How Modified Gene-Editing Can Bring HIV Out of Hiding
Last week HIV Equal reported how scientists using a gene editing system called CRISPR Cas9 have successfully snipped HIV right out of T cells, at least in an experiment conducted “ex vivo,” or outside the body.
But researchers also have figured out a way to use CRISPR Cas9 to attack HIV. In the current edition of Molecular Therapy, scientists at The Scripps Research Institute and other laboratories report how they have used a version of the gene editing system to reactivate latent HIV that hides throughout the body, also known as “the shock” or “the kick” approach.
The issue of latent HIV that squirrels away in the gut, lymphoid tissues, bone marrow and the brain and essentially “goes to sleep” is one of the greatest obstacles to curing HIV. While modern antiretroviral therapy keeps the virus from replicating, once a person goes off their medication the virus usually comes roaring back to life because the latent HIV comes out of hiding.
So finding a way to blast that latent HIV out of its hiding spots is an important part of the goal of eradicating the virus.
“Several latency-reversing agents (LRAs) have been investigated to drive HIV out of hibernation by activating transcription of the HIV genome, yet many have nonspecific and unpredictable effects on cells, leading to a disruption of normal cell division or toxicity and making them unfavorable as therapeutics,” writer Elie Diner reported in the latest issue of Scripps News and Views.
Diner reports that the Scripps team used what’s called the “dead” (dCas9) system to go after latent HIV in a more targeted manner.
“RNA-guided CRISPR activation provides an exciting new avenue for targeted reactivation of latent HIV,” the researchers report in their paper. “Should a large subset of the latent reservoir be found to exist independent of cell state, such treatments may prove largely ineffective. Because of this, targeting the viral promoter using a CRISPR activation approach may prove to be a more efficient long-term treatment strategy as activation is decoupled from cellular activity.”
In other words, therapies currently being investigated to rouse latent HIV from a cell depend on that cell having working machinery. But recent research shows that HIV can awaken from a cell even when the cells itself isn’t working properly.
“That an intrinsic viral program autonomously regulates viral latency independently of the cellular state may prove problematic to current proposed treatment strategies that depend largely on the use of cellular transcription factors and epigenetic regulators to activate latent virus,” the researchers reported in their paper.
The scientists believe they have found an RNA, sgRNA, sg362F, “that is not only potent across a plethora of latency cell models but also highly specific in its actions by not involving cellular activation pathways,” they report.
“These elements all represent highly desirable features in the quest for a novel latency-purging agent,” the authors conclude. “We have identified and characterized a highly potent latency activator using the CRISPR activation machinery and unique sgRNA that target the viral enhancer sequence. While more is needed to develop a targeted delivery approach and functional analysis of latency reactivation in a clinical setting (on tests inside the human body), CRISPR activation represents a promising tool for the specific and targetable activation of latent HIV reservoirs.”