COVID-19 is currently a global pandemic, but human immune responses to the virus remain poorly understood. We analyzed 125 COVID-19 patients, and compared recovered to healthy individuals using high dimensional cytometry. Integrated analysis of ~200 immune and ~50 clinical features revealed activation of T cell and B cell subsets in a proportion of patients. A subgroup of patients had T cell activation characteristic of acute viral infection and plasmablast responses reaching >30% of circulating B cells. However, another subgroup had lymphocyte activation comparable to uninfected subjects. Stable versus dynamic immunological signatures were identified and linked to trajectories of disease severity change. These analyses identified three “immunotypes” associated with poor clinical trajectories versus improving health. These immunotypes may have implications for the design of therapeutics and vaccines for COVID-19.

evere infection with COVID-19 has been linked to immune dysregulation, including impaired or delayed production of type I and type III interferons 1-5 , marked lymphopenia [6][7][8][9][10] and a paradoxical increase in pro-inflammatory cytokines, such as TNF-α, IL-1β and IL-6 1,4,6,[11][12][13] . Alteration of T cell compartments include increases in effector and activated CD4 and CD8 T cells [14][15][16][17] , CD8 + T cells contribute to survival in patients with COVID-19 and hematologic cancer

COVID-19 has become a global pandemic. Immune dysregulation has been implicated, but immune responses remain poorly understood. We analyzed 71 COVID-19 patients compared to recovered and healthy subjects using high dimensional cytometry. Integrated analysis of ~200 immune and >30 clinical features revealed activation of T cell and B cell subsets, but only in some patients. A subgroup of patients had T cell activation characteristic of acute viral infection and plasmablast responses could reach >30% of circulating B cells. However, another subgroup had lymphocyte activation comparable to uninfected subjects. Stable versus dynamic immunological signatures were identified and linked to trajectories of disease severity change.These analyses identified three "immunotypes" associated with poor clinical trajectories versus improving health. These immunotypes may have implications for therapeutics and vaccines.

Research and practice in critical care medicine have long been defined by syndromes, which, despite being clinically recognizable entities, are, in fact, loose amalgams of heterogeneous states that may respond differently to therapy. Mounting translational evidence-supported by research on respiratory failure due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection-suggests that the current syndrome-based framework of critical illness should be reconsidered. Here we discuss recent findings from basic science and clinical research in critical care and explore how these might inform a new conceptual model of critical illness. De-emphasizing syndromes, we focus on the underlying biological changes that underpin critical illness states and that may be amenable to treatment. We hypothesize that such an approach will accelerate critical care research, leading to a richer understanding of the pathobiology of critical illness and of the key determinants of patient outcomes. This, in turn, will support the design of more effective clinical trials and inform a more precise and more effective practice at the bedside.

In a large health system in the United States, investigators examined whether mortality, receipt of mechanical ventilation, and patient acuity changed over time among adult patients with COVID-19–related critical illness admitted to intensive care units.

Rationale: Red blood cell (RBC) transfusions are associated with increased risk of acute respiratory distress syndrome (ARDS) in the critically ill, yet the mechanisms for enhanced susceptibility to ARDS conferred by RBC transfusions remain unknown.Objectives: To determine the mechanisms of lung endothelial cell (EC) High Mobility Group Box 1 (HMGB1) release following exposure to RBCs and to determine whether RBC transfusion increases susceptibility to lung inflammation in vivo through release of the danger signal HMGB1.Methods: In vitro studies examining human lung EC viability and HMGB1 release following exposure to allogenic RBCs were conducted under static conditions and using a microengineered model of RBC perfusion. The plasma from transfused and nontransfused patients with severe sepsis was examined for markers of cellular injury. A murine model of RBC transfusion followed by LPS administration was used to determine the effects of RBC transfusion and HMGB1 release on LPS-induced lung inflammation.Measurements and Main Results: After incubation with RBCs, lung ECs underwent regulated necrotic cell death (necroptosis) and released the essential mediator of necroptosis, receptor-interacting serine/threonine-protein kinase 3 (RIP3), and HMGB1. RIP3 was detectable in the plasma of patients with severe sepsis, and was increased with blood transfusion and among nonsurvivors of sepsis. RBC transfusion sensitized mice to LPS-induced lung inflammation through release of the danger signal HMGB1.Conclusions: RBC transfusion enhances susceptibility to lung inflammation through release of HMGB1 and induces necroptosis of lung EC. Necroptosis and subsequent danger signal release is a novel mechanism of injury following transfusion that may account for the increased risk of ARDS in critically ill transfused patients.

PURPOSE: A causal biomarker for acute respiratory distress syndrome (ARDS) could fuel precision therapy options. Plasma angiopoietin-2 (ANG2), a vascular permeability marker, is a strong candidate based on experimental and observational evidence. We used genetic causal inference methods – Mendelian Randomization and mediation – to infer potential effects of plasma ANG2. METHODS: We genotyped 703 septic subjects, measured ICU admission plasma ANG2, and performed a quantitative trait loci (QTL) analysis to determine variants in the ANGPT2 gene associated with plasma ANG2 (p < 0.005). We then used linear regression and post-estimation analysis to genetically predict plasma ANG2 and tested genetically-predicted ANG2 for ARDS association using logistic regression. We estimated the proportion of the genetic effect explained by plasma ANG2 using mediation analysis. RESULTS: Plasma ANG2 was strongly associated with ARDS (OR 1.59 (95% CI 1.35, 1.88) per log). Five ANGPT2 variants were associated with ANG2 in European ancestry subjects (n=404). Rs2442608C, the most extreme cis QTL (coefficient 0.22, 95% CI 0.09 – 0.36, p=0.001), was associated with higher ARDS risk: adjusted OR 1.38 (95% CI 1.01, 1.87), p=0.042. No significant QTL were identified in African ancestry subjects. Genetically-predicted plasma ANG2 was associated with ARDS risk: adjusted OR 2.25 (95% CI 1.06 – 4.78), p=0.035. Plasma ANG2 mediated 34% of the rs2442608C - ARDS risk. CONCLUSIONS: In septic European ancestry subjects, the strongest ANG2-determining ANGPT2 genetic variant associates with higher ARDS risk. Plasma ANG2 may be a causal factor in ARDS development. Strategies to reduce plasma ANG2 warrant testing to prevent or treat sepsis-associated ARDS.

BACKGROUND: Critically ill patients who develop ARDS have substantial associated morbidity and mortality. Circulating mitochondrial DNA (mtDNA) released during critical illness causes endothelial dysfunction and lung injury in experimental models. This study hypothesized that elevated plasma mtDNA is associated with ARDS in critically ill patients with trauma and sepsis.METHODS: Plasma mtDNA concentrations were measured at ED presentation and approximately 48 h later in separate prospective cohorts of critically ill patients with trauma and sepsis. ARDS was classified according to the Berlin definition. The association of mtDNA with ARDS was tested by using multivariable logistic regression, adjusted for covariates previously shown to contribute to ARDS risk in each population.RESULTS: ARDS developed in 41 of 224 (18%) trauma patients and in 45 of 120 (38%) patients with sepsis. Forty-eight-hour mtDNA levels were significantly associated with ARDS (trauma: OR, 1.58/log copies/mL; 95% CI, 1.14-2.19 [P ¼ .006]; sepsis: OR, 1.52/log copies/ mL; 95% CI, 1.12-2.06 [P ¼ .007]). Plasma mtDNA on presentation was not significantly associated with ARDS in either cohort. In patients with sepsis, 48-h mtDNA was more strongly associated with ARDS among those with a nonpulmonary infectious source (OR, 2.20/log copies/mL; 95% CI, 1.36-3.55 [P ¼ .001], n ¼ 69) than those with a pulmonary source (OR, 1.04/log copies/mL; 95% CI, 0.68-1.59 [P ¼ .84], n ¼ 51; P ¼ .014 for interaction).CONCLUSIONS: Plasma mtDNA levels were associated with incident ARDS in two critical illness populations. Given supportive preclinical data, our findings suggest a potential link between circulating mtDNA and lung injury and merit further investigation as a potentially targetable mediator of ARDS. CHEST 2020; 157(1):67-76