Tuffin Gérald, Huwyler Jörg, Waelti Ernst, Hammer Caroline, Marti Hans-Peter
Division of Nephrology and Hypertension, Inselspital, Bern, Switzerland.
J Drug Target. 2008 Feb;16(2):156-66. doi: 10.1080/10611860701848944.
OX7 monoclonal antibody F((ab')2) fragments directed against Thy1.1 antigen can be used for drug targeting by coupling to the surface of drug-loaded liposomes. Such OX7-conjugated immunoliposomes (OX7-IL) were used recently for drug delivery to rat glomerular mesangial cells, which are characterized by a high level of Thy1.1 antigen expression. In the present study, the relationship between OX7-IL tissue distribution and target Thy1.1 antigen localization in different organs in rat was investigated. Western blot and immunohistofluorescence analysis revealed a very high Thy1.1 expression in brain cortex and striatum, thymus and renal glomeruli. Moderate Thy1.1 levels were observed in the collecting ducts of kidney, lung tissue and spleen. Thy1.1 was not detected in liver and heart. There was a poor correlation between Thy1.1 expression levels and organ distribution of fluorescence- or (14)C-labeled OX7-IL. The highest overall organ density of OX7-IL was observed in the spleen, followed by lung, liver and kidney. Heart and brain remained negative. With respect to intra-organ distribution, a localized and distinct signal was observed in renal glomerular mesangial cells only. As a consequence, acute pharmacological (i.e. toxic) effects of doxorubicin-loaded OX7-IL were limited to renal glomeruli. The competition with unbound OX7 monoclonal antibody F((ab')2) fragments demonstrated that the observed tissue distribution and acute pharmacological effects of OX7-IL were mediated specifically by the conjugated OX7 antibody. It is concluded that both the high target antigen density and the absence of endothelial barriers are needed to allow for tissue-specific accumulation and pharmacological effects of OX7-IL. The liposomal drug delivery strategy used is therefore specific toward renal glomeruli and can be expected to reduce the risk of unwanted side effects in other tissues.
针对Thy1.1抗原的OX7单克隆抗体F((ab')2)片段可通过与载药脂质体表面偶联用于药物靶向。这种OX7偶联免疫脂质体（OX7-IL）最近被用于向大鼠肾小球系膜细胞递送药物，这些细胞的特征是Thy1.1抗原表达水平高。在本研究中，研究了OX7-IL在大鼠不同器官中的组织分布与靶Thy1.1抗原定位之间的关系。蛋白质免疫印迹和免疫荧光分析显示，大脑皮层、纹状体、胸腺和肾小球中Thy1.1表达非常高。在肾集合管、肺组织和脾脏中观察到中等水平的Thy1.1。在肝脏和心脏中未检测到Thy1.1。Thy1.1表达水平与荧光或(14)C标记的OX7-IL的器官分布之间相关性较差。OX7-IL在脾脏中的总体器官密度最高，其次是肺、肝脏和肾脏。心脏和大脑呈阴性。关于器官内分布，仅在肾小球系膜细胞中观察到局部且明显的信号。因此，载有多柔比星的OX7-IL的急性药理（即毒性）作用仅限于肾小球。与未结合的OX7单克隆抗体F((ab')2)片段的竞争表明，观察到的OX7-IL的组织分布和急性药理作用是由偶联的OX7抗体特异性介导的。得出的结论是，高靶抗原密度和不存在内皮屏障对于允许OX7-IL的组织特异性积累和药理作用都是必需的。因此，所使用的脂质体药物递送策略对肾小球具有特异性，并且有望降低其他组织中不良副作用的风险。
