Novel vaccine strategies to induce V2 apex-directed broad neutralizing antibodies

项目摘要/摘要 开发有效的HIV-1疫苗仍然是全球卫生领域的一项主要优先事项。广谱中和抗体 预防HIV-1感染的(BNAbs)不能通过接种疫苗来激发。其中一个原因是bNAbs 具有不寻常的特征，这些特征虽然对广度发展至关重要，但对疫苗诱导是有问题的。 令人困惑的是，缺乏关于哪些特征对疫苗接种有问题的信息。因此， 我们创造了一系列表达bNAbs原型前体的敲入(KI)小鼠，使其能够研究它们的 体内成熟。这类研究有助于确定更易于处理的候选bNAbs，以便疫苗诱导。 其中一个有希望的线索是V2顶点定向的bNAbs集合，CH01-04。我们最近发现了一名艾滋病毒 包膜(Env)稳定的三聚体疫苗方案可重复性诱导异源第2层NAB应答 CH01前体(UCA)“仅限HC”Ki小鼠，迄今为止在 半多克隆模型。然而，在完全多克隆模型中，即使是单一表位免疫原也不能诱导和 如果在天真的剧目中不经常出现，则扩展相关克隆。事实上，像我们的KI中引发的bNab反应 小鼠在完全多克隆的动物模型中无法发育，因为幼稚的前体频率是 即使是简单的抗原也太低了，更不用说环境病毒了，它会导致许多相互竞争的克隆出现非靶标表位。 然而，当CH01前体在 在嵌合Ki小鼠中类似的极限频率，表明设计方法克隆扩大以上 这样的门槛可能是一种有效的方法。因此，我们假设限速步骤为CH01型 应答产生是它们的前体频率在当前基于环境的方案中非常低。这个 这一假设的推论是，将它们扩大到激活阈值以上将是变革性的，但 在现有的环境免疫之前，需要添加预启动步骤。我们的主要目标是筛选各种不同的 合理选择/设计非艾滋病毒(或非典型艾滋病毒)“前原基”，以扩大更大的“替代品”的能力 通过一种新的方法，即基于欺骗的概念，将CH01型前驱体池称为“代理启动” 免疫系统诱导功能独立但结构趋同的携带抗体的前体细胞 结合适合bNab成熟和功能的位点。在目标1中，我们将从基因上决定 允许Env方案诱导V2峰值的最小数量的收敛前体(“CH01代理”)- 定向广度。在目标2中，我们将测试新的“前原始人”预扩展有限数量的能力。 CH01代理，同时测试各种新环境(或其他环境)的广度诱导潜力 启动免疫原)被设计成更具针对性地针对它们。最后，在目标3中，我们将确定“CH01 多克隆人免疫球蛋白TrianniTM小鼠在候选Pre-R扩增前后的“代理”频率 Primogen/Env组合。这些研究将提供关于如何增强劣势疫苗反应的信息， 尤其是对其他闭塞的Env部位(或病原体)，需要非典型的抗体结合区。

PROJECT SUMMARY / ABSTRACT Developing an effective HIV-1 vaccine remains a major global health priority. Broadly neutralizing antibodies (bnAbs) that protect against HIV-1 infection cannot be elicited by vaccination. A reason for this is that bnAbs have unusual features that while critical for breadth development, are problematic for vaccine induction. Confounding this, information regarding which features are problematic for vaccination is lacking. Accordingly, we created a series of knock-in (KI) mice expressing precursors of prototype bnAbs, allowing the study of their in vivo maturation. Such studies have helped in identifying candidate bnAbs more tractable for vaccines to elicit. One such promising lead is the V2 apex-directed set of bnAbs, CH01-04. We recently identified an HIV Envelope (Env) stabilized trimer vaccine regimen that reproducibly elicits heterologous tier 2 nAb responses in CH01 precursor (UCA) “HC only” KI mice, the most potent and consistent serum breadth elicited to date in a semi-polyclonal model. However, in fully polyclonal models, even single epitope immunogens fail to elicit and expand relevant clones if infrequent in the naïve repertoire. Indeed, bnAb responses like those elicited in our KI mice fail to develop in animal models with fully polyclonal repertoires, because naive precursor frequencies are far too low for even simple antigen, let alone Env, which induces many competing clones to off-target epitopes. However, suboptimal yet detectable responses do develop when CH01 precursors are introduced at comparable limiting frequencies in chimeric KI mice, suggesting that devising methods to clonally expand above such thresholds may be an effective approach. Thus, we hypothesize that the rate-limiting step to CH01-type response generation is their precursor frequencies being prohibitively low for current Env-based regimens. The corollary of this posit is that expanding them above activation thresholds would be transformative, but will require adding a pre-priming step, prior to existing Env immunization. Our main objective is to screen various rationally selected/designed non-HIV (or atypical HIV) “pre-primogens”, for the ability to expand a larger “proxy” pool of CH01-type precursors via a novel approach we term “priming by proxy”, a concept based on tricking the immune system into eliciting functionally-independent yet structurally-convergent precursors bearing Ab- combining sites amenable for both bnAb maturation and function. In Aim 1, we will genetically determine the minimal number of convergent precursors (“CH01 proxies”) that permit Env regimens to induce V2 apex- directed breadth. In Aim 2, we will test novel “pre-primogens” for their ability to pre-expand limiting numbers of CH01 proxies, while at the same time, test the breadth-inducing potential of various novel Envs (or other priming immunogens) engineered to more specifically target them. Finally, in Aim 3, we will determine “CH01 proxy” frequencies in polyclonal, human Ig TrianniTM mice before and after expansion with candidate pre- primogen/Env combinations. These studies will inform on how to potentiate subdominant vaccine responses, particularly those to other occluded Env sites (or pathogens), needing atypical Ab-combining regions.