{"id":1769,"date":"2023-06-01T21:55:27","date_gmt":"2023-06-01T21:55:27","guid":{"rendered":"https:\/\/www.idtdna.com\/page\/an-optimized-workflow-for-virus-free-generation-of-trac-replaced-car-t-cells"},"modified":"2025-10-01T17:54:42","modified_gmt":"2025-10-01T17:54:42","slug":"an-optimized-workflow-for-virus-free-generation-of-trac-replaced-car-t-cells","status":"publish","type":"post","link":"https:\/\/www.idtdna.com\/page\/support-and-education\/decoded-plus\/an-optimized-workflow-for-virus-free-generation-of-trac-replaced-car-t-cells\/","title":{"rendered":"An optimized workflow for virus-free generation of TRAC-replaced CAR T cells"},"content":{"rendered":"

Introduction<\/h2>\n

Chimeric antigen receptors (CAR) are proteins that can be expressed by genetically modified T cells (immune response cells) to allow them to react with specified targets. These CAR T cells can currently be used to target some hematological malignancies (cancers that originate in the blood or bone marrow). Research is also currently underway to assess the utility of CAR T cells for targeting autoimmune diseases, solid tumor cancers, as well as liver and cardiac fibrosis [1-3<\/a>].<\/p>\n

Currently, lentiviral or adeno-associated virus (AAV)-mediated gene transfer is the standard method for CAR T cell manufacturing. This method uses viruses to introduce genetic information in T cells in a highly efficient manner. However, there are important issues that surround these manufacturing processes such as excessive CAR expression levels which can lead to cell exhaustion and death [1,4<\/a>] as well as high production costs . An alternative approach to manufacturing CAR-T cells involves the targeted integration of CAR trans gene into the T cell receptor (TCR) alpha constant chain (TRAC) gene locus using CRISPR\/Cas9 technology. Early studies have found that this approach can help solve the problem of excessive expression, provide control of site integration, and allow for the monitoring off-target effects [4<\/a>].<\/p>\n

Studies that have used the TRAC approach have largely relied on transduction with a recombinant adeno-associated virus serotype 6 (rAAV6), meaning that to manufacture CAR T cells at-scale would still be resource heavy and expensive. To solve this issue, Kath et al<\/em>. aimed to use a virus-vector-free method to integrate CARs into the TRAC locus of T cells. Previous work has successfully generated CAR T cells without relying on viral vectors [5,6<\/a>]. Kath et al<\/em>. built upon these findings and optimized this process.<\/p>\n

Optimization of virus-free CAR T cell engineering<\/h2>\n

The first step in optimizing a virus-free CAR T cell engineering workflow using CRISPR\/Cas9 technology was to select the correct guide RNA (gRNA)<\/a> for inserting their CD19-targeting CAR. This first step is important because each gRNA will have a unique off-target profile and because off-target effects can have severe detrimental impacts on cells [7<\/a>] it is important to choose a gRNA with the lowest amount of these effects as possible. Off-target effects can also be limited by the use of engineered nucleases, such as HiFi-Cas9, which result in lower off-target editing while maintaining on-target potency [8<\/a>]. Following gRNA and nuclease selection, a donor template for homology-directed repair (HDR) can be designed<\/a> that has the homology arms aligned with the cut-site.<\/p>\n

Then, Kath et al<\/em>. needed to optimize the conditions in which pre-electroporated T cells were prepared as well as the actual electroporation conditions. More specifically this involved determining how many activated T cells were needed in their electroporation solution, how much Cas9 enzyme, gRNA, and HDR template<\/a> were needed per electroporation, and determining how different pre-electroporation conditions impacted CAR insertion rates — i.e., T cells stimulation with activator beads vs plate-bound antibodies and commercial electroporation buffer. The researchers determined that plate-bound antibodies in combination with the self-made buffer would result in the ideal CAR insertion rate.<\/p>\n

HDR enhancer with dsDNA sensory inhibitor increases knock in efficiency and CAR T cell yield<\/h2>\n

The next hurdle to overcome was prevent the loss of viability to T cells once the HDR template<\/a> was transfected. This largely happens as a result of the immune pathways that are present in T cells, when large amounts of DNA are detected, the T cell has natural defense system to prevent that DNA from replicating [9<\/a>]. To work around this, the researchers temporarily inhibited the cell’s intracellular dsDNA sensors using small molecules. However, their results showed that it was more effective to expose the T cells to smaller amounts of dsDNA during electroporation, rather than to use an intracellular dsDNA sensory inhibitor.<\/p>\n

Interestingly, other efforts to increase the efficiency of CAR insert rates showed more promising results. The use of an HDR enhancer<\/a> showed an average of 38% increase in CAR insertion rate. Further, when the HDR enhancer was combined with the previously tested dsDNA sensory inhibitors, Kath et al<\/em>. observed an even further increase in TRAC CAR T cell yields. The synergistic enhancement of relative knock-in rate and absolute CAR T cell yield using these two reagents is important because it makes a virus-free approach to CAR T cell engineering much more efficient. <\/p>\n

Kath et al<\/em>. then went on to test the functionality of the TRAC-replaced CAR T cells they generated using their workflow. More specifically, they needed to check that the HDR enhancer and dsDNA sensory inhibitors did not influence the way the CAR T cells behaved in vitro. They found that the CAR T cells generated using the new workflow were as effective as CAR T cells generated without the enhancer and inhibitors. These research findings were further confirmed in vivo using animal models.<\/p>\n

Conclusion<\/h2>\n

The optimization of virus-free TRAC-replaced CAR T cell generation is an important milestone for this field of research. By using commercially available reagents, Kath et al. has provided a workflow that can be easily implemented in labs without needing to rely on time and resource consuming viral production. Further, the use of an HDR enhancer and a dsDNA sensory inhibitor to increase the efficiency of CAR T cell generation without adverse effects to functionality, makes this workflow an attractive alternative to retroviral transduction manufacturing techniques.<\/p>\n

Further research is needed to fully evaluate the CAR T cells generated through this method, however the results presented by Kath et al<\/em>. clearly illustrate the promise that this new workflow has in circumventing the issues currently presented by CAR T cell manufacturing.<\/p>\n","protected":false},"excerpt":{"rendered":"

Introduction Chimeric antigen receptors (CAR) are proteins that can be expressed by genetically modified T cells (immune response cells) to allow them to react with specified targets. These CAR T cells can currently be used to target some hematological malignancies (cancers that originate in the blood or bone marrow). Research is also currently underway to […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"ct_builder_shortcodes":"","ct_template_type":"","ct_parent_template":0,"inline_featured_image":false,"footnotes":""},"class_list":["post-1769","post","type-post","status-publish","format-standard","hentry"],"acf":[],"yoast_head":"\nAn optimized workflow for virus-free generation of TRAC-replaced CAR T cells | IDT<\/title>\n<meta name=\"description\" content=\"Kath J, Du W, Pruene A, et al. 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