Cornu Tatjana I, Mussolino Claudio, Bloom Kristie, Cathomen Toni
Institute for Cell and Gene Therapy, University Medical Center Freiburg, Hugstetter Str. 55, Freiburg, 79106, Germany,
Adv Exp Med Biol. 2015;848:117-30. doi: 10.1007/978-1-4939-2432-5_6.
Acquired immunodeficiency syndrome (AIDS) is a life-threatening disorder caused by infection of individuals with the human immunodeficiency virus (HIV). Entry of HIV-1 into target cells depends on the presence of two surface proteins on the cell membrane: CD4, which serves as the main receptor, and either CCR5 or CXCR4 as a co-receptor. A limited number of people harbor a genomic 32-bp deletion in the CCR5 gene (CCR5∆32), leading to expression of a truncated gene product that provides resistance to HIV-1 infection in individuals homozygous for this mutation. Moreover, allogeneic hematopoietic stem cell (HSC) transplantation with CCR5∆32 donor cells seems to confer HIV-1 resistance to the recipient as well. However, since Δ32 donors are scarce and allogeneic HSC transplantation is not exempt from risks, the development of gene editing tools to knockout CCR5 in the genome of autologous cells is highly warranted. Targeted gene editing can be accomplished with designer nucleases, which essentially are engineered restriction enzymes that can be designed to cleave DNA at specific sites. During repair of these breaks, the cellular repair pathway often introduces small mutations at the break site, which makes it possible to disrupt the ability of the targeted locus to express a functional protein, in this case CCR5. Here, we review the current promise and limitations of CCR5 gene editing with engineered nucleases, including factors affecting the efficiency of gene disruption and potential off-target effects.
获得性免疫缺陷综合征（艾滋病）是一种由人类免疫缺陷病毒（HIV）感染个体所引起的危及生命的疾病。HIV-1进入靶细胞取决于细胞膜上两种表面蛋白的存在：作为主要受体的CD4，以及作为共受体的CCR5或CXCR4。少数人在CCR5基因中存在一个32碱基对的基因组缺失（CCR5∆32），导致截短的基因产物表达，该产物使携带此突变纯合子的个体对HIV-1感染具有抗性。此外，用CCR5∆32供体细胞进行异基因造血干细胞（HSC）移植似乎也能使受体对HIV-1产生抗性。然而，由于∆32供体稀缺，且异基因HSC移植并非没有风险，因此开发基因编辑工具以敲除自体细胞基因组中的CCR5非常必要。靶向基因编辑可以通过设计核酸酶来实现，这些核酸酶本质上是经过工程改造的限制酶，可被设计为在特定位点切割DNA。在这些断裂的修复过程中，细胞修复途径通常会在断裂位点引入小的突变，这使得有可能破坏靶向基因座表达功能性蛋白质（在这种情况下为CCR5）的能力。在此，我们综述了利用工程核酸酶对CCR5进行基因编辑的当前前景和局限性，包括影响基因破坏效率的因素以及潜在的脱靶效应。
