Aberrant production of soluble inducible T-cell co-stimulator (sICOS) and soluble programmed cell death protein 1 (sPD-1) in patients with chronic hepatitis C.

Previous studies have indicated that immune dysregulation is an important cause of HCV‑mediated damage to the liver. Co‑stimulation signals, including programmed cell death protein 1 (PD‑1) and inducible T‑cell co‑stimulator (ICOS), have been demonstrated to be involved in the pathogenesis of HCV. The purpose of this study was to investigate the soluble PD‑1 (sPD‑1) and soluble ICOS (sICOS) serum levels in chronic HCV patients, and to elucidate the association of sPD‑1 and sICOS levels with pathological injury of chronic HCV infection. Sixty‑three patients with chronic HCV and 30 normal controls were recruited for this study. The serum concentration levels of sPD‑1 and sICOS were measured by enzyme‑linked immunosorbent assay, and the mRNA levels of PD‑1 and ICOS were detected using real‑time RT‑PCR. The serum sPD‑1 and sICOS levels were significantly elevated in the chronic HCV patient group compared with the normal control group. Furthermore, the relative mRNA expression levels of these proteins were also increased in chronic HCV patients. sPD‑1 and sICOS serum levels were significantly correlated with anti‑HCV antibody levels, but not with HCV RNA. Aberrant sPD‑1 and sICOS serum levels may reflect the dysregulation of T‑cell activation, and are associated with the pathological injury of chronic HCV infection.