Induction of tumor-specific immune response by gene transfer of Hsp70-cell-penetrating peptide fusion protein to tumors in mice

Abstract

To induce a tumor-specific immune response by delivering tumor-associated antigens in tumor cells to antigen-presenting cells (APCs), we designed a fusion protein which consists of heat-shock protein 70 (Hsp70) and the C-terminal 34 amino acids of herpes simplex virus VP22 protein (VP22 268-301), the former having a peptide binding domain and an ability to be recognized by APCs, and the latter able to achieve cell penetration. Hsp70-VP22 268-301, the fusion protein, was efficiently taken up by mouse dendritic cell (DC) line DC2.4. Major histocompatibility complex (MHC) class I-restricted presentation of an epitope peptide of ovalbumin (OVA) was examined in DC2.4, and Hsp70-VP22 268-301 significantly increased the presentation of the peptide compared with Hsp70. Electroporation-assisted injection of naked plasmid vector expressing Hsp70-VP22 268-301 (pHsp70-VP22 268-301) into subcutaneous tumors of EG7-OVA, a mouse lymphoma-expressing OVA, significantly increased the survival of mice compared with the same treatment with pHSp70, a plasmid expressing Hsp70. Splenocytes from the pHsp70-VP22 268-301-treated mice exhibited cytolytic activity against both EG7-OVA and the parent EL4, but not against mouse melanoma B16-F10, suggesting that not only OVA-derived antigens but those common to EG7-OVA and EL4 are delivered to APCs. These results provide a new therapeutic method to induce tumor-specific antitumor immunity without identifying nor isolating tumor-associated antigens. © The American Society of Gene & Cell Therapy.