Recently, several oligonucleotides have been launched for clinical use and a number of therapeutic oligonucleotides are under clinical trials. Aptamer is one of the oligonucleotide therapeutics and has received a lot of attention as a new technology and an efficacious pharmaceutical compound comparable to antibody. Aptamer could be used for various purposes, not only therapeutics but also diagnostics, and applicable to affinity chromatography as a carrier molecule to purify proteins of interest. Here we demonstrate the usage and advantages of RNA aptamer to Fc region of human IgG (i.e., IgG aptamer) for purification of human antibodies. IgG aptamer requires divalent cations for binding to IgG and bound IgG dissociates easily upon treatment with chelating reagent, such as EDTA, under neutral conditions. This elution step is very mild and advantageous for maintaining active conformations of therapeutic antibodies compared to the widely used affinity purification with Protein A/G, which requires acidic elution that often damages the active conformation of antibodies. In fact, of several monoclonal antibodies tested, three antibodies were prone to aggregate on acidic elution from the Protein A/G resin, while remained fully active upon neutral elution from the IgG aptamer resin. The IgG aptamer was fully manipulated to alkaline resistant by ribose 2′-modifications, and thereby reusable numerous times with 1 N NaOH washing. The capacity of the aptamer resin to bind IgG was equivalent to that of the Protein A/G resin. Therefore, the IgG aptamer will provide us with a unique tool to uncover and purify human monoclonal antibodies, which hold therapeutic potential but lose the activity upon acidic elution from Protein A/G-based affinity resin.

最近，已经推出了几种寡核苷酸用于临床，并且许多治疗性寡核苷酸正在临床试验中。适体是寡核苷酸治疗剂之一，作为一种新技术和可与抗体媲美的有效药物而受到了广泛关注。适体可以用于多种目的，不仅用于治疗而且用于诊断，并且适用于亲和色谱法作为纯化目的蛋白的载体分子。在这里，我们证明了用于人IgG纯化的人IgG（即，IgG适体）的RNA适体对人IgG的用途和优点。IgG适体需要二价阳离子才能与IgG结合，并且在中性条件下用螯合剂（如EDTA）处理后，结合的IgG容易解离。与广泛使用的蛋白A / G亲和纯化相比，该洗脱步骤非常温和并且有利于维持治疗性抗体的活性构象，后者需要酸性洗脱，而酸性洗脱通常会破坏抗体的活性构象。实际上，在测试的几种单克隆抗体中，三种抗体在从A / G蛋白树脂酸性洗脱时倾向于聚集，而在从IgG适体树脂中性洗脱时仍保持完全活性。IgG适体通过核糖2'修饰被完全操纵成具有耐碱性，因此可通过1 N NaOH洗涤多次重复使用。适体树脂结合IgG的能力与蛋白A / G树脂相同。因此，IgG适体将为我们提供发现和纯化人单克隆抗体的独特工具，