Novel mouse model of HIV broad neutralizing antibody induction

 描述（由申请方提供）：诱导HIV广谱中和抗体（bnAb）是HIV疫苗开发的主要目标。虽然bnAb出现在大约20%的HIV慢性感染个体中;但它们不会在动物或人中的HIV包膜疫苗接种后出现。BnAb往往具有独特的性状，如长HCDR 3、广泛的体细胞超突变和多反应性，所有这些性状都使抗体易于受到耐受机制的控制。因此，bnAb B细胞谱系的发育可能由于其独特的性状而受到阻碍。迄今为止，研究中和宽度发展的唯一体内模型是在患有慢性HIV感染的人中。最近的研究使用表达种系版本的宽中和和窄中和（nNa B）CD4结合位点抗体的稳定转化的B细胞系，证明表达种系版本的非中和抗体的B细胞更容易被HIV Env激活（29）。此外，当表达bnAb和nNA B UCA的细胞池混合时，表达nNA B UCA的B细胞由于其对HIV Env的较高亲和力而被优先活化。总之，这些体外研究提供了关于Env不能诱导bnAb的原因的重要假设，并提供了在对Env的抗体应答期间可能在生殖中心发生的事件的体外模型。然而，该数据没有考虑可以降低bnAb前体的适合度的体内因素，从而有助于bnAb亚显性。在本研究中，我们将通过构建由CH01 UCA和CH58 UCA敲入小鼠骨髓组成的嵌合体，建立一种新的和相关的bnAb/non-bnAb B细胞在生发中心竞争的体内模型。我们将使用这个模型来定义bnAb前体激活和选择在生发中心的机制。通过从敲入小鼠骨髓中构建具有不同比例的CH01 UCA和CH58 UCA的小鼠嵌合体，我们可以研究bnAb和菌株特异性抗体UCA的个体发育以及接种后的亲和力成熟途径。我们预计该项目将确定HIV-1 bnAb亚优势的机制，从而为未来开发一种有效的预防性HIV-1疫苗提供信息。

 DESCRIPTION (provided by applicant): Induction of HIV broad neutralizing antibodies (bnAbs) is a major goal of HIV vaccine development. While bnAbs arise in roughly 20% of HIV chronically infected individuals; they do not arise following HIV Envelope vaccination in animal or man. BnAbs tend to have unique traits such as long HCDR3s, extensive somatic hypermutation, and polyreactivity, all traits that predispose antibodies to be controlled by tolerance mechanisms. Thus, development of bnAb B cell lineages may be impeded due to their unique traits. To date the only in vivo models to study development of neutralization breadth are in humans with chronic HIV infection. Recent studies using stably transformed B cell lines expressing germline versions of broad neutralizing and narrow neutralizing (nNab) CD4 binding site antibodies demonstrated that B cells expressing germline versions of non-neutralizing antibodies were more easily activated by HIV Env (29). Furthermore, when pools of cells expressing bnAb and nNAb UCAs were mixed, B cells expressing nNAb UCA were preferentially activated, owing to their higher affinity for HIV Env. Taken together, these in vitr studies provide important hypotheses as to reasons why Env fails to induce bnAbs and provide an in vitro model for events that might transpire in germinal centers during the antibody response to Env. This data however, does not account for in vivo factors that can reduce fitness of bnAb precursors, thus contributing to bnAb subdominance. In this grant, we will establish a novel and relevant in vivo model of bnAb/non-bnAb B cell competition in the germinal center by constructing chimeras comprised of CH01 UCA and CH58 UCA knock-in mouse bone marrow. We will use this model to define the mechanisms of bnAb precursor activation and selection in germinal centers. By constructing mouse chimeras with varying ratios of CH01 UCA and CH58 UCA from knock-in mouse bone marrow, we can study ontogeny of bnAb and strain-specific antibody UCAs and affinity maturation pathways after vaccination. We anticipate this project will define mechanisms of HIV-1 bnAb subdominance, thus informing future directions to create a potent and effective prophylactic HIV-1 vaccine.