含体内激活启动子的重组减毒鼠伤寒沙门菌诱导转基因鼠细胞免疫应答

摘要

To explore the approaches and mechanisms for reversing the immune tolerance in transgenic mouse, and the pathogenicity of hepatitis G virus (HGV), the promoter of phoP-activated gene (PpagC) of Salmonella typhimurium was used as a transcriptionally regulating element to construct an attenuated S. typhimurium expressing HGV NS3. The recombinant S. typhimurium was orally administered to HGV transgenic mice. As the results, HGV antigen in serum and liver as well as HGV mRNA in liver were decreased significantly, although the serum anti-HGV NS3 remained undetectable as the control transgenic mice. The spleen cell proliferation, in vitro HGV NS3 specific CTL, and IFN-γ assays with the primed cultured splenocytes indicated the induction of Th1 immune responses in those administered transgenic mice. Adoptive transfer of fractionated primed spleen cells to the transgenic mice showed that T lymphocytes were responsible for, 05-be through IFN-γ, the down-regulation of HGV mRNA transcription. Histological examination found no significant inflammatory changes in liver of the transgenic mice. These findings suggested that the oral inoculation of the HGV NS3-expressed attenuated S. typhimurium driven by an in vivo-activated promoter should be a simple and effective approach for potential treatment of chronic viral infection.%以庚型肝炎病毒 (hepatitis G virus, HGV) 转基因小鼠为模型, 探讨逆转免疫耐受的方法及与HGV致病性的关系. 首先采用鼠伤寒沙门菌pagC基因的启动子(PpagC)为转录调控元件, 构建宿主体内表达HGV NS3抗原的重组减毒鼠伤寒沙门菌, 并口服接种免疫HGV转基因小鼠. 结果证明对诱导转基因小鼠血清HGV NS3抗体无明显影响, 但对小鼠血清HGV抗原含量、肝组织HGV抗原及HGV mRNA表达量有明显抑制作用. 体外培养脾细胞表现出针对HGV NS3抗原的细胞免疫反应, 并检测到Th1型细胞因子IFN-γ. 过继转移实验证明T细胞可能是通过IFN-γ介导的机制抑制转基因鼠体内HGV的表达及复制. 组织病理学检查显示, 转基因小鼠肝组织见淋巴细胞浸润等轻度炎性变. T细胞免疫耐受消除的结果提示, 这种宿主体内激活目的抗原表达的口服疫苗有望成为治疗病毒性肝炎的新方法.