Therapeutic vaccines in treating chronic hepatitis B: the end of the beginning or the beginning of the end?
The antiviral treatment of chronic hepatitis B virus (HBV) infection has greatly improved over the last 20 years since it has allowed a disappearance of cirrhosis decompensation and a significant reduction of the incidence of hepatocellular carcinoma. However, a complete HBV cure has not been achieved, and alternative treatments are still needed to optimize the current treatments. Therapeutic vaccination is a promising new strategy for controlling persistent infections and tumors. However, this approach has not been as successful as initially anticipated for chronic hepatitis B. General impairment of the immune responses generated during persistent HBV infection, with exhausted T cells not responding correctly to therapeutic vaccination, is most likely responsible for the poor clinical responses observed to date. We describe here the past approaches of therapeutic vaccination, in the hope that useful lessons will emerge from these previous clinical trials. Intensive research efforts are now focusing on a better understanding of immune responses in liver, on mechanisms by which HBV escapes innate immunity and on an accurate selection of the patients susceptible to benefit of immune therapy, which could increase the efficacy of therapeutic vaccination.