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Taking a breakthrough in HIV research, scientists at Temple University’s Lewis Katz School of Medicine successfully modified SIV, a virus closely related to HIV, the cause of AIDS, from the genomes of non-human primates. The breakthrough brings Temple researchers and their collaborators closer than ever to developing a cure for human HIV infection.
“We show for the first time that a single inoculation of our CRISPR gene modification construct, carried by an adeno-associated virus, can modify the SIV genome from infected cells in rhesus macaque monkeys,” said Kamel Khalili, PhD, 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 Temple University’s Lewis Katz School of Medicine (LKSOM).
Dr. Khalili was a senior co-researcher on the new study, with Tricia H. Burdo, PhD, Associate Professor and Associate Professor of Education in the Department of Neuroscience at LKSOM, who is an expert on the use of SIV (monkey model macaque immunodeficiency rhesus treated with virus-infected antiretroviral therapy (ART) for studies on the pathogenesis and treatment of HIV; and with Andrew G. MacLean, PhD, Associate Professor at the Tulane National Primate Research Center and the Department of Microbiology and Immunology at Tulane University School of Medicine; and Binhua Ling, PhD, Associate Professor at the Southwest National Primate Research Center, Texas Biomedical Research Institute. Dr. Ling was previously an Associate Professor at the Tulane National Primate Research Center and the Department of Microbiology and Immunology at Tulane University School of Medicine Pietro Mancuso, PhD, an assistant scientist in the laboratory by Dr. Khalili in the Department of Neuroscience at LKSOM, was the first author of the report, which was published online November 27 in the journal Nature Communications.
Of particular importance, the new work shows that the gene-editing construct developed by Dr. Khalili’s team can reach infected cells and tissues known to be viral reservoirs for SIV and HIV. These reservoirs, which are cells and tissues in which viruses integrate into the host’s DNA and hide for years, represent one of the main barriers to curing infections. SIV or HIV in these reservoirs is out of reach for ART, which suppresses viral replication and clears the virus from the blood. As soon as ART is disrupted, viruses emerge from their reservoirs and renew replication.
In non-human primates, SIV behaves very similarly to HIV. “The SIV-infected rhesus macaque model studied in Dr. Burdo’s laboratory is a large animal model that is ideal for recapitulating HIV infection in humans,” explained Dr. Khalili.
Temple scientists have successfully removed viral DNA from non-human primates, a step that could lead to a cure for HIV. Watch this video to find out more.
For the new study, the researchers began by designing a CRISPR-Cas9 gene editing construct specific to SIV. Cell culture experiments confirmed that the editing tool cleaved the SIV integrated DNA in the correct position from the host cell DNA, with a limited risk of potentially damaging gene modification at off-target sites. The research team then packaged the construct into an adeno-associated virus vector 9 (AAV9), which could be injected intravenously into SIV-infected animals.
Dr Burdo, in collaboration with colleagues at the Tulane National Primate Research Center, randomly selected three SIV-infected macaques to each receive a single infusion of AAV9-CRISPR-Cas9, with another animal acting as a control. After three weeks, the researchers collected blood and tissue from the animals. Analyzes showed that in macaques treated with AAV9-CRISPR-Cas9, the gene-editing construct had been distributed to a wide range of tissues, including bone marrow, lymph nodes, and spleen, and reached CD4 + T cells. , which are a significant viral reservoir.
Furthermore, the Temple researchers showed that the SIV genome was indeed cleaved from the infected cells, based on genetic analyzes of the tissues of the treated animals. “The gradual excision of SIV DNA occurred with high efficiency from tissues and blood cells,” explained Dr. Mancuso. The efficiency of excision varied by tissue but reached remarkably high levels in the lymph nodes.
The new study is a continuation of efforts by Dr. Khalili and his colleagues to develop a new gene editing system using CRISPR-Cas9 technology – the subject of the 2020 Nobel Prize in Chemistry – to specifically remove HIV DNA from genomes that host the virus. Researchers have previously shown that their system can effectively clear HIV DNA from cells and tissues in small HIV-infected animal models, including HIV-1 humanized mice.
Co-correspondent author Dr. MacLean is encouraged by the results. “This is a major development in what we hope will be the end of HIV / AIDS,” says MacLean. “The next step is to evaluate this treatment over a longer period of time to determine if we can achieve complete elimination of the virus, possibly even removing subjects from ART.”
Dr. MacLean hopes this treatment strategy will translate into the human population. The biotech company Excision BioTherapeutics, of which Dr. Khalili is a scientific founder and where Dr. Burdo contributes to preclinical research and development and is part of the scientific advisory board, will provide funding and infrastructure for large-scale studies and future clinical trials after approval from the Food and Drug Administration.
“We hope to move our work into human clinical trials soon,” added Dr. Khalili. “People around the world have been suffering from HIV for 40 years and we are now very close to clinical research that could lead to a cure for HIV infection.”
Other contributing researchers include Chen Chen, Dr. Rafal Kaminski, Dr. Jennifer Gordon, Dr. Shuren Liao, Jake A. Robinson, Mandy D. Smith, Dr. Hong Liu, Dr. Ilker K. Sarriyer, Rahsan Sariyer, and Dr. Martina Donadoni, Department of Neuroscience, Center of Neurovirology, Lewis Katz School of Medicine at Temple University; the late Dr. Tiffany A. Peterson, Jaclyn B. Williams and Summer Siddiqui, Division of Comparative Pathology at the Tulane National Primate Research Center; and Dr. Bruce A. Bunnell, Division of Comparative Pathology at Tulane National Primate Research Center, Tulane Brain Institute, the Department of Pharmacology at Tulane University School of Medicine, and the Department of Microbiology, Immunology and Genetics at the University of North Texas Health Science Center, Fort Worth.
Reference: Mancuso P, Chen C, Kaminski R, et al. CRISPR-based modification of proviral SIV DNA in ART-treated non-human primates. Nat Common. 2020; 11 (6065). doi: 10.1038 / s41467-020-19821-7
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