High Levels of the Cleaved Form of Galectin-9 and Osteopontin in the Plasma Are Associated with Inflammatory Markers That Reflect the Severity of COVID-19 Pneumonia

Abstract

Numbers of patients with coronavirus disease 2019 (COVID-19) have increased rapidly worldwide. Plasma levels of full-length galectin-9 (FL-Gal9) and osteopontin (FL-OPN) as well as their truncated forms (Tr-Gal9, Ud-OPN, respectively), are representative inflammatory biomarkers. Here, we measured FL-Gal9, FL-OPN, Tr-Gal9, and Ud-OPN in 94 plasma samples obtained from 23 COVID-19-infected patients with mild clinical symptoms (CV), 25 COVID-19 patients associated with pneumonia (CP), and 14 patients with bacterial infection (ID). The four proteins were significantly elevated in the CP group when compared with healthy individuals. ROC analysis between the CV and CP groups showed that C-reactive protein had the highest ability to differentiate, followed by Tr-Gal9 and ferritin. Spearman's correlation analysis showed that Tr-Gal9 and Ud-OPN but not FL-Gal9 and FL-OPN, had a significant association with laboratory markers for lung function, inflammation, coagulopathy, and kidney function in CP patients. CP patients treated with tocilizumab had reduced levels of FL-Gal9, Tr-Gal9, and Ud-OPN. It was suggested that OPN is cleaved by interleukin-6-dependent proteases. These findings suggest that the cleaved forms of OPN and galectin-9 can be used to monitor the severity of pathological inflammation and the therapeutic effects of tocilizumab in CP patients.

Keywords: COVID pneumonia; COVID-19; full-length galectin-9; full-length osteopontin; infectious diseases; inflammatory markers; therapy; tocilizumab; truncated galectin-9; undefined osteopontin.

Figure 1

Patients over the age of 20 years participated in this study. Adults who did not have sufficient judgment, were unconscious, or who need consideration for the name of the disease were excluded. Laboratory tests included C-reactive protein (CRP), chest CT and SpO₂. COVID-19-infected patients with mild clinical symptoms (CV), COVID-19 patients associated with pneumonia (CP), and patients with bacterial infection (ID) were studied. Patients suspected of having cytokine storm (CS) were treated with TCZ. The treatment policy depended on the patient’s clinical situation.

Figure 2

Levels of FL-Gal9 (A), Tr-Gal9 (B), FL-OPN (C), and Ud-OPN (D) in CV, CP, ID, and HC. HC: healthy control; CV: COVID-19 infection with mild clinical symptoms; CP: COVID-19 associated with pneumonia; ID: infectious diseases FL-Gal9; Full-length Gal-9, Tr-Gal9; truncated Gal-9, FL-OPN; full-length OPN, Ud-OPN; undefined OPN, **** p < 0.0001, *** p < 0.001, ** p < 0.01, * p < 0.05.

Figure 3

Levels of inflammatory, coagulation, kidney and respiratory indicators in COVID-19 patients (CV, CP) and patients with bacterial infection (ID). Only those with data are shown in the figure. CRP (A), Lymphocyte number (B), sIL-2R; soluble IL-2 receptor α (C), Ferritin (D), D-dimer; d-dimer (E), B2M; urinary β₂-microglobulin (F), Crea; creatinine (G), SpO₂; peripheral capillary oxygen saturation (H), S/F; SpO₂/FiO₂ ratio (I). CRP, ferritin, and creatinine were measured in plasma and d-dimer was measured in serum. **** p < 0.0001, ** p < 0.01, * p < 0.05; ns; not significant.

Figure 4

ROC analysis of Gal-9 (FL-Gal9 and Tr-Gal9) and OPN (FL-OPN and Ud-OPN) between the HC and CV groups (A), the CP group (B) and the ID group (C).

Figure 5

ROC analysis of inflammatory, coagulation, kidney and respiratory indicators between the CV and CP groups. Gal-9 and OPN (A), inflammatory markers (B), and respiratory, kidney and hematological markers (C).

Figure 6

Associations of studied indicators in the CV (A), CP (B), and ID (C) groups. The correlation was measured by the Spearman t-test. The correlation R-value is written in each well and displayed as colors ranging from blue to red as shown in the legend key. p-value is written significant as * p < 0.05.

Figure 7

Effects of TCZ therapy on markers. Only those with data are shown in the figure. FL--Gal9 (A), Tr-Gal9 (B), FL-OPN (C), Ud-OPN (D), CRP (E), Lymphocyte (F), SpO2 (G), S/F ratio (H). TCZ; tocilizumab, **** p < 0.0001, *** p < 0.001, ** p < 0.01, * p < 0.05.