Gene Therapy with pCCLchimP47-phox Lentiviral Vector Achieves Long-term Reconstitution of NADPH Oxidase Activity in p47-phox Chronic Granulomatous Disease (CGD) Mouse Model

RATIONALE: We propose to use a lentiviral gene therapy strategy to restore the expression of the p47^-phox NADPH oxidase component, coded by the NCF1 gene, to correct the second most common form of CGD.

METHODS: We have made a lentiviral vector, pCCLchimP47^-phox, that contains the chimeric cathepsin G/c-fes myeloid promoter and a codon optimized version of the human p47^-phox gene. We have introduced the lentiviral vector in a mouse model of p47^-phox CGD. The peripheral blood of mice was analysed at regular intervals for the NADPH oxidase activity using Dihydrorhodamine (DHR) tests. We analyzed the NADPH oxidase function as percentage of DHR⁺ out of CD11b⁺/Gr-1⁺ cells and related median fluorescence intensity (MFI) in bone marrow and peripheral blood samples from p47^-phox CGD mice, six months after transplant with the pCCLchimP47^-phox transduced cells.

RESULTS: The lentiviral gene therapy promoted long-term reconstitution of NADPH oxidase activity and p47^-phox expression. The percentage of functional cells was similar at 2 and 5 months of follow up. As expected, given the myeloid specificity of the chimeric promoter used, the majority of neutrophils (CD11b⁺/Gr-1^high) and a high percentage of monocytes (CD11b⁺/Gr-1^low) were positive for p47^-phox protein while only a low percentage of B (B220⁺) and T (CD3⁺) cells expressed the transgene.

CONCLUSIONS: Our results show that the pCCLchimP47^-phox vector is a promising tool for the clinical application of p47^-phox CGD gene therapy.