CAR gene delivery by T-cell targeted lentiviral vectors is enhanced by rapamycin induced reduction of antiviral mechanisms

Lentiviral vectors (LV) have become the dominant tool for stable gene transfer into lymphocytes including chimeric antigen receptor (CAR) gene delivery to T cells, a major breakthrough in cancer therapy. Yet, room for improvement remains, especially for the latest LV generations delivering genes selectively into T cell subtypes, a key requirement for in vivo CAR T cell generation. Towards improving gene transfer rates with these vectors, we conducted whole transcriptome analyses on human T lymphocytes after exposure to CAR-encoding conventional vector VSV-LV, and vectors targeted to CD8+ (CD8-LV) or CD4+ T cells (CD4-LV). Genes related to quiescence and antiviral restriction were found to be upregulated in CAR-negative cells exposed to all types of LVs. Down-modulation of various antiviral restriction factors including the interferon-induced transmembrane proteins (IFITMs) was achieved with rapamycin as verified by mass spectrometry (LC-MS). Strikingly, rapamycin enhanced transduction by up to 7-fold for CD8-LV and CD4-LV without compromising CAR T cell activities, but did not improve VSV-LV. When administered to humanized mice, CD8-LV resulted in higher rates of GFP gene delivery as well as faster in vivo CAR T cell generation and tumor control. The data favors multi-omics approaches for improvements in gene delivery.