Optimizing CD8+ T-cell responses against C clade HIV infection in subSaharan Afri

描述(由申请人提供)：CD8+T细胞T细胞在HIV感染的免疫控制中发挥核心作用。然而，HIV疫苗应该诱导的CD8+T细胞反应才能达到最佳效果，这一点尚未确定。在这笔赠款的前5年中，我们所做的工作侧重于南部非洲艾滋病毒疫情，该地区受艾滋病毒影响最严重，最迫切需要有效的疫苗。 从我们在过去5年的这笔赠款中所做的工作中可以得出的一个主要结论是，HIV感染的免疫控制受到广泛的GAG特异性CD8+T细胞反应的促进，特别是GAG中的反应，但在POL中的反应程度较小，这可以推动对病毒的选择压力。很明显，一些最有效的反应低于其他无效的反应。不同蛋白质(GAG&GT；POL&GT；ACC-REG&GT；Env)的表位效力不同，但在蛋白质内也不同。不同的限制条件，其表位效力也不同。人类白细胞抗原-B限制性反应对病毒的设定点影响最大，对病毒的选择压力最大。HL A-C限制性反应与高病毒设定点相关，即使它们是Gag特异性的。 这些研究的第一个具体目标是，使用一种新的方法来实现CTL表位的快速定义，以确定在Gag和POL中最有效地抑制HIV复制的反应，包括亚显性反应。很明显，目前对最佳靶点和CD8+T细胞反应层级的了解仍然不足以理解自然感染HIV中的CD8+T细胞反应，以及需要对这个反应层级进行什么扰动才能优化CD8+T细胞对HIV免疫控制的贡献。对于像A*6802这样的等位基因，存在于1/6的南部非洲人口中，目前所描述的最佳表位仅占受该等位基因限制的A*6802阳性受试者实际反应的1%。这种新的方法，包括使用多肽-MHC四聚体，是快速和廉价的，我们已经验证了所提供的初步数据，关键是提供了进一步的机会来评估纯化的抗原特异性细胞在病毒抑制试验中的有效性。 这些研究的第二个目的是调查T细胞疫苗在人类中改变自然感染中观察到的反应等级的能力。我们将研究接种了MRK Ad5疫苗(HVTN 503，‘Phambili’Study)的南非受试者，该疫苗表达Gag、Pol和Nef。利用我们对1,015名南非研究对象的数据库，我们已经确定了CD8+T细胞对C分支感染的反应，使用了一组410个重叠的18聚体多肽，我们将能够确定这种MRK Ad5 T细胞疫苗是否可以改变在未接种疫苗的感染者中看到的反应层次。这将是T细胞疫苗有效的重要先决条件。 这些拟议研究的最终特定目标是调查病毒适应对CD8+T细胞反应等级的影响。我们在过去5年的工作中已经表明，病毒适应是在种群水平上发生的，因此即使是最具保护性的表位中的逃逸突变也会随着时间的推移而积累。这些拟议的工作室将考虑这些逃逸突变体积累的速度和程度，以确定病毒适应实际上是否可能对当前的T细胞疫苗设计产生影响。

DESCRIPTION (provided by applicant): CD8+ T-cell T-cells can be a central role in immune control of HIV infection. However, the CD8+ T-cell responses that should be induced by an HIV vaccine in order to be optimally effective are yet to be established. Work we have done in the course of the previous 5 years of this grant have focused on the southern African HIV epidemic, the region worst affected by HIV and most urgently in need of an effective vaccine. One major conclusion that can be drawn from the work we have done in the past 5 years of this grant is that immune control of HIV infection is facilitated by a broad Gag-specific CD8+ T-cell response, in particular by responses in Gag, but also to a lesser extent in Pol, that can drive selection pressure on the virus. It is apparent that some of the most efficacious responses are subdominant to other, ineffective responses. Epitope efficacy differs between proteins (Gag>Pol>Acc-Reg>Env), but also within proteins. Epitope efficacy also differs acording to HLA restriction. HLA-B-restricted responses have the greatest impact on viral setpoint, and drive the strongest selection pressure on the virus. HLA-C-restricted responses are associated with high viral setpoint even when they are Gag-specific. The goal of the first specific aim of these proposed studies is, using a novel approach to achieve rapid definition of CTL epitopes, to identify those responses, including subdominant responses, in Gag and Pol that are most effective in inhibition of HIV replication. It is quite clear that current knowledge of the optimal epitopes targeted, and the CD8+ T-cell response hierarchy even for the most prevalent HLA alleles, remains inadequate in order to understand the CD8+ T-cell response in natural HIV infection and what perturbations of this response hierarchy may be needed to optimise the CD8+ T-cell contribution to immune control of HIV. For an allele such as A*6802, present in 1/6 of the southern African population, currently described optimal epitopes account for only 1% of the actual responses made by A*6802-positive subjects that are restricted by that alelle. The novel approach, involved use of peptide-MHC tetramers, is rapid and inexpensive, has been validated by us as shown in preliminary data presented, and crucially provides the further opportunity to assess the efficacy of purified antigenic-specific cells in viral inhibition assays. The second aim of these studies is to investigate the ability of a T-cell vaccine in humans to alter the response hierarchy observed in natural infection. We will study the South African subjects who were vaccinated with the MRK Ad5 vaccine (HVTN 503, 'Phambili' study), which expressed Gag, Pol and Nef. Using our database of 1,015 south African study subjects in whom we have characterized the CD8+ T-cell responses against C clade infection, using a panel of 410 overlapping 18mer peptides, we will be able to determine whether this MRK Ad5 T-cell vaccine, which has already been shown to boost specifically Gag, Pol and Nef responses in post-infection vaccinees, can alter the response hierarchy that is seen in non-vaccinated infected people. This would be an important prerequisite for a T-cell vaccine to be effective. The final specific aim of these proposed studies is to investigate the impact of viral adaptation to the CD8+ T-cell response hierarchy. We have shown in the previous 5 years' work that viral adaptation is occurring at a population level, such that escape mutants in even the most protective epitopes are accumulating over time. How fast, and the extent to which, these escape mutants accumulate will be considered in these proposed studioes, to determine whether viral adaptation in fact is likely to have an impact on current T-cell vaccine design.