HIV Vaccines Based on GP120-CD4 Mimetic Complexes

描述（由申请人提供）：阻止艾滋病毒流行的最终手段是一种预防性疫苗，它可以阻止病毒在普通人群中的传播。现在人们普遍认为，这种疫苗必须引起抗艾滋病毒抗体反应以及细胞免疫才能提供保护。为了实现这一目标，迫切需要的是一种免疫原，这种免疫原将引发能够预防（中和）世界各地发现的原发性艾滋病毒株感染的广泛中和抗体。我们开发这种免疫原的方法是基于由CD4结合诱导的gpl20的“受限”过渡态结构。在之前的研究中，我们发现交联的gpl20可溶性CD4复合物在猕猴中引发抗体，可以中和各种初级分离株，而不考虑Clade。我们还表明，这些“广泛中和”抗体是通过亲和层析从免疫血清中分离出来的，其中含有gpl20与CD4模拟微小蛋白（CD4M9）相连接的约束单链复合物（称为SCBaL/M9）。因此，单链gpl20-CD4模拟复合物值得探索作为疫苗亚单位免疫原，以安全地在人体内引发广泛中和抗体。然而，在初步实验中，SCBaL/M9诱导广泛中和抗体的效率低于单链gpl20-CD4复合物（FLSC）。这种低效率可以从逻辑上解释为SCBaL/M9免疫原的可变部分失去了其链内复合物，无法呈现受限的gpl20结构。考虑到CD4M9序列对gp 120的结合亲和力仅为CD4的1%，这种不稳定性是可以预测的。与此一致的是，其他初步研究表明SCBaL/M9的分子内相互作用比FLSC更不稳定。因此，我们的中心假设将在本项目中进行评估，即SCBaL/M9的免疫原性将通过产生高度稳定的分子内复合物的序列修饰而得到改善。为了探索这一假设，本项目的目的1将是设计和评估SCBaL/M9的修饰版本，以提高链内结合稳定性。目的2将比较修饰复合物与SCBaL/M9在兔体内的免疫原性。我们期望这些努力产生新的候选免疫原，可以在各种疫苗环境中可行地用于引发广泛中和抗体。

DESCRIPTION (provided by applicant): The ultimate means for stopping the HIV epidemic is a prophylactic vaccine that blocks virus transmission in the general population. It is now accepted that such a vaccine will have to elicit anti-HIV antibody responses as well as cellular immunity to provide protection. What is desperately needed to meet this goal is an immunogen that will elicit broadly neutralizing antibodies capable of preventing (neutralizing) infection by primary HIV strains found worldwide. Our approach toward developing such an immunogen is based on the "constrained" transition state structure of gpl20 that is induced by CD4 binding. In previous studies, we showed that crosslinked gpl20-soluble CD4 complexes elicited antibodies in macaques that neutralized a wide variety of primary isolates regardless of Clade. We also showed that these "broadly neutralizing" antibodies were isolated from immune sera by affinity chromatography with a constrained single chain complex (called SCBaL/M9) containing gpl20 linked to a CD4 mimetic miniprotein (CD4M9). Thus, single chain gpl20-CD4 mimetic complexes warrant exploration as vaccine subunit immunogens to safely elicit broadly neutralizing antibodies in humans. However, in preliminary experiments SCBaL/M9 elicited broadly neutralizing antibodies less efficiently than a single chain gpl20-CD4 complex (FLSC). Such inefficiency can be logically interpreted to mean that a variable fraction of the SCBaL/M9 immunogen loses its intrachain complex and fails to present a constrained gpl20 structure. Such instability is predicted given that the CD4M9 sequence has a binding affinity for gp 120 that is only about 1% that of CD4. In agreement, other preliminary studies show that the intramolecular interactions in SCBaL/M9 are less stable than in FLSC. Accordingly, our central hypothesis, which will be evaluated in this project, is that the immunogenicity of SCBaL/M9 will be improved by sequence modifications that produce highly stabilized intramolecular complexes. In order to explore this hypothesis, Aim 1 of this project will be to design and evaluate modified versions of SCBaL/M9 for improved intrachain binding stability. Aim 2 will be to compare the immunogenicity of modified complexes versus SCBaL/M9 in rabbits. We expect these efforts to yield new candidate immunogens that can be feasibly used to elicit broadly neutralizing antibodies in a variety of vaccine contexts.