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For the first time, researchers completely eliminate HIV from mouse genome


HIV is a retrovirus that integrates into the genome of target cells with the aim of multiplying and eventually leading to widespread infection leading to AIDS. It also has the ability to camouflage itself in the eyes of the immune system. Current treatments are based on the use of antiretroviraldrugs aimed at reducing the viral load in the body, without eliminating the virus itself. However, a new study, combining modified anti-retroviraldrugs and the genetic editing technique CRISPR, has completely eliminated the virus in mice.


Anti-retroviral drugs work best on viruses that actively multiply and infect healthy cells. HIV has evolved to "learn" this and can mutate to become resistant to antiretrovirals, so that as soon as the antiviral molecule fades, the viruses replicate again in large quantities. HIV can also be preserved by hiding, resting and not reproducing, in the lymph and other body tissues.

When the immune system drops its guard, these latent viruses can start to replicate again. This means that once a person is infected, these viruses remain in the body, waiting to overwhelm the immune system of millions of viruses, years or even decades after HIV has infected its first cell. Finding and eliminating all traces of the virus would be a much better solution than antivirals. But so far, researchers have not been able to do so.

In a study published in the journal Nature Communications, researchers report a possible new way to eliminate HIV from the genome of an infected animal. In a study of 29 mice, the team used a combination of modified antiretroviral therapy to maintain low activity levels and a powerful gene-editing technique to extract HIV genes infected cells.

More effective antiretrovirals thanks to the LASER ART technique

In various tests, scientists found no trace of the virus in 30% of the animals. "This observation is the first step in showing, to my knowledge, that HIV is a curable disease," says one of the study's lead authors, Kamel Khalili, director of the Neurovirology Centre at the University's Lewis Katz School of Medicine.

A diagram illustrating the cycle of HIV infection and replication. Anti-retroviral drugs work by blocking the back-transcription of viral RNA. Credits: study.com

First, the researchers reduced the active replication rate of the virus in the blood using conventional antiretroviral drugs modified by a process called LASER ART. The process was developed by Dr. Howard Gendelman, Chair of Pharmacology and Experimental Neuroscience at the University of Nebraska Medical Center, and the second lead author of the study.

With LASER ART, traditional anti-HIV drugs are refined to develop a crystalline structure and then enclosed in fat-soluble particles. This allows them to slip through cell membranes in places where HIV tends to hide, such as the liver, lymphatic tissue squeals and spleen. Once inside, cell enzymes begin to release the drug.

An anti-retroviral/CRISPR combination to effectively eliminate HIV

The crystalline structure releases drugs more slowly, allowing them to continue to eliminate dormant viruses as they appear and replicate them for months rather than days or weeks, such as forms conventional drug products. The second step was to use the CRISPR-cas9 gene-editing tool to dissociate HIV from all circulating cells infected with viral genes, cells that anti-HIV drugs have missed.


Khalili had previously used CRISPR to successfully extract HIV genes from human cells in the laboratory, as well as those from animals. But, used alone, CRISPR is not enough; once HIV replicates, so many copies are released that it is not possible for CRISPR to edit them all. In fact, some of the mice were treated with CRISPR alone, and some with LASER ART alone; in both groups, HIV levels finally rebounded over the five- to eight-week study period.

The graph at the top shows the evolution of CD4 lymphocyte levels in a healthy (green) and HIV-infected (red) individual. The bottom graph shows changes in CD4 levels in an untreated infected individual (red), treated with CRISPR (black), treated with LASER ART (blue), and with a COMBINATION of LASER ART-CRISPR (green). In the latter case, the results show a complete elimination of the virus. Credits: Prasanta K. Dash et al. 2019

However, when combined with laser treatment, both treatments effectively eliminated HIV from animals in the trials.

The Power of Genetic Therapy Against HIV

« Over the years, we have considered HIV an infectious disease. But once it enters the cell, it is no longer an infectious disease, but becomes a genetic disease because the viral genome is incorporated into the host genome," Khalili explains. "In order to cure the disease, we need a genetic strategy. Gene editing gives us the opportunity to remove viral DNA from host chromosomes without harming the host's genome ».

CRISPR-cas9 technology was remarkably accurate in animal testing, purifying only HIV genes without making unwanted cuts elsewhere in mouse DNA. In addition, the researchers also took immune cells, targeted by HIV as hosts, from animals treated with LASER ART and CRISPR, and transferred them to healthy animals to determine if they were developing HIV infection that could have persisted. No infections occurred.

We are quite confident of the result and delighted to find that in small animals, using the technology and method we have developed, we can get what we call a sterilizing treatment or elimination of the virus. Khalili said.

The team is already testing the therapy in non-human primates and hopes to confirm the same results. If the tests are successful, this would pave the way for human testing.

In 2015, Khalili co-founded Philadelphia-based Excision Biotherapeuticsto conduct future human trials using this treatment method, and is optimistic about this approach. "It seems that CRISPR could be the way to eliminate HIV permanently, that's what we hope," he concludes.



Bibliography:

Sequential LASER ART and CRISPR Treatments Eliminate HIV-1 in a Subset of Infected Humanized Mice
Prasanta K. Dash, Rafal Kaminski, Ramona Bella, Hang Su, Saumi Mathews, Taha M. Ahooyi, Chen Chen, Pietro Mancuso, Rahsan Sariyer, Pasquale Ferrante, Martina Donadoni, Jake A. Robinson, Brady Sillman, Zhiyi Lin, James R. Hilaire, Mary Banoub, Monalisha Elango, Nagsen Gautam, R. Lee Mosley, Larisa Y. Poluektova, JoEllyn McMillan, Aditya N. Bade, Santhi Gorantla, Ilker K. Sariyer, Tricia H. Burdo, Won-Bin Young, Shohreh Amini, Jennifer Gordon, Jeffrey M. Jacobson, Benson Edagwa, Kamel Khalili & Howard E. Gendelman
Nature Communications
volume 10, Article number: 2753 (2019)

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