Characteristics and Determinants of Pulmonary Long COVID (preprint)

RATIONALE: Persistent cough and dyspnea are prominent features of post-acute sequelae of SARS-CoV-2 (termed 'Long COVID'); however, physiologic measures and clinical features associated with these pulmonary symptoms remain poorly defined. OBJECTIVES: Using longitudinal pulmonary function testing (PFTs) and CT imaging, this study aimed to identify the characteristics and determinants of pulmonary Long COVID. METHODS: The University of Alabama at Birmingham Pulmonary Long COVID cohort was utilized to characterize lung defects in patients with persistent pulmonary symptoms after resolution primary COVID infection. Longitudinal PFTs including total lung capacity (TLC) and diffusion limitation of carbon monoxide (DLCO) were used to evaluate restriction and diffusion impairment over time in this cohort. Analysis of chest CT imaging was used to phenotype the pulmonary Long COVID pathology. Risk factors linked to development of pulmonary Long COVID were estimated using univariate and multivariate logistic regression models. MEASUREMENTS AND MAIN RESULTS: Longitudinal evaluation 929 patients with post-COVID pulmonary symptoms revealed diffusion impairment (DLCO ≤80%) and restriction (TLC ≤80%) in 51% of the cohort (n=479). In multivariable logistic regression analysis (adjusted odds ratio; aOR, 95% confidence interval [CI]), invasive mechanical ventilation during primary infection conferred the greatest increased odds of developing pulmonary Long COVID with diffusion impaired restriction (aOR=10.9 [4.09-28.6]). Finally, a sub-analysis of CT imaging identified evidence of fibrosis in this population. CONCLUSIONS: Persistent diffusion impaired restriction was identified as a key feature of pulmonary Long COVID. Subsequent clinical trials should leverage combined symptomatic and quantitative PFT measurements for more targeted enrollment of pulmonary Long COVID patients.

Spatial transcriptomic profiling of coronary endothelial cells in SARS-CoV-2 myocarditis (preprint)

Objectives: Our objective was to examine coronary endothelial and myocardial programming in patients with severe COVID-19 utilizing digital spatial transcriptomics. Background: Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has well-established links to thrombotic and cardiovascular events. Endothelial cell infection was initially proposed to initiate vascular events; however, this paradigm has sparked growing controversy. The significance of myocardial infection also remains unclear. Methods: Autopsy-derived cardiac tissue from control (n = 4) and COVID-19 (n = 8) patients underwent spatial transcriptomic profiling to assess differential expression patterns in myocardial and coronary vascular tissue. Our approach enabled transcriptional profiling in situ with preserved anatomy and unaltered local SARS-CoV-2 expression. In so doing, we examined the paracrine effect of SARS-CoV-2 infection in cardiac tissue. Results: We observed heterogeneous myocardial infection that tended to colocalize with CD31 positive cells within coronary capillaries. Despite these differences, COVID-19 patients displayed a uniform and unique myocardial transcriptional profile independent of local viral burden. Segmentation of tissues directly infected with SARS-CoV-2 showed unique, pro-inflammatory expression profiles including upregulated mediators of viral antigen presentation and immune regulation. Infected cell types appeared to primarily be capillary endothelial cells as differentially expressed genes included endothelial cell markers. However, there was limited differential expression within the endothelium of larger coronary vessels. Conclusions: Our results highlight altered myocardial programming during severe COVID-19 that may in part be associated with capillary endothelial cells. However, similar patterns were not observed in larger vessels, diminishing endotheliitis and endothelial activation as key drivers of cardiovascular events during COVID-19.

Type I interferon-dependent IFIT3 signaling is critical for viral clearance in airway neutrophils (preprint)

Neutrophilic inflammation characterizes several respiratory viral infections including COVID-19-related ARDS, although its contribution to disease pathogenesis remains poorly understood. Here, we identified two neutrophil subpopulations (A1 and A2) in the airway compartment of 52 severe COVID-19 subjects, where loss of the A2 subset correlated with increased viral burden and reduced 30-days survival. A2 neutrophils showcased a discrete antiviral response with an increased interferon signature. Blockade of type I interferon attenuated viral clearance in A2 neutrophils and downregulated IFIT3 and key catabolic genes, demonstrating direct antiviral neutrophil function. Knockdown of IFIT3 in A2 neutrophils led to loss of IRF3 phosphorylation with consequent reduced viral catabolism, providing the first discrete mechanism of type I interferon signaling in neutrophils. The identification of this novel neutrophil phenotype and its association with severe COVID-19 outcomes emphasizes its likely importance in other respiratory viral infections and potential for new therapeutic approaches in viral illness.

Megakaryocytes are a Novel SARS-CoV-2 Infection Target and Risk Factor for Mortality and Multi-Organ Failure (preprint)

Discovery of a biomarker for patients at high risk of progression to severe Coronavirus Disease 2019 (COVID-19) is critical for clinical management, particularly in areas of the world where widespread vaccine distribution and herd immunity have yet to be achieved. Herein, we characterize peripheral blood from 218 COVID-19 patients with flow cytometry and provide evidence that megakaryocytes are a target for infection by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). We demonstrate a positive correlation between infected megakaryocytes expressing the protein calprotectin (also called S100A8/A9), a known marker of COVID-19 severity. Additionally, we show that infected, calprotectin expressing megakaryocytes are correlated with COVID-19 severity and are a prognostic indicator of 30-day clinical outcomes including respiratory failure, thrombotic events, acute kidney injury (AKI), ICU admission, and mechanical ventilation. These findings represent a novel SARS-CoV-2 infection target with significant clinical implications as a biomarker for clinical outcomes associated with severe COVID-19.