Figure 4.

Analysis of total and integrated vector copy number (VCN) of integration-deficient lentiviral vectors (IDLVs) and integrase-competent lentiviral vectors (ICLVs) in mouse tissues demonstrated low illegitimate integration and a high therapeutic/genotoxic index of IDLVs. VCN in tissues was assessed at 1 year postintraperitoneal vector administration of ICLVs (65 µg p24^gag) and IDLVs (250 µg p24^gag). (a) A multiplex quantitative polymerase chain reaction analysis of total VCN per host genome of ICLV and IDLV in mouse tissues. (b) The relative integration level of IDLVs (n = 3) normalized to the level of ICLV integration in mouse livers was analyzed by the S1/B1-quantitative polymerase chain reaction assay. Integrated VCN (iVCN) in a single mouse liver treated with ICLVs (65 µg p24^gag) served as a baseline (valued as 1.00) for the analysis of two additional ICLV-treated mice and to establish the standard curve in the analysis of three IDLV (250 µg p24^gag)-treated mice. The relative therapeutic/genotoxic index (TGI) of ICLV and IDLV vectors was calculated as the overall increase in human FIX percentage activity per iVCN. (c) Graph demonstrating TGI values of IDLVs and ICLVs following intraperitoneal administration to hemophilia B mice. P value was assessed by a paired Student's t-test. BM, bone marrow.