高度选择性突变对艾滋病病毒适应性影响机制的研究

During natural infection, HIV is under constant selection pressure from hosts. The potent immune selection pressure can quickly drive the viruses to escape through mutations in the viral genome. These immune escape mutations can cause significant fitness loss and result in reduced replication capability. Thus, a less fit virus is likely to lead to lower viral loads (VLs), which can render the virus less pathogenic and less likely to transmit to a new host. Importantly, epitopes with significant fitness loss due to immune escape mutations can be desirable targets for development of effective HIV vaccines. Recent studies have demonstrated that fitness loss caused by immune escape mutations can be restored by compensatory mutations in or outside of epitopes. However, fitness costs of a limited number of immune escape mutations have only been studied in heterologous viral genomes. Thus, the impact of immune escape mutations on their cognate viral genomes has not.been investigated. We have recently analyzed whole genome sequences of longitudinal samples from a number of acutely infected individuals. More importantly, we established a novel PASS fitness assay (PFA) that allows us to determine fitness costs of mutations in their cognate transmitted/founder (T/F) viral genomes. Thus in this study, we will construct the infectious molecular clones of the inferred T/F whole genome sequences and escape mutants based on the results of sequence analysis and immune recognition assays. By using our established PFA method, we will investigate the impact of CTL immune escape mutations on the fitness of cognate and heterologous T/F viruses. We will identify mechanisms for how frequently fitness loss caused by immune escape mutations can be restored by compensatory mutations/amino acids. We will further study various viral mutations accumulated during the acute infection period, including the CTL escape mutations, compensatory mutations, and non-immune pressure selected mutations, and their relationship with fitness, transmission and disease progression in patients. The knowledge gained from this study will also has significant implications in designing more effective HIV-1 vaccines targeting the epitopes induced by CTL immune responses.

HIV-1在感染人体后，病毒适应性的变化同病毒繁殖能力成正比，即病毒适应性损伤则病毒繁殖能力下降。宿主体内的免疫选择压力所导致的遗传突变会导致病毒适应性损伤，而这种损伤又可能被补偿性突变所修复。研究免疫压力选择突变对HIV-1适应性的影响，有助于深入地理解病毒适应性与感染进程之间的关系，为有效地控制病毒感染提供理论依据。在本课题中，我们将通过分析HIV-1急性期感染者的病毒全基因组纵向样本，推测并构建奠基病毒及其同源突变体的感染性分子克隆，利用前期建立的PFA适应性检测法，研究CTL免疫逃逸突变对同源T/F病毒及异源病毒适应性的影响，阐明补偿性突变修复逃逸突变所造成的适应性损害的机制，深入研究在急性感染期过程中病毒逐渐积累的各种选择突变（CTL逃逸、补偿性和非免疫压力选择突变）对病毒适应性与病毒感染机制和感染者病情进展之间的关系，为设计有效的以诱导CTL免疫反应为靶向的艾滋病疫苗奠定基础。

HIV-1在感染人体后，宿主体内的免疫选择压力所导致的遗传突变大多会导致病毒适应性损伤，而这种损伤又可能被补偿性突变所修复。研究免疫压力选择突变对HIV-1适应性的影响，有助于深入地理解病毒适应性与感染进程之间的关系，为更有效地控制病毒感染提供理论依据。在前期研究中，我们通过分析多个HIV-1急性感染期患者的病毒全基因组纵向样本，推测并构建了建立初始感染的不同奠基（T/F）病毒及其同源突变体病毒的感染性分子克隆（IMC）。在本项目中，我们利用这些IMCs和已建立的PFA适应性检测法，研究了不同患者体内病毒在急性感染期产生的每一个突变对其同源T/F病毒适应性的影响，并根据已报道的T细胞表位信息，分析得到了由CTL免疫反应所导致的逃逸突变和能够修复适应性损伤的补偿性突变。同时，我们首次证明了病毒的突变也可以在非免疫选择压力下产生，并且可以像在后天免疫选择压力下产生的突变那样造成病毒适应性损伤。我们还深入研究了在急性感染期中病毒逐渐积累的各种选择性突变对病毒适应性的总体影响，发现这些选择性突变累积的综合后果是导致病毒适应性损伤，且病毒的适应性损伤程度与急性感染期血浆病毒载量的下降水平呈正相关性。这些结果对于预测艾滋病患者疾的疾病进程和预后具有重要指导意义，并能为设计有效的以诱导CTL免疫反应为靶向的艾滋病疫苗奠定基础。

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