Reconstituted complexes of mycobacterial HSP70 and EBV LMP2A-derived peptides elicit peptide-specific cytotoxic T lymphocyte responses and anti-tumor immunity.

Epstein-Barr virus (EBV) latent membrane protein 2A (LMP2A) is a subdominant antigen expressed in EBV-associated malignancies, such as Hodgkin's diseases (HD) and nasopharyngeal carcinoma. A large number of previous studies have described LMP2A as an ideal target antigen in immunotherapy of EBV-related diseases, while limited successes have been achieved in clinical trials. Mycobacterium tuberculosis heat shock protein 70 (MtHsp70) is known as an effective molecular adjuvant for protein- or epitope-based vaccines. In the present study, we reconstituted two chaperone complexes of MtHsp70 and LMP2A-derived peptides (LMP2A(356-364) FLYALALLL and LMP2A(426-434) CLGGLLTMV) in vitro. We then investigated LMP2A-specific immune responses induced by reconstituted complexes of MtHsp70 and LMP2A-peptides using both EBV infected healthy donor PBMCs and HLA-A2.1 transgenic mouse models. We found that reconstituted complexes of MtHsp70 and LMP2A-peptides significantly elicit LMP2A-specific IFN-γ-producing cells and rousted cytotoxic T lymphocytes (CTLs) in vitro and in vivo. In addition, LMP2A-specific immune responses induced by the reconstituted complexes of MtHsp70 and LMP2A-peptides mediated potently protective activity as well as therapeutic efficacy against LMP2A-expressed tumor challenge in mouse models. These studies provide new insights for the development of novel LMP2A-based vaccines against EBV-associated malignancies.