Mechanisms of Interferon Action and Resistance in Hepatitis C Virus Infection

为了了解干扰素在体内的耐药性，我们在黑猩猩模型中检测了人干扰素(h干扰素)-α、-γ和共识干扰素的动态反应。用幼年黑猩猩和健康人类捐献者的外周血单核细胞(PBMC)进行的体外研究表明，黑猩猩对hIFN的反应不如人类。用较高剂量的hIFN治疗幼稚的和感染了丙型肝炎病毒的黑猩猩，以弥补hIFN对黑猩猩的较低疗效。在感染丙型肝炎病毒的黑猩猩中，PBMC对这三种干扰素的体内反应比未感染的黑猩猩低得多。在肝脏中的差异更为显著，因为在感染的动物中几乎检测不到肝脏干扰素诱导的基因诱导。对多种干扰素信号抑制剂的评估表明，给予干扰素后，细胞因子信号转导抑制因子3(SOCS3)的表达显著上调，这可能是通过诱导IL-6来实现的。总之，这些数据表明，感染丙型肝炎病毒的黑猩猩对干扰素的反应存在缺陷，特别是在肝脏，这种缺陷可能是通过激活SOCS3来调节的。进一步研究丙型肝炎病毒感染对黑猩猩体内干扰素效应途径的抑制机制，可能为解决干扰素治疗无应答的临床问题提供新的思路。 为了进一步探索干扰素在丙型肝炎患者中的作用和耐药性的机制，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。在接受治疗的患者中，患者在活组织检查前24小时接受单独的聚乙二醇干扰素α-2a或利巴韦林72小时和聚乙二醇干扰素-α。到第4周时，患者被分成快速应答组(RR)和慢应答组(SR)，其中丙型肝炎病毒核糖核酸(HCVRNA)下降2个对数。治疗前活检标本来自匹配的对照组。根据随后的治疗反应，将治疗前患者分为RR组或SR组。使用Affymetrix微阵列技术进行基因表达谱分析。已知的ISG在接受治疗的患者中被诱导。在治疗前组中，未来慢反应组(SR)的ISG表达高于快速反应组(RR)。在治疗时，RR和SR具有相似的ISG绝对表达，但当使用治疗前组校正基线表达时，RR显著诱导ISG，而SR显示上调干扰素抑制途径。接受利巴韦林治疗的患者干扰素相关基因的诱导增强，与干扰素抑制和肝星状细胞(HSC)激活相关的基因下调。这些数据表明，ISG的诱导性对治疗反应很重要，利巴韦林可能通过增强肝脏对聚乙二醇干扰素的基因反应来改善预后。总的来说，这些机制可能为提高联合治疗的疗效提供了分子基础。

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.