Bull Rowena A, Leung Preston, Gaudieri Silvana, Deshpande Pooja, Cameron Barbara, Walker Melanie, Chopra Abha, Lloyd Andrew R, Luciani Fabio
Systems Medicine, Inflammation and Infection Research Centre, School of Medical Sciences, Faculty of Medicine, UNSW Australia, Sydney, New South Wales, Australia.
School of Anatomy, Physiology and Human Biology, University of Western Australia, Nedlands, Western Australia, Australia Institute for Immunology and Infectious Disease, Murdoch University, Perth, Western Australia, Australia.
J Virol. 2015 May;89(10):5478-90. doi: 10.1128/JVI.03717-14. Epub 2015 Mar 4.
The interaction between hepatitis C virus (HCV) and cellular immune responses during very early infection is critical for disease outcome. To date, the impact of antigen-specific cellular immune responses on the evolution of the viral population establishing infection and on potential escape has not been studied. Understanding these early host-virus dynamics is important for the development of a preventative vaccine. Three subjects who were followed longitudinally from the detection of viremia preseroconversion until disease outcome were analyzed. The evolution of transmitted/founder (T/F) viruses was undertaken using deep sequencing. CD8(+) T cell responses were measured via enzyme-linked immunosorbent spot (ELISpot) assay using HLA class I-restricted T/F epitopes. T/F viruses were rapidly extinguished in all subjects associated with either viral clearance (n = 1) or replacement with viral variants leading to establishment of chronic infection (n = 2). CD8(+) T cell responses against 11 T/F epitopes were detectable by 33 to 44 days postinfection, and 5 of these epitopes had not previously been reported. These responses declined rapidly in those who became chronically infected and were maintained in the subject who cleared infection. Higher-magnitude CD8(+) T cell responses were associated with rapid development of immune escape variants at a rate of up to 0.1 per day. Rapid escape from CD8(+) T cell responses has been quantified for the first time in the early phase of primary HCV infection. These rapid escape dynamics were associated with higher-magnitude CD8(+) T cell responses. These findings raise questions regarding optimal selection of immunogens for HCV vaccine development and suggest that detailed analysis of individual epitopes may be required.
A major limitation in our detailed understanding of the role of immune response in HCV clearance has been the lack of data on very early primary infection when the transmitted viral variants successfully establish the acute infection. This study was made possible through the availability of specimens from a unique cohort of asymptomatic primary infection cases in whom the first available viremic samples were collected approximately 3 weeks postinfection and at regular intervals thereafter. The study included detailed examination of both the evolution of the viral population and the host cellular immune responses against the T/F viruses. The findings here provide the first evidence of host cellular responses targeting T/F variants and imposing a strong selective force toward viral escape. The results of this study provide useful insight on how virus escapes the host response and consequently on future analysis of vaccine-induced immunity.
丙型肝炎病毒（HCV）与极早期感染期间细胞免疫反应之间的相互作用对疾病转归至关重要。迄今为止，抗原特异性细胞免疫反应对建立感染的病毒群体进化及潜在逃逸的影响尚未得到研究。了解这些早期宿主 - 病毒动态对于预防性疫苗的研发很重要。分析了3名从病毒血症检测到血清阳转前一直纵向随访直至疾病转归的受试者。通过深度测序研究传播/奠基（T/F）病毒的进化。使用HLA I类限制性T/F表位，通过酶联免疫斑点（ELISpot）测定法测量CD8(+) T细胞反应。在所有受试者中，T/F病毒迅速被清除，这与病毒清除（n = 1）或被导致慢性感染建立的病毒变体替代（n = 2）相关。感染后33至44天可检测到针对11个T/F表位的CD8(+) T细胞反应，其中5个表位此前未见报道。这些反应在慢性感染的受试者中迅速下降，而在清除感染的受试者中得以维持。更高强度的CD8(+) T细胞反应与免疫逃逸变体的快速出现相关，出现速率高达每天0.1。在原发性HCV感染的早期阶段首次对CD8(+) T细胞反应的快速逃逸进行了量化。这些快速逃逸动态与更高强度的CD8(+) T细胞反应相关。这些发现对HCV疫苗研发中免疫原的最佳选择提出了疑问，并表明可能需要对单个表位进行详细分析。
我们对免疫反应在HCV清除中作用的详细理解的一个主要限制是缺乏关于极早期原发性感染的数据，此时传播的病毒变体成功建立急性感染。这项研究得以开展是因为有来自一组独特的无症状原发性感染病例的标本，在这些病例中，首次可获得的病毒血症样本在感染后约3周采集，此后定期采集。该研究包括对病毒群体进化和宿主针对T/F病毒的细胞免疫反应的详细检查。此处的发现首次证明了宿主细胞针对T/F变体的反应，并对病毒逃逸施加了强大的选择压力。这项研究的结果为病毒如何逃避宿主反应以及因此对疫苗诱导免疫的未来分析提供了有用的见解。
