Search

Purpose The SARS-CoV-2 infection can lead to a severe acute respiratory distress syndrome (ARDS) with prolonged mechanical ventilation and high mortality rate. Interestingly, COVID-19-associated ARDS share biological and clinical features with sepsis-associated immunosuppression since lymphopenia and acquired infections associated with late mortality are frequently encountered. Mechanisms responsible for COVID-19-associated lymphopenia need to be explored since they could be responsible for delayed virus clearance and increased mortality rate among intensive care unit (ICU) patients. Methods A series of 26 clinically annotated COVID-19 patients were analyzed by thorough phenotypic and functional investigations at days 0, 4, and 7 after ICU admission. Results We revealed that, in the absence of any difference in demographic parameters nor medical history between the two groups, ARDS patients presented with an increased number of myeloid-derived suppressor cells (MDSC) and a decreased number of CD8pos effector memory cell compared to patients hospitalized for COVID-19 moderate pneumonia. Interestingly, COVID-19-related MDSC expansion was directly correlated to lymphopenia and enhanced arginase activity. Lastly, T cell proliferative capacity in vitro was significantly reduced among COVID-19 patients and could be restored through arginine supplementation. Conclusions The present study reports a critical role for MDSC in COVID-19-associated ARDS. Our findings open the possibility of arginine supplementation as an adjuvant therapy for these ICU patients, aiming to reduce immunosuppression and help virus clearance, thereby decreasing the duration of mechanical ventilation, nosocomial infection acquisition, and mortality. Supplementary Information The online version contains supplementary material available at 10.1007/s10875-020-00920-5.

Staphylococcus aureus is the main bacterial pathogen encountered in mediastinitis after cardiac surgical procedures; it remains a devastating complication with a high mortality rate. As neutrophils have a primordial role in the defense against staphylococcus infection and cardiopulmonary bypass (CPB) is known to induce immunosuppression, the aim of this study was to investigate CPB impact on neutrophil functions. Patients without known immunosuppression scheduled for cardiac surgery with CPB were included. Bone marrow and blood samples were harvested before, during, and after surgery. Neutrophil phenotypic maturation and functions (migration, adhesion, neutrophil extracellular trap [NET] release, reactive oxygen species (ROS) production, phagocytosis, and bacteria killing) were investigated. Two types of Staphylococcus aureus strains (one from asymptomatic nasal carriage and another from mediastinitis infected tissues) were used to assess in vitro bacterial direct impact on neutrophils. We found that CPB induced a systemic inflammation with an increase in circulating mature neutrophils after surgery. Bone marrow sample analysis did not reveal any modification of neutrophil maturation during CPB. Neutrophil lifespan was significantly increased and functions such as NET release and ROS production were enhanced after CPB whereas bacteria killing and phagocytosis were not impacted. Results were similar with the two different isolates of Staphylococcus aureus. These data suggest that CPB induces a recruitment of mature neutrophils via a demargination process rather than impacting their maturation in the bone marrow. In addition, neutrophils are fully efficient after CPB and do not contribute to postoperative immunosuppression.

Metabolic and bioenergetic plasticity of immune cells is essential for optimal responses to bacterial infections. AMPK and Parkin ubiquitin ligase are known to regulate mitochondrial quality control mitophagy that prevents unwanted inflammatory responses. However, it is not known if this evolutionarily conserved mechanism has been coopted by the host immune defense to eradicate bacterial pathogens and influence post-sepsis immunosuppression. Parkin, AMPK levels, and the effects of AMPK activators were investigated in human leukocytes from sepsis survivors as well as wild type and Park2−/− murine macrophages. In vivo, the impact of AMPK and Parkin was determined in mice subjected to polymicrobial intra-abdominal sepsis and secondary lung bacterial infections. Mice were treated with metformin during established immunosuppression. We showed that bacteria and mitochondria share mechanisms of autophagic killing/clearance triggered by sentinel events that involve depolarization of mitochondria and recruitment of Parkin in macrophages. Parkin-deficient mice/macrophages fail to form phagolysosomes and kill bacteria. This impairment of host defense is seen in the context of sepsis-induced immunosuppression with decreased levels of Parkin. AMPK activators, including metformin, stimulate Parkin-independent autophagy and bacterial killing in leukocytes from post-shock patients and in lungs of sepsis-immunosuppressed mice. Our results support a dual role of Parkin and AMPK in the clearance of dysfunctional mitochondria and killing of pathogenic bacteria, and explain the immunosuppressive phenotype associated Parkin and AMPK deficiency. AMPK activation appeared to be a crucial therapeutic target for the macrophage immunosuppressive phenotype and to reduce severity of secondary bacterial lung infections and respiratory failure.

Acute respiratory distress syndrome (ARDS) is the main complication of COVID-19, requiring admission to Intensive Care Unit (ICU). Despite extensive immune profiling of COVID-19 patients, to what extent COVID-19-associated ARDS differs from other causes of ARDS remains unknown. To address this question, we build 3 cohorts of patients categorize in COVID-19negARDSpos, COVID-19posARDSpos, and COVID-19posARDSneg, and compare their immune landscape analyze by high-dimensional mass cytometry on peripheral blood. A cell signature associating S100A9/calprotectin-producing CD169pos monocytes, plasmablasts, and Th1 cells is found in COVID-19posARDSpos, unlike COVID-19negARDSpos patients. Moreover, this signature is essentially share with COVID-19posARDSneg patients, suggesting that severe COVID-19 patients, whatever they experience or not ARDS, display similar immune profiles. We show an increase in CD14posHLA-DRlow and CD14lowCD16pos monocytes correlate to the occurrence of adverse events during ICU stay. We demonstrate that COVID-19-associated ARDS display a specific immune profile, and might benefit from personalize therapy in addition to standard ARDS management., Graphical Abstract, Roussel et al. characterize the immune profile of COVID-19+ and COVID-19- patients, both presenting an acute respiratory distress syndrome (ARDS) and COVID-19+ without ARDS. They identify a COVID-19 signature associating CD169+S100A9+ monocytes, plasmablasts, and Th1 cells. CD14+HLA-DRlo and CD14loCD16+ monocytes increase during the ICU stay correlate with unfavorable clinical course.

Acute respiratory distress syndrome (ARDS) is the main complication of COVID-19, requiring admission to Intensive Care Unit (ICU). Despite recent immune profiling of COVID-19 patients, to what extent COVID-19-associated ARDS specifically differs from other causes of ARDS remains unknown, To address this question, we built 3 cohorts of patients categorized in COVID-19negARDSpos, COVID-19posARDSpos, and COVID-19posARDSneg, and compared their immune landscape analyzed by high-dimensional mass cytometry on peripheral blood followed by artificial intelligence analysis. A cell signature associating S100A9/calprotectin-producing CD169pos monocytes, plasmablasts, and Th1 cells was specifically found in COVID-19posARDSpos, unlike COVID-19negARDSpos patients. Moreover, this signature was shared by COVID-19posARDSneg patients, suggesting severe COVID-19 patients, whatever they experienced or not ARDS, displayed similar immune dysfunctions. We also showed an increase in CD14posHLA-DRlow and CD14lowCD16pos monocytes correlated to the occurrence of adverse events during ICU stay. Our study demonstrates that COVID-19-associated ARDS display a specific immune profile, and might benefit from personalized therapy in addition to standard ARDS management.One Sentence SummaryCOVID-19-associated ARDS is biologically distinct from other causes of ARDS.

Acute respiratory distress syndrome (ARDS) is the main complication of COVID-19, requiring admission to Intensive Care Unit (ICU). Despite extensive immune profiling of COVID-19 patients, to what extent COVID-19-associated ARDS specifically differs from other causes of ARDS remains unknown. To address this crucial question, we built 3 cohorts of patients categorized in COVID-19neg ARDSpos, COVID-19pos ARDSpos, and COVID-19pos ARDSneg, and compared their immune landscape analyzed by high-dimensional mass cytometry on peripheral blood followed by artificial intelligence analysis. A cell signature associating S100A9/calprotectin-producing CD169pos monocytes, plasmablasts, and Th1 cells was specifically found in COVID-19pos ARDSpos, unlike COVID-19neg ARDSpos patients. Moreover, this signature was essentially shared with COVID-19pos ARDSneg patients, suggesting that severe COVID-19 patients, whatever they experienced or not ARDS, display similar immune profiles. We also showed an increase in CD14pos HLA-DRlow and CD14low CD16pos monocytes correlated to the occurrence of adverse events during ICU stay. Our study demonstrates that COVID-19-associated ARDS display a specific immune profile, and might benefit from personalized therapy in addition to standard ARDS management. Funding: This work was supported by the University hospital of Rennes, CFTR² (COVID-19 Fast Track Recherche Rennes) grant (to F.R.)and by the Fondation pour la Recherche Medicale (FRM) and the Agence Nationale de la Recherche (ANR), Flash Covid-19 joint grant (HARMONICOV to M.Cog.) Conflict of Interest: J.Fer., F.R., S.L.G., J.D., M.Le., M.G., N.B., C.V., M.La., I.B., M.Cor., S.L., J.Feu., M. Cog. declare no competing interest. M.R., S.C., V.K.T., J.M.T., and K.T. are the inventors of a patent EP 20305642.9 “A method for early detection of propensity to severe clinical manifestations Methods” submitted June 11th 2020 under University hospital of Rennes and Scailyte AG names. Ethical Approval: The study design was approved by our ethic committee (CHU Rennes, n°35RC20_9795_HARMONICOV, ClinicalTrials.gov Identifier: NCT04373200) and informed consent was obtained from patients in accordance with the Declaration of Helsinki.

International audience; Exaggerated release of neutrophil extracellular traps (NETs) along with decreased NET clearance and inability to remove apoptotic cells (efferocytosis) may contribute to sustained inflammation in acute respiratory distress syndrome (ARDS). Recent studies in experimental models of ARDS have revealed the crosstalk between AMP-activated protein kinase (AMPK) and high-mobility group box 1 (HMGB1), which may contribute to effectiveness of efferocytosis, thereby reducing inflammation and ARDS severity.We investigated neutrophil and NET clearance by macrophages from control and ARDS patients and examined how bronchoalveolar lavage (BAL) fluid from control and ARDS patients could affect NET formation and efferocytosis. Metformin (an AMPK activator) and neutralising antibody against HMGB1 were applied to improve efferocytosis and NET clearance.Neutrophils from ARDS patients showed significantly reduced apoptosis. Conversely, NET formation was significantly enhanced in ARDS patients. Exposure of neutrophils to ARDS BAL fluid promoted NET production, while control BAL fluid had no effect. Macrophage engulfment of NETs and apoptotic neutrophils was diminished in ARDS patients. Notably, activation of AMPK in macrophages or neutralisation of HMGB1 in BAL fluid improved efferocytosis and NET clearance.In conclusion, restoration of AMPK activity with metformin or specific neutralisation of HMGB1 in BAL fluid represent promising therapeutic strategies to decrease sustained lung inflammation during ARDS.

Sepsis induces a sustained immune dysfunction responsible for poor outcome and nosocomial infections. Myeloid-derived suppressor cells (MDSCs) described in cancer and inflammatory processes may be involved in sepsis-induced immune suppression, but their clinical impact remains poorly defined.To clarify phenotype, suppressive activity, origin, and clinical impact of MDSCs in patients with sepsis.Peripheral blood transcriptomic analysis was performed on 29 patients with sepsis and 15 healthy donors. A second cohort of 94 consecutive patients with sepsis, 11 severity-matched intensive care patients, and 67 healthy donors was prospectively enrolled for flow cytometry and functional experiments.Genes involved in MDSC suppressive functions, including S100A12, S100A9, MMP8, and ARG1, were up-regulated in the peripheral blood of patients with sepsis. CD14M-MDSCs and G-MDSCs strongly contribute to T-cell dysfunction in patients with sepsis. More specifically, G-MDSCs producing arginase 1 are associated with a higher incidence of nosocomial infections and seem to be major actors of sepsis-induced immune suppression.

Although resistin was recently found to modulate insulin resistance in preclinical models of type II diabetes and obesity, recent studies also suggested that resistin has proinflammatory properties. We examined whether the human-specific variant of resistin affects neutrophil activation and the severity of LPS-induced acute lung injury. Because human and mouse resistin have distinct patterns of tissue distribution, experiments were performed using humanized resistin mice that exclusively express human resistin (hRTN+/−/−) but are deficient in mouse resistin. Enhanced production of TNF-α or MIP-2 was found in LPS-treated hRtn+/−/− neutrophils compared with control Rtn−/−/− neutrophils. Expression of human resistin inhibited the activation of AMP-activated protein kinase, a major sensor and regulator of cellular bioenergetics that also is implicated in inhibiting inflammatory activity of neutrophils and macrophages. In addition to the ability of resistin to sensitize neutrophils to LPS stimulation, human resistin enhanced neutrophil extracellular trap formation. In LPS-induced acute lung injury, humanized resistin mice demonstrated enhanced production of proinflammatory cytokines, more severe pulmonary edema, increased neutrophil extracellular trap formation, and elevated concentration of the alarmins HMGB1 and histone 3 in the lungs. Our results suggest that human resistin may play an important contributory role in enhancing TLR4-induced inflammatory responses, and it may be a target for future therapies aimed at reducing the severity of acute lung injury and other inflammatory situations in which neutrophils play a major role.

Sepsis is accompanied by the initial activation of proinflammatory pathways and long-lasting immunosuppression that appears to contribute to late-occurring mortality. Although high-mobility group box 1 (HMGB1) is involved in many aspects of inflammation, its role in sepsis-induced immune suppression remains unclear. In this study, we examined HMGB1’s contribution to neutrophil NADPH oxidase activity dysfunction and associated neutrophil-dependent bacterial clearance in mice subjected to sepsis and in patients who survive septic shock. Using a murine model of polymicrobial septic peritonitis, we demonstrated that treatment with anti-HMGB1 Ab significantly diminished sepsis-induced dysfunction of neutrophil NADPH oxidase activity. In a subsequent set of experiments, we found that blocking HMGB1 preserved the ability of neutrophils from patients recovering from septic shock to activate NADPH oxidase. Taken together, our data suggest that HMGB1 accumulation in the late phase of sepsis plays a specific role in the development of postsepsis immunosuppression and specifically affects neutrophil-dependent antibacterial defense mechanisms. Thus, blocking HMGB1 may be a promising therapeutic intervention to diminish the adverse effects of sepsis-induced immunosuppression.

International audience; Unlabelled - Cardiac surgery with cardiopulmonary bypass (CPB) induces postoperative immunosuppression and impaired pulmonary function. Maintaining mechanical ventilation (MV) during CPB improves pulmonary function and diminishes postoperative systemic inflammation. However, there are no data about the influence of maintaining MV during CPB on postoperative immune dysfunction. Methods - Fifty patients were prospectively divided into two groups: without MV during bypass (n = 25) and dead space MV with positive end-expiratory pressure (n = 25). PaO2 (arterial oxygen tension)/FIO2 (inspired oxygen fraction) ratio, CXCL10 (C-X-C motif chemokine 10), CCL2 (chemokine ligand 2), tumor necrosis factor α (TNF-α), interleukin 10 (IL-10), human leukocyte antigen-DR antigen (HLA-DR), monocytic myeloid-derived suppressor cells (Mo-MDSCs, CD14HLA-DR monocytes), and blood cell count were collected before and after surgery. Results - Cardiopulmonary bypass induced a marked immunosuppression with a significant increase in plasmatic levels of TNF-α and IL-10 and a significant decrease in HLA-DR monocytic expression. The postoperative proportion of Mo-MDSCs was subsequently significantly increased. Maintaining MV during CPB significantly improved PaO2/FIO2 ratio and decreased postoperative plasmatic levels of TNF-α and IL-10 compared with patients without MV during CPB. Furthermore, nonventilated patients had a lower lymphocyte count after surgery compared with patients with MV during CPB. Conclusion - Our study suggests that maintaining MV during CPB for cardiac surgery decreases postoperative immune dysfunction and could be an interesting strategy to diminish the occurrence of postoperative nosocomial infection without hampering the surgical procedure. However, these findings have to be confirmed in a clinical trial using the incidence of nosocomial infection as an endpoint.