Telbivudine preserves T‐helper 1 cytokine production and downregulates programmed death ligand 1 in a mouse model of viral hepatitis

Abstract

Summary. Telbivudine is an orally bioavailable L‐nucleoside with potent and specific anti‐hepatitis B virus activity. The higher rate of hepatitis B e antigen (HBeAg) seroconversion during telbivudine treatment than other potent anti‐HBV agents suggests a potential immunomodulatory effect. We sought to determine the effects of telbivudine on the immune system, particularly on cytokine production and T‐cell response, using an animal model with mouse hepatitis virus strain 3 (MHV‐3)‐induced hepatitis. The effects of telbivudine on virus replication and cytokine production were investigated in vitro using MHV‐3‐infected macrophages, and the effects on T‐cell response were investigated in vivo in an MHV‐3‐induced viral hepatitis model. Telbivudine had no effect on MHV‐3 replication in macrophages. However, the production of tumour necrosis factor‐α and interleukin‐12 was increased significantly in MHV‐3‐induced macrophages treated with telbivudine. In vivo survival was enhanced in telbivudine‐treated mice, with marked normalization in clinical conditions and histological lesions. Serum levels of interferon‐γ were elevated significantly after telbivudine treatment in MHV‐3‐infected C3H mice. In contrast, serum interleukin‐4 levels were decreased significantly. Furthermore, telbivudine treatment enhanced the ability of T cells to undergo proliferation and secrete cytokines but did not affect cytotoxicity of infected hepatocytes. Of note, we found that telbivudine treatment suppressed programmed death ligand 1 expression on T cells. The results demonstrate the immunomodulatory properties of telbivudine, independent of its antiviral activity, in a mouse model of MHV‐3‐induced hepatitis.