Immune responses to antigens expressed by tumor cells can be exploited for treating cancer patients. Recent clinical trials have shown that adoptive T cell transfer (ACT) in combination with non-myeloablative chemotherapy frequently cause objective clinical responses in patients with advanced melanoma. However, tumor reactive T cells are difficult to obtain from most malignancies and the majority of cancer patients are thus ineligible for ACT. To circumvent this hurdle, we have developed a TCR gene transfer approach which can provide a source of autologous tumor reactive T cell from any patient. Results from early clinical trials using TCR gene-modified T cells have been relatively disappointing. One potential reason is that the T cells used, in order to be efficiently transduced, were fully activated. Regrettably, this may render the effector cells incapable of persisting and differentiating into the 'correct' phenotype needed for effective anti-tumor activity in vivo. We have recently developed a novel method for selecting transduced cells based on the inclusion of a modified CD34 cassette in our viral vectors. This modified CD34 cassette allows us to rapidly enrich transduced T cell cultures for redirected effector cells to high purity using clinically applicable methodologies. In this exploratory application, we proposed to combine this CD34 selection system with lentiviral vectors to determine if it is feasible to enrich transduced quiescent human T cells, with moderate frequency of redirected T cells, to sufficient purity for therapy. The function of the resting redirected T cells will be evaluated in vitro and in a xenogenic in vivo model to determine if quiescent TCR transduced T cells are superior to their fully activated counterparts. This study represents the first evaluation of resting TCR gene-modified T cells and the results from this study could be rapidly incorporated into future TCR gene transfer clinical trials that offer patients a novel type of autologous tumor reactive T cells with greater therapeutic potential.
The relevance of this proposal to public health is to generate a novel type of effector T cell population that can be used for adoptive T cell transfer. Using a combination of novel technologies we developed, we will redirect the specificity of naove resting human T cells to recognize the melanoma/melanocyte associated antigen tyrosinase; we hope to demonstrate in a mouse model for human melanoma that these TCR gene- modified naove T cells are superior to their fully activated counterparts. If true, the next step would be to evaluate these novel effectors in clinical trial treating advanced stage melanoma patients.
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