Mechanisms of Interferon Action and Resistance in Hepatitis C Virus Infection

为了了解干扰素在体内的阻力，我们研究了动态响应人干扰素（hIFN）-α，γ和共识干扰素的黑猩猩模型。在体外研究与幼稚的黑猩猩和健康的人类供体的外周血单核细胞（PBMC）表明，黑猩猩响应不如人类的hIFN。使用较高剂量的hIFN治疗幼稚和HCV感染的黑猩猩，以补偿hIFN在黑猩猩中的较低功效。在体内的PBMC的反应，所有三个IFN的HCV感染的黑猩猩比那些在幼稚的黑猩猩低得多。肝脏中的差异更显着，因为在感染动物中几乎检测不到肝脏IFN诱导的基因诱导。各种IFN信号抑制剂的评估表明，IFN给药后，细胞因子信号抑制因子3（SOCS 3）的表达显着上调，可能是通过诱导IL-6，在HCV感染的黑猩猩的肝脏。总之，这些数据表明HCV感染的黑猩猩对IFN的反应有缺陷，特别是在肝脏中，这种缺陷可能是通过SOCS 3的激活介导的。进一步研究HCV感染对IFN效应通路的抑制机制，可能为IFN治疗无效的临床问题提供新的见解。 为了进一步探讨干扰素的作用机制和HCV患者的耐药，我们比较了患者在聚乙二醇干扰素和利巴韦林治疗前和治疗期间的肝脏基因表达。在治疗组中，患者在活检前接受聚乙二醇干扰素α-2a或利巴韦林72小时和聚乙二醇干扰素α-24小时。在第4周，患者被分为HCV RNA下降>2-log的快速应答者（RR）和HCV RNA下降<2-log的缓慢应答者（SR）。从匹配的对照组获得治疗前活检标本。根据后续治疗应答，将治疗前患者分组为RR或SR。基因表达谱分析使用Affyssin微阵列技术进行。在接受治疗的患者中诱导了已知的ISG。在预治疗组中，未来慢反应者（SR）的预治疗ISG表达高于快速反应者（RR）。在治疗中，RR和SR具有相似的ISG绝对表达，但当使用预处理组校正基线表达时，RR具有显著的ISG诱导，而SR显示IFN抑制途径的上调。利巴韦林预处理的患者IFN相关基因的诱导增强，以及IFN抑制和肝星状细胞（HSC）激活相关基因的下调。这些数据表明，ISG诱导对于治疗反应是重要的，利巴韦林可能通过增强肝脏基因对聚乙二醇干扰素的反应来改善结果。总的来说，这些机制可以为联合治疗的疗效改善提供分子基础。

To understand IFN resistance in vivo, we examined the dynamic responses to human IFN (hIFN)-alfa, -gamma and consensus IFN in the chimpanzee model. In vitro study with peripheral blood mononuclear cells (PBMCs) of naive chimpanzees and healthy human donors showed that chimpanzee responded less well than human to hIFNs. Naive and HCV-infected chimpanzees were treated with hIFNs using higher doses to compensate for the lower efficacy of hIFNs in chimpanzees. The in vivo responses of PBMCs to all three IFNs were much lower in the HCV-infected chimpanzees than those in the naive chimpanzees. The difference was more dramatic in the liver as the hepatic IFN-induced gene inductions were barely detectable in the infected animals. Assessment of various IFN signaling inhibitors showed that following IFN administration, the expression of suppressor of cytokine signaling 3 (SOCS3) was significantly upregulated, possibly through the induction of IL-6, in the liver of HCV-infected chimpanzees. In conclusion, these data indicate a defective response, particularly in the liver, to IFNs in HCV-infected chimpanzees, and this defect is possibly mediated through the activation of SOCS3. Further study on the inhibitory mechanism of IFN effector pathway by HCV infection in chimpanzee may provide novel insights into the clinical issue of nonresponse to IFN therapy. To further explore the mechanisms of IFN action and resistance in HCV patients, we compared hepatic gene expression in patients prior to and during peginterferon and ribavirin therapy. In the on-treatment group patients received either peginterferon alfa-2a alone or ribavirin for 72 hours and peginterferon-alfa 24 hours prior to biopsy. Patients were grouped into rapid responders (RR) with >2-log drop and slow responders (SR) with <2-log drop in HCV RNA by week 4. Pre-treatment biopsy specimens were obtained from a matched control group. Pre-treatment patients were grouped as RR or SR based on subsequent treatment response. Gene expression profiling was performed using Affymetrix microarray technology. Known ISGs were induced in treated patients. In the pre-treatment group, future slow responders (SR) had higher pretreatment ISG expression than rapid responders (RR). On treatment, RR and SR had similar absolute ISG expression but when corrected for baseline expression using the pre-treatment group, RR had marked induction of ISGs while SR showed up-regulation of IFN-inhibitory pathways. Patients pretreated with ribavirin had heightened induction of IFN-related genes as well as down-regulation of genes involved in IFN-inhibition and hepatic stellate cell (HSC) activation. These data suggest that ISG inducibility is important for treatment response and ribavirin may improve outcomes by enhancing hepatic gene responses to peginterferon. Collectively these mechanisms may provide a molecular basis for the improved efficacy of combination therapy.