Project 2- Mechanism of How Vaccine-Elicited CD4+ T Cells Attenuate Antibody Mediated Protection

STEP/Phambili试验中获得的增加，加上在HVTN-505中缺乏疗效，表明 疫苗引发的CD4+T细胞反应可以减轻保护，在某些情况下，还会增加获得性。这 提出了HIV疫苗开发中的一个主要问题：如何诱导B细胞所必需的CD4+T细胞反应 在不增加HIV感染的目标细胞数量或表型的情况下帮助削弱保护作用？ 早期对非人类灵长类动物的研究表明，水痘带状疱疹gp120-siv免疫。 (VZV-gp120)显著增加了SIV的复制，预测了STEP/Phambili试验。NHP研究如下 AdHu5疗效试验证实，AdHu5免疫增加了SIV的传播，可能是由于 粘膜中CD4+CCR5+T细胞的增加似乎是该载体系统的一种普遍特性。在……里面 在这个项目中，我们展示了疫苗诱导的CD4+T细胞减弱保护的能力延伸到其他 载体系统和NHP中的亚单位蛋白质佐剂配方。目前，还没有直接测试 疫苗诱导的CD4+T细胞可以减弱抗体介导的保护的假说。这一差距在 知识是艾滋病毒疫苗研发中的一个关键问题。我们的长期目标是开发出一种有效的艾滋病毒 疫苗，这得到了我们在这个项目中的总体目标的支持，即确定疫苗引发的CD4+ T细胞在减弱抗体介导的保护中起着因果作用。这个项目的中心假设是 疫苗诱导的CD4+CCR5+T细胞可以通过广泛的中和来减弱被动保护 单抗。这一假设是根据NHP保护研究得出的，在这些研究中， 重复低剂量激发试验中的保护作用与疫苗诱导的CD4+T细胞水平的相关性 即使在假定的保护性抗体效价下也能观察到细胞。我们的方法将采用一种新的聚糖膜 BnmAb，N60-B1.1，它被动地保护NHP免受SHIV162P3的直肠高剂量挑战。N60- B1.1将用于测试疫苗诱导的CD4+CCR5+T细胞是否减弱其保护效果。这个 这项拟议研究的基本原理是，如果疫苗引发的CD4+T细胞反应减弱N60-B1.1 保护，将证明这种反应和减弱的抗体介导之间的因果关系。 保护。检验我们的中心假设，从而实现我们的总体目标将通过 三个具体目标。目标1将滴定N60-B1.1以确定提供最佳衰减灵敏度的剂量 通过疫苗激发的CD4+T细胞反应。目标3将直接检验AdHu5载体引发的假设 CD4+T细胞减弱被动注射N60-B1.1对抗大剂量直肠攻击的效果 使用SHIV162P3。这将使用AdHu5-SIV-Gag/Tat免疫原来完成，已知该免疫原可诱导 直肠高水平的CD4+CCR5+T细胞。目标3将检验亚基/佐剂诱导的CD4+T细胞的假设 细胞减弱被动给药N60-B1.1的疗效。这将利用Gag/Tat亚单位蛋白 在Iscomatrix中配制的一种佐剂，我们的初步数据显示，比起保护，更倾向于收购。

Increased acquisition in the Step/Phambili trials, coupled with the lack of efficacy in HVTN-505 indicate that vaccine-elicited CD4+ T cell responses can mitigate protection and, in some cases, increase acquisition. This frames a major issue in HIV vaccine development; how to elicit the CD4+ T cell responses necessary for B cell help without increasing the numbers or phenotypes of target cells for HIV infection that attenuate protection? Early studies in non-human primates (NHPs) showed that immunization with a varicella zoster gp120-SIV (VZV-gp120) dramatically increased SIV replication, prefiguring the Step/Phambili trials. NHP studies following the AdHu5 efficacy trials confirmed that AdHu5 immunization increases transmission of SIV, probably due to the increase of mucosal CD4+ CCR5+ T cells that appears to be a general property of this vector system. In this Program, we show that the ability of vaccine-elicited CD4+ T cells to attenuate protection extends to other vector systems and to subunit protein-adjuvant formulations in NHPs. Currently, there is no direct test of the hypothesis that vaccine elicited CD4+ T cells can attenuate antibody-mediated protection. This gap in knowledge is a key problem in HIV vaccine development. Our long-term goal is to develop an effective HIV vaccine, which is supported by our overall objective in this project to determine whether vaccine-elicited CD4+ T cells play a causal role in attenuating antibody-mediated protection. The central hypothesis of this project is that vaccine-elicited CD4+CCR5+ T cells can attenuate passive protection by a broadly neutralizing monoclonal antibody. This hypothesis was developed pursuant to NHP protection studies where inverse correlations between protection in repeat low-dose challenge studies and levels of vaccine-elicited CD4+ T cells are observed, even at putative protective antibody titers. Our approach will employ a new glycan-shield bnmAb, N60-B1.1, which passively protects NHPs against a rectal high-dose challenge with SHIV162P3. N60- B1.1 will be used to test whether vaccine-elicited CD4+ CCR5+ T cells attenuate its protective efficacy. The rationale for the proposed research is that if vaccine-elicited CD4+ T cell responses attenuate N60-B1.1 protection, causality will be demonstrated between such responses and attenuated antibody-mediated protection. Testing our central hypothesis and thereby accomplishing our overall objective will be pursued via three specific Aims. Aim 1 will titrate N60-B1.1 to define a dose that affords optimal sensitivity for attenuation by vaccine-elicited CD4+ T cell responses. Aim 3 will directly test the hypothesis that AdHu5 vector-elicited CD4+ T cells attenuate the efficacy of passively administered N60-B1.1 against a high-dose rectal challenge with SHIV162P3. This will be accomplished using an AdHu5-SIV-Gag/Tat immunogen that is known to elicit high levels of rectal CD4+ CCR5+ T cells. Aim 3 will test the hypothesis that subunit/adjuvant-elicited CD4+ T cells attenuate the efficacy of passively administered N60-B1.1. This will employ a Gag/Tat subunit protein formulated in Iscomatrix, an adjuvant that our preliminary data shows favors acquisition over protection.