A team of researchers from the Lewis Katz School of Medicine at Temple University (LKSOM) and the University of Nebraska Medical Center (UNMC) has brought us one step closer toward the development of a possible cure for human HIV infection. Their collaborative efforts have for the first time eliminated replication-competent HIV-1 DNA—the virus responsible for AIDS—from the genomes of living animals. The study was published in the journal Nature Communications.
Kamel Khalili, Ph.D., Laura H. Carnell Professor and Chair of the Department of Neuroscience, Director of the Center for Neurovirology, and Director of the Comprehensive NeuroAIDS Center at LKSOM, and one of the (two) senior investigators on the new study said:
Our study shows that treatment to suppress HIV replication and gene editing therapy, when given sequentially, can eliminate HIV from cells and organs of infected animals.
Howard Gendelman, MD, Margaret R. Larson Professor of Infectious Diseases and Internal Medicine, Chair of the Department of Pharmacology and Experimental Neuroscience and Director of the Center for Neurodegenerative Diseases at UNMC, also a senior investigator on the new study, added:
This achievement could not have been possible without an extraordinary team effort that included virologists, immunologists, molecular biologists, pharmacologists, and pharmaceutical experts. Only by pooling our resources together were we able to make this groundbreaking discovery.
ART
Currently, the only treatment for HIV is antiretroviral therapy (ART). It involves powerful anti-HIV medications called anti-retroviral drugs (ARVs) which can suppress HIV enough to keep it at levels so low they’re undetectable in the blood. These drugs drastically lower the chance of someone spreading the virus during sexual activity or transfusions. But the person has to take the medication for the rest of their lives because as soon as they stop, the dormant virus comes out of hiding and starts replicating again and fueling the development of AIDS. That’s because ART suppresses HIV replication but does not eliminate the virus from the body.
The HIV virus is able to rebound because it integrates its DNA sequence into the genomes of cells of the immune system, where it lies dormant and beyond the reach of antiretroviral drugs. Time explains it as such: “Once a person is infected, these viruses remain in the body like an uncapped grenade, just waiting to overwhelm the immune system with millions of infectious virus, years, or even decades, after HIV infected its first cell.” Of course, finding and eliminating every trace of the virus would be a far better solution; one that researchers have been searching for with no avail, until maybe now.
Gene Editing
In a previous study, Dr. Khalili’s team used CRISPR-Cas9 technology to develop a novel gene editing and gene therapy delivery system designed to remove the HIV DNA from genomes harboring the virus. The team tested out their system in rats and mice. The results revealed that the gene-editing system was able to effectively excise large fragments of HIV DNA from infected cells, thus significantly impacting viral gene expression. Although, it could not completely eliminate HIV on its own. Nonetheless, the CRISPR-cas9 technology was remarkably accurate and precise, splicing out just HIV genes without making unwanted cuts elsewhere in the DNA of the mice.
Dr. Khalili said:
Over the years, we have looked at HIV as an infectious disease. But once it gets into the cell, it’s no longer an infectious disease but becomes a genetic disease because the viral genome is incorporated into the host genome. In order to cure the disease, we need a genetic strategy. Gene editing gives us the opportunity to eliminate viral DNA from host chromosomes without hurting the host genome.
In another study with CRISPR, Dr. Khalili used the technology to successfully snip out HIV genes from human cells in a lab dish, as well as from lab animals. These experiments also failed, in the long run, proving that when used alone, CRISPR isn’t enough; once HIV replicates, it churns out so many copies that it’s not possible for CRISPR to edit them all.
Gene Editing + LASER ART
In the new study, the team used a combination of a modified ARV treatment to keep the virus at low activity levels, along with a powerful gene-editing technique that snipped out HIV genes from infected cells. The modified ARV treatment is a process called LASER ART that was developed by Dr. Gendelman.
With LASER ART, traditional anti-HIV drugs are tweaked so they develop a crystal structure. They are then encased in fat-soluble particles thus enabling them to slip through the membranes of cells in places where HIV tends to hide, like the liver, lymph tissue, and spleen. The cells’ enzymes start to release the drug once they are inside. The crystal structure releases the drugs more slowly, allowing them to continue killing off dormant viruses for months as they start to emerge and replicate. In comparison, conventional forms of medicine release drugs for only days or weeks.
“We wanted to see whether LASER ART could suppress HIV replication long enough for CRISPR-Cas9 to completely rid cells of viral DNA,” said Dr. Khalili. So they conducted another study.
The Study
- 29 mice were involved.
- First, ARV drugs modified by LASER ART were administered to reduced actively replicating virus in the blood.
- Second, the gene-editing tool CRISPR-cas9 was used to splice out HIV from any circulating cells that are infected with viral genes—cells that the ARV drugs missed.
The Results
The mice that were treated with CRISPR alone, or with LASER ART alone were not cured. The levels of HIV rebounded in both of these groups at some point during the five to eight week study period. But, when combined, the two therapies effectively eliminated HIV from animals in the trials.
Dr. Khalili said:
We’re pretty confident with the outcome and very pleased to see that in small animals, using the technology and method we developed, one can achieve what we call a sterilizing cure, or elimination of the virus. It seems that CRISPR might be the way to cure HIV—that’s what we’re hoping.
After various tests, the scientists could find no trace of the virus in 30% of the animals. They even took immune cells (which HIV tends to target as hosts) from the animals treated with both LASER ART and CRISPR and transferred them to healthy animals to see if they developed HIV infection from any virus that may have remained. None did. “This observation is the first step toward showing for the first time, to my knowledge, that HIV is a curable disease,” said Dr. Khalili.
Human Trials On The Horizon
The team has begun testing the therapy in non-human primates. They are hopeful that they will achieve the same results. If so, they will be able to begin testing on humans.
Dr. Khalili said:
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. 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.
