Generation of tumor-reactive CTL against the tumor-associated antigen HER2using retrovirally transduced dendritic cells derived from CD34(+) hemopoietic progenitor cells

Ag-specific CD8(+) CTL are crucial for effective tumor rejection, Attempts to treat human malignancies by adoptive transfer of tumor-reactive CTL have been limited due to the difficulty of generating and expanding autologous CTL with defined Ag specificity. The current study examined whether human C TL can be generated against the tumor-associated Ag HER2 using autologous d endritic cells (DC) that had been genetically engineered to express HER2. D C progenitors were expanded by culturing CD34(+) hemopoietic progenitor cel ls in the presence of the designer cytokine HyperIL-6. Proliferating precur sor cells were infected by a retroviral vector encoding the HER2 Ag and fur ther differentiated into CD83(+) DC expressing high levels of MHC, adhesion , and costimulatory molecules. Retroviral transduction of DC resulted in th e expression of the HER2 molecule with a transduction efficiency of 15%. HE R2-transduced DC correctly processed and presented the Ag, because HLA-A*02 01-positive DC served as targets for CTL recognizing the HLA-A*0201-binding immunodominant peptide HER2(369-377). HER2-transduced DC were used as prof essional APCs for stimulating autologous T lymphocytes. Following repetitiv e stimulation, a HER2-specific, HLA-A*0201-restricted CTL line was generate d that was capable of lysing HLA-A*0201-matched tumor cells overexpressing HER2, A CD8(+) T cell clone could be generated that displayed the same spec ificity pattern as the parenteral CTL line. The ability to generate and exp and HER2-specific, MHC class I-restricted CTL clones using HER2-transduced autologous DC in vitro facilitates the development of adoptive T cell trans fer for patients with HER2-overexpressing tumors without the requirement of defining immunogenic peptides.