Determinants of Neutralization Breadth in Early HIV-1 Infection

描述（由申请人提供）：诱导抗体中和（nAb）循环HIV-1毒株的能力将是疫苗对HIV-1表现出最佳保护功效的关键。为了确定能够刺激这些反应的表位，从一些表现出优质血浆nAb的慢性感染个体中恢复了具有广泛和有效中和能力的单克隆抗体（mAb），但是在这种广泛和有效中和表型之前的病毒和宿主B细胞事件尚未确定。早期感染的样本尚未从这些广泛中和的个体中获得，因此关于nAb广度如何发展的问题尚未得到回答。在这里，我们鉴定了17名甲型和丙型HIV-1感染的血清转化者中的5名，他们在感染后约3年出现了相对有效的跨枝nAb宽度。本提案将研究nAb宽度如何以及为什么在这些个体中发展，而不是在其他低或未检测到宽度水平的个体中发展。我们的初步数据表明，这两种患者群体之间存在基本的病毒学和免疫差异，这可以解释为什么早期nAb是菌株特异性的，但后来nAb在一部分受试者中继续发展异种宽度。这种对早期感染的关注与nAb宽度通常存在或不存在的观察结果是一致的

DESCRIPTION (provided by applicant): The ability to induce antibodies that neutralize (nAb) circulating HIV-1 strains will be critical for a vaccine to exhibit optimal protective efficacy aganst HIV-1. To define the epitopes that can stimulate these responses, monoclonal antibodies (mAb) with broad and potent neutralization capacity have been recovered from a few chronically infected individuals that exhibited superior plasma nAb, but the viral and host B cell events that preceded this broad and potent neutralization phenotype have not been defined. Samples from early infection have not been available from these broadly neutralizing individuals, so questions about how nAb breadth developed cannot yet be answered. Here we identified 5 subtype A and C HIV-1 infected seroconvertors, out of 17, who developed relatively potent cross-clade nAb breadth at ~3 years post-infection. This proposal will investigate how and why nAb breadth developed in these individuals, but not in others who had low or undetectable levels of breadth. Our Preliminary Data suggest that there are fundamental virologic and immune differences between these two patient populations that could explain why early nAb are strain-specific, but later nAb go on to develop heterologous breadth in a subset of subjects. This focus on early infection is consistent with the observation that nAb breadth is generally either present or absent by ~3 years post-infection. Furthermore, our Preliminary Data show that autologous nAb from broad neutralizers in our panel targeted V1V2 and the CD4 binding site, both targets of mAbs with 'elite' heterologous neutralizing activity. We will utilize stored plasma and viable PBMC samples to define the initial nAb targets and viral escape pathways in 5 subjects with nAb breadth and 5 subjects without. We will recover mAbs from single B cell sorts using envelope (Env) gp140 B cell probes and PBMC samples collected at two early time points, and ~3 years post-infection, from these 10 subjects. The mAbs will be characterized genetically and functionally, and a representative subset, including those with breadth, will also be crystallized. To our knowledge, this type of comparative investigation into the early viral and immune determinants of neutralization breadth has not been performed. The proposed aims also provide a strong likelihood of recovering and characterizing broadly neutralizing mAbs that could represent early versions of those isolated from chronic infection. Our hypothesis is that the initil targeting of certain nAb epitopes, such as the CD4 binding site or V1V2, combined with the subsequent influence of escape pathways, leads to the development of nAb breadth in a subset of HIV-1 infected individuals. Specifically, the aims are to (i) Identify the initial neutralizing antibody target and define the viral escape pathways in 5 recently infected subjects who developed heterologous neutralization breadth and 5 subjects that lack breadth and (ii) Determine the genotypic, functional, and structural characteristics of early mAbs that are strain-specific and those that have acquired autologous or heterologous neutralization breadth.