The first study performed by Hervás-Stubbs et al. was based on lamivudine therapy [108] . Five chronically WHVinfected woodchucks were treated orally with the drug for 23 weeks. At week 10, after decline of WHV DNA by 3-5 logs, three animals were vaccinated with 3 doses of serum-purified WHsAg combined with T-helper FIS peptide derived from sperm whale myoglobin. The vaccination induced T-helper responses against WHV antigens, shifting the cytokine profile from Th2 to Th0/Th1. However, no beneficial effect on WHV viral load and WHsAg levels was observed in comparison to nonimmunized animals. After withdrawal of the lamivudine treatment the values of viremia returned to the pre-treatment levels.