Recombinant human interleukin 28B: anti-HCV potency, receptor usage and restricted cell-type responsiveness.

OBJECTIVES Interleukin 28B (IL28B) genetic variation has been recently reported as a potent predictor of hepatitis C virus (HCV) response to interferon (IFN) therapy. The aim of this study was to produce recombinant human IL28B (rhIL28B) in yeast and explore the action mechanisms of rhIL28B as a novel anti-HCV agent. METHODS A simple and efficient protocol for producing rhIL28B in the methylotrophic yeast Pichia pastoris was developed. The anti-HCV activity, induction of IFN-stimulated genes (ISGs), receptor usage and cellular responsiveness of rhIL28B were characterized. RESULTS The yield of secreted rhIL28B was optimized to 200 mg/L, and soluble rhIL28B that was approximately 95% pure was achieved using a one-step ion-exchange purification procedure. rhIL28B inhibited HCV propagation in Huh7.5.1 cells with an IC(50) of 0.15 × 10(-3) mg/L. Treatment of hepatoma cells with rhIL28B resulted in the phosphorylation of STAT1 within 1 h and expression of ISGs. The HCV inhibitory effects of rhIL28B were antagonized by the antibody neutralization of receptors IL10R2 and IL28R1. The combination of rhIL28B and ribavirin synergistically inhibited HCV production in cell culture. Importantly, compared with the broad-spectrum activity of IFN-α, we demonstrated restricted cell-type responsiveness of rhIL28B in liver, lung and prostate cells. CONCLUSIONS This study established an easy and highly efficient approach for the production of rhIL28B with potent in vitro antiviral activity and restricted cell tropism, and thus provides a novel antiviral candidate for improving the treatment of HCV-infected patients.