Abstract
Despite the great success of highly active antiretroviral therapy (HAART) in ameliorating the course of HIV infection, alternative therapeutic approaches are being pursued because of practical problems associated with life-long therapy. The eradication of HIV in the so-called “Berlin patient” who received a bone marrow transplant from a CCR5-negative donor has rekindled interest in genome engineering strategies to achieve the same effect. Precise gene editing within the cells is now a realistic possibility with recent advances in understanding the DNA repair mechanisms, DNA interaction with transcription factors and bacterial defense mechanisms. Within the past few years, four novel technologies have emerged that can be engineered for recognition of specific DNA target sequences to enable site-specific gene editing: Homing Endonuclease, ZFN, TALEN, and CRISPR/Cas9 system. The most recent CRISPR/Cas9 system uses a short stretch of complementary RNA bound to Cas9 nuclease to recognize and cleave target DNA, as opposed to the previous technologies that use DNA binding motifs of either zinc finger proteins or transcription activator-like effector molecules fused to an endonuclease to mediate sequence-specific DNA cleavage. Unlike RNA interference, which requires the continued presence of effector moieties to maintain gene silencing, the newer technologies allow permanent disruption of the targeted gene after a single treatment. Here, we review the applications, limitations and future prospects of novel gene-editing strategies for use as HIV therapy.
Highlights
With the development of anti-retroviral therapy, HIV-1 infection is manageable as a chronic disease
Showed that zinc finger nucleases (ZFNs) was able to efficiently and precisely disrupt CCR5 in embryonic and induced pluripotent stem cells (ESCs and iPSCs), and that these cells could be differentiated into CD34+ hematopoietic stem cells (HSCs) [42]
After engraftment into NSG mice, these cells supported multilineage reconstitution of human immune system, and the gene modified cells persisted even after 6 months of reconstitution [59]. Another exciting development in this regard is the finding by Gaj et al that the Zinc finger proteins (ZFP) has an intrinsic cell-penetrating property that allows entry of the protein into cells without need for a delivery vehicle. They recently incubated CD4+ T cells with recombinant CCR5-ZFP protein and found that this led to gene disruption, the efficiency was in the lower range of ~8% [60]
Summary
With the development of anti-retroviral therapy, HIV-1 infection is manageable as a chronic disease. It has become clear that following double stranded break, DNA is repaired either by HR (when a homologous DNA template is provided) or by the error prone non-homologous end joining (NHEJ) pathway, attended with small nucleotide additions or deletions that results in disruption of the reading frame and gene expression. Use of this strategy for targeted gene disruption has been made possible by the development of engineered nucleases. Developing three kinds of site-specific nucleases, namely zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and most recently, the CRISPR/Cas system; and discuss their application towards HIV-1 therapy
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
