Retrovirus gene therapy for X-linked chronic granulomatous disease can achieve stable long-term correction of oxidase activity in peripheral blood neutrophils.

Chronic granulomatous disease (CGD) is associated with significant morbidity and mortality from infection. The first CGD gene therapy trial resulted in only short-term marking of 0.01% to 0.1% of neutrophils. A recent study, using busulfan conditioning and an SFFV retrovirus vector, achieved more than 20% marking in 2 patients with X-linked CGD. However, oxidase correction per marked neutrophil was less than normal and not sustained. Despite this, patients clearly benefited in that severe infections resolved. As such, we initiated a gene therapy trial for X-CGD to treat severe infections unresponsive to conventional therapy. We treated 3 adult patients using busulfan conditioning and an MFGS retroviral vector encoding gp91(phox), achieving early marking of 26%, 5%, and 4% of neutrophils, respectively, with sustained long-term marking of 1.1% and 0.03% of neutrophils in 2 of the patients. Gene-marked neutrophils have sustained full correction of oxidase activity for 34 and 11 months, respectively, with full or partial resolution of infection in those 2 patients. Gene marking is polyclonal with no clonal dominance. We conclude that busulfan conditioning together with an MFGS vector is capable of achieving long-term correction of neutrophil oxidase function sufficient to provide benefit in management of severe infection. This study was registered at www.clinicaltrials.gov as #NCT00394316.

Severe phenotype of chronic granulomatous disease presenting in a female with a de novo mutation in gp91-phox and a non familial, extremely skewed X chromosome inactivation.

Chronic granulomatous disease (CGD) is an inherited immunodeficiency resulting from defects in the multienzyme complex NADPH-oxidase (phagozyte oxidase, phox), which normally produces microbicidal reactive oxygen metabolites (ROM). The reason for our patient's CGD was unusual, as revealed by the following in vitro findings in neutrophils and EBV-transformed B-cells: lack of flavocytochrome b(558) expression, restoration of significant ROM production after transduction with gp91-phox cDNA by a retrovirus vector, an 879G-->A, Trp289-->Stop mutation in one X chromosomal gp91-phox allele, a one-sided paternal X chromosome inactivation, as shown by a lyonization assay at the HUMARA locus, and the result of a dihydrorhodamine 123 flow cytometry assay revealing consistently that 1 in 2500 neutrophils produced ROM at normal levels. Our conclusion: A presumed autosomal form of CGD has been excluded. Instead, a spontaneous mutation in gp91-phox coinciding with an extreme X chromosome inactivation ratio resulted in X-linked CGD in this young woman.