Experimental schema and maps of retroviral vectors carrying the normal human ADA cDNA. (A) The experimental schema for the clinical trial is shown. Flt-3L indicates Flt-3 ligand; MGDF, megakaryocyte growth and differentiation factor; rFBN, recombinant fibronectin; and SCF, stem cell factor. (B) The elements of the proviral forms of the 2 retroviral vectors used to transfer normal human ADA cDNA are depicted. A indicates common qPCR primer; B, vector-specific qPCR primer; dl587, endogenous murine retrovirus dl587rev; LTR, long terminal repeat; MMLV, Moloney murine leukemia virus; MND, MPSV LTR, ncr-deleted, coupled to dl587rev pbs; MPSV, myeloproliferative sarcoma virus; P, common qPCR probe; pbs, primer-binding site; Ψ, packaging signal; SA, splice acceptor site; and SD, splice donor site.