Targeted gene disruption to cure HIV.
ABSTRACT PURPOSE OF REVIEW: Recent clinical research suggests that an HIV-infected patient with lymphoma who was transplanted with bone marrow homozygous for a disrupted mutant CCR5 allele has no remaining HIV replication and is effectively cured of HIV. Here, we discuss the approaches of disrupting host and viral genes involved in HIV replication and pathogenesis with the aim of curing patients with HIV. RECENT FINDINGS: Data from the 'Berlin patient' suggest that targeted gene disruption can lead to an HIV cure. This review discusses the recent advances in the field of gene disruption toward the development of an anti-HIV therapy. We will introduce the strategies to disrupt host and viral genes using precise disruptions, imprecise disruptions, or site-specific recombination. Furthermore, the production of engineered rare-cutting endonucleases (zinc finger nucleases, TAL effector nucleases, and homing endonucleases) and recombinases that can recognize specific DNA target sequences and facilitate gene disruption will be discussed. SUMMARY: The discovery of a gene disruption approach that would cure or efficiently confine HIV infection could have broad implications for the treatment of millions of people infected with HIV. An efficient 'one-shot' curative therapy not only would give infected patients hope of a drug-free or treatment-free future, but also could reduce the huge financial burden faced by many countries because of widespread administration of highly active antiretroviral therapy.
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ABSTRACT: Most chronic viral infections are managed with small molecule therapies that inhibit replication but are not curative because non-replicating viral forms can persist despite decades of suppressive treatment. There are therefore numerous strategies in development to eradicate all non-replicating viruses from the body. We are currently engineering DNA cleavage enzymes that specifically target hepatitis B virus covalently closed circular DNA (HBV cccDNA), the episomal form of the virus that persists despite potent antiviral therapies. DNA cleavage enzymes, including homing endonucleases or meganucleases, zinc-finger nucleases (ZFNs), TAL effector nucleases (TALENs), and CRISPR-associated system 9 (Cas9) proteins, can disrupt specific regions of viral DNA. Because DNA repair is error prone, the virus can be neutralized after repeated cleavage events when a target sequence becomes mutated. DNA cleavage enzymes will be delivered as genes within viral vectors that enter hepatocytes. Here we develop mathematical models that describe the delivery and intracellular activity of DNA cleavage enzymes. Model simulations predict that high vector to target cell ratio, limited removal of delivery vectors by humoral immunity, and avid binding between enzyme and its DNA target will promote the highest level of cccDNA disruption. Development of de novo resistance to cleavage enzymes may occur if DNA cleavage and error prone repair does not render the viral episome replication incompetent: our model predicts that concurrent delivery of multiple enzymes which target different vital cccDNA regions, or sequential delivery of different enzymes, are both potentially useful strategies for avoiding multi-enzyme resistance. The underlying dynamics of cccDNA persistence are unlikely to impact the probability of cure provided that antiviral therapy is given concurrently during eradication trials. We conclude by describing experiments that can be used to validate the model, which will in turn provide vital information for dose selection for potential curative trials in animals and ultimately humans.PLoS Computational Biology 07/2013; 9(7):e1003131. DOI:10.1371/journal.pcbi.1003131 · 4.83 Impact Factor
- Molecular Therapy 10/2013; 21(10):1819-1820. DOI:10.1038/mt.2013.208 · 6.43 Impact Factor
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ABSTRACT: Recent studies have highlighted the importance of eradication of human immunodeficiency virus (HIV) and cure of acquired immunodeficiency syndrome (AIDS). However, a pivotal point that the patient immunity controls HIV reactivation after highly active anti-retroviral therapy [HAART or combination anti-retroviral therapy (cART)] remains less well addressed. In spite of the fact that both innate and adaptive immunities are indispensable and numerous cells participate in the anti-HIV immunity, memory CD4 T-cells are indisputably the key cells organizing all immune actions against HIV while being the targets of HIV. Here we present a view and multidisciplinary approaches to HIV/AIDS eradication and cure. We aim at memory CD4 T-cells, utilizing the stem cell properties of these cells to reprogram an anti-HIV memory repertoire to eliminate the viral reservoir, toward achieving an AIDS-free world.Frontiers in Immunology 10/2013; 4:337. DOI:10.3389/fimmu.2013.00337