Retroviral gene delivery is widely used in T cell therapies for hematological cancers. However, viral vectors are expensive to manufacture, integrate genes in semirandom patterns, and their transduction efficiency varies between patients. In this study, several nonviral gene delivery vehicles, promoters, and additional variables were compared to optimize nonviral transgene delivery and expression in both Jurkat and primary T cells. Transfection of Jurkat cells was maximized to a high efficiency (63.0% ± 10.9% EGFP+ cells) by transfecting cells with Lipofectamine LTX in X‐VIVO 15 media. However, the same method yielded a much lower transfection efficiency in primary T cells (8.1% ± 0.8% EGFP+). Subsequent confocal microscopy revealed that a majority of the lipoplexes did not enter the primary T cells, which might be due to relatively low expression levels of heparan sulfate proteoglycans detected via messenger RNA‐sequencing. Pyrin and HIN (PYHIN) DNA sensors (e.g., AIM2 and IFI16) that can induce apoptosis or repress transcription after binding cytoplasmic DNA were also detected at high levels in primary T cells. Therefore, transfection of primary T cells appears to be limited at the level of cellular uptake or DNA sensing in the cytoplasm. Both of these factors should be considered in the development of future viral and nonviral T cell gene delivery methods.

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The innate immune response to cytosolic DNA is intended to protect the host from viral infections, but it can also inhibit the delivery and expression of therapeutic transgenes in gene and cell therapies. The goal of this work was to use mRNA-sequencing to reveal correlations between the transfection efficiencies of four cell types (PC-3, Jurkat, HEK-293T, and primary CD3+ T cells) and their innate immune responses to nonviral gene delivery. Overall, the highest transfection efficiency was observed in HEK-293T cells (87%), which upregulated only 142 genes with no known anti-viral functions. Lipofection upregulated a much larger number (n = 1,057) of cytokine-stimulated genes (CSGs) in PC-3 cells, which also exhibited a significantly lower transfection efficiency. However, the addition of serum during Lipofection and electroporation significantly increased transfection efficiencies and decreased the number of upregulated genes in PC-3 cells. Finally, while Lipofection of Jurkat and Primary T cells only upregulated a few genes, several anti-viral CSGs that were absent in HEK and upregulated in PC-3 cells were observed to be constitutively expressed in T cells, which may explain their relatively low Lipofection efficiencies (8-21%). Indeed, overexpression of one such CSG (IFI16) significantly decreased transfection efficiency in HEK cells to 33%.

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Nonviral gene delivery (NVGD) is an appealing alternative to viral gene delivery for clinical applications due to its lower cost and increased safety. A variety of promising nonviral vectors are under development, including cationic polymers, lipids, lipid-polymer hybrids (LPHs) and inorganic nanoparticles. However, some NVGD strategies have disadvantages that have limited their adoption, including high toxicity and low efficiency. This review focuses on the most common NVGD vehicles with an emphasis on recent developments in the field.