Priming of Naïve Melanoma and HIV-specific Human CD8+ T Cells by the Immuno-STAT Immunostimulatory Protein Framework

Adoptive cell transfer (ACT), an increasingly used immunotherapeutic approach for the treatment of cancer and infectious diseases, typically infuses antigen-specific CD8+ T cells obtained after ex vivo stimulation with patient-derived dendritic cells (DC) loaded with defined peptides. However, broader use of this approach is limited by logistical complexity, variability, cost, and inconsistency in cell quality. To overcome these limitations, we developed a dimeric protein scaffold-based antigen-presentation platform, Immuno-STAT (IST), which delivers peptide-specific TCR activation and costimulatory signaling to robustly expand highly functional antigen-specific CD8+ T cells. We demonstrate that delivering TCR and CD28 signals by IST selectively activates and expands highly functional cytotoxic CD8+ T cells from the naïve CD8+ T cell repertoire specific for the melanoma-associated MART-1 antigen and the HIV-associated SL9 antigen. While naïve MART-1-specific CD8+ T cells were expanded by both MART-1-peptide loaded DC and MART-1-specific IST, naïve SL9-specific CD8+ T cells were expanded only by SL9-specific IST and not by SL9-peptide loaded DC. By enabling ex-vivo expansion of naïve antigen-specific T cells without generation of autologous DC, IST may overcome the practical hurdles limiting the wider use of ACT and expand its use as a therapeutic strategy for both cancer and infectious disease. Overall design: 6 replicates of UNSTIM samples, 4 replicates of MART DC samples, 4 replicates of MART IST samples, 4 replicates of SL9 IST samples