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Scientists eliminate HIV from DNA of human cells

Tuesday, Mar 22, 2016,16:54 IST By Metrovaartha A A A

Washington | Using a specialised gene editing system, scientists have shown that they can effectively eliminate HIV from the DNA of human cells, paving the way for a cure for patients infected with the virus that causes AIDS.

Antiretroviral drugs are very good at controlling HIV infection. But patients on antiretroviral therapy who stop taking the drugs suffer a rapid rebound in HIV replication, said Kamel Khalili, at the Lewis Katz School of Medicine at Temple University in US. The presence of numerous copies of HIV weakens the immune system and eventually causes acquired immune deficiency syndrome, or AIDS. Eliminating the HIV virus after it has become integrated into CD4+ T-cells, the cells primarily infected with the virus, has proven difficult. Recent attempts have focused on intentionally reactivating HIV, aiming to stimulate a robust immune response capable of eradicating the virus from infected cells.

However, none of these shock and kill approaches has been successful. Researchers targeted HIV-1 proviral DNA (the integrated viral genome) using uniquely tailored gene editing technology. Their system includes a guide RNA that specifically locates HIV-1 DNA in the T-cell genome, and a nuclease enzyme, which cuts the strands of T-cell DNA. Once the nuclease has edited out the HIV-1 DNA sequence, the loose ends of the genome are reunited by the cell’s own DNA repair machinery.

Researchers focused on infected CD4+ T cells to show that the technology eliminates the virus from cells and also its persistent presence in HIV-1-eradicated cells protects them against reinfection. The researchers carried their work over to ex vivo experiments, in which T-cells from patients infected with HIV were grown in cell culture, showing that treatment with the gene editing system can suppress viral replication and dramatically reduce viral load in patient cells.

Using an approach known as ultra-deep whole-genome sequencing, researchers analysed the HIV-1-eradicated cell genomes for mutations in genes outside the region targeted by the guide RNA. Their analyses ruled out off-target effects on genes, including potential collateral effects on cellular gene expression. Studies of cell viability and proliferation showed that HIV-1-eradicated cells were growing and functioning normally.

The findings demonstrate the effectiveness of our gene editing system in eliminating HIV from the DNA of CD4 T-cells and, by introducing mutations into the viral genome, permanently inactivating its replication, Khalili said. They show that the system can protect cells from reinfection and that the technology is safe for the cells, with no toxic effects, he said.

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