血友病B（HB）是X染色体连锁性凝血因子IX缺陷导致的单基因遗传性疾病。患者中约一半以上属于重型并伴有反复自发性出血及继发关节畸形和功能障碍。最近基因治疗HB在临床试验上有一定进展，但是临床疗效还有待增高。自我失活型慢病毒载体（LV）因其强大的转染效率、可塑性及安全性被广泛应用于基因治疗。在此我们提出了一种基因治疗策略，利用慢病毒载体转染整合造血干细胞（HSC），在HSC向红细胞分化成熟过程中以β珠蛋白LCR/启动子驱动高效特异的高凝血活性FIX蛋白突变体表达。我们将以HB小鼠为模型评估这种策略中基因的传递效率，功能蛋白的浓度和活性以及宿主与载体的相互作用，从而探索为更多的HB患者提供一项终生有效的一次性治疗手段。

Hemophilia B is an X-linked bleeding disorder resulted from mutations in the coagulation factor IX (FIX) gene. A majority of HB patients have less than 1% of normal FIX activity with life-threatening phenotypes. Protein replacement therapy (PRT) only have transient effects with high-expense pressure and infusion-associated complications. Recent advances in gene therapy showed promising effects in treatment of HB yet having limited efficacy as well as safety drawbacks related to the vector design. Here we propose an alternative gene therapy strategy with a self-inactivation lentiviral vector (LV) configuration for ex vivo gene therapy. Upon LV transduction of hematopoietic stem cells, the hyper-functional human hFIX protein carrying the R338L mutation under the transcriptional control of β-globin LCR/promoter is specifically expressed in red blood cells during HSC differentiation. With this strategy, we propose that transplantation of gene-modified HSCs can mediate efficient expression of hFIX protein with hyper activity to a therapeutic level and consequently correct bleeding phenotypes in hemophilia B (HB) mice. More importantly, the efficacy and safety of this vector will be verified in hFIX-immunized HB mice mimicking the patients with existing anti-FIX inhibitors after protein replacement therapy. Our gene therapy strategy is very promising to overcome the host immune response against the delivery vector and transgene product to generate therapeutic effects. This therefore will provide a potential one-off therapeutic approach with life-long effects in treatment of naive and PRT-treated HB patients in the future.