Inducing HIV-1 NAb Breadth by Native Trimer Prime-Boost Vaccination

 描述（由申请人提供）：激发针对HIV-1的广泛保护性nAb（bnAb）仍然是疫苗开发人员面临的巨大挑战。无一例外，迄今为止描述的所有候选疫苗都未能引发针对相关2级分离株的bnAb，这与传播感染的那些分离株相似。基本问题可能是这种失败的基础：这是一个记录不多的事实，迄今为止测试的几乎所有候选疫苗都未能引起针对自体菌株的可检测的2级nAb，更不用说任何2级宽度了。与疫苗诱导的抗体一样，绝大多数在自然HIV-1感染期间形成的抗体也无法中和2级毒株。然而，与接种疫苗的受试者不同，自体nAb最终在大多数HIV-1感染的过程中发展，并且bnAb后来在约25%的病例中进化。虽然这个过程缓慢且不一致，但它是bnAb开发的唯一已知范例。因此，nAb广度发展的进化步骤已被深入研究。我们很高兴地报告，我们的“三聚体VLP”候选疫苗可以可预测地诱导有效的自体（JR-FL）2级nAb。这一结果验证了我们先前的假设，即nAb可能最好由它们必须结合以中和病毒的相同抗原（即天然三聚体）引发。然而，我们尚未诱导广泛交叉中和的2级nAb（bnAb）。我们假设，bnAb可能是由旨在以模拟自然感染期间宽度演变中的关键事件的方式修改自体nAb特异性的加强诱导的。我们的具体目标是： 具体目的1：表征一组聚糖修饰的VLP引发免疫原。将评价一组三聚体VLP，其允许可变地接近已知的bnAb但不允许接近非nAb，以用作目的3和4中的引发免疫原。 具体目标2：改进VLP疫苗生产方法。为了解决对高VLP剂量和更复杂工艺的日益增长的需求，将修改VLP生产以：i）使Env三聚体表达最大化，ii）允许通过过滤进行高通量浓缩和iii）提高安全性。 具体目标3：改善疫苗诱导的兔nAb应答。我们寻求提高兔中nAb的一致性、效力和广度。将设计引发-加强免疫以模拟天然感染中bnAb发育的方面，其中携带轻微糖基化不足的三聚体（“引发”）的病毒诱导自体nAb，并且随后通过完全糖基化的三聚体和随后通过异源三聚体“加强”。因此，我们希望确定一种逐渐发展nAb宽度的途径。初步数据支持这种方法的可行性。 具体目标4：改善NHP中疫苗诱导的nAb。将调整目标3中的策略，以尝试改善NHP中的nAb应答。NHP的获取、免疫接种和采血都将在VRC免费进行。我们仅请求VLP生产和血清分析方面的支持。

 DESCRIPTION (provided by applicant): Eliciting broadly protective nAbs (bnAbs) against HIV-1 remains an enormous challenge for vaccine developers. Without exception, all vaccine candidates described to date have failed to elicit bnAbs against relevant tier 2 isolates similar t those that transmit infection. Fundamental problems could underlie this failure: it is a poorly documented fact that nearly all vaccine candidates tested to date fail to elicit detectable tier 2 nAbs against the autologous strain, let alone any tier 2 breadth. Like vaccine-induced Abs, the vast majority of Abs that develop during natural HIV-1 infection also fail to neutralize tier 2 strains. However, unlike vaccinated subjects, autologous nAbs do eventually develop during the course of most HIV-1-infections and bnAbs later evolve in ~25% of cases. Although this process is slow and inconsistent, it is the only known paradigm of bnAb development. Consequently, the evolutionary steps of nAb breadth development have been studied intensively. We are pleased to report that our "trimer VLP" vaccine candidates can predictably induce potent autologous (JR-FL) tier 2 nAbs. This result validates our earlier hypothesis that nAbs might best be elicited by the same antigen (viz. native trimer) that they must bind to neutralize the virus. However, we have yet to induce broadly cross- neutralizing tier 2 nAbs (bnAbs). We hypothesize that bnAbs might be induced by boosts designed to modify autologous nAb specificity in a manner that mimics key events in the evolution of breadth during natural infection. Our Specific Aims are: Specific Aim 1: To characterize a panel of glycan-modified VLP priming immunogens. A panel of trimer VLPs that grant variable access to known bnAbs but no access to non-nAbs will be evaluated for use as priming immunogens in Aims 3 and 4. Specific Aim 2: To improve VLP vaccine production methods. To address increasing demands for high VLP doses and a more sophisticated process, VLP manufacture will be modified to: i) maximize Env trimer expression, ii) allow high throughput concentration via filtration and iii) improve safety. Specific Aim 3: To improve vaccine-elicited nAb responses in rabbits. We seek to improve nAb consistency, potency and breadth in rabbits. Prime-boost immunizations will be designed to mimic aspects of bnAb development in natural infection, where viruses bearing slightly underglycosylated trimers ("primes") induce autologous nAbs and are later "boosted" by fully glycosylated trimers and later by heterologous trimers. Thus, we hope to identify a pathway that incrementally evolves nAb breadth. Preliminary data supports the feasibility of this approach. Specific Aim 4: To improve vaccine-elicited nAbs in NHPs. Strategies from Aim 3 will be adapted to try to improve nAb responses in NHPs. NHP acquisition, immunizations and bleeds will all be conducted at the VRC at no cost. We request support only for VLP production and serum analysis.