纳米抗体的稳定性及其结构基础研究进展

驼类纳米抗体结构简单、易于改造,且具有低免疫原性、高稳定性、高特异性、高亲和力等特点,因而具有广泛的应用前景。纳米抗体的优势之一在于其具有较高的稳定性,比常规抗体更易于储藏和运输,甚至在高温、化学和压力等极端条件下变性后仍可有效地重折叠并恢复其抗原亲和力。本文综述了纳米抗体稳定性与其结构基础方面的研究进展,阐述了纳米抗体氨基酸序列、二硫键、结构域等与其稳定性的关系,揭示了高度稳定性的纳米抗体普遍具有的结构特征。基于这些结构特征,讨论了几种纳米抗体的稳定性优化策略,包括共有序列驱动的序列修复、替换易于修饰的氨基酸、净蛋白质电荷的改变、非天然二硫键的引入以及CDR超变区的移植。预期对纳米抗体的稳定性调控提供理论指导,以拓展其作为治疗药物、诊断试剂和生物传感器等方面的应用。

Advances on The Relationship Between Stability and Structure of Nanobody

Camel nanobody has a wide range of application prospects due to its simple structure, easy modification, and the characteristics of low immunogenicity, high stability, high specificity as well as high affinity. It is reported that nanobody with high stability could be stored and transported in more easily way compared with conventional antibodies. It can evenly refold and recover its antigen binding affinity after being denatured under polar conditions such as high temperature, high concentration organic solvents, high pressure, chemical reagents, extreme acid-base environments, and proteases. This review summarized the stability characterization of nanobody under these conditions. It is shown that nanobody can not only expand its application in the detection of targets under complex polar conditions but also enrich multiple routes of drug delivery in medical therapy, including intravenous and subcutaneous injection, nasal inhalation, and oral administration. Emphasis was made on describing the relationship between amino acid sequence, number and position of disulfide bonds, structural domains, and stability, which revealed that highly stable nanobody have common structural features such as higher net charge surfaces, disulfide bonds that limit conformational migration, framework regions with more hydrophilic amino acid substitutions, conserved hydrophobic pockets, and highly interacting structural domains. Based on these structural features, several strategies for stability structure optimization of nanobody were also discussed in this paper, including shared sequence-driven sequence repair, the substitution of easily modified amino acids, alteration of net protein charge, the introduction of unnatural disulfide bonds, and transposition of CDRs. It is expected to provide theoretical guidance on the stability regulation of nanobody to expand their wide applications as therapeutic drugs, diagnostic reagents, and biosensors.