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CRISPR-Cas9 gene editing removes HIV-1 from the DNA of human immune cells, preventing reinfection by other, unedited cells.

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While many patients benefits greatly from antiretroviral drugs, once they are stopped, HIV in T-cells start replicating and increasing viral load again. Scientists say this could be preventable by editing patients' DNA:

Scientists edited HIV-1 DNA out of the genome of human immune cells, preventing virus replication and reinfection of the cleared cells.

Using the CRISPR/Cas9 gene editing technique, scientists at Temple University eliminated HIV-1 DNA from T cell genomes in lab experiments, and prevented reinfection after the cells were re-exposed to the virus, they report in a study published in Nature: Scientific Reports.

The CRISPR/Cas9 gene editing method uses RNA proteins to alter targeted sections of DNA in a cell. Previously, scientists at Temple had edited HIV DNA out of human cell lines. The new study, using patient cells grown in the lab, showed cleared cells were no longer susceptible to infection by HIV.

Top Reddit comment:

This sort of thing has been done before (in different ways), by using genetically modified cells to express a Tre recombinase targeting HIV-1 integrated DNA, as well as editing the human CCR5 gene to have the delta-32 mutation, so this approach is not exactly new. What is different however, is that they stably transduced cells to express both the Cas9 protein and the guide RNAs (gRNAs) in a latently-infected human T cell line. This way, the cells persistanly expressed the Cas9/gRNAs capable of excising integrated HIV-1 DNA and were able to prevent further infections by the virus.

The problem here is that current methods of introducing stable exogenous DNA into eukaryotic genomes involve using lentivirus vectors (which is what they do in this paper) that integrate at unpredictable sites within the genome, and risk interrupting a gene important in, say, preventing uncontrolled cell division. This method of transduction runs a considerable risk of the development of cancer. It would be great to introduce CRISPR/Cas9 to the stem cells that give rise to CD4+ T cells, but the method mentioned above, as well as other vectors of delivery, such as adeno-associated virus, form episomes within the nucleus containing the gene(s) of interest, but these are lost upon cell division (as stem cells are certainly wont to do).

Therefore, this isn't exactly an approach that is currently ready for therapeutic use. There are currently ongoing efforts to enhance the ability of Cas9/gRNAs to more specifically target certain sites within the human genome, but these are still a ways off.

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