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HVTN-505缺乏疗效表明， 疫苗引起的CD 4 + T细胞应答可以减轻保护，并且在某些情况下增加获得。这 这是HIV疫苗开发中的一个主要问题：如何诱导B细胞所必需的CD 4 + T细胞应答， 在不增加HIV感染的靶细胞数量或表型的情况下帮助减弱保护作用？ 在非人灵长类动物（NHP）中的早期研究表明，用水痘带状疱疹gp 120-SIV免疫 （VZV-gp 120）显著增加SIV复制，预示Step/Phambili试验。NHP研究， AdHu 5效力试验证实，AdHu 5免疫增加SIV的传播，可能是由于 粘膜CD 4 + CCR 5 + T细胞的增加似乎是该载体系统的一般特性。在 在本项目中，我们发现疫苗诱导的CD 4 + T细胞减弱保护作用的能力延伸到其他免疫系统。 载体系统和NHP中的亚单位蛋白-佐剂制剂。目前，还没有直接测试 假设疫苗诱导的CD 4 + T细胞可以减弱抗体介导的保护。中的这一空白 知识是艾滋病毒疫苗开发的一个关键问题。我们的长期目标是开发一种有效的艾滋病毒 疫苗，这是我们在这个项目中的总体目标，以确定是否疫苗引起的CD 4 + T细胞在减弱抗体介导的保护中起因果作用。这个项目的核心假设是 疫苗诱导的CD 4 + CCR 5 + T细胞可以通过广泛的中和作用减弱被动保护， 单克隆抗体这一假设是根据NHP保护研究开发的， 重复低剂量攻毒研究中的保护作用与疫苗诱导的CD 4 + T细胞水平之间的相关性 即使在假定的保护性抗体滴度下，也观察到细胞。我们的方法将采用一种新的聚糖保护层 bnmAb，N60-B1.1，被动保护NHP免受SHIV 162 P3直肠高剂量激发。N60- B1.1将用于检测疫苗诱导的CD 4 + CCR 5 + T细胞是否减弱其保护效力。的 这项研究的基本原理是，如果疫苗诱导的CD 4 + T细胞应答减弱了N60-B1.1， 保护，将证明这种反应和减弱的抗体介导的 保护测试我们的中心假设，从而实现我们的总体目标，将通过以下方式进行： 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 通过疫苗引发的CD 4 + T细胞反应。目的3将直接检验AdHu 5载体诱导的AdHu 5表达的假设。 CD 4 + T细胞减弱被动给予N60-B1.1对抗高剂量直肠激发的功效 SHIV162P3这将使用已知可引发免疫应答的AdHu 5-SIV-Gag/达特免疫原来完成。 直肠CD 4 + CCR 5 + T细胞水平较高。目的3将检验亚单位/趋化剂诱导的CD 4 + T细胞的假说， 细胞减弱被动施用的N60-B1.1的功效。这将使用Gag/达特亚基蛋白 在Iscomatrix中配制，我们的初步数据显示，这种佐剂有利于获得而不是保护。

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.