How CRISPR-Cas genome editing might one day be used to cure HIV

One of the most significant challenges in treating HIV is the virus’ ability to integrate its genome into the host’s DNA. This means that lifelong antiretroviral therapy is essential as latent HIV can reactivate from reservoirs as soon as treatment ends.

One potential technique being developed to address this problem is the use of gene editing technology to cut out and incapacitate HIV from infected cells. Currently, there is a Phase I/II Clinical Trial underway in people with HIV-1 (the most common strain of HIV)

Now, new research from another team shows that gene editing can be used to eliminate all traces of the HIV virus from infected cells in the laboratory.

The research is being presented early ahead of the European Congress of Clinical Microbiology and Infectious Diseases, which will be held from 27-30 April in Barcelona, Spain. It’s been carried out by scientists from the Amsterdam Medical University in the Netherlands, and the Paul Ehrlich Institute in Germany, and has not yet been submitted for peer review.

“Our aim is to develop a robust and safe combinatorial CRISPR-Cas regimen, striving for an inclusive ‘HIV cure for all’ that can inactivate diverse HIV strains across various cellular contexts,” they write in a conference abstract submitted ahead of ECCMID.

CRISPR-Cas gene editing technology acts like molecular scissors to cut DNA and either delete unwanted genes or introduce new genetic material, while guidance RNA (gRNA) tells CRISPR-Cas exactly where to cut at designated spots on the genome.

In this research, the authors used 2 gRNAs that target “conserved” parts of the viral genome – this means they remain the same or conserved across all known HIV strains. This genetic sequence does not have a match in human genes, to prevent the system going off target and causing mutations elsewhere in the human genome.

The hope is to one day provide a broad-spectrum therapy capable of combating multiple HIV variants effectively. But before this dream can become a reality, the researchers had to address a number of issues with getting the CRISPR-Cas reagents into the right cells.

To delivered CRISPR components into cells in the body a viral vector, containing genes that code for the CRISPR-Cas proteins and gRNA, is used. This is the vehicle that delivers into the host cell the instructions to make all necessary components, but these instructions need to be kept as simple and short as possible.

Another issue is making sure the viral vector enters HIV reservoir cells– specifically cells that express the receptors CD4+ and CD32a+ on their surface.

They found that in one system, saCas9, the vector size was minimised, which enhanced its delivery to HIV-infected cells. They also included proteins that target the CD4+ and CD32a+ receptors specifically in the vector.

This system showed outstanding antiviral performance, managing to completely inactivate HIV with a single guide RNA (gRNA) and excise (cut out) the viral DNA with two gRNAs in cells in the lab.

“We have developed an efficient combinatorial CRISPR-attack on the HIV virus in various cells and the locations where it can be hidden in reservoirs and demonstrated that therapeutics can be specifically delivered to the cells of interest,” the authors write.

“These findings represent a pivotal advancement towards designing a cure strategy.”

But the researchers stress that, while these preliminary findings are very encouraging, it is premature to declare that there is a functional HIV cure on the horizon.

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