Pulmonary Procoagulant and Innate Immune Responses in Critically Ill COVID-19 Patients

Abstract

Rationale: Systemic activation of procoagulant and inflammatory mechanisms has been implicated in the pathogenesis of COVID-19. Knowledge of activation of these host response pathways in the lung compartment of COVID-19 patients is limited.

Objectives: To evaluate local and systemic activation of coagulation and interconnected inflammatory responses in critically ill COVID-19 patients with persistent acute respiratory distress syndrome.

Methods: Paired bronchoalveolar lavage fluid and plasma samples were obtained from 17 patients with COVID-19 related persistent acute respiratory distress syndrome (mechanical ventilation > 7 days) 1 and 2 weeks after start mechanical ventilation and compared with 8 healthy controls. Thirty-four host response biomarkers stratified into five functional domains (coagulation, complement system, cytokines, chemokines and growth factors) were measured.

Measurements and main results: In all patients, all functional domains were activated, especially in the bronchoalveolar compartment, with significantly increased levels of D-dimers, thrombin-antithrombin complexes, soluble tissue factor, C1-inhibitor antigen and activity levels, tissue type plasminogen activator, plasminogen activator inhibitor type I, soluble CD40 ligand and soluble P-selectin (coagulation), next to activation of C3bc and C4bc (complement) and multiple interrelated cytokines, chemokines and growth factors. In 10 patients in whom follow-up samples were obtained between 3 and 4 weeks after start mechanical ventilation many bronchoalveolar and plasma host response biomarkers had declined.

Conclusions: Critically ill, ventilated patients with COVID-19 show strong responses relating to coagulation, the complement system, cytokines, chemokines and growth factors in the bronchoalveolar compartment. These results suggest a local pulmonary rather than a systemic procoagulant and inflammatory "storm" in severe COVID-19.

Keywords: COVID-19; bronchoalveolar space; coagulation; innate immune response; persistent ARDS.

Figure 1

Coagulation activation. Bronchoalveolar lavage fluid and plasma were obtained from 17 critically ill COVID-19 patients who had been on mechanical ventilation for at least 7 days and 8 healthy control subjects. Data are expressed as box and whisker diagrams depicting the median and lower quartile, upper quartile, and their respective 1.5 interquartile range as whiskers (as specified by Tukey). Comparisons between groups were performed using the Wilcoxon rank sum test. *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, ****p = ≤ 0.0001. BALF, bronchoalveolar lavage fluid; C1-INH, C1-inhibitor; Kallikrein-C1-INH, Kallikrein-C1-inhibitor complexes; PAI-1, plasminogen activator inhibitor type I; sCD40L, soluble CD40 Ligand; sP-selectin, soluble P-selectin; TATc, thrombin-antithrombin complexes; tPA, tissue type plasminogen activator.

Figure 2

Complement activation. Bronchoalveolar lavage fluid and plasma were obtained from 17 critically ill COVID-19 patients who had been on mechanical ventilation for at least 7 days and 8 healthy control subjects. Data are expressed as box and whisker diagrams depicting the median and lower quartile, upper quartile, and their respective 1.5 interquartile range as whiskers (as specified by Tukey). Comparisons between groups were performed using the Wilcoxon rank sum test. *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, ****p ≤ 0.0001. BALF, bronchoalveolar lavage fluid; C3bc, complement 3bc; C4bc, complement 4bc; MBL, mannose binding lectin.

Figure 3

Cytokine release. Bronchoalveolar lavage fluid and plasma were obtained from 17 critically ill COVID-19 patients who had been on mechanical ventilation for at least 7 days and 8 healthy control subjects. Data are expressed as box and whisker diagrams depicting the median and lower quartile, upper quartile, and their respective 1.5 interquartile range as whiskers (as specified by Tukey). Comparisons between groups were performed using the Wilcoxon rank sum test. *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, ****p ≤ 0.0001. BALF, bronchoalveolar lavage fluid; IL, interleukin; IL-1RA, interleukin-1 receptor antagonist; TNF-α, tumor necrosis factor-α.

Figure 4

Chemokine release. Bronchoalveolar lavage fluid and plasma were obtained from 17 critically ill COVID-19 patients who had been on mechanical ventilation for at least 7 days and 8 healthy control subjects. Data are expressed as box and whisker diagrams depicting the median and lower quartile, upper quartile, and their respective 1.5 interquartile range as whiskers (as specified by Tukey). Comparisons between groups were performed using the Wilcoxon rank sum test. *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, ****p ≤ 0.0001. BALF, bronchoalveolar lavage fluid; IL, interleukin; MIP, macrophage inflammatory protein; PARC, pulmonary and activation-regulated chemokine; RANTES, Regulated upon Activation, Normal T Cell Expressed and Presumably Secreted.

Figure 5

Growth factor release. Bronchoalveolar lavage fluid and plasma were obtained from 17 critically ill COVID-19 patients who had been on mechanical ventilation for at least 7 days and 8 healthy control subjects. Data are expressed as box and whisker diagrams depicting the median and lower quartile, upper quartile, and their respective 1.5 interquartile range as whiskers (as specified by Tukey). Comparisons between groups were performed using the Wilcoxon rank sum test. **p ≤ 0.01, ***p ≤ 0.001, ****p ≤ 0.0001. BALF, bronchoalveolar lavage fluid; FTL3L, fms like tyrosine kinase 3 ligand; GM-CSF, granulocyte-macrophage colony-stimulating factor; PDGF, platelet derived growth factor; VEGF, vascular endothelial growth factor.