T-follicular helper cells in Env-immunized macaques

描述（由申请人提供）：在用金丝雀痘vCP 1521初免加包膜糖蛋白加强免疫低风险志愿者（RV 144试验）后12个月，对HIV的保护为60%，但在42个月后下降至29%，与瞬时Env特异性抗体一致（Kim等人，2010年）。提高保护性免疫的持久性是改进疫苗的关键目标。我们的目标是确定对抗原的免疫应答中的缺陷，这些缺陷阻断了产生B细胞记忆的正常途径，并且不能产生持久的抗体。我们重点研究了CD 4 +/CXCR 5+滤泡辅助性T细胞（Tfh）与抗原特异性B细胞共同启动生发中心反应，促进抗体亲和力成熟，产生记忆B细胞。我们假设Tfh受到Env的负面影响，不能支持正常的B细胞发育。 Tfh尚未在HIV或SIV疫苗研究中进行评估。它们在非人灵长类动物（NHP）中了解甚少，其中产生Tfh的条件未知，并且该子集的功能尚未测试。我们的努力将Tfh与免疫NHP中的记忆B细胞联系起来。比较接受载体（金丝雀痘）、初免/加强（vCP 1521重组金丝雀痘/Env糖蛋白）或单独Env的动物组，我们询问Env是否对Tfh生成具有vCP 1521初免免疫克服的负面影响。免疫猕猴进行重复的，低剂量的直肠内病毒攻击（作为资助的临床前疫苗研究的一部分），使我们能够测试是否Tfh和/或抗体分泌记忆B细胞的保护，可能是有用的人类疫苗试验的相关性。 这些研究的结果将显示对疫苗的瞬时抗体应答是否反映了用Env抗原产生记忆B细胞的途径中的根本缺陷。缓解策略可能包括Env的修饰（改变蛋白质或聚糖结构）、掺入细胞因子或添加TLR 7/8激动剂的疫苗制剂，所有策略均改善Tfh应答和记忆B细胞形成。很少有努力来确定众所周知的瞬时抗体应答Env糖蛋白的机制。我们的工作集中在抗体产生的一个方面，并测试其与疫苗效力的关系。

DESCRIPTION (provided by applicant): Protection from HIV was 60% at 12 months after immunizing low-risk volunteers with canarypox vCP1521 priming plus Envelope glycoprotein boosting (RV144 trial), but dropped to 29% after 42 months consistent with transient Env-specific antibodies (Kim, et al., 2010). Increasing the durability of protective immunity is a critcal objective for improving vaccines. Our goals are to identify defects in the immune response to antigen which block the normal pathways for generating B cell memory and fail to produce durable antibodies. We focus on CD4+/CXCR5+ T follicular helper cells (Tfh) which, together with antigen-specific B cells, normally initiate the germinal center reaction, promote affinity maturation of antibody and generate memory B cells. We postulate that Tfh are negatively impacted by Env and fail to support normal B cell development. Tfh have not been evaluated in HIV or SIV vaccine studies. They are poorly understood in nonhuman primates (NHP), where conditions for generating Tfh are unknown and functions of this subset have not been tested. Our efforts will relate Tfh to memory B cells in immunized NHP. Comparing animal groups that receive vector (canarypox), prime/boost (vCP1521 recombinant canarypox/Env glycoprotein), or Env alone, we ask whether Env has a negative effect on Tfh generation that is overcome by the vCP1521 priming immunization. Immunized macaques undergo repetitive, low-dose intrarectal virus challenge (as part of a funded preclinical vaccine study), allowing us to test whether Tfh and/or antibody-secreting memory B cells are correlates of protection that might be useful in human vaccine trials. Results from these studies will show whether transient antibody responses to vaccine reflect a fundamental defect in the pathway for memory B cell generation with Env antigens. Mitigation strategies might include modification of Env (changing protein or glycan structures), incorporation of cytokines, or vaccine formulations which add TLR7/8 agonists, all strategies to improve the Tfh response and memory B cell formation. There have been few efforts to determine mechanisms underlying the well-known transient antibody responses to Env glycoproteins. Our work concentrates on one aspect of antibody generation and tests its relationship to vaccine efficacy.