Antigen-specific cancer immunotherapy using a GM-CSF secreting allogeneic tumor cell-based vaccine

Granulocyte-macrophage colony-stimulating factor (GMCSF)-transduced autolog ous tumor cell-based vaccines are currently one of the major forms of cance r vaccines. However, the preparation of GM-CSF-transduced autologous tumor vaccines is time-consuming and technically challenging. In addition, the ho st antigen presenting cells, rather than the tumor vaccine cells themselves , present tumor-specific antigens and prime the host T cells. Therefore, we tested the efficacy of antigen-specific allogeneic tumor vaccines. We used human papillomavirus 16 (HPV-16) E7 protein as a model tumor antigen, whic h is associated with the development of most cervical carcinoma. B16, a C57 BL/6 (H-2(b)) derived melanoma cell line, was genetically engineered to pro duce GM-CSF alone (B16CM), HPV-16 E7 alone (B16E7), or both (B16CME7), Thes e vaccine cells were injected into BALB/c (H-2(d)) mice (10(6) cells/mouse) , Two weeks later, mice were challenged with 10(5) live HPV-16 E7(+) BL-I ( H-2d) tumor cells and monitored for tumor progression twice weekly. To dete rmine the effective cell population in the antitumor immunity elicited by B 16GME7, we carried out in vivo antibody depletion experiments using CD4 and CD8 specific antibodies. In addition, as a measure of the immune responses produced by B16GME7, we performed an in vitro cytotoxic T lymphocyte assay using a standard chromium release method. We found that all of the mice va ccinated with B16GME7 remained tumor free 49 days post-BL-l challenge. In c ontrast, mice vaccinated with B16GM and B16E7 did not show any tumor protec tion against a similar dose of BL-I cells. Furthermore, the antitumor immun ity produced by B16GME7 was dependent on both CD4 and CD8 T cells. In addit ion, E7-specific cytotoxic T lymphocyte activity could be readily demonstra ted in mice immunized with B16GME7. These results suggest that allogeneic t umor cells transduced with GM-CSF and the tumor antigen, HPV-16 E7, cannot only generate an E7-specific cytotoxic T lymphocytes response in vitro, but can also elicit a potent antitumor immune response against an E7 expressin g tumor in vivo. (C) 2000 Wiley-Liss. Inc.