OBJECTIVETo investigate the dynamic changes that occur in T cell subsets, particularly involving the surface expression of programmed death 1 (PD-1), in response to pegylated (Peg)-interferon (IFN) a-2a therapy in patients with chronic hepatitis C virus (HCV) infection.

METHODSTwenty-five patients with HCV genotype 1b chronic infection and 10 healthy controls were enrolled in the study. All the HCV patients received combination antiviral therapy of Peg-IFNa-2a (180 mug/week) plus ribavirin. At treatment weeks 0 (baseline), 4, 12, 24 and 48, the level of PD-1 protein expression on the surface of total peripheral CD8+ and CD4+ T cells was determined by flow cytometry and the level of PD-1 mRNA expression in peripheral blood mononuclear cells (PBMCs) was determined by reverse transcription-polymerase chain reaction. Independent student's t-test were used to compare mean values between the two groups, repeat measure variance analysis was used to compare mean values among multiple groups, and Pearson's correlation coefficient was used to assess correlation significance.

RESULTSOver the course of antiviral therapy, the proportions of CD4+ T cells and CD8+ T cells, as well as the CD4+/CD8+ ratio, increased (F = 81.23, 39.28, and 7.01 respectively; all P less than 0.01). In contrast, the PD-1 protein expression frequency on CD4+ T cells and CD8+ T cells significantly declined (F = 100.11 and 158.40 respectively; all P less than 0.01). The PD-1-mRNA expression level in PBMCs was: 1.40+/-0.26 at baseline, 1.30+/-0.27 at week-4, 1.14+/-0.18 at week-12, 1.06+/-0.26 at week-24, and 0.83+/-0.25 at week-48 (F = 20.09; P less than 0.01). A positive correlation existed between the PD-1 protein expression frequencies on CD4+ T cells and CD8+ T cells and the HCV RNA load detected at baseline (r = 0.82 and 0.75 respectively; all P less than 0.01).

CONCLUSIONThe ability of Peg-IFN-a-2a-based antiviral therapy to suppress HCV replication may involve reduction of PD-1 protein expression on the surface of CD8+ T cells and CD4+ T cells.