May 01, 2017
HIV researchers at Temple University have become the first in their field to successfully remove the viral infection from the genomes of living animals, advancing progress in the use of powerful gene-editing technology to search for a potential cure in human beings.
Scientists at the Lewis Katz School of Medicine built on a breakthrough reached last spring, when university researchers removed HIV-1 from human T-cells. This time, partnering with colleagues at the University of Pittsburgh, a study team led by Wenhui Hu demonstrated the ability to shut down HIV-1 replication in three different live animal models.
The research, published in the journal Molecular Therapy, relies on the CRISPR/Cas9 genome editing tool, a versatile system that can identify genetic diseases and introduce corrective new genes into living organisms. Bioengineered RNA guides are used to detect and then edit viral strands of DNA.
As a retrovirus, HIV has proven resistant to cures because it introduces replicating copies of itself into the genomes of its host cells. Current antiretroviral drugs can contain the virus and prevent the onset of AIDS, but how to permanently eradicate the infection is still an elusive goal for medical researchers.
Last year, Dr. Hu's team performed a series of proof-of-concept experiments using transgenic mouse and rat models. After introducing HIV-1 DNA into the genome of every tissue in each animal's body, they were able to demonstrate the ability to remove such genetic fragments using CRISPR/Cas9.
In the new study, three different models tested transgenic mice with HIV-1, mice acutely infected with their own equivalent EcoHIV infection, and "humanized" mice with latent HIV-1 placed inside engrafted human immune cells.
"Our new study is more comprehensive," Dr. Hu said. "We confirmed the data from our previous work and have improved the efficiency of our gene editing strategy. We also show that the strategy is effective in two additional mouse models, one representing acute infection in mouse cells and the other representing chronic, or latent, infection in human cells."
In the first model, the RNA expression of viral genes was reduced 60 to 95 percent as shown in the previous study. In the EcoHIV mice, excision efficiency reached 96 percent, marking the first evidence that this method can eradicate the virus. The third model took just one CRISPR/Cas9 treatment to excise viral fragments of latently infected human cells that were embedded in the mice.
"The next stage would be to repeat the study in primates, a more suitable animal model where HIV infection induces disease, in order to further demonstrate elimination of HIV-1 DNA in latently infected T cells and other sanctuary sites for HIV-1, including brain cells," said Dr. Kamel Khalili, a lead researcher who spearheaded the study behind last year's breakthrough. "Our eventual goal is a clinical trial in human patients."