优化密码促进HPV 6b E7蛋白表达及DNA疫苗诱导的细胞免疫反应

目的：探讨优化密码对人乳头瘤病毒6b型（HPV 6b）基因表达及免疫原性的影响，为治疗性DNA疫苗的研究奠定基础。方法：设计合成含优化密码及pRB结合位点突变的HPV 6bE7(humE7）全长基因。测序验证无误后，定向克隆于pcDNA3的Kpn I和EcoR I位点，成功构建真核表达质粒pcDNA3-hu-mE7。体外转染COS－1细胞，免疫荧光检测其E7蛋白表达。C57BL／6小鼠胫前肌内接种裸DNA，观察其诱导的细胞免疫反应。结果：pcDNA3-hu-mE7在COS－1细胞获得明显表达，表达产物主要位于细胞核中。DNA免疫结果显示，与含有野生型E7基因的表达质粒pcDNA3-wtE7比较，pcDNA3-hu-mE7免疫小鼠脾细胞培养上清中IFN-γ产生明显升高，CD8^ 和CD4^ 淋巴细胞活性增强。结论：优化密码能促进HPV 6b E7蛋白表达及DNA疫苗诱导的细胞免疫反应。

Optimized codon usage enhances the expression and immunogenicity of DNA vaccine encoding the HPV 6b E7 gene

OBJECTIVE: To analyze the influence of optimal codon usage on the expression levels and immunogenicity of DNA vaccines, encoding the human papillomavirus type 6b (HPV 6b) E7 gene. METHODS: The full length E7 gene of HPV 6b was modified to substitute human preferred codon for rarely used codon, and three mutations were introduced into the pRB binding site of HPV 6b E7 to eliminate its transformation potential. The codon optimized and mutated E7 gene (hu-mE7) were cloned into the Kpn I and EcoR I site of the pcDNA3 mammalian expression vector, the in vitro expression of the hu-mE7 gene and the immunogenicity of hu-mE7 DNA vaccine were compared with the wt-E7gene. RESULTS: The in vitro expression of pcDNA3-hu-mE7 was much higher than the classical wt-E7 plasmid in monkey COS-1 cell line. Mice immunized intramuscularly with the pcDNA3-hu-mE7 showed that the codon modified E7 gene induced a stronger IFN-gamma ratios than the wt-E7 gene. CONCLUSIONS: These results suggest that the optimized codon usage contributes to the enhancement of gene expression and immunogenicity of HPV 6b E7 gene.