Refocusing the Immune Response to the HIV Envelope Glycoprotein

描述（由申请人提供）：每天大约有14 000个新感染病例，迫切需要开发一种安全有效的艾滋病毒疫苗。然而，迄今为止测试的所有策略都未能达到这一目标。因此，如果要研制出安全有效的预防艾滋病毒感染的疫苗，就需要制定新的战略。2008年3月在美国国立卫生研究院举行的HIV疫苗峰会列出了9个对HIV疫苗开发至关重要的高优先级研究目标。这项拨款中提出的工作直接解决了列出的九个最高研究重点之一，即：“确定为什么广泛中和抗体（bNAbs）不常见以及如何诱导它们”。我们解决这个问题的新方法是基于令人惊讶的初步结果，这些结果表明HIV gp120上的切割位点是高度保守的，这些位点被细胞内和分泌的酶识别，已知对抗原加工、肿瘤生长和寄生虫感染很重要。令人惊讶的是，这些位点也位于或毗邻对受体结合或中和抗体结合很重要的特定氨基酸。由于病毒的高变异率，这些位点一定是由于强大的选择压力而被保存下来的，可能是为了逃避免疫反应。在这个建议中，我们希望灭活HIV包膜蛋白上的这些保守切割位点，以产生蛋白酶抗性包膜糖蛋白。然后，我们将按兔免疫原性研究所需的数量表达这些蛋白。由此产生的血清将被检测是否存在广泛中和抗体。我们假设这些位点的失活将保留重要的表位，这些表位在能够刺激强大的免疫反应之前通常在体内降解。这些表位的保存应该使我们能够以一种改善广泛中和抗体形成的方式，重新定向对HIV包膜蛋白的免疫反应。这些实验有可能解释为什么迄今为止测试的疫苗很难产生中和抗体，以及多年来困扰该领域的其他观察结果。

DESCRIPTION (provided by applicant): With approximately 14,000 new infections per day, there is an urgent need to develop a safe and effective HIV vaccine. However, all of the strategies tested to date have fallen short of this goal. Thus, new strategies are required if the development of a safe and effective vaccine to prevent HIV infection is ever to be realized. A recent HIV Vaccine Summit held at NIH in March 2008 listed nine high priority research objectives essential for the development of an HIV vaccine. The work proposed in this grant directly addresses one of the nine highest research priorities listed, namely: "Determine why broadly neutralizing antibodies (bNAbs) are uncommon and how they can be elicited". Our new approach to this problem is based on surprising preliminary results showing that cleavage sites on HIV gp120, recognized by intracellular and secreted enzymes known to be important for antigen processing, tumor growth, and parasitic infection, are highly conserved. Surprisingly, these sites are also located at, or adjacent to, specific amino acids important for receptor binding or the binding of neutralizing antibodies. Because of the high rate of virus variation, these sites must have been conserved as the result of strong selective pressure, possibly to evade the immune response. In this proposal we wish to inactivate these conserved cleavage sites on HIV envelope proteins to create protease resistant envelope glycoproteins. We will then express these in quantities required for rabbit immunogenicity studies. The resulting sera will be assayed for the presence of broadly neutralizing antibodies. We postulate that inactivation of these sites will preserve important epitopes that are normally degraded in vivo before they are able to stimulate robust immune responses. Preservation of these epitopes should allow us to redirect the immune response to HIV envelope proteins in a way that improves the formation of broadly neutralizing antibodies. These experiments have the potential to explain why it has been so difficult to elicit neutralizing antibodies with the vaccines tested to date, as well as other observations that have perplexed the field for many years. PUBLIC HEALTH RELEVANCE: In these studies we propose a new approach to the development of HIV vaccine antigens. We will attempt to improve the immunogenicity of epitopes on the envelope protein recognized by broadly neutralizing antibodies by mutation of conserved sites recognized by antigen processing enzymes.