Using the modified CRISPR-Cas9 gene-editing system and a therapeutic strategy known as long-acting slow-effective release antiviral therapy (LASER ART), a team of researchers has eliminated replication-competent HIV-1 DNA from the genomes of living mice. Published in the journal Nature Communications, the study marks a critical step toward the development of a possible cure for human HIV infection.
“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,” said Professor Kamel Khalili, from the Lewis Katz School of Medicine at Temple University.
Current HIV treatment focuses on the use of antiretroviral therapy (ART), which suppresses HIV replication but does not eliminate the virus from the body.
Therefore, the therapy is not a cure for HIV, and it requires life-long use. If it is stopped, HIV rebounds, renewing replication and fueling the development of AIDS.
HIV rebound is directly attributed to the ability of the virus to integrate its DNA sequence into the genomes of cells of the immune system, where it lies dormant and beyond the reach of antiretroviral drugs.
In previous work, Professor Khalili and colleagues used CRISPR-Cas9 to develop a novel gene editing and gene therapy delivery system aimed at removing HIV DNA from genomes harboring the virus.
In rats and mice, they showed that the gene-editing system, dubbed AAV9-CRISPR-Cas9, could effectively excise large fragments of HIV DNA from infected cells, significantly impacting viral gene expression. Similar to ART, however, gene editing cannot completely eliminate HIV on its own.
For the new study, the researchers combined their gene-editing system with the LASER ART therapy, which targets viral sanctuaries and maintains HIV replication at low levels for extended periods of time, reducing the frequency of ART administration.
The long-lasting medications were made possible by pharmacological changes in the chemical structure of the antiretroviral drugs. The modified drug was packaged into nanocrystals, which readily distribute to tissues where HIV is likely to be lying dormant. From there, the nanocrystals, stored within cells for weeks, slowly release the drug.
“We wanted to see whether LASER ART could suppress HIV replication long enough for CRISPR-Cas9 to completely rid cells of viral DNA,” Professor Khalili said.
To test their idea, Professor Khalili and co-authors used mice engineered to produce human T cells susceptible to HIV infection, permitting long-term viral infection and ART-induced latency.
Once infection was established, mice were treated with LASER ART and subsequently with CRISPR-Cas9.
At the end of the treatment period, mice were examined for viral load.
Analyses revealed complete elimination of HIV DNA in about one-third of HIV-infected mice.
“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,” Professor Khalili said.
“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.”
Prasanta K. Dash et al. 2019. Sequential LASER ART and CRISPR Treatments Eliminate HIV-1 in a Subset of Infected Humanized Mice. Nature Communications 10, article number: 2753; doi: 10.1038/s41467-019-10366-y