Synthetic bacterial analogs of mammalian oligomannose for eliciting neutralizing antibodies to the high-mannose patch on HIV Env

近年来，关于广泛交叉反应的报告越来越多。 对HIV包膜上的寡甘露糖型聚糖具有特异性的中和抗体（nAb） 加标（Env）。因此，可以产生这种nAb的免疫策略将是期望的。之一 引发寡聚甘露糖特异性nAb的努力所面临的挑战是聚糖的宿主来源， 免疫耐受机制可能限制B细胞的频率或发育， 产生对哺乳动物寡甘露糖具有特异性的抗体。例如，Abs在典型的 通过呈递寡甘露糖苷的糖缀合物免疫原的实验动物通常不能 结合Env上的寡聚甘露糖，甚至当已经获得Env结合Ab时，例如 重组酵母，他们似乎结合不够亲病毒，并未能发挥 有意义的中和活性。在这里，我们建议利用细菌衍生的低聚糖 低聚甘露糖的类似物来克服这些挑战。 在本申请中，我们将重点放在一个相当保守的高甘露糖聚糖补丁上， Asn 301和Asn 332在HIV gp 120上。靶向这些寡甘露糖型聚糖的Ab的原型是 抗体的PGT 128家族，其表现出有效的中和活性。一种疫苗组分，其能够 因此，引发类似的nAb可以在甚至适度的血清Ab滴度下提供保护。 不久前，我们发现了一种细菌寡糖，它非常类似于 哺乳动物低聚甘露糖，随后制备了具有D3臂样延伸的合成类似物。 这些类似物之一，以新糖缀合物的形式，被PGT 128的成员强烈结合。 Ab家族及其预测的生殖系前身。更关键的是，初步数据显示， 用该缀合物免疫表达未排列的人Ab库的转基因动物 产生具有HIV 2级交叉中和活性的聚糖特异性Ab。在此，我们建议 扩大这些令人鼓舞的初步成果。具体来说，我们试图详细说明我们的共轭 设计和利用转基因动物以鉴定最佳佐剂+缀合物组合， 最大化nAb应答。我们还试图剖析抗体反应在血清和库水平， 比较引发的和现有的nAb之间的相似性，这可能会为加强策略提供信息。 最后，我们建议在猕猴中测试我们的策略，以评估它在多大程度上可能起作用。 远系繁殖系统。 总之，本项目将研究聚糖模拟是否可以轻易地触发 开发针对HIV Env上高度脆弱的寡甘露糖补丁的交叉反应性nAb。如果是这样， 这项工作可以为靶向HIV-1上其他糖表位的策略提供信息。

In recent years there have been an increasing number of reports on broadly cross-reactive neutralizing antibodies (nAbs) with specificity for oligomannose-type glycans on the HIV envelope spike (Env). Immunization strategies that could yield such nAbs would therefore be desirable. One of the challenges faced by efforts to elicit oligomannose-specific nAbs is the host origin of the glycans, with immune tolerance mechanisms possibly limiting the frequency or development of B cells capable of producing Abs with specificity for mammalian oligomannose. For example, Abs elicited in typical experimental animals by glycoconjugate immunogens presenting oligomannosides are generally unable to bind oligomannose on Env and even when Env-binding Abs have been obtained, such as with recombinant yeast, they appear to bind insufficiently avid to the virus and fail to exert meaningful neutralizing activity. Here, we propose to utilize bacterially derived oligosaccharide analogs of oligomannose to overcome these challenges. We focus in this application on a fairly conserved patch of high-mannose glycans at and surrounding Asn301 and Asn332 on HIV gp120. Prototypic for Abs targeting these oligomannose-type glycans is the PGT128 family of Abs, which exhibit potent neutralizing activity. A vaccine component capable of eliciting similar nAbs could thus offer protection at even modest serum Ab titers. We not long ago discovered a bacterial oligosaccharide that closely resembles the D1 arm of mammalian oligomannose and subsequently made synthetic analogs of it with a D3 arm-like extension. One of these analogs, in the form of a neoglycoconjugate, is bound avidly by members of the PGT128 Ab family and their predicted germline predecessor. More crucially, preliminary data show that immunization of transgenic animals expressing an unarranged human Ab repertoire with this conjugate results in glycan- specific Abs with HIV tier 2 cross-neutralizing activity. Here, we propose to expand on these encouraging first results. Specifically, we seek to elaborate on our conjugate design and utilize transgenic animals to identify an optimal adjuvant+conjugate combination to maximize nAb responses. We also seek to dissect Ab responses at the serum and repertoire levels to compare similarities between the elicited and existing nAbs, which may inform boosting strategies. Finally, we propose to test our strategy in macaques to assess the extent to which it may work in outbred systems. In sum, this project will investigate whether glycan mimicry can serve to readily trigger the development of cross-reactive nAbs to the highly vulnerable oligomannose patch on HIV Env. If so, this work could inform strategies for targeting other glyco-epitopes on HIV-1.