Department of Gastroenterology & Hepatology and Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, University of Amsterdam, 1105 BK Amsterdam, The Netherlands.
Hum Gene Ther. 2013 Sep;24(9):807-13. doi: 10.1089/hum.2013.086.
Adeno-associated virus serotype 8 (AAV8) has been demonstrated to be effective for liver-directed gene therapy in humans. Although hepatocytes are the main target cell for AAV8, there is a loss of the viral vector because of uptake by macrophages and Kupffer cells. Reducing this loss would increase the efficacy of viral gene therapy and allow a dose reduction. The receptor mediating this uptake has not been identified; a potential candidate seems the macrophage scavenger receptor A (SR-A) that is involved in the endocytosis of, for instance, adenovirus. In this study we show that SR-A can mediate scAAV8 endocytosis and that blocking it with polyinosinic acid (poly[i]) reduces endocytosis significantly in vitro. Subsequently, we demonstrate that blocking this receptor improves scAAV-mediated liver-directed gene therapy in a model for inherited hyperbilirubinemia, the uridine diphospho-glucuronyl transferase 1A1-deficient Gunn rat. In male rats, preadministration of poly[i] increases the efficacy of a low dose (1×10¹¹ gc/kg) but not of a higher dose (3×10¹¹ gc/kg) scAAV8-LP1-UT1A1. Administration of poly[i] just before the vector significantly increases the correction of serum bilirubin in female rats. In these, the effect of poly[i] is seen by both doses but is more pronounced in the females receiving the low vector, where it also results in a significant increase of bilirubin glucuronides in bile. In conclusion, this study shows that SR-A mediates the endocytosis of AAV8 in vitro and in vivo and that blocking this receptor can improve the efficacy of AAV-mediated liver-directed gene therapy.
腺相关病毒血清型 8（AAV8）已被证明在人体肝靶向基因治疗中是有效的。尽管肝细胞是 AAV8 的主要靶细胞，但由于巨噬细胞和库普弗细胞的摄取，病毒载体会丢失。减少这种丢失将提高病毒基因治疗的效果，并允许减少剂量。介导这种摄取的受体尚未确定；一个潜在的候选者似乎是巨噬细胞清道夫受体 A（SR-A），它参与了例如腺病毒的内吞作用。在这项研究中，我们表明 SR-A 可以介导 scAAV8 的内吞作用，并且用聚肌苷酸（poly[i]）阻断它可以显著减少体外的内吞作用。随后，我们证明在遗传性高胆红素血症的模型（尿苷二磷酸葡萄糖醛酸转移酶 1A1 缺陷 Gunn 大鼠）中，阻断该受体可以改善 scAAV 介导的肝靶向基因治疗。在雄性大鼠中，poly[i] 的预先给药增加了低剂量（1×10¹¹ gc/kg）但不增加高剂量（3×10¹¹ gc/kg）scAAV8-LP1-UT1A1 的疗效。在载体前给予 poly[i]可显著增加雌性大鼠血清胆红素的校正。在这些大鼠中，poly[i] 的作用可见于两种剂量，但在接受低载体的雌性大鼠中更为明显，其中它还导致胆汁中胆红素葡萄糖醛酸苷的显著增加。总之，这项研究表明 SR-A 介导 AAV8 的体外和体内内吞作用，并且阻断该受体可以提高 AAV 介导的肝靶向基因治疗的效果。
