Human hematopoietic stem/progenitor cells modified by zinc-finger nucleases targeted to CCR5 control HIV-1 in vivo

Holt et al . describe an anti-HIV strategy in which human hematopoietic stem/progenitor cells are modified with zinc-finger nucleases to knock out the viral co-receptor CCR5. Transplantation of these cells into mice confers resistance to HIV, as shown by higher human T-cell counts and lower viral loads compared with animals that received unmodified cells. CCR5 is the major HIV-1 co-receptor, and individuals homozygous for a 32-bp deletion in CCR5 are resistant to infection by CCR5-tropic HIV-1. Using engineered zinc-finger nucleases (ZFNs), we disrupted CCR5 in human CD34 + hematopoietic stem/progenitor cells (HSPCs) at a mean frequency of 17% of the total alleles in a population. This procedure produces both mono- and bi-allelically disrupted cells. ZFN-treated HSPCs retained the ability to engraft NOD/SCID/IL2rγ null mice and gave rise to polyclonal multi-lineage progeny in which CCR5 was permanently disrupted. Control mice receiving untreated HSPCs and challenged with CCR5-tropic HIV-1 showed profound CD4 + T-cell loss. In contrast, mice transplanted with ZFN-modified HSPCs underwent rapid selection for CCR5 −/− cells, had significantly lower HIV-1 levels and preserved human cells throughout their tissues. The demonstration that a minority of CCR5 −/− HSPCs can populate an infected animal with HIV-1-resistant, CCR5 −/− progeny supports the use of ZFN-modified autologous hematopoietic stem cells as a clinical approach to treating HIV-1.