Genomic editing of the HIV-1 coreceptor CCR5 in adult hematopoietic stem and progenitor cells using zinc finger nucleases

Abstract

The HIV-1 coreceptor CCR5 is a validated target for HIV/AIDS therapy. The apparent elimination of HIV-1 in a patient treated with an allogeneic stem cell transplant homozygous for a naturally occurring CCR5 deletion mutation (CCR5(Δ32/Δ32)) supports the concept that a single dose of HIV-resistant hematopoietic stem cells can provide disease protection. Given the low frequency of naturally occurring CCR5(Δ32/Δ32) donors, we reasoned that engineered autologous CD34(+) hematopoietic stem/progenitor cells (HSPCs) could be used for AIDS therapy. We evaluated disruption of CCR5 gene expression in HSPCs isolated from granulocyte colony-stimulating factor (CSF)-mobilized adult blood using a recombinant adenoviral vector encoding a CCR5-specific pair of zinc finger nucleases (CCR5-ZFN). Our results demonstrate that CCR5-ZFN RNA and protein expression from the adenoviral vector is enhanced by pretreatment of HSPC with protein kinase C (PKC) activators resulting in >25% CCR5 gene disruption and that activation of the mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathway is responsible for this activity. Importantly, using an optimized dose of PKC activator and adenoviral vector we could generate CCR5-modified HSPCs which engraft in a humanized mouse model (albeit at a reduced level) and support multilineage differentiation in vitro and in vivo. Together, these data establish the basis for improved approaches exploiting adenoviral vector delivery in the modification of HSPCs.

Figure 1

Protein kinase C (PKC) activators (PMA and bryostatin) significantly enhanced CCR5-ZFN activity in CD34⁺ hematopoietic stem/progenitor cells (HSPC). Adult HSPCs were stimulated with SFT in SCGM medium overnight followed by PMA or bryostatin treatment for 30 minutes before CCR5-ZFN transduction (multiplicity of infection (MOI) 150). The percent CCR5 disruption was obtained by surveyor nuclease assay from transduced cells (MOI 150) without PKC activator treatment (left), with 20 ng/ml PMA treatment (middle), and 10 nmol/l bryostatin treatment (right). Percent of CCR5 disruption is indicated under each lane. PMA, phorbol 12-myristate 13-acetate; ZFN, zinc finger nuclease.

Figure 2

Effect of PMA and bryostatin treatment and vector transduction on hematopoietic stem/progenitor cell (HSPC) CD34⁺ cell growth and hematopoietic potential. (a) Colony-forming unit (CFU) assay. A total of 500 cells were plated in methylcellulose medium in triplicates for each condition and the average ± SD of CFU are shown. One way analysis of variance (ANOVA) with Dunnett's multiple comparison test was used for statistical analysis as compared with the untransduced control. *P < 0.05. (b) Growth of untransduced, PMA-, and bryostatin-treated, CCR5-ZFN–transduced cells cultured in bulk culture medium for 28 days. Average ± SD fold growth over starting cell number is shown, N = 3. (c) Phenotypic analysis of 2-week bulk culture and an one-way ANOVA performed with Bonferroni post-test. Error bars indicate average ± SEM of percent of total cells with each phenotype is shown, N = 3. ns, not significant; PMA, phorbol 12-myristate 13-acetate; Untd, untransduced; ZFN, zinc finger nuclease.

Figure 3

Protein kinase C activators induce phosphorylation of ERK1/2 in hematopoietic stem/progenitor cell (HSPC) CD34⁺ cells and result in enhancement of CCR5-ZFN activity. (a) CD34⁺ HSPCs from four healthy donors were stimulated with 1 ng/ml PMA and stained with anti-phospho-signal protein antibodies as indicated. Mean fluorescence intensity (MFI) of each phospho-signal protein was displayed. Two-way analysis of variance with Bonferroni post-test was used for statistical analysis, ***P < 0.001. (b) CD34⁺ HSPC from four donors were either untreated or treated in parallel with 1 ng/ml PMA or 5 nmol/l bryostatin. (c,d) CD34⁺ HSPCs from three donors were either mock-treated or treated with bryostatin (Bryo) and MEK1/2 inhibitor GSK1120212 (Bryo + 5 or 50 nmol/l GSK) at the concentration indicated 1 hour before bryostatin stimulation, followed by CCR5-ZFN vector transduction at multiplicity of infection 10 (all samples). (c) MFI of pERK and (d) % CCR5 disruption of the same samples as in c were measured. The relative fold change of the parameters listed was normalized to samples treated with bryostatin and vector only. Average ± SEM is shown for (c) pERK MFI and (d) CCR5 disruption. ERK, extracellular signal-regulated kinase; MAPK, mitogen-activated protein kinase; NF-κB, nuclear factor-κB; PMA, phorbol 12-myristate 13-acetate; ZFN, zinc finger nuclease.

Figure 4

Protein kinase C (PKC) activation increases CCR5-ZFN RNA expression leading to enhanced protein production. (a) Reverse transcription-PCR analysis of CCR5-ZFN mRNA using CCR5-ZFN-Fok1 endonuclease-specific primers. Untreated, CCR5-ZFN transduced (multiplicity of infection (MOI) 50) without PMA treatment (0PMA-50), and 1 ng/ml PMA-treated and CCR5-ZFN–transduced (1PMA-50) CD34⁺ cells from five donors were analyzed. (b) Western blot analysis of Fok1 endonuclease protein expression in hematopoietic stem/progenitor cells treated with PKC activators at the concentrations indicated and transduced with CCR5-ZFN vector (MOI 50). (c) Dose-dependent inhibition of the Fok1 endonuclease protein by MEK inhibitor GSK1120212 at indicated concentrations before bryostatin treatment (5 nmol/l) and CCR5-ZFN transduction (MOI 50). PMA, phorbol 12-myristate 13-acetate; ZFN, zinc finger nuclease.