Significant elevation of plasma cathepsin B and cystatin C in patients with community-acquired pneumonia

Background: We identified the relationship between plasma level changes of cathepsin B and cystatin C before and after antibiotic treatment in hospitalized adult patients with community-acquired pneumonia (CAP). Methods: We collected blood specimens from 61 adult patients with CAP before and after antibiotic treatment and from 60 healthy controls and measured the plasma concentrations of cathepsin B and cystatin C expression using the enzyme-linked immunosorbent assay (ELISA). The APACHE II, CURB-65, and Pneumonia Severity Index (PSI) scores were determined to assess CAP severity in patients upon initial hospitalization. Results: The results showed a decline in the number of WBCs and neutrophils, with decreases in the concentrations of CRP, cathepsin B, cystatin C, and the cathepsin B/cystatin C ratio being observed after antibiotic treatment. The plasma concentration of cathepsin B correlated with severity of CAP with the PSI score (r=0.290, p=0.025) and the CURB-65 score (r=0.258, p=0.047), respectively. The plasma concentration of cystatin C correlated with the APACHE II score (r=0.523, p<0.001), severity of CAP in the PSI score (r=0.721, p<0.001) and the CURB-65 score (r=0.609, p<0.001), respectively. Conclusions: Cathepsin B and cystatin C may play a role in the diagnosis and clinical assessment of the severity of CAP, which could potentially guide the development of treatment strategies.