Washington: Scientists are one step closer to creating a drug that could prevent HIV infection and even remove all the dormant copies of the deadly virus from patients with the more advanced disease.
Researchers at Salk Institute for Biological Studies in the US said such a drug could become a reality by customising a powerful defense system used by many bacteria and training this scissor-like machinery to recognise the HIV virus.
When a copy of the HIV virus sneaks into a human cell, it co-opts the cell's own molecular machinery to make copies of the virus's genetic material and then buries these copies in the cell's own genes.
From there, the host's cell becomes an HIV factory, making new copies of the virus to spread throughout the body.
Existing HIV drugs target individual steps of this lifecycle; some stop the virus from integrating into cells' DNA, for instance, while others try to stop the affected cells from producing more virus.
Hsin-Kai Liao, first author of the study and a research associate in the lab of Juan Carlos Izpisua Belmonte, a professor of Salk's Gene Expression Laboratory and senior author of the study, said the problem with these drugs is that they don't actually remove the copies of the virus that are hidden within cells' DNA.
These copies can remain dormant for years and then activate again.
Liao and Belmonte turned to a molecular defense system called CRISPR that bacteria use to cut up foreign DNA at specified spots.
Liao and Belmonte were intrigued by its defensive ability and wondered if CRISPR could be programmed to slice and destroy viruses inside human cells.
CRISPR uses bits of genetic material called guide RNAs to dictate its cuts, so the scientists developed guide RNAs that bind to unique spots on the HIV virus.
They added CRISPR, the guide RNAs and other molecules needed for the system to work to immune cells that had been infected with HIV, and found that CRISPR successfully cut the right spots in HIV's genes, inactivating the virus.
This resulted in the virus being completely removed from up to 72 per cent of cells. CRISPR chopped up loose copies of the virus as they initially infected the cell and also cut up HIV that was hidden and dormant within the cells' DNA.
The Salk team also illustrated in a more complete way how CRISPR targets HIV in living human cells, verifying that it works both before and after the virus is embedded in the genome.
Researchers also added the CRISPR system to human cells before they became infected with HIV. Having the system in place prevented an infection - CRISPR chopped up any copies of the virus before they could start replicating.
The study was published in the journal Nature Communications.