Controversial gene-editing procedure to fight AIDS is again being considered by scientists, despite disastrous results a decade ago

Monday, March 05, 2018 by

When the Centers for Disease Control and Prevention announced last year that people who take HIV medication religiously for six months can theoretically get to point where they can’t transmit the virus, it was considered a huge advancement. There remains no cure for HIV and AIDS, although it is not the death sentence that it used to be. There have been triumphs and setbacks in the quest to find a cure, and now scientists are considering revisiting a past disaster in hopes of emerging victorious this time around.

A controversial gene editing procedure is at the heart of the new approach. Gene editing recently gained FDA approval for treating cancer and one type of blindness, and some researchers are hoping that HIV/AIDS can soon be added to the list.

Gene therapy has already helped some patients make their cells more resistant to HIV. In 2014, scientists removed some of Matt Chappell’s blood cells, disabled a gene in order to help the cells resist the HIV virus, and then returned the edited cells to his body. It has been the closest thing to a cure for Chappell, who has gone from taking the strongest AIDS drugs available for more than a decade to not needing the medications at all for more than three years. His body even managed to keep the virus in check in the midst of cancer treatments that wreaked havoc on his immune system last year.

Chappell’s story is far from ordinary. Of the 100 people who took part in those experiments, just a few of them were able to give up their HIV drugs in the long run. The rest of them still have to take medication to suppress their HIV.

Despite these discouraging numbers, the researchers want to give it another try. They believe that they can improve this treatment and are now testing some tweaked approaches in which they’ve doctored DNA in a different way.

Temple University researchers have developed a method of gene editing that can detect HIV DNA in a person’s T-cell genome, which is a set of DNA pertaining to a certain kind of white blood cells. When this DNA has been edited out, the loose genome ends that were previously attached to the HIV will be rejoined by the DNA repair system within the cell. This leaves the cell free from HIV and protected from new infections.

Success is far from guaranteed

Gene editing approaches were inspired by the case of Timothy Brown, who is one of just two people in history who have been cured of HIV. His remarkable cure came after a bone marrow transplant for leukemia involving stem cells from a donor who was naturally immune to HIV. Because the donor did not have the common gene that creates the entryway used by HIV to infect T cells, he was given protection from the virus. Past attempts at replicating this procedure have been deadly, however, with all six patients dying within a year. Now, the scientists are using gene editing tools to edit the patient’s own T cells instead.

Meanwhile, scientists at the University of Pennsylvania are working on a two-pronged approach. In addition to editing out the HIV entryway gene, they are adding a gene that will help T cells to identify HIV and kill it.

These developments would be exciting were it not for the fact that interfering with nature in the way that gene editing does can lead to unintended mutations in genomes with far-reaching consequences. Researchers from Columbia University Medical Center warned last year that this is a distinct possibility with methods like CRISPR and urged scientists to consider the potential dangers of off-target mutations.

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