Pilot studies have demonstrated that recombinant interleukin 2 (rIL-2) has an indirect antiviral activity against hepatitis B virus, but the minimal dose of rIL-2 for induction of this effect was not defined. The aim of the study was to ascertain the most efficient dose of rIL-2 for induction of the loss of detectable serum HBV-DNA or a 50% or greater decrease in its level. Thirty-one patients with chronic hepatitis B, hepatitis B e antigen and serum HBV-DNA positive were enrolled in this double-blind randomized controlled trial. Patients were divided: Group I (n = 8) placebo; Group II (n = 7) treated with 0.9 MU of rIL-2 subcutaneously administered daily for 8 weeks; Group III (n = 8) treated with 1.8 MU of rIL-2 under the same schedule; Group IV (n = 8) which received 3.6 MU of rIL-2 under the same conditions. At the end of treatment 25% of the patients in the placebo group, and 13% and 25% in rIL-2 groups III and IV, respectively, had a decrease in HBV-DNA higher than 50% of the basal value. None of the patients lost serum HBV-DNA. Only three patients (one from group II and two from group IV) normalized the ALT levels. Overall, during treatment, ALT levels decreased in the treated groups. This decrease occurred simultaneously with an increase in serum HBV-DNA concentration. Since the response rate in the treated groups was similar to that of the placebo group, rIL-2 is not useful as monotherapy for the treatment of chronic hepatitis B at the doses and schedules used in this study.

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