Memory T Cells Masquerading as Naïve Cells: Implications on Adoptive T Cell Immunotherapy.

Abstract 1471

Differentiation stage of adoptively transferred T cells has a critical impact on the success of immune-gene therapy. Ex vivo T cell manipulation often induces their terminal differentiation, resulting in poor persistence and activity of transferred cells. We previously showed that costimulation and culture with γ-chain cytokines generates gene modified T cells with a functional central memory (T_CM) phenotype superior to effector/effector memory (T_EM) counterparts for expansion potential and antitumor activity. Here we investigated the consequence of initial targeting of selected T cell subpopulations. We activated and efficiently transduced FACS-sorted T Naïve (T_N), T_CM and T_EM cells by viral vectors. In contrast to T_CM and T_EM, T_N had a greater expansion potential and more sustained expression of IL7-Rα. Strikingly, manipulation of T_N resulted in a predominant population of post-mitotic lymphocytes expressing the CD45RA+CD62L+CCR7+ naïve phenotype. These cells expressed markers common to early differentiated cells (CD27, CD28, CD127 and Bcl2) and markers proper of memory lymphocytes (CD45RO, CD122 and CXCR3). Post-mitotic T_N produced lower levels of IFNg and Granzyme A, expressed higher levels of c-Kit and CXCR4, and lower levels of HLA-DR, CCR5 and PD1 than memory counterparts. To verify their self-renewal and differentiation potential upon antigen stimulations, T_N, T_CM and T_EM were transduced to express a WT1-specific TCR. Upon multiple stimulations T_N expanded at higher numbers and were unique in the ability to generate a mixed population of CD127+/CD127- lymphocytes. When infused in immunodeficient mice, transduced T_N proved higher engraftment and persistence potential than memory counterparts, reconstituted a mixed CD45RA±CD62L± phenotype and were significantly higher xenoreactive. These results suggest that gene transfer into T_N lymphocytes might increase the efficacy of cancer immunotherapy.