噬菌体抗体库筛选技术及在肿瘤研究中的应用

噬菌体抗体是指表达在噬菌体表面的抗体分子Fab或scFv,这些分子的群体称为抗体库。经特定抗原或细胞筛选后可以获得针对该抗原或细胞表面标志物的特异性抗体。经典的筛选方法为固相或液相抗原识别,前提条件是能得到抗原纯品,对于抗原无法提纯或抗原性质不确定的情况则不能适用,所以又出现全细胞筛选,直接利用肿瘤细胞或组织细胞进行筛选,无需纯抗原,但目标抗原一定要有较高的表达水平,对于表达较低的情况,一种策略是先利用正常细胞筛选,去掉无关抗原后,再利用肿瘤细胞筛选;另一种策略是细胞内化筛选,特异性抗体被内化入细胞,然后用酸性洗脱液洗脱掉细胞膜上非特异结合的噬菌体抗体后裂解细胞,获得特异性抗体。其余筛选方法还有切片组织筛选、体内筛选等,适用面较窄,未获推广。筛选效率主要通过以下几项的检测:转化数,即被感染的噬菌体数,它随筛选轮数的增加而增加;抗体基因插入载体的频率,高比例的丢失意味着筛选的低效率;抗体亲和性。抗体库技术避免了杂交瘤技术中的许多难点,如细胞融合、动物免疫等,目前该技术已逐渐在肿瘤诊断和肿瘤治疗中发挥重要作用。

Selection technology of phage antibody library and its application in tumor research

Phage antibody means those Fab or scFv, which display in the membrane of phages. The repertoires of these antibodies are antibody library. Biopinned by antigen or cell, relevant antibody can be got. Classical biopanning technique is antigen(solidified or liquefied) recognition by purified antigen ,when the purified antigen can not be obtained, the classical technique can not be applied. So full cell biopanning has appeared, which needs not purify antigen, but the target antigen must be highly expressed, otherwise, some strategy can be used. One is wiping off the irrespective antigen by normal cells, then tumor cell antigen is relatively high, another strategy is internalizing biopanning: special antibody is internalized by certain technique, then the irrelative antibody is washed off, special antibody is got by splitting the cells. Other techniques such as in tissue sections selection and in vivo selection were narrowly applied. The biopanning efficiency is detected by following aspects: transforming unit, enhanced with the round of biopanning; the frequency of gene fusing, high deletion of antibody gene meaning low efficiency; the affinity of antibody. The antibody library technique can avoid many problems of hybridoma such as cell fusion and animal immunity. It has been used in tumor diagnosis and treatment.