细胞内单域抗体的研究及应用进展

Research and application progress in intracellular single domain antibodies

来自骆驼或鲨鱼的单域抗体(Single domain antibodies,sd Ab)仅包含抗体的重链可变区,而从人抗体中筛选到的人sd Ab中包含重链(Heavy chain,VH)或轻链(Light chain,VL)的可变区。与完整抗体和sc Fv(Single chain antibody fragment)相比,sd Ab是体外和体内都稳定的非聚合分子。与sc Fv片段不同,sd Ab是细胞质/细胞核蛋白质的新型抑制剂,并可以在细胞质中正确折叠。sd Ab能特异性抑制翻译后修饰,如磷酸化位点,构象异构体或蛋白质的相互作用区域,这些区域不适合使用基因敲除及RNAi技术进行研究。作为细胞质/细胞核蛋白质的抑制剂,使用sd Ab的研究数量持续增加,同时使用无需免疫动物的合成单域抗体文库中,研究者筛选出一些有成药应用前景的药物分子。目前,研究涉及的抗原靶点包括病毒蛋白、癌相关蛋白、毒素、神经系统相关蛋白、植物和果蝇蛋白等,可以针对几乎所有的细胞质/细胞核中的抗原表位,进行功能性sd Ab的筛选。逃逸蛋白结构和细胞穿透肽的高效转染的研究,拓宽了sd Ab的应用领域。新一代细胞特异性纳米颗粒,将携带细胞质/细胞核sd Ab作为蛋白抑制剂,开拓病毒感染及癌症新的治疗领域。

Single domain antibodies （sdAbs） from camels or sharks comprise only the variable heavy chain domain. Human sdAbs comprise the variable domain of the heavy chain （VH） or light chain （VL） and can be select- ed from human antibodies. SdAbs are stable, non-aggregating molecules in vitro and in vivo compared to complete anti- bodies and scFv fragments. They are excellent novel inhibitors of cytosolic/nuclear proteins because they are correctly folded inside the cytosol in contrast to scFv fragments. SdAbs are unique because of their excellent specificity and pos- sibility to target posttranslational modifications such as phosphorylation sites,conformers or interaction regions of pro- teins that cannot be targeted with genetic knockout techniques and are impossible to knockdown with RNAi. The num- ber of inhibiting cytosolic/nuclear sdAbs is increasing and use of synthetic single pot single domain libraries will boost the generation of these fascinating molecules without the need of immunization. The most frequently selected antigenic epitopes belong to viral and oncogenic proteins, followed by toxins,proteins of the nervous system as well as plant- and drosophila proteins. It is now possible to select functional sdAbs against virtually every cytosolic/nuclear protein and desired epitope. The development of new endosomal escape protein domains and cell-penetrating peptides for efficient transfection broadens the application of inhibiting sdAbs. Last but not least,the generation of relatively new cell-specific nanoparticles such as polymersomes and polyplexes carrying cytosolic/nuclear sdAb-DNA or-protein will pave the way to apply cytosolic/nuclear sdAbs in the treatment of viral infection and cancer in the clinic.