Immunization with a Recombinant Vaccinia Virus That Encodes Nonstructural Proteins of the Hepatitis C Virus Suppresses Viral Protein Levels in Mouse Liver

Chronic hepatitis C, which is caused by infection with the hepatitis C virus (HCV), is a global health problem. Using a mouse model of hepatitis C, we examined the therapeutic effects of a recombinant vaccinia virus (rVV) that encodes an HCV protein. We generated immunocompetent mice that each expressed multiple HCV proteins via a Cre/loxP switching system and established several distinct attenuated rVV strains. The HCV core protein was expressed consistently in the liver after polyinosinic acid–polycytidylic acid injection, and these mice showed chronic hepatitis C-related pathological findings (hepatocyte abnormalities, accumulation of glycogen, steatosis), liver fibrosis, and hepatocellular carcinoma. Immunization with one rVV strain (rVV-N25), which encoded nonstructural HCV proteins, suppressed serum inflammatory cytokine levels and alleviated the symptoms of pathological chronic hepatitis C within 7 days after injection. Furthermore, HCV protein levels in liver tissue also decreased in a CD4 and CD8 T-cell-dependent manner. Consistent with these results, we showed that rVV-N25 immunization induced a robust CD8 T-cell immune response that was specific to the HCV nonstructural protein 2. We also demonstrated that the onset of chronic hepatitis in CN2-29(+/−)/MxCre(+/−) mice was mainly attributable to inflammatory cytokines, (tumor necrosis factor) TNF-α and (interleukin) IL-6. Thus, our generated mice model should be useful for further investigation of the immunological processes associated with persistent expression of HCV proteins because these mice had not developed immune tolerance to the HCV antigen. In addition, we propose that rVV-N25 could be developed as an effective therapeutic vaccine.

由丙型肝炎病毒（hepatitis C virus, HCV）感染引发的慢性丙型肝炎是全球性公共卫生难题。本研究借助丙型肝炎小鼠模型，探究了编码HCV蛋白的重组痘苗病毒（recombinant vaccinia virus, rVV）的治疗效果。我们通过Cre/loxP重组系统构建了可表达多种HCV蛋白的免疫健全小鼠模型，并成功获得数株特性各异的减毒重组痘苗病毒株。经聚肌胞苷酸（polyinosinic acid–polycytidylic acid）注射后，小鼠肝脏可持续表达HCV核心蛋白，且呈现慢性丙型肝炎相关病理特征：肝细胞异常、糖原蓄积、脂肪变性，同时伴随肝纤维化与肝细胞癌。针对其中一株编码HCV非结构蛋白（HCV nonstructural proteins）的重组痘苗病毒株rVV-N25进行免疫，可在注射后7天内降低小鼠血清炎症细胞因子水平，缓解病理性慢性丙型肝炎症状。此外，肝脏组织内的HCV蛋白表达水平同样呈现CD4与CD8 T细胞依赖性下降趋势。与上述结果一致，rVV-N25免疫可诱导出针对HCV非结构蛋白2（HCV nonstructural protein 2）的强效特异性CD8 T细胞免疫应答。我们还证实，CN2-29(+/−)/MxCre(+/−)小鼠发生慢性肝炎的主要诱因是炎症细胞因子肿瘤坏死因子-α（TNF-α）与白细胞介素-6（IL-6）的介导作用。综上，本研究构建的小鼠模型未对HCV抗原产生免疫耐受，可用于后续探究HCV蛋白持续表达相关的免疫过程，具备良好的研究价值。此外，本研究提示rVV-N25有望开发为高效治疗性疫苗。