Bacteriophage T4 model for viral basis to advance gene therapy
Benigara B. Rao.Victor Padilla-Sanchez, Andrew Fokine, Zingen Zhu
Modified bacteria-killing viruses known as phages can deliver much more DNA to human cells than is possible with existing technology. This ability could lead to major advances in cell and gene therapy, as more sophisticated modifications can be made to cells in one step.
This modified virus can carry DNA strands up to 171,000 base pairs long. This is about 20 times larger than the largest existing virus used for gene therapy. In addition to this DNA, it can carry more than 1,000 other molecules, including RNA and proteins, said Benigara Rao of the Catholic University of America in Washington, DC.
“All of these things can be combined in one particle, and not just treatment, but potentially healing,” says Rao.
Although there are an increasing number of therapeutic modalities that modify cells inside or outside the body, delivering the necessary components to the cells remains a major challenge.
For example, some people develop a disorder called Duchenne muscular dystrophy that causes progressive muscle weakness because of mutations in the gene for a protein called dystrophin. Efforts to develop a gene therapy for this condition are hampered by the fact that a DNA approximately 11,000 base pairs long is required to make the full-size dystrophin protein. This exceeds the amount compatible with existing viruses.
In one experiment, Rao’s team introduced the dystrophin gene into human cells growing in culture and showed that the cells produced the full-size protein.
In another experiment, the researchers were able to pump multiple molecules into human cells at once, edit multiple genes, switch off others, and enable each cell to make a variety of proteins, all of which is possible. enabled at the same time.
Modified delivery viruses are usually based on the T4 bacteriophage, which infects only specific types of bacteria. Thanks to work by Rao’s team and other research groups, the T4 virus is well understood enough to be significantly modified and customized.
In particular, Rao’s team added a coating that allows the virus to be engulfed by human cells and take its cargo inside.
These modified viruses don’t need to be propagated inside human cells, making them much easier and cheaper to produce than the viruses currently used for gene therapy, Rao said.
But Rao and colleagues have yet to demonstrate that viruses can be used to carry genes to cells in the body, says Jeffrey Chamberlain of the University of Washington in Seattle. His team is trying to develop a gene therapy for splitting Duchenne muscular dystrophy. Genes among multiple viruses.
“Nonetheless, the early data are encouraging, and it will be interesting to follow developments going forward,” says Chamberlain. Additional systems that deliver gene therapy to different cells and organs in the body are sorely needed, he says.
Rao said it may take a lot of extra work to get the virus to work well in humans, but he believes it’s doable. More directly, the modified virus could be used to modify cells outside the body to treat humans.
For example, some cancers are now treated by modifying immune cells to target tumors. This often involves several steps. A virus is first used to introduce the targeted gene, and then the gene-editing components are separately introduced to make additional modifications. The result is a mix of cells that do not have the desired changes, making them less effective when injected into cancer patients.
The ability to deliver targeted genes and gene-editing components in a single virus would greatly improve the process.
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