Antiretroviral therapy (ART) is the standard of care for HIV. These drugs can prevent HIV from replicating but they can’t clear the virus from the body altogether. Now, in a step closer to a possible cure for the infection, a team of scientists has removed HIV from mice using the CRISPR-Cas9 gene-editing technology and long-acting ART.
HIV integrates its genetic material into the genomes of the host’s cells, which currently available ART can’t target. In a study in Nature Communications, scientists at Temple University and the University of Nebraska Medical Center said the combination of CRISPR and a newly developed ART successfully eliminated HIV DNA from about 30% of infected mice.
Excision BioTherapeutics, a biotech focused on using CRISPR to treat viral infections, has licensed the gene-editing technology from Temple University, with a plan to advance the platform into human clinical trials. Senior author Kamel Khalili, Ph.D., professor and chair of neuroscience at Temple's Lewis Katz School of Medicine at Temple University, is the founder and principal scientific advisor of Philadelphia-based Excision.
Khalili and his Temple colleagues previously used CRISPR to cut off large fragments of HIV DNA from infected immune cells. However, similar to ART, gene editing alone didn’t completely eliminate HIV. So they figured that a CRISPR-based system could be more effective when the HIV viral load is already controlled at low levels.
For the study, Khalili’s team used a new therapeutic called long-acting slow effective release antiviral therapy (LASER ART), which was co-developed by Howard Gendelman and Benson Edagwa at UNMC. LASER ART packages HIV drugs into nanoparticles that target tissues where latent HIV resides. It dissolves and releases ART slowly, with a higher proportion of the drug entering the circulation, the researchers said. That also helps lessen off-target toxicity.
To test their idea, the team built a mouse model that was engineered to resemble human HIV infection. In two separate experiments, infected mice received either the combination therapy, solo CRISPR or solo LASER ART, or they were left untreated. In the combo group, LASER ART was given used to suppress HIV growth, and then CRISPR was used to eliminate the remaining HIV DNA.
Eight weeks following the last administration of LASER ART and five weeks after the single CRISPR treatment, the animals were observed for evidence of viral rebound. Notably, about one-third of the rodents that got the combo therapy showed no sign of HIV, according to the team. DNA and RNA analysis of the spleen, bone marrow, gut, brain, liver, kidney and lung tissues of the rodents showed no traces of the virus’ genomic material. What’s more, the researchers also found no off-target effects that could be attributed to CRISPR.
The use of CRISPR in HIV stirred up much controversy after Chinese scientist He Jiankui claimed to have used the technology to edit human embryos, resulting in the birth of babies with a mutated form of the CCR5 gene that rendered them resistant to HIV. However, in the current research, CRISPR was not used for germline editing as it was in the China study.
Khalili, Gendelman and colleagues believe that their new approach marks the first time that replication-competent HIV DNA has been eliminated from the genomes of living animals.
“The big message of this work is that it takes both CRISPR-Cas9 and virus suppression through a method such as LASER ART, administered together, to produce a cure for HIV infection,” Khalili said in a statement. “We now have a clear path to move ahead to trials in non-human primates and possibly clinical trials in human patients within the year.”