错配PCR技术提高抗hIL17A单链抗体亲和力的研究

Affinity optimization of an anti-hIL17A single-chain Fv antibody through error-prone PCR technique

目的:通过错配PCR技术提高1株人源化抗hIL17A单链抗体(scFv)的亲和力,为进一步开发治疗类风湿性关节炎(RA)的人源化抗体药物奠定基础。方法:本研究采用错配PCR和重叠PCR的方法,对抗体的重链、轻链可变区分别随机引入突变,并将细菌内膜展示技术和流式细胞技术(FCM)相结合进行高通量筛选,获得高亲和力突变株。由于hIL17A能刺激HeLa细胞产生白细胞介素IL-6和IL-8,因此scFv突变株经表达纯化后,利用real-time PCR技术在mRNA转录水平上检测其阻断hIL17A刺激HeLa细胞产生IL-6和IL-8的能力。结果:筛选出5株突变株,经流式细胞仪检测其中有3株亲和力与亲本相比有很大程度的提高,2株与亲本相当,而且所有突变株均保留了亲本与hIL17A的结合能力,经real-time PCR检测证明这5株突变株均有阻断hIL17A刺激HeLa细胞产生IL-6和IL-8的能力,突变株的亲和力与中和效果成正比。结论:错配PCR技术是抗体体外亲和力提高的一种可行性方法,在保证与抗原结合能力的基础上提高了其亲和力和中和活性。该实验结果为RA的靶向治疗提供了候选药物,而且也为抗体的体外亲和力的提高提供了参考方法。

AIM： To optimize antibody affinity of a humanized anti-hIL17A single-chain Fv （scFV） antibody through error-prone polymerase chain reaction （PCR） so as to develop a therapeutic humanized antibody for the treatment of rheumatoid arthritis （RA）. METHODS： Variable regions of heavy chain and light chain were subjected to random mutation by error-prone PCR and a scFv library was constructed by overlapping PCR. The library was screened for improved mutants by the bacterial inner membrane display technique and flow cytometry （FCM）. Real-time PCR was used to detect neutralization effects of the purified scFv antibody mutants on mRNA expressions of IL-6 and IL-8 in HeLa cells stimulated by hIL17A. RESULTS： We obtained five mutants with improved affinity. FCM revealed that the affinity of three clones was greatly enhanced as compared with the parent clone. All mutants retained binding specificity to hIL17A. Real-time PCR results showed that all five mu- tants could block hIL17A stimulation of HeLa cells to express IL-6 and IL-8, and the neutralization effects were positively related to mutant affinity. CONCLUSION： Error-prone PCR technique is a feasible method for antibody affinity optimization in vitro, which is able to improve the affinity and neutralization capacity of antibody on the basis of its unchanged antigen binding specificity. This study provides potential drug candidates aimed for the treatment of rheumatoid arthritis and an alternative method of optimizing antibody affinity in vitro.