Background/aims: Treatment of hepatitis B virus carriers by vaccine containing hepatitis B surface antigen with Pre-S protein and HBsAg/ anti-HBs complex has been reported and these studies have constituted a new and promising concept for the treatment of HBV-carriers. The present communication, a placebo-controlled trial of vaccination in HBV-transgenic mice, was designed to examine the impact of vaccination using a high dose of HBsAg for a duration of 12 months to achieve further insights about the dose, duration and effectiveness of vaccine therapy. Another aim of this study was to analyse the mechanism underlying the antiviral and immunomodulatory potentiality of vaccine therapy in HBV-transgenic mice.
Methods: HBV-transgenic mice positive for HBV DNA, hepatitis B surface antigen and hepatitis B e antigen in sera received either HBV-vaccine containing HBsAg in complete Freund's adjuvant (CFA), intraperitoneally, once a month for 12 consecutive months (vaccine recipients), or only CFA, intraperitoneally once in a month for 12 consecutive months (placebo recipients). Thirty-two vaccine-recipient and 16 placebo-recipient HBV-transgenic mice were injected, checked and followed on a monthly basis for the entire duration of 12 months.
Results: Of the 32 transgenic mice from the vaccine-recipient group, 25 became completely negative for HBsAg and 30 for HBeAg. Five mice developed anti-HBs in sera after the observation period of 12 months. Semiquantitative estimation of HBV DNA by polymerase chain reaction showed that vaccination resulted in a decrease of HBV DNA in sera. Placebo-recipient transgenic mice did not show any significant change in the titres of HBV markers after receiving 12 monthly injections of CFA. Interleukin-2 could be detected in sera from vaccine-recipient transgenic mice, but not in placebo-recipient transgenic mice.
Conclusions: Vaccination with a high dose of HBsAg in adjuvant over a long period had a significant antiviral as well as immunomodulatory potential in HBV-transgenic mice. This inspires optimism that vaccine alone or in combination with antiviral agents can be used successfully for the treatment of human HBV-carriers.