Researchers attempting to “cut” HIV out of a host cell were surprised to find the virus not only struck back, but grew stronger.
The CRISPR gene-editing tool has been making headlines ever since Chinese researchers last April announced they had used it to modify human embryos in order to cure a fatal blood disorder known as beta thalassemia.
CRISPR are short sections of DNA found in bacteria to help them fight off viruses. The bacteria use a protein called Cas9 like a pair of “scissors” to cut out pieces of the invader’s DNA. They then incorporate that into their own genomes so they can recognise the enemy in future.
In 2012, University of California biochemist Jennifer Doudna and French biologist Emmanuelle Charpentier realised this same system could be used to edit the DNA of any organism, including humans.
Choose which gene you want to modify, use the Cas9 “scissors” to snip it out, swap in the upgrade and the cell repairs the DNA. Here’s the picture version:
Many in the scientific community think it’s was far too early to start experimenting on humans. And a patent war has broken out after a rival method was used to tweak a child’s genes to cure her leukemia.
The implications are as fraught with danger as they are with wonder at the possibility of wiping out all of humanity’s unfortunate and fatal afflictions.
But right now, it looks like CRISPR has met its match – in HIV.
HIV, despite reports of cures three years ago, remains indestrucible. It can be held at bay with antiretroviral drugs, but never eliminated.
And Chen Liang of McGill University AIDS Center in Montreal, Canada, and his team have just found out that so far, HIV can’t even be “edited out”.
They used CRISPR to cut up the viral DNA that had been incorporated into the host’s cell, in the hope that when the cell patched its DNA up again, the scar tissue would hold the viral component at bay.
There was some hope in that it actually succeeded – in some cases.
But in the others, the team found that not only did the scar tissue make the virus stronger, it enabled it to replicate faster.
Worse, because the host cell DNA was patched up with scar tissue, CRISPR wasn’t able to recognise it and go back in for another attack.
According to New Scientist:
“HIV had become resistant to the gene-editing technique.”
So it’s back to the drawing board for Liang and his team, who say that at the very least they have a better understanding of how HIV defends itself against the technique.
“Just as HIV is able to escape all antiretroviral drugs, understanding how HIV escapes only helps you discover better drugs or treatments.”