可复制型抗肿瘤DNA疫苗PSCK-2PFcGB的构建及体内外表达

Construction of a replicative anti-tumor DNA vaccine PSCK-2PFcGB and its expression in vivo and in vitro

目的构建以塞姆利基森林病毒复制子载体为基础的可复制型抗肿瘤DNA疫苗PSCK-2PFcGB,验证其在人胚肾293T细胞及免疫小鼠肌肉组织内的表达情况。方法首先用NheI酶切既往构建的pVAX1-2PFcGB重组质粒,补平酶切后的粘末端,然后再用限制性内切酶BssHII继续酶切该线性化质粒,补平粘末端后即获得含有编码Survivin及hCGβ-CTP37肿瘤抗原的融合基因片段2PFcGB,接着利用DNA重组技术将该片段克隆入基于塞姆利基森林病毒复制子载体改造的PSCK载体,筛选阳性重组质粒。接着,利用阳离子脂质体介导法将其瞬时转染入人胚肾293T细胞,利用流式细胞术及免疫荧光法检测融合抗原在293T细胞中的表达;利用电脉冲基因导入仪将该重组质粒递送至BALB/C小鼠股四头肌,利用免疫组化法验证肿瘤抗原在小鼠体内的表达。结果琼脂糖凝胶电泳结果显示酶切片段大小与预期一致,流式细胞术检测该重组质粒瞬时转染的293T细胞,可见大量的阳性荧光细胞,其IRES序列上游融合肿瘤抗原分子阳性表达率为5.70%,下游佐剂分子阳性表达率为19.75%;同时,利用两种肿瘤抗原特异抗体在免疫小鼠股四头肌组织切片上均检测到了相应表达。结论成功构建了可复制型抗肿瘤DNA疫苗PSCK-2PFcGB,该重组质粒在体内外均能高效表达外源肿瘤抗原及佐剂分子,这些结果为该抗肿瘤DNA疫苗进一步的抑瘤活性及免疫学作用机制的研究奠定了坚实的实验基础。

Objective To construct a replicative anti-tumor DNA vaccine PSCK-2PFcGB based on Semiliki Forest Virus （SFV） replicon vector and observe its expression in vivo and in vitro. Methods The plasmid pVAX1-2PFcGB was digested with Nhe I, and the digestion product was blunted prior to further digestion with BssH II to obtain the fragment 2PFcGB, a fusion gene containing the multitarget complex antigen 2PAG encoding both the most cytotoxic T lymphocyte epitopes of human survivin and chorionic gonadotropin β chain-CTP37 of human and monkey. The 2PFcGB fragment was inserted into the PSCK vector digested by Sma I. The products with the expected size were extracted and ligated, and the positive clones were screened by kannamycin and amplified. The recombinant PSCK-2PFcGB, following identification by colony PCR and restriction endonuclease Nde I, was transfected into 293T cells via lipofectamine 2000 and its expression was detected. The recombinant plasmid was also transfected into mouse quadriceps femoris muscle to observe its expression in vivo by immunohistochemistry. Results Nde I digestion resulted in a fragment of the expected size. Transfection with the recombinant plasmid PSCK-2PFcGB resulted in successful expression of the antigen and adjuvant molecular protein in 293T cells, with the positivity rates of 5.70% and 19.75%, respectively. The fusion tumor antigen survivin and hCGβ-CTP37 were also detected in the muscular tissues of the mice. Conclusion A novel replicative anti-tumor DNA vaccine PSCK-2PFcGB has been successfully constructed and can be expressed in 293T cells and in the muscular tissues of immunized mice, which provide a basis for further studies of the antitumor activity and immunological mechanism of the DNA vaccine.