Xu L, Mei M, Ma X, Ponder K P
Department of Internal Medicine and Biochemistry, Washington University School of Medicine, St Louis, MO 63110, USA.
J Thromb Haemost. 2007 Sep;5(9):1805-12. doi: 10.1111/j.1538-7836.2007.02629.x. Epub 2007 May 21.
Gene therapy could prevent bleeding in patients with hemophilia A, but might induce antibodies that block factor VIII (FVIII) function.
To test the efficacy of gene therapy in the newborn period for preventing a response to human FVIII (hFVIII) because of immaturity of the immune system.
Varying doses of a retroviral vector (RV) expressing a B domain-deleted hFVIII cDNA were injected i.v. into newborn hemophilia A C57BL/6 or normal C3H mice. Mice were evaluated for hFVIII expression, hemostasis, and development of anti-hFVIII antibodies with inhibitory activity.
Injection of a high RV dose [10(10) transducing units (TU) kg(-1)] into newborn hemophilia A or C3H mice resulted in 61% and 13% of normal hFVIII antigen in plasma, respectively; most mice did not produce anti-hFVIII antibodies, and hemophilia A mice did not bleed. Furthermore, most mice with >20 ng mL(-1) of hFVIII in plasma (10% normal, 1 x 10(-10) m) were tolerant to hFVIII, as an antibody response was markedly reduced after challenge with hFVIII with or without adjuvant. However, most RV-treated animals with lower antigen levels developed antibodies before or after challenge. Thus, initiation of a gene therapy trial with low RV doses might increase inhibitor formation. Furthermore, frequent hFVIII infusions in newborns with hemophilia A might reduce inhibitor formation. Finally, difficulties in achieving tolerance after gene therapy for hemophilia A as compared to hemophilia B may relate to lower expression of FVIII than FIX, as high antigen levels are most effective at inducing tolerance.
基因疗法可预防甲型血友病患者出血，但可能诱导产生阻断凝血因子VIII（FVIII）功能的抗体。
测试新生儿期基因疗法预防因免疫系统不成熟而对人FVIII（hFVIII）产生反应的疗效。
将表达缺失B结构域的hFVIII cDNA的逆转录病毒载体（RV）以不同剂量静脉注射到新生甲型血友病C57BL/6小鼠或正常C3H小鼠体内。评估小鼠的hFVIII表达、止血情况以及具有抑制活性的抗hFVIII抗体的产生情况。
向新生甲型血友病小鼠或C3H小鼠注射高剂量RV[10(10)转导单位（TU）kg(-1)]后，血浆中正常hFVIII抗原水平分别达到61%和13%；大多数小鼠未产生抗hFVIII抗体，甲型血友病小鼠未出现出血情况。此外，血浆中hFVIII水平>20 ng mL(-1)（为正常水平的10%，即1 x 10(-10) m）的大多数小鼠对hFVIII具有耐受性，因为在使用或不使用佐剂的hFVIII激发后，抗体反应明显降低。然而，大多数抗原水平较低的经RV处理的动物在激发前或激发后产生了抗体。因此，低剂量RV启动基因治疗试验可能会增加抑制剂的形成。此外，对甲型血友病新生儿频繁输注hFVIII可能会减少抑制剂的形成。最后，与乙型血友病相比，甲型血友病基因治疗后难以实现耐受性可能与FVIII的表达低于FIX有关，因为高抗原水平在诱导耐受性方面最为有效。
