Scallan Ciaran D, Jiang Haiyan, Liu Tongyao, Patarroyo-White Susannah, Sommer Jurg M, Zhou Shangzhen, Couto Linda B, Pierce Glenn F
Avgen, Alameda, CA, USA.
Blood. 2006 Mar 1;107(5):1810-7. doi: 10.1182/blood-2005-08-3229. Epub 2005 Oct 25.
Long-term cures of hemophilia B have been achieved using AAV2 delivering the factor IX gene to the liver of adeno-associated virus (AAV)-naive hemophilic animals. However, the clinical success of this approach requires overcoming pre-existing AAV neutralizing antibodies prevalent in humans. To better define the inhibition of neutralizing antibodies on AAV2-mediated liver transduction, we developed an in vivo passive immunity model. SCID mice were first reconstituted to a defined neutralizing titer with pooled plasma-derived human immunoglobulin. AAV2-FIX vectors then were administered to the liver, and the transduction efficiency was measured by plasma FIX levels. Unexpectedly, AAV2 neutralizing titers lower than 1:10 were sufficient to neutralize 4 to 20 x 10(12) vg/kg of AAV2 vectors in vivo, a capacity that was underestimated by in vitro neutralizing assays. We also evaluated strategies to evade neutralization, including the use of alternative delivery routes, infusion parameters, empty capsids, and alternative AAV serotypes 6 and 8. The results indicate that low AAV2 neutralizing titers can be inhibitory to the tested human and primate AAV vectors delivered into the circulatory system. Therefore, novel nonprimate AAV vectors or compartmentalized delivery may offer more consistent therapeutic effects in the presence of pre-existing AAV neutralizing antibodies.
通过腺相关病毒（AAV）初免的血友病动物肝脏中，使用携带FIX基因的AAV2已实现血友病B的长期治愈。然而，这种方法的临床成功需要克服人类中普遍存在的预先存在的AAV中和抗体。为了更好地定义中和抗体对AAV2介导的肝脏转导的抑制作用，我们建立了一种体内被动免疫模型。首先用混合的血浆来源的人免疫球蛋白将SCID小鼠重建到确定的中和滴度。然后将AAV2-FIX载体注入肝脏，并通过血浆FIX水平测量转导效率。出乎意料的是，低于1:10的AAV2中和滴度足以在体内中和4至20 x 10(12) vg/kg的AAV2载体，这一能力被体外中和试验低估了。我们还评估了逃避中和的策略，包括使用替代递送途径、输注参数、空衣壳以及替代AAV血清型6和8。结果表明，低AAV2中和滴度可抑制注入循环系统的受试人类和灵长类AAV载体。因此，在预先存在AAV中和抗体的情况下，新型非灵长类AAV载体或分区递送可能提供更一致的治疗效果。
