Abstract:Objective To investigate the changes in serum levels of soluble programmed cell death protein 1（sPD-1）and its ligand（sPD-L1）in patients with chronic hepatitis C（CHC）and their relationship with hepatitis C viral load（HCV RNA）and degree of liver fibrosis. Methods A total of 70 CHC patients who visited the Infectious Disease Outpatient Clinic of the Fourth Affiliated Hospital of Nanjing Medical University from October 2022 to October 2023 were respectively selected as the study group，and 70 healthy individuals who underwent physical examination during the same period were selected as the control group. Serum levels of sPD-1 and sPD-L1 were measured by enzyme-linked immunosorbent assay（ELISA）. The correlations of serum levels of sPD-1 and sPD-L1 with disease activity indicators［alanine aminotransferase（ALT），aspartate aminotransferase（AST）］，hepatitis C viral load indicator（HCV RNA）and liver fibrosis indicator［AST/platelet index（APRI）］were analyzed by Pearson correlation. Results Compared to the control group，CHC patients had significantly elevated serum levels of sPD-1，sPD-L1，ALT，and AST，with statistically significant differences（P <0.01）. Pearson correlation analysis showed that serum sPD-1 levels in the CHC group were positively correlated with ALT，AST，and HCV RNA，respectively（P<0.05）. Moreover，APRI was positively correlated with serum sPD-1 levels（P<0.05），with patients in the high APRI（≥1.2）group displaying significantly higher serum sPD-1 level than that in the low APRI（≤0.42）group（P<0.05）. Conclusion The level of sPD-1 in CHC patients may be served as an important indicator reflecting the disease activity，viral load，and the degree of liver fibrosis，while the specific mechanism of sPD-L1 in disease progression requires further investigation.