Production of hepatitis B surface antigen-pulsed dendritic cells from immunosuppressed murine hepatitis B virus carrier: evaluation of immunogenicity of antigen-pulsed dendritic cells in vivo

Vaccines containing hepatitis B surface antigen (HBsAg) induce antibody to HBsAg (anti-HBs) in most normal individuals and protects them from hepatitis B virus (HBV) infection. However, these vaccines are not efficient at inducing anti-HBs in immunosuppressed individuals, especially in immunosuppressed HBV carriers. The aim of this study was to prepare and to assess the efficacy of a dendritic cell (DC)-based vaccine in an immunosuppressed HBV transgenic mouse (HBV-Tg), an animal model of the HBV carrier state. In order to prepare immunosuppressed HBV-Tg, HBV-Tg were injected with FK-506, an immunosuppressive agent, once daily, intraperitoneally for 15 days. Spleen cells of immunosuppressed HBV-Tg expressed very little mRNAs for interleukin-2 and interferon-gamma. DCs were isolated from the spleen of immunosuppressed HBV-Tg and cultured with HBsAg (100 microg) for 48 h to prepare HBsAg-pulsed DCs. Immunosuppressed HBV-Tg expressing HBsAg in the sera were administered with HBsAg-pulsed DCs or unpulsed DCs or HBsAg in adjuvant for different durations. Immunosuppressed HBV-Tg (n = 8) twice administered with HBsAg-pulsed DCs expressed anti-HBs in the sera within 6 weeks of first injection. Seven of eight immunosuppressed HBV-Tg remained positive for anti-HBs in the sera for the next 12 weeks of observation in spite of receiving daily injection of FK-506 for the entire duration. However, immunosuppressed HBV-Tg administered with unpulsed DCs or HBsAg in adjuvant did not express anti-HBs in the sera. The data show that DCs from immunosuppressed HBV-Tg can be loaded with HBsAg to prepare immunogenic HBsAg-pulsed DCs. HBsAg-pulsed DCs induced anti-HBs in immunosuppressed HBV-Tg. This approach may be of use to induce and maintain anti-HBs in immunosuppressed human HBV carriers.