Enveloped viruses get their outer coat by budding from cells they've invaded. CRISPR-Cas9 researchers coopted this behavior to produce envelope-derived vehicles that encapsulate Cas9 proteins (dark green), guide RNA and transgenes. These loaded carriers target and invade specific types of human T-cells, where they simultaneously edit and insert new genes, turning the T-cells into cancer fighters. Credit: Jenny Hamilton, IGI/UC Berkeley
Key points:
- A new delivery method for CRISPR-Cas9 allows for gene editing on specific subsets of cells while they are still in the body.
- This carrier method—enveloped delivery vehicles (EDVs)—involved wrapping the Cas9 editing proteins and guide RNA in a membrane bubble featuring monoclonal antibody pieces to guide them to specific types of blood cells.
- Researchers used EDVs in live mice to selectively edit T-cells to create CAR T-cells that could target and eliminate B cells—a proxy for cancer cells.
A new paper, published in Nature Biotechnology, outlines the recently developed precision-targeted delivery method for CRISPR-Cas9. This technique allows for gene editing on specific subsets of cells while they are still in the body, which is a major step toward a programmable delivery method that would eliminate the need for destroying a patients’ bone marrow and immune system.
“What we’ve tried to achieve in this paper is skipping that whole step of having to engineer cells outside the body,” explained Jennifer Hamilton of the Innovative Genomics Institute. “We aimed to systematically administer a single vector that would do both gene delivery and gene knockout in specific cell types inside the body.”
Researchers wrapped the Cas9 editing proteins and guide RNA in a membrane bubble featuring monoclonal antibody pieces to guide them to specific types of blood cells. This carrier method—enveloped delivery vehicles (EDVs)—was originally developed by altering the viral envelope of an HIV-1 virus and then improved by decorating the outer envelope with more than one antibody fragment or targeting ligand.
The research team employed EDVs to target an immune system T-cell, which is the starting point for the cancer treatment chimeric antigen receptor (CAR) T-cell therapy. They knocked out the native T-cell receptor and delivered a transgene for a receptor that targeted B cells – a proxy for cancer cells.
In their experiment, the researchers treated live mice that were equipped with a humanized immune system. As a result, they transformed the mice’s human T-cells into CAR T-cells that could target and kill immune B cells.
These exciting results demonstrate the potential of the EDVs method to target and edit blood cells in living animals and eventually humans. In fact, the lab’s ultimate goal is to use vectors that work in vivo to make CRISPR therapies more broadly available and cheaper.