Gene Editing of CCR5 in Autologous CD4 T Cells of Persons Infected with HIV

BackgroundCCR5 is the major coreceptor for human immunodeficiency virus (HIV). We investigated whether site-specific modification of the gene (gene editing) in this case, the infusion of autologous CD4 T cells in which the CCR5 gene was rendered permanently dysfunctional by a zinc-finger nuclease (ZFN) is safe. MethodsWe enrolled 12 patients in an open-label, nonrandomized, uncontrolled study of a single dose of ZFN-modified autologous CD4 T cells. The patients had chronic aviremic HIV infection while they were receiving highly active antiretroviral therapy. Six of them underwent an interruption in antiretroviral treatment 4 weeks after the infusion of 10 billion autologous CD4 T cells, 11 to 28% of which were genetically modified with the ZFN. The primary outcome was safety as assessed by treatment-related adverse events. Secondary outcomes included measures of immune reconstitution and HIV resistance. ResultsOne serious adverse event was associated with infusion of the ZFN-modified autologous CD4 T cells and was attributed to a transfusion reaction. The median CD4 T-cell count was 1517 per cubic millimeter at week 1, a significant increase from the preinfusion count of 448 per cubic millimeter (P<0.001). The median concentration of CCR5-modified CD4 T cells at 1 week was 250 cells per cubic millimeter. This constituted 8.8% of circulating peripheral-blood mononuclear cells and 13.9% of circulating CD4 T cells. Modified cells had an estimated mean half-life of 48 weeks. During treatment interruption and the resultant viremia, the decline in circulating CCR5-modified cells (-1.81 cells per day) was significantly less than the decline in unmodified cells (-7.25 cells per day) (P=0.02). HIV RNA became undetectable in one of four patients who could be evaluated. The blood level of HIV DNA decreased in most patients. ConclusionsCCR5-modified autologous CD4 T-cell infusions are safe within the limits of this study. (Funded by the National Institute of Allergy and Infectious Diseases and others; ClinicalTrials.gov number, NCT00842634.) In this small study, investigators genetically disrupted the HIV receptor CCR5 in CD4 T cells of aviremic persons who were infected with HIV. After reinfusion and during viremia, the modified cells declined at a significantly slower rate than did the unmodified cells. The ability to make site-specific modifications to (or edit) the human genome has been an objective in medicine since the recognition of the gene as the basic unit of heredity.(1),(2) The challenge of genome editing is the ability to generate a single double-strand break at a specific point in the DNA molecule. Numerous agents, including meganucleases, oligonucleotides that form DNA triplexes, and peptide nucleic acids, have been tested and shown to be limited by inefficiency.(3)-(5) Another class of reagents, the zinc-finger nucleases (ZFNs), have proved versatile for genome editing, and the use of ZFNs is now well established ...