these cells accumulated in the brain parenchyma and we detected replacement of perivascular macrophages by peripheral monocytic cells in the sub-acute phase of stroke. In line with the animal results, post-mortem brain samples from human ischemic stroke cases showed time-dependent accumulation of CD163 cells in the ischemic parenchyma. Our findings indicate a unique transcriptional signature of BAMs, their local proliferation and migration of inflammatory BAMs to the brain parenchyma after stroke in animal models and humans. ; Studies were supported by the FP7-PEOPLE-2013-ITN grant n607962 (WDR) and CePT infrastructure fund from the European Union – the European Regional development Fund within the Operational Programme "Innovative Economy" for 2007–2013 and the Spanish Ministerio de Economia y Competitividad (MINECO, SAF2017-87459-R). We thank the Cytometry and Image Platforms of IDIBAPS and the Nencki institute for technical support. We are indebted to the Neurological Tissue Bank of the Biobank-Hospital Clinic-IDIBAPS for sample and data procurement, and to patient's relatives for giving consent to use the brain tissue. The use of CePT infrastructure financed by the European Union - The European Regional Development Fund within the Operational Programme "Innovative economy" for 2007-2013 is highly appreciated.

The establishment and validation of reliable induced pluripotent stem cell (iPSC)-derived in vitro models to study microglia and monocyte/macrophage immune function holds great potential for fundamental and translational neuro-immunology research. In this study, we first demonstrate that ramified CX(3)CR1(+) iPSC-microglia (cultured within a neural environment) and round-shaped CX(3)CR1(-) iPSC-macrophages can easily be differentiated from newly established murine CX(3)CR1(eGFP/+)CCR2(RFP/+) iPSC lines. Furthermore, we show that obtained murine iPSC-microglia and iPSC-macrophages are distinct cell populations, even though iPSC-macrophages may upregulate CX(3)CR1 expression when cultured within a neural environment. Next, we characterized the phenotypical and functional properties of murine iPSC-microglia and iPSC-macrophages following classical and alternative immune polarisation. While iPSC-macrophages could easily be triggered to adopt a classically-activated or alternatively-activated phenotype following, respectively, lipopolysaccharide + interferon gamma or interleukin 13 (IL13) stimulation, iPSC-microglia and iPSC-macrophages cultured within a neural environment displayed a more moderate activation profile as characterised by the absence of MHCII expression upon classical immune polarisation and the absence of Ym1 expression upon alternative immune polarisation. Finally, extending our preceding in vivo studies, this striking phenotypical divergence was also observed for resident microglia and infiltrating monocytes within highly inflammatory cortical lesions in CX(3)CR1(eGFP/+)CCR2(RFP/+) mice subjected to middle cerebral arterial occlusion (MCAO) stroke and following IL13-mediated therapeutic intervention thereon. In conclusion, our study demonstrates that the applied murine iPSC-microglia and iPSC-macrophage culture models are able to recapitulate in vivo microglia and monocyte/macrophage ontogeny and corresponding phenotypical/functional properties upon classical and alternative immune polarisation, and therefore represent a valuable in vitro platform to further study and modulate microglia and (infiltrating) monocyte immune responses under neuro-inflammatory conditions within a neural environment. ; This work was supported by research grant G091518N (granted to PP) of the Fund for Scientific Research-Flanders (FWO-Vlaanderen, Belgium), by a Methusalem research grant from the Flemish government (granted to HG and ZB), by funding received from the Belgian Charcot Foundation (granted to PP and DLB) and by the ASCID (Antwerp Study Centre for Infectious Diseases). AQ and EL are holders of a PhD studentship from the FWO-Vlaanderen. EVB is holder of a PhD studentship from the University of Antwerp. DLB is holder of a postdoctoral fellowship from the FWO-Vlaanderen. FM is supported by the Penis 2016 from the Health Department of Generalitat de Catalunya. Research in the Pasque lab is supported by the Research Foundation - Flanders (FWO) (Odysseus Return Grant G0F7716N, to V.P.), the KU Leuven Research Fund (BOFZAP starting grant StG/15/021BF to V.P. Cl grant C14/16/077 to V.P. and Project financing).

The establishment and validation of reliable induced pluripotent stem cell (iPSC)-derived in vitro models to study microglia and monocyte/macrophage immune function holds great potential for fundamental and translational neuro-immunology research. In this study, we first demonstrate that ramified CXCR1 iPSC-microglia (cultured within a neural environment) and round-shaped CXCR1 iPSC-macrophages can easily be differentiated from newly established murine CXCR1CCR2 iPSC lines. Furthermore, we show that obtained murine iPSC-microglia and iPSC-macrophages are distinct cell populations, even though iPSC-macrophages may upregulate CXCR1 expression when cultured within a neural environment. Next, we characterized the phenotypical and functional properties of murine iPSC-microglia and iPSC-macrophages following classical and alternative immune polarisation. While iPSC-macrophages could easily be triggered to adopt a classically-activated or alternatively-activated phenotype following, respectively, lipopolysaccharide + interferon γ or interleukin 13 (IL13) stimulation, iPSC-microglia and iPSC-macrophages cultured within a neural environment displayed a more moderate activation profile as characterised by the absence of MHCII expression upon classical immune polarisation and the absence of Ym1 expression upon alternative immune polarisation. Finally, extending our preceding in vivo studies, this striking phenotypical divergence was also observed for resident microglia and infiltrating monocytes within highly inflammatory cortical lesions in CXCR1CCR2 mice subjected to middle cerebral arterial occlusion (MCAO) stroke and following IL13-mediated therapeutic intervention thereon. In conclusion, our study demonstrates that the applied murine iPSC-microglia and iPSC-macrophage culture models are able to recapitulate in vivo microglia and monocyte/macrophage ontogeny and corresponding phenotypical/functional properties upon classical and alternative immune polarisation, and therefore represent a valuable in vitro platform to further study and modulate microglia and (infiltrating) monocyte immune responses under neuro-inflammatory conditions within a neural environment. ; This work was supported by research grant G091518N (granted to PP) of the Fund for Scientific Research-Flanders (FWO-Vlaanderen, Belgium), by a Methusalem research grant from the Flemish government (granted to HG and ZB), by funding received from the Belgian Charcot Foundation (granted to PP and DLB) and by the ASCID (Antwerp Study Centre for Infectious Diseases). AQ and EL are holders of a PhD studentship from the FWO-Vlaanderen. EVB is holder of a PhD studentship from the University of Antwerp. DLB is holder of a postdoctoral fellowship from the FWO-Vlaanderen. FM is supported by the Peris 2016 from the Health Department of Generalitat de Catalunya. Research in the Pasque lab is supported by the Research Foundation – Flanders (FWO) (Odysseus Return Grant G0F7716N, to V.P.), the KU Leuven Research Fund (BOFZAP starting grant StG/15/021BF to V.P. C1 grant C14/16/077 to V.P. and Project financing).

Brain CD11c+ cells share features with microglia and dendritic cells (DCs). Sterile inflammation increases brain CD11c+ cells, but their phenotype, origin, and functions remain largely unknown. We report that, after cerebral ischemia, microglia attract DCs to the inflamed brain, and astroglia produce Flt3 ligand, supporting development and expansion of CD11c+ cells. CD11c+ cells in the inflamed brain are a complex population derived from proliferating microglia and infiltrating DCs, including a major subset of OX40L+ conventional cDC2, and also cDC1, plasmacytoid, and monocyte-derived DCs. Despite sharing certain morphological features and markers, CD11c+ microglia and DCs display differential expression of pattern recognition receptors and chemokine receptors. DCs excel CD11c- and CD11c+ microglia in the capacity to present antigen through MHCI and MHCII. Of note, cDC1s protect from brain injury after ischemia. We thus reveal aspects of the dynamics and functions of brain DCs in the regulation of inflammation and immunity. ; This work was funded by Ministerio de Ciencia, Innovacion y Universidades (MICINN) co-financed by Fondo Europeo de Desarrollo Regional (FEDER) (SAF2017-87459-R), the European Union (EU) (H2020-ITN-2018-813294-ENTRAIN), and Fundacio Marato TV3 (201723 to A.M.P. and D.S.). Work in the D.S. laboratory is funded by Centro Nacional de Investigaciones Cardiovasculares (CNIC), the European Research Council (ERC-2016-Consolidator Grant 725091), the EU (635122-PROCROP H2020), and MICINN-FEDER (SAF2016-79040-R). The EU (FP7-PEOPLE-2013-ITN-n 07962) supported M. Gallizioli. The PERIS program of Generalitat de Catalunya supported F.M.-M. A.O.-d.-A. had a fellowship from MICINN-FPI (BES-2015-074419). C.d.F. is supported by the AECC Foundation (INVES192DELF). ; Sí

Detrimental inflammatory responses in the central nervous system are a hallmark of various brain injuries and diseases. With this study we provide evidence that lentiviral vector-mediated expression of the immune-modulating cytokine interleukin 13 (IL-13) induces an alternative activation program in both microglia and macrophages conferring protection against severe oligodendrocyte loss and demyelination in the cuprizone mouse model for multiple sclerosis (MS). First, IL-13 mediated modulation of cuprizone induced lesions was monitored using T-2-weighted magnetic resonance imaging and magnetization transfer imaging, and further correlated with quantitative histological analyses for inflammatory cell influx, oligodendrocyte death, and demyelination. Second, following IL-13 immune gene therapy in cuprizone-treated eGFP(+) bone marrow chimeric mice, we provide evidence that IL-13 directs the polarization of both brain-resident microglia and infiltrating macrophages towards an alternatively activated phenotype, thereby promoting the conversion of a pro-inflammatory environment toward an anti-inflammatory environment, as further evidenced by gene expression analyses. Finally, we show that IL-13 immune gene therapy is also able to limit lesion severity in a pre-existing inflammatory environment. In conclusion, these results highlight the potential of IL-13 to modulate microglia/macrophage responses and to improve disease outcome in a mouse model for MS. ; This work was supported by research grants G.0136.11 (granted to PP, AVDL and ZB), G.0130.11 (granted to PP, AVDL and ZB) and G.0834.11 (granted to PP and SH) of the Fund for Scientific Research-Flanders (FWO-Vlaanderen, Belgium), in part by a Methusalem research grant from the Flemish government (granted to HG), in part by funding received from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement 278850 (INMiND) (granted to AVdL and AMP), in part by the Brainpath project (MSCA IAPP project granted to AVdL) and in part by funding received from the Belgian Charcot Foundation (granted to PP and AVdL). DLB, DS and CG hold a PhD-studentship from the Flemish Institute for Science and Technology (IWT-Vlaanderen). NDV and CH hold a PhD-studentship from the FWO-Vlaanderen. FK and JP hold a post-doctoral fellowship from the FWO-Vlaanderen.

Background There is considerable variability in COVID-19 outcomes amongst younger adults—and some of this variation may be due to genetic predisposition. We characterized the clinical implications of the major genetic risk factor for COVID-19 severity, and its age-dependent effect, using individual-level data in a large international multi-centre consortium. Method The major common COVID-19 genetic risk factor is a chromosome 3 locus, tagged by the marker rs10490770. We combined individual level data for 13,424 COVID-19 positive patients (N=6,689 hospitalized) from 17 cohorts in nine countries to assess the association of this genetic marker with mortality, COVID-19-related complications and laboratory values. We next examined if the magnitude of these associations varied by age and were independent from known clinical COVID-19 risk factors. Findings We found that rs10490770 risk allele carriers experienced an increased risk of all-cause mortality (hazard ratio [HR] 1·4, 95% confidence interval [CI] 1·2–1·6) and COVID-19 related mortality (HR 1·5, 95%CI 1·3–1·8). Risk allele carriers had increased odds of several COVID-19 complications: severe respiratory failure (odds ratio [OR] 2·0, 95%CI 1·6-2·6), venous thromboembolism (OR 1·7, 95%CI 1·2-2·4), and hepatic injury (OR 1·6, 95%CI 1·2-2·0). Risk allele carriers ≤ 60 years had higher odds of death or severe respiratory failure (OR 2·6, 95%CI 1·8-3·9) compared to those > 60 years OR 1·5 (95%CI 1·3-1·9, interaction p-value=0·04). Amongst individuals ≤ 60 years who died or experienced severe respiratory COVID-19 outcome, we found that 31·8% (95%CI 27·6-36·2) were risk variant carriers, compared to 13·9% (95%CI 12·6-15·2%) of those not experiencing these outcomes. Prediction of death or severe respiratory failure among those ≤ 60 years improved when including the risk allele (AUC 0·82 vs 0·84, p=0·016) and the prediction ability of rs10490770 risk allele was similar to, or better than, most established clinical risk factors. Interpretation The major common COVID-19 risk locus on chromosome 3 is associated with increased risks of morbidity and mortality—and these are more pronounced amongst individuals ≤ 60 years. The effect on COVID-19 severity was similar to, or larger than most established risk factors, suggesting potential implications for clinical risk management. ; AG has received support by NordForsk Nordic Trial Alliance (NTA) grant, by Academy of Finland Fellow grant N. 323116 and the Academy of Finland for PREDICT consortium N. 340541. The Richards research group is supported by the Canadian Institutes of Health Research (CIHR) (365825 and 409511), the Lady Davis Institute of the Jewish General Hospital, the Canadian Foundation for Innovation (CFI), the NIH Foundation, Cancer Research UK, Genome Quebec, the Public Health Agency of Canada, the McGill Interdisciplinary Initiative in Infection and Immunity and the Fonds de Recherche Quebec Sante (FRQS). TN is supported by a research fellowship of the Japan Society for the Promotion of Science for Young Scientists. GBL is supported by a CIHR scholarship and a joint FRQS and Quebec Ministry of Health and Social Services scholarship. JBR is supported by an FRQS Clinical Research Scholarship. Support from Calcul Quebec and Compute Canada is acknowledged. TwinsUK is funded by the Welcome Trust, the Medical Research Council, the European Union, the National Institute for Health Research-funded BioResource and the Clinical Research Facility and Biomedical Research Centre based at Guy's and St. Thomas' NHS Foundation Trust in partnership with King's College London. The Biobanque Quebec COVID19 is funded by FRQS, Genome Quebec and the Public Health Agency of Canada, the McGill Interdisciplinary Initiative in Infection and Immunity and the Fonds de Recherche Quebec Sante. These funding agencies had no role in the design, implementation or interpretation of this study. The COVID19-Host(a)ge study received infrastructure support from the DFG Cluster of Excellence 2167 Precision Medicine in Chronic Inflammation (PMI) (DFG Grant: EXC2167). The COVID19-Host(a)ge study was supported by the German Federal Ministry of Education and Research (BMBF) within the framework of the Computational Life Sciences funding concept (CompLS grant 031L0165). Genotyping in COVID19-Host(a)ge was supported by a philantropic donation from Stein Erik Hagen. The COVID GWAs, Premed COVID-19 study (COVID19-Host(a)ge_3) was supported by Grupo de Trabajo en Medicina Personalizada contra el COVID-19 de Andalucia and also by the Instituto de Salud Carlos III (CIBERehd and CIBERER). Funding comes from COVID-19-GWAS, COVID-PREMED initiatives. Both of them are supported by Consejeria de Salud y Familias of the Andalusian Government. DMM is currently funded by the the Andalussian government (Proyectos Estrategicos-Fondos Feder PE-0451-2018). The Columbia University Biobank was supported by Columbia University and the National Center for Advancing Translational Sciences, NIH, through Grant Number UL1TR001873. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH or Columbia University. The SPGRX study was supported by the Consejeria de Economia, Conocimiento, Empresas y Universidad #CV20-10150. The GEN-COVID study was funded by: the MIUR grant Dipartimenti di Eccellenza 2018-2020 to the Department of Medical Biotechnologies University of Siena, Italy; the Intesa San Paolo 2020 charity fund dedicated to the project NB/2020/0119; and philanthropic donations to the Department of Medical Biotechnologies, University of Siena for the COVID-19 host genetics research project (D.L n.18 of March 17, 2020). Part of this research project is also funded by Tuscany Region Bando Ricerca COVID-19 Toscana grant to the Azienda Ospedaliero Universitaria Senese (CUP I49C20000280002). Authors are grateful to: the CINECA consortium for providing computational resources; the Network for Italian Genomes (NIG) (http://www.nig.cineca.it) for its support; the COVID-19 Host Genetics Initiative (https://www.covid19hg.org/); the Genetic Biobank of Siena, member of BBMRI-IT, Telethon Network of Genetic Biobanks (project no. GTB18001), EuroBioBank, and RD-Connect, for managing specimens. Genetics against coronavirus (GENIUS), Humanitas University (COVID19-Host(a)ge_4) was supported by Ricerca Corrente (Italian Ministry of Health), intramural funding (Fondazione Humanitas per la Ricerca). The generous contribution of Banca Intesa San Paolo and of the Dolce&Gabbana Fashion Firm is gratefully acknowledged. Data acquisition and sample processing was supported by COVID-19 Biobank, Fondazione IRCCS Ca Granda Milano; LV group was supported by MyFirst Grant AIRC n.16888, Ricerca Finalizzata Ministero della Salute RF-2016-02364358, Ricerca corrente Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, the European Union (EU) Programme Horizon 2020 (under grant agreement No. 777377) for the project LITMUS- Liver Investigation: Testing Marker Utility in Steatohepatitis, Programme Photonics under grant agreement 101016726 for the project REVEAL: Neuronal microscopy for cell behavioural examination and manipulation, Fondazione Patrimonio Ca' Granda Liver Bible PR-0361. DP was supported by Ricerca corrente Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, CV PREVITAL Strategie di prevenzione primaria nella popolazione Italiana Ministero della Salute, and Associazione Italiana per la Prevenzione dell'Epatite Virale (COPEV). Genetic modifiers for COVID-19 related illness (BeLCovid_1) was supported by the Fonds Erasme. The Host genetics and immune response in SARS-Cov-2 infection (BelCovid_2) study was supported by grants from Fondation Leon Fredericq and from Fonds de la Recherche Scientifique (FNRS). The INMUNGEN-CoV2 study was funded by the Consejo Superior de Investigaciones Cientificas. KUL is supported by the German Research Foundation (LU 1944/3-1) SweCovid is funded by the SciLifeLab/KAW national COVID-19 research program project grant to Michael Hultstrom (KAW 2020.0182) and the Swedish Research Council to Robert Frithiof (2014-02569 and 2014-07606). HZ is supported by Jeansson Stiftelser, Magnus Bergvalls Stiftelse. The COMRI cohort is funded by Technical University of Munich, Munich, Germany. Genotyping for the COMRI cohort was performed and funded by the Genotyping Laboratory of Institute for Molecular Medicine Finland FIMM Technology Centre, University of Helsinki, Helsinki, Finland. ; No

Circulating autoantibodies (auto-Abs) neutralizing high concentrations (10 ng/ml; in plasma diluted 1:10) of IFN-α and/or IFN-ω are found in about 10% of patients with critical COVID-19 (coronavirus disease 2019) pneumonia but not in individuals with asymptomatic infections. We detect auto-Abs neutralizing 100-fold lower, more physiological, concentrations of IFN-α and/or IFN-ω (100 pg/ml; in 1:10 dilutions of plasma) in 13.6% of 3595 patients with critical COVID-19, including 21% of 374 patients >80 years, and 6.5% of 522 patients with severe COVID-19. These antibodies are also detected in 18% of the 1124 deceased patients (aged 20 days to 99 years; mean: 70 years). Moreover, another 1.3% of patients with critical COVID-19 and 0.9% of the deceased patients have auto-Abs neutralizing high concentrations of IFN-β. We also show, in a sample of 34,159 uninfected individuals from the general population, that auto-Abs neutralizing high concentrations of IFN-α and/or IFN-ω are present in 0.18% of individuals between 18 and 69 years, 1.1% between 70 and 79 years, and 3.4% >80 years. Moreover, the proportion of individuals carrying auto-Abs neutralizing lower concentrations is greater in a subsample of 10,778 uninfected individuals: 1% of individuals 80 years. By contrast, auto-Abs neutralizing IFN-β do not become more frequent with age. Auto-Abs neutralizing type I IFNs predate SARS-CoV-2 infection and sharply increase in prevalence after the age of 70 years. They account for about 20% of both critical COVID-19 cases in the over 80s and total fatal COVID-19 cases. ; The Laboratory of Human Genetics of Infectious Diseases is supported by the Howard Hughes Medical Institute, the Rockefeller University, the St. Giles Foundation, the National Institutes of Health (NIH) (R01AI088364), the National Center for Advancing Translational Sciences (NCATS), NIH Clinical and Translational Science Awards (CTSA) program (UL1 TR001866), a Fast Grant from Emergent Ventures, Mercatus Center at George Mason University, the Yale Center for Mendelian Genomics and the GSP Coordinating Center funded by the National Human Genome Research Institute (NHGRI) (UM1HG006504 and U24HG008956), the Yale High Performance Computing Center (S10OD018521), the Fisher Center for Alzheimer's Research Foundation, the Meyer Foundation, the JPB Foundation, the French National Research Agency (ANR) under the "Investments for the Future" program (ANR-10-IAHU-01), the Integrative Biology of Emerging Infectious Diseases Laboratory of Excellence (ANR-10-LABX-62-IBEID), the French Foundation for Medical Research (FRM) (EQU201903007798), the FRM and ANR GENCOVID project (ANR-20-COVI-0003), ANRS Nord-Sud (ANRS-COV05), ANR GENVIR (ANR-20-CE93-003) and ANR AABIFNCOV (ANR-20-CO11-0001) projects, the European Union's Horizon 2020 research and innovation programme under grant agreement no. 824110 (EASI-Genomics), the Square Foundation, Grandir–Fonds de solidarité pour l'Enfance, the Fondation du Souffle, the SCOR Corporate Foundation for Science, Institut National de la Santé et de la Recherche Médicale (INSERM), REACTing-INSERM; and the University of Paris. P.B. was supported by the FRM (EA20170638020). P.B., J.R., and T.L.V. were supported by the MD-PhD program of the Imagine Institute (with the support of the Fondation Bettencourt Schueller). Work in the Laboratory of Virology and Infectious Disease was supported by the NIH (P01AI138398-S1, 2U19AI111825, and R01AI091707-10S1), a George Mason University Fast Grant, and the G. Harold and Leila Y. Mathers Charitable Foundation. The French COVID Cohort study group was sponsored by INSERM and supported by the REACTing consortium and by a grant from the French Ministry of Health (PHRC 20-0424). The Cov-Contact Cohort was supported by the REACTing consortium, the French Ministry of Health, and the European Commission (RECOVER WP 6). This work was also partly supported by the Intramural Research Program of the NIAID and NIDCR, NIH (grants ZIA AI001270 to L.D.N. and 1ZIAAI001265 to H.C.S.). This program is supported by the Agence Nationale de la Recherche (reference ANR-10-LABX-69-01). K.K.'s group was supported by the Estonian Research Council grants PRG117 and PRG377. R.H. was supported by an Al Jalila Foundation Seed Grant (AJF202019), Dubai, UAE, and a COVID-19 research grant (CoV19-0307) from the University of Sharjah, UAE. S.G.T. is supported by Investigator and Program Grants awarded by the National Health and Medical Research Council of Australia and a UNSW Sydney COVID Rapid Response Initiative Grant. L.I. reported funding from Regione Lombardia, Italy (project "Risposta immune in pazienti con COVID-19 e co-morbidità"). L.I. and G. L. Marseglia reported funding from Regione Lombardia, Italy (project Risposta immune in pazienti con COVID-19 e co-morbidità). This research was partially supported by the Instituto de Salud Carlos III (COV20/0968). J.R.H. reported funding from Biomedical Advanced Research and Development Authority HHSO10201600031C. S.O. reports funding Research Program on Emerging and Re-emerging Infectious Diseases from Japan Agency for Medical Research and Development, AMED (grant number JP20fk0108531). G.G. was supported by ANR Flash COVID-19 program and SARS-CoV-2 Program of the Faculty of Medicine from Sorbonne University iCOVID programs. The Three-City (3C) Study was conducted under a partnership agreement among the INSERM, the Victor Segalen Bordeaux 2 University, and Sanofi-Aventis. The Fondation pour la Recherche Médicale funded the preparation and initiation of the study. The 3C Study was also supported by the Caisse Nationale d'Assurance Maladie des Travailleurs Salariés, Direction générale de la Santé, Mutuelle Générale de l'Education Nationale (MGEN), Institut de la Longévité, Conseils Régionaux of Aquitaine and Bourgogne, Fondation de France, and Ministry of Research–INSERM Programme "Cohortes et collections de données biologiques". S. Debette was supported by the University of Bordeaux Initiative of Excellence. P.K.G. reports funding from the National Cancer Institute, NIH, under contract no. 75N91019D00024, task order no. 75N91021F00001. J.W. is supported by an FWO Fundamental Clinical Mandate (1833317N). Sample processing at IrsiCaixa was possible thanks to the crowdfunding initiative YoMeCorono. Work at Vall d'Hebron was also partly supported by research funding from Instituto de Salud Carlos III grant PI17/00660 cofinanced by the European Regional Development Fund (ERDF). C.R.-G. and colleagues of the Canarian Health System Sequencing Hub were supported by the Instituto de Salud Carlos III (COV20_01333 and COV20_01334, Spanish Ministry for Science and Innovation RTC-2017-6471-1; AEI/FEDER, UE), Fundación DISA (OA18/017 and OA20/024), and Cabildo Insular de Tenerife (CGIEU0000219140 and "Apuestas científicas del ITER para colaborar en la lucha contra la COVID-19"). C.M.B. is supported by a MSFHR Health Professional-Investigator Award. P.Q.H. and L.H. were funded by the European Union's Horizon 2020 research and innovation program (ATAC, 101003650). Work at Y.-L.L.'s laboratory in the University of Hong Kong (HKU) was supported by the Society for the Relief of Disabled Children. MBBS/PhD study of D.L. in HKU was supported by the Croucher Foundation. J.L.F. was supported in part by the Coopération Scientifique France-Colciencias (ECOS-Nord/COLCIENCIAS/MEN/ICETEX (806-2018) and Colciencias contract 713-2016 (code 111574455633)]. A.K. was in part supported by grants NU20-05-00282 and NV18-05-00162 issued by the Czech Health Research Council and Ministry of Health, Czech Republic. L.P. was funded by Program Project COVID-19 OSR-UniSR and Ministero della Salute (COVID-2020-12371617). I.M. is a Senior Clinical Investigator at the Research Foundation–Flanders and is supported by the CSL Behring Chair of Primary Immunodeficiencies; by the KU Leuven C1 grant C16/18/007; by a VIB-GC PID grant; by the FWO frants G0C8517N, G0B5120N, and G0E8420N; and by the Jeffrey Modell Foundation. I.M. has received funding under the European Union's Horizon 2020 research and innovation programme (grant agreement no. 948959). E.A. received funding from the Hellenic Foundation for Research and Innovation (INTERFLU, no. 1574). M.Vi received funding from the São Paulo Research Foundation (FAPESP) (grant number 2020/09702-1) and JBS SA (grant number 69004). The NH-COVAIR study group consortium was supported by a grant from the Meath Foundation ; Peer reviewed