Gene editing approaches to develop anti-HIV therapies

Cannon P

University of Southern California.

Gene editing uses targeted nucleases such as CRISPR/Cas9 to create sequence-specific breaks in DNA, whose subsequent repair is then exploited to achieve different genetic outcomes. If the cell’s error-prone non-homologous end joining (NHEJ) pathway is used to repair the DNA break, insertions or deletions (indels) can also be introduced that lead to gene disruption. In contrast, homology directed repair (HDR) pathways allow for more precise repair, since they copy genetic information from a homologous sequence. However, this pathway can be hijacked by introducing an exogenous DNA template into the cell, and thereby direct a specific DNA mutation, or promote the site-specific insertion of a larger DNA cassette. My lab works to develop gene editing technologies and in particular for use in hematopoietic stem cells (HSC). Much of our work has focused on HIV, whose life-cycle involves its integration into the chromosome of a target cell, where the virus becomes a permanent genetic passenger. HIV replication can be controlled by life-long adherence to antiretroviral drugs, but cannot currently be cured, and gene editing technologies are being considered as novel strategies to fight this disease. For example, NHEJ-mediated gene knockout can disrupt the CCR5 co-receptor, and a clinical trial is underway to evaluate this approach. In addition, the integrated HIV genome itself is also considered a possible target for NEHJ-mediated disruption. Finally, certain host genes can be edited to acquire gain-of-function mutations that enhance their anti-HIV activity. I will discuss gene editing in general, and use the example of HIV to show the potential - and the challenges - for this new class of gene therapeutics.