Bacterial antivirus system repurposed to attack HIV where it’s hiding

As part of its normal life cycle, HIV inserts a copy of itself into the genome of every cell it infects. Most of these copies go on to cause an active infection, pumping out new copies of the virus. A few of them, however, go quiet and can persist even during aggressive antiviral treatments. These infected cells act as a reservoir for the virus, reestablishing an active infection if antiviral therapies are ever stopped. Eliminating this viral reservoir has proven extremely difficult.

Now, researchers are reporting on some of the first tests of a technique that targets the copies of the virus that are lurking in cells with a quiescent infection. Using a system that bacteria utilize to disable viruses, they've shown that it's possible to precisely edit out key HIV DNA sequences, essentially inactivating any copies of the virus. And if placed in cells prior to exposure to HIV, the same system effectively blocks infection.

Bacteria don't have an immune system, but that doesn't mean they have no defenses against viruses. When infected, the bacteria can make special RNAs that match the DNA sequences of the virus. These RNAs then guide a protein called Cas9 to the viral DNA, which the protein then cuts. The cut inactivates the virus, protecting the bacteria. The whole system (called CRISPR/Cas) is incredibly flexible; given the right RNA, it can be turned loose on pretty much any DNA sequence. Researchers have shown that it can be used to cut the DNA of living human cells, effectively editing their contents.