From the Departments of Microbiology, Immunology, and Molecular Genetics (D.B.K., K.L.S., D.A.C.-S., D.T., A.D., A. Icreverzi, P.B., B.C.F., R.P.H., M.C., A.Y., K.M.C., C.E.C., R.Z.), Pediatrics (D.B.K., T.B.M., S.D.O., S.S.), and Pathology and Laboratory Medicine (G.M.C.) and the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research (D.B.K., G.M.C.), University of California, Los Angeles (UCLA), and the Department of Pharmaceutical Services, Ronald Reagan UCLA Medical Center (J.T.), Los Angeles, and Stanford School of Medicine, Palo Alto (A.J.S.) - all in California; University College London Great Ormond Street Institute of Child Health and Great Ormond Street Hospital for Children NHS Foundation Trust (C.B., J.X.-B., V.T., K. Soni, K. Snell, D.L.-R., K.F.B., K.C.G., C.R., N.I., S.A., H.R., C.U., A.J.T., H.B.G.), and Orchard Therapeutics (Europe) (D.A.C.-S., S.A., F.L., M.K., A.S., H.B.G.) - all in London; the National Institute of Allergy and Infectious Diseases (H.L.M.) and the National Human Genome Research Institute (E.G., R.S., F.C.), National Institutes of Health, Bethesda, MD; Cure 4 The Kids Foundation, Las Vegas (A. Ikeda); Cincinnati Children's Hospital Medical Center, Cincinnati (L.R.); Indiana University School of Medicine, Indianapolis (K.C.); Duke University, Durham, NC (R.P., R.H.B., M.H.); Division of Immunology and Allergy, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland (F.C.); and GeneWerk (M.Z., R.H., I.L., M.S.) and the German Cancer Research Center and the National Center for Tumor Diseases (M.Z., M.S.) - all in Heidelberg, Germany.