Ide Lucienne M, Gangadharan Bagirath, Chiang Kuang-Yueh, Doering Christopher B, Spencer H Trent
Department of Pediatrics, Aflac Cancer Center and Blood Disorders Service, Emory University and Children's Healthcare of Atlanta, GA, USA.
Blood. 2007 Oct 15;110(8):2855-63. doi: 10.1182/blood-2007-04-082602. Epub 2007 Jun 14.
Insufficient expression of factor VIII (fVIII) is a major hurdle in the development of successful nucleic acid treatments for hemophilia. However, we recently showed that under myeloablative and reduced-intensity total body irradiation (TBI) conditioning, transplantation of hematopoietic stem cells (HSCs) transduced with recombinant retroviruses containing B domain-deleted porcine fVIII (BDDpfVIII) sequences provides curative fVIII levels in a hemophilia A mouse model. In the current study, we tested BDDpfVIII activity after nonmyeloablative conditioning with busulfan, cyclophosphamide, or fludarabine and immunosuppressive agents CTLA4-Ig + anti-CD40L or anti-(murine)thymocyte serum (ATS). ATS is similar in action to anti-(human)thymocyte globulin (ATG), which is used clinically with busulfan in bone marrow transplantations to increase donor cell engraftment. Mice conditioned with busulfan + ATS and that received a transplant of BDDpfVIII-transduced stem-cell antigen 1-positive cells exhibited moderate levels of donor cell chimerism (between 20% and 60%) and achieved sustained fVIII levels more than 1 U/mL. Similar results were observed in mice preimmunized with human fVIII and conditioned with 5 Gy TBI + ATS or busulfan + ATS. These data demonstrate that it is possible to achieve sufficient fVIII expression after transplantation of BDDpfVIII-transduced HSCs following low-toxicity pretransplantation conditioning with targeted immunosuppression, potentially even in the context of preexisting inhibitors.
因子VIII（fVIII）表达不足是血友病成功进行核酸治疗发展的主要障碍。然而，我们最近发现，在清髓性和减低强度的全身照射（TBI）预处理下，用含有缺失B结构域的猪fVIII（BDDpfVIII）序列的重组逆转录病毒转导的造血干细胞（HSCs）移植，可在甲型血友病小鼠模型中提供治愈性的fVIII水平。在本研究中，我们测试了用白消安、环磷酰胺或氟达拉滨以及免疫抑制剂CTLA4-Ig + 抗CD40L或抗（鼠）胸腺细胞血清（ATS）进行非清髓性预处理后BDDpfVIII的活性。ATS的作用与抗（人）胸腺细胞球蛋白（ATG）相似，ATG在临床上与白消安一起用于骨髓移植以增加供体细胞植入。用白消安 + ATS预处理并接受BDDpfVIII转导的干细胞抗原1阳性细胞移植的小鼠表现出中等水平的供体细胞嵌合率（20%至60%之间），并实现了超过1 U/mL的持续fVIII水平。在用人类fVIII进行预免疫并用5 Gy TBI + ATS或白消安 + ATS预处理的小鼠中也观察到了类似结果。这些数据表明，在进行低毒性移植前预处理并采用靶向免疫抑制的情况下，移植BDDpfVIII转导的HSCs后有可能实现足够的fVIII表达，甚至在存在预先存在的抑制剂的情况下也可能如此。
