Identification of LAG3 high affinity aptamers by HT-SELEX and Conserved Motif Accumulation (CMA)

LAG3 receptor belongs to a family of immune-checkpoints expressed in T lymphocytes and other cells of the immune system. It plays an important role as a rheostat of the immune response. Focus on this receptor as a potential therapeutic target in cancer immunotherapy has been underscored after the success of other immune-checkpoint blockade strategies in clinical trials. LAG3 showcases the interest in the field of autoimmunity as several studies show that LAG3-targeting antibodies can also be used for the treatment of autoimmune diseases. In this work we describe the identification of a high-affinity LAG3 aptamer by High Throughput Sequencing SELEX in combination with a study of potential conserved binding modes according to sequence conservation by using 2D-structure prediction and 3D-RNA modeling using Rosetta. The aptamer with the highest accumulation of these conserved sequence motifs displays the highest affinity to LAG3 recombinant soluble proteins and binds to LAG3-expressing lymphocytes. The aptamer described herein has the potential to be used as a therapeutic agent, as it enhances the threshold of T-cell activation. Nonetheless, in future applications, it could also be engineered for treatment of autoimmune diseases by target depletion of LAG3-effector T lymphocytes.

LAG3受体属于在T淋巴细胞及其他免疫细胞中表达的免疫检查点（immune-checkpoint）家族，作为免疫应答的调谐器发挥关键调控作用。随着其他免疫检查点阻断策略在临床试验中取得成功，将该受体作为肿瘤免疫治疗潜在治疗靶点的研究价值得到了凸显。LAG3在自身免疫领域同样受到广泛关注，多项研究表明靶向LAG3的抗体亦可用于自身免疫疾病的治疗。本研究通过高通量测序SELEX（High Throughput Sequencing SELEX）技术筛选获得高亲和力LAG3适配体（aptamer），并基于序列保守性特征，采用二维结构预测与Rosetta软件进行三维RNA建模的方法，分析其潜在的保守结合模式。携带此类保守序列基序最多的适配体，对重组可溶性LAG3蛋白具有最高亲和力，且可结合表达LAG3的淋巴细胞。本研究报道的适配体可提升T细胞激活阈值，因此具备开发为治疗性制剂的潜力；此外在未来的应用中，还可通过工程化改造，借助靶向清除LAG3效应T细胞来用于自身免疫疾病的治疗。