Scientists at UC San Francisco scientists say that they have genetically reprogrammed T cells without using viruses to insert DNA. The researchers said they expect their technique, which employs CRISPR gene-editing technology, to be widely adopted in the development of cellular therapeutics.
The new method, described in Nature today, offers a molecular "cut and paste" system to rewrite genome sequences in human T cells. It relies on electroporation, a process in which an electrical field is applied to cells to make their membranes temporarily more permeable. After experimenting with thousands of variables over the course of a year, the UCSF researchers found that when certain quantities of T cells, DNA, and the CRISPR "scissors" are mixed together and then exposed to an appropriate electrical field, the T cells will take in these elements and integrate specified genetic sequences precisely at the site of a CRISPR-programmed cut in the genome.
"This is a rapid, flexible method that can be used to alter, enhance, and reprogram T cells so we can give them the specificity we want to destroy cancer, recognize infections, or tamp down the excessive immune response seen in autoimmune disease," said UCSF's Alex Marson, associate professor of microbiology and immunology and senior author of the new study.
But just as important as the new technique's speed and ease of use, said Marson, is that the approach makes it possible to insert substantial stretches of DNA into T cells, which can endow the cells with powerful new properties. To demonstrate the new method's versatility and power, the researchers used it to repair a disease-causing genetic mutation in T cells from children with a rare genetic form of autoimmunity, and also created customized T cells to seek out and kill human melanoma cells.
"There has been thirty years of work trying to get new genes into T cells," said first author Theo Roth, a student pursuing MD and PhD degrees at UCSF, who designed and led the study. "Now there should no longer be a need to have six or seven people in a lab working with viruses just to engineer T cells, and if we begin to see hundreds of labs engineering these cells instead of just a few, and working with increasingly more complex DNA sequences, we'll be trying so many more possibilities that it will significantly speed up the development of future generations of cell therapy."