[转移帖] 研究揭示丙肝治疗失败过程中病毒变异进化特征

cao1976

原帖由503814发表于 2011-1-18 21:11



钟劲小组与谢青小组合作完成；为改善丙肝临床疗效提供新思路

近日，《感染、遗传和进化》（Infection, Genetics and Evolution）杂志在线发表了中国科学院上海巴斯德研究所钟劲研究组与上海瑞金医院感染科谢青教授研究组合作研究的最新成果。他们通过对两例不同类别的干扰素治疗失败的慢性丙肝患者进行长期随访，从病毒学角度深入研究了各随访时间点丙型肝炎病毒（HCV）全长基因序列的变异和进化情况。结果提示，治疗中反弹（breakthrough）患者中HCV的变异有可能是丙肝治疗失败的重要因素，这一发现将有助于进一步揭示难治性丙型肝炎的分子机制，为改善临床疗效提供新的思路。

HCV感染是导致慢性肝炎相关的慢性肝病、肝硬化、终末期肝病和肝癌的主要原因，同时也是肝移植的一个重要指证。世界卫生组织报道的全球HCV感染率超过3%，估计感染人口接近1.8亿人。在中国，感染率超过3.2%，感染人口接近4100万。HCV感染人体后，超过85%的感染者会转变为慢性感染。迄今，仍无有效的疫苗预防HCV感染，仅有的治疗方案就是干扰素联合利巴韦林进行为期半年到一年的治疗。来自西方国家的数据显示，在HCV基因1型的患者中，治疗有效率（达到持续病毒学应答）约为50%；而HCV基因2型、3型的感染者有效率能够达到75-80%。HCV基因1型是中国最主要的HCV流行基因型，被列入典型的“难治性丙型肝炎”范畴。抗病毒治疗失败一般分为以下3种类别：完全无应答、治疗中反弹和停药后复发。遗憾的是，干扰素治疗失败的分子机制至今仍然不明确。

钟劲研究组与谢青教授的临床团队展开深入合作，将临床研究与基础研究进行系统的结合。通过对两例完全无应答和治疗中反弹的治疗失败的慢性丙肝患者进行了5年长期随访，研究人员系统地收集了患者的临床资料及血清标本，深入研究了各随访时间点HCV全长基因序列的变异和进化情况。结果发现，治疗中反弹患者的HCV变异率明显高于完全无应答患者，而且这些变异主要发生在干扰素治疗期间，大多数变异在停药后都保留下来了，提示这些变异可能对HCV的病毒适应性（viral fitness）影响不大，但却能够帮助HCV在干扰素治疗压力下生存，有可能是治疗失败的关键因素。该研究提示，病毒学因素在难治性丙型肝炎的治疗中不可忽视，并为丙肝患者新型抗病毒药物靶点的选择提供了新的方向。

该项工作主要由瑞金医院与巴斯德研究所联合培养博士生项晓刚在钟劲研究员与谢青教授的指导下完成。该杂志审稿人对此工作给与高度评价，认为这类长期治疗随访的关于HCV病毒变异和进化的研究目前尚无报道并且非常难得，具有原创性和重要价值。

该项研究成果得到了国家“十一五”传染病重大专项、973项目、国家自然科学基金、中国科学院知识创新工程重大项目、上海市科委、上海巴斯德健康研究基金和上海市卫生局等的资助。

Infection, Genetics and Evolution
Article in Press, Corrected Proof - Note to users
doi:10.1016/j.meegid.2010.11.011 | How to Cite or Link Using DOI

Viral sequence evolution in Chinese genotype 1b chronic hepatitis C patients experiencing unsuccessful interferon treatment

Xiaogang Xianga, b, Jie Lub, Zhixia Donga, Huijuan Zhoua, Wanyin Taob, Qing Guoa, Xiaqiu Zhoua, Shisan Baoc, Qing Xiea, b, ,  and Jin Zhongb, ,
a Department of Infectious Diseases, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, 197 Ruijin Er Road, Shanghai 20005, China
b Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 225 South Chongqing Road, Shanghai 200025, China
c Discipline of Pathology (D06), Bosch Institute and School of Medical Sciences, The University of Sydney, New South Wales 2006, Australia

Received 6 July 2010;  revised 12 November 2010;  accepted 24 November 2010.  Available online 13 December 2010.

Abstract
The efficiencies of IFN-α based therapy in chronic genotype 1b HCV patients are still unsatisfied to date. The mechanisms underlining treatment failure remain unclear and controversial. To investigate HCV sequence evolution in unsuccessfully treated genotype 1b patients before, during and after the therapy, full-length open-reading-frame of HCV genomes at week 0, week 48 and year 5 in one breakthrough and one nonresponse patients were amplified by reverse transcription (RT)-nested-PCR and sequenced. Mutations were scored and analyzed according to their locations in the HCV genome. HCV sequences in the breakthrough patient displayed significantly more mutations during the one-year therapy than that in the nonresponse patient, with p7 and NS2 encoding regions having the highest mutation rates. Most of the mutations selected during the therapy phase in the breakthrough patient were maintained and few new mutations arose in the four-year post-therapy phase, suggesting these mutations might not compromise viral fitness. Altogether our data suggest that mutations occurred during the therapy phase in the breakthrough patient are likely driven by the action of interferon and ribavirin, and these mutations may have important effects on the responses to interferon based therapy in genotype 1b HCV patients.

Research highlights
Longitudinal sequencing analysis of HCV genomes in unsuccessfully treated patients.  HCV genome mutation rate in the breakthrough patient was high during the therapy.  HCV genome mutation rate in the nonresponse patient was low during the therapy.  Most HCV mutations in the breakthrough patient were kept in the post-therapy phase.  Viral mutations may account for interferon resistance in HCV breakthrough patients.
Keywords: Hepatitis C virus; Interferon therapy; Sustained virological response; Breakthrough; Nonresponse; Sequence evolution

Abbreviations: HCV, hepatitis C virus; CHC, chronic hepatitis C; SVR, sustained virological response; IFN-α, interferon alpha; ORF, open reading frame; HCC, hepatocellular carcinoma