Ridirezionamento dell'immunità anti-tumorale in terapia cellulare adottiva: trasferimento genico del T-Cell Receptor mediato da vettori lentivirali

Genetic modification of T cells with genes encoding a tumor-specific T-cell Receptor (TCR) represents a novel strategy to obtain large quantities of tumor-reactive T lymphocytes to be employed in adoptive cell therapy protocols. As a transfer method, lentiviral vectors might represent an appealing alternative to the most widely used oncoretroviral vectors, because they do not require cell division for nuclear uptake. We have characterized the TCR of a highly cytotoxic T lymphocyte (CTL) clone recognizing the HLA-A2-restricted Melan-A/MART-1 melanocyte differentiation antigen on both pulsed T2 cells and SK-23 MEL melanoma tumor cells. The ? (V?2.2) e ? (V?14) chains of the TCR were cloned and used to construct a lentiviral vector carrying a bidirectional promoter and capable of a robust and coordinated expression of the two transgenes. Transduction of Jurkat T leukemia cells showed that more than 60% of cells could be transduced without selection at a low MOI, as assessed by antigen-specific tetramer staining. High expression Jurkat clones disclosed that the new assembled TCR was at high intensity, very stable over time, and fully functional, as demonstrated by intracellular signaling upon TCR triggering. Transduction of activated PBMC produced a highly expressed transgenic TCR in around 5-10% of cells. This initial low, but clearly detectable, fraction of transduced lymphocytes could be quickly expanded (4-6 weeks) upon subsequent antigen-specific in vitro restimulation. The resulting population had a 50-70% of transgenic TCR expression and mainly a CD8+ phenotype, specifically recognized antigen-expressing melanoma cells (cytokine production and cytotoxic activity), and exerted relevant therapeutic effects in vitro upon adoptive transfer in SK-23 MEL-bearing mice. Our results indicate that LV constitute a valid tool for stable and high-intensity expression of transgenic TCR, and support further studies to address potential feasibility of this approach for clinical application.