胰岛素瘤相关蛋白-2在HEK293中的重组生产及抗原性分析

胰岛素瘤相关蛋白-2（insulinoma-associated protein-2，IA-2），是属于酪氨酸磷酸酶样蛋白家族的跨膜糖蛋白，也是诊断1型糖尿病的重要自身抗原，相关产品已在欧美国家上市。目前，商业化的IA-2抗原主要为重组IA-2ic结构域，或从牛胰岛中天然提取的IA-2，其中重组IA-2抗原在临床上存在弱阳性漏检的问题，无法完全替代天然提取IA-2抗原。本研究利用HEK293表达系统探究IA-2的重组生产。通过瞬时表达IA-2的第449-979位氨基酸跨膜片段（IA-2 transmembrane fragment，IA-2 TMF）这一天然形式的膜蛋白，并优化表达条件和膜蛋白溶解条件，纯化后膜蛋白得率为0.78 mg/L细胞发酵液。随后，通过酶联免疫吸附（enzyme linked immunosorbent assay，ELISA），对比IA-2 TMF与RSR rhIA-2的抗原活性，检测了77位1型糖尿病患者血清和32位健康志愿者血清，测试的结果通过接受者操作特性曲线（receiver operating characteristic curve，ROC）表征敏感性和特异性。结果表明：IA-2 TMF的敏感性为71.4%（55/77），而RSR rhIA-2的敏感性为63.6%（49/77），2种抗原特异性均为100%。2种抗原在特异性上无明显差异，而IA-2 TMF的敏感性略优于进口金标RSR rhIA-2抗原。综上所述，本研究基于HEK293重组表达的IA-2 TMF能够作为1型糖尿病体外诊断试剂开发的原料。

Production and antigenicity analysis of a recombinant insulinoma associated protein-2 in HEK293 cells

Insulinoma-associated protein-2 (IA-2) is a transmembrane glycoprotein belonging to the tyrosine phosphatase-like protein family as well as an important autoantigen in the diagnosis of type 1 diabetes. IA-2 products have been marketed in Europe and the United States. At present, commercially available IA-2 antigens are either the recombinant IA-2ic domain or the IA-2 naturally extracted from bovine islets. However, the recombinant IA-2 antigen displays weak positive in clinic practice, which often results in occasional detection failures, thus cannot completely replace the naturally extracted IA-2 antigen. In this study, an HEK293 expression system was used to explore the production of recombinant IA-2. An IA-2 transmembrane fragment (IA-2 TMF) located at amino acid position 449-979, also known as the natural membrane protein form of IA-2, was produced in HEK293 through transfection, and both the expression conditions and dissolution conditions of the membrane protein were also optimized. The purified membrane protein yield was 0.78 mg/L cell culture. Subsequently, the antigen activity of IA-2 TMF was compared with RSR rhIA-2 through enzyme linked immunosorbent assay. The serum of 77 type 1 diabetes patients and 32 healthy volunteers were detected. Receiver operating characteristic curve (ROC) curve was used to characterize the sensitivity and specificity of the test results. The results showed that the sensitivity of IA-2 TMF was 71.4% (55/77), while the sensitivity of RSR rhIA-2 was 63.6% (49/77), and the specificity of both antigens were all 100%. There was no significant difference in specificity between the two antigens, but the sensitivity of IA-2 TMF was appreciably better than that of the imported gold standard RSR rhIA-2 antigen. In conclusion, the recombinant IA-2 TMF produced in HEK293 cells can be used as a raw material to develop in vitro diagnostic reagents for type 1 diabetes.