Development of multiple formulations of heat shock protein based vaccines for cancer immunotherapy
The studies described explore multiple heat shock protein (Hsp) -based vaccine formulations for tumor immunotherapy. While earlier studies often focused on microbial Hsps in mice, the studies presented in this thesis examine mouse Hsps in mice. First, we studied DNA vaccination approach with autologous Hsp70 or Hsp110-based vaccines targeting a tumor-associated antigen, human papilloma virus (HPV) type 16 E7. The DNA vaccine with the E7 gene fused to the 5' end of the mouse Hsp70 gene not only elicits an E7-specific CTL response, but also protects mice against challenge with E7 expressing tumor. CD8 + T-cells are crucial for the antitumor immunity, whereas CD4 + T-cells and NK cells do not appear to play a major role. Furthermore, it is shown that the peptide-binding region, not the ATPase domain of Hsp70, is required for the vaccine activity of the E7-Hsp70 DNA. Second, we studied the Hsp-based fusion protein vaccines using E7 as a target antigen. E7 was fused to mouse Hsp70 or Hsp110 and the fusion protein was used as vaccines in mice. However, we were not able to observe either E7-specific CTL response or antitumor response against an E7 expressing tumor with these vaccines. Lastly, we examined the Hsp110-based whole cell vaccination. A colon tumor cell line CT26 was engineered to over-express mouse Hsp110. Immunization of mice with irradiated CT26-Hsp110 cells significantly inhibits the growth of wild-type CT26 tumor. This immunity is associated with increased frequency of the tumor-specific T cells. The elicited anti-tumor response involves CD8 + T cells and NK cells, but not CD4 + T cells. In addition, immunization with CT26-Hsp110 cells combined with GM-CSF producing bystander cells results in complete inhibition of CT26 tumor growth, indicating a synergy between irradiated CT26-Hsp110 vaccine activity and GM-CSF. These studies demonstrate that autologous Hsp70 is highly potent in enhancing antigen-specific immune responses. Functional domain mapping of Hsp70 in the fusion gene may have clinical implications for the design and optimization of Hsp70-based DNA vaccines. Further, manipulation of Hsp110 expression in tumors, specifically when combined with GM-CSF, represents a potentially powerful cell-based approach to cancer vaccine formulation.