ABSTRACT
Mortality among patients with COVID-19 and respiratory failure is high and there are no known lower airway biomarkers that predict clinical outcome. We investigated whether bacterial respiratory infections and viral load were associated with poor clinical outcome and host immune tone. We obtained bacterial and fungal culture data from 589 critically ill subjects with COVID-19 requiring mechanical ventilation. On a subset of the subjects that underwent bronchoscopy, we also quantified SARS-CoV-2 viral load, analyzed the microbiome of the lower airways by metagenome and metatranscriptome analyses and profiled the host immune response. We found that isolation of a hospital-acquired respiratory pathogen was not associated with fatal outcome. However, poor clinical outcome was associated with enrichment of the lower airway microbiota with an oral commensal (Mycoplasma salivarium), while high SARS-CoV-2 viral burden, poor anti-SARS-CoV-2 antibody response, together with a unique host transcriptome profile of the lower airways were most predictive of mortality. Collectively, these data support the hypothesis that 1) the extent of viral infectivity drives mortality in severe COVID-19, and therefore 2) clinical management strategies targeting viral replication and host responses to SARS-CoV-2 should be prioritized.
ABSTRACT
<p><b>BACKGROUND</b>The cardioprotective effects of soluble receptor for advanced glycation end-products (sRAGE) have not been evaluated in large animals and the underlying mechanisms are not fully understood. This study aimed to evaluate the effects of intra-coronary administration of sRAGE on left ventricular function and myocardial remodeling in a porcine model of ischemia-reperfusion (I/R) injury.</p><p><b>METHODS</b>Ten male minipigs with I/R injury were randomly allocated to receive intra-coronary administration of sRAGE (sRAGE group, n = 5) or saline (control group, n = 5). Echocardiography was performed before and 2 months after infarction. Myocardial expression of transforming growth factor (TGF)-beta1 was determined by immunohistochemistry and fibrosis was evaluated by Sirius red staining.</p><p><b>RESULTS</b>As compared with the baseline values in the control animals, left ventricular end-diastolic volume (from (19.5 +/- 5.1) to (32.3 +/- 5.6) ml, P < 0.05) and end-systolic volume (from (8.3 +/- 3.2) to (15.2 +/- 4.1) ml, P< 0.05) were significantly increased, whereas ejection fraction was decreased (from (61.6 +/- 13.3)% to (50.2 +/- 11.9)%, P < 0.05). No obvious change in these parameters was observed in the sRAGE group. Myocardial expression of TGF-beta1 was significantly elevated in the infarct and non-infarct regions in the control group, as compared with sRAGE group (both P< 0.01). Fibrotic lesions were consistently more prominent in the infarct region of the myocardium in the control animals (P < 0.05).</p><p><b>CONCLUSION</b>Intra-coronary sRAGE administration attenuates RAGE-mediated myocardial fibrosis and I/R injury through a TGF-beta1-dependent mechanism, suggesting a clinical potential in treating RAGE/ligand-associated cardiovascular diseases.</p>
