The development of genome-editing tools, such as zinc finger nucleases, could have promising therapeutic possibilities. One group has now shown that infusion of autologous CD4+ T cells after modification of the CCR5 gene—the major co-receptor for HIV—in patients is safe (N. Engl. J. Med. 370, 901–910, 2014).

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Tebas et al. enrolled 12 patients with HIV infections that were undetectable in the blood during highly active antiretroviral treatment in a trial in which the patients received one dose of CD4-enriched T cells, consisting of 11–28% T cells with CCR5 disrupted by zinc finger nuclease modification. The infusion increased the overall number of circulating CD4+ T cells. These cells, however, declined in number upon withdrawal of antiretroviral therapy, though the decline was smaller in the CCR5-engineered cells, and the overall CD4+ T cell number was still higher than before infusion. There was also a decrease in viral RNA in four patients who were able to finish the 12-week withdrawal, and only one individual had an adverse effect due to the infusion.

Although the number of patients enrolled in the study is too small to make any strong conclusions regarding safety and efficacy, it seems that gene editing to create immune cells resistant to HIV infection might be safe and shows promise for the treatment of HIV.