T-follicular helper cells in Env-immunized macaques

描述(由申请人提供)：在使用金丝雀痘vCP1521启动剂加包膜糖蛋白加强免疫(RV144试验)接种低风险志愿者后12个月，对艾滋病毒的保护率为60%，但与瞬时环境特异性抗体一致的42个月后，保护率下降到29%(Kim等人，2010年)。提高保护性免疫的持久性是改进疫苗的重要目标。我们的目标是识别对抗原的免疫反应中的缺陷，这些缺陷阻碍了产生B细胞记忆的正常途径，并无法产生持久的抗体。我们关注的是CD4+/CXCR5+T滤泡辅助细胞(TFH)，它与抗原特异性B细胞一起，正常情况下启动生发中心反应，促进抗体的亲和力成熟，并产生记忆B细胞。我们推测，TFH受到环境病毒的负面影响，无法支持正常的B细胞发育。 TFH尚未在HIV或SIV疫苗研究中进行评估。在非人类灵长类动物(NHP)中对它们的了解很少，在NHP中，产生TFH的条件尚不清楚，这个子集的功能也没有被测试。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)、Prime/Boost(vCP1521重组金丝雀痘/Env糖蛋白)或仅接受Env的动物组，我们询问Env是否对Tfh的产生有负面影响，而vCP1521免疫可克服这种负面影响。免疫猕猴接受重复的、低剂量的直肠内病毒攻击(作为一项资助的临床前疫苗研究的一部分)，使我们能够测试TFH和/或分泌抗体的记忆B细胞是否与保护相关，这可能在人类疫苗试验中有用。 这些研究的结果将表明，疫苗的瞬时抗体反应是否反映了带有环境抗原的记忆B细胞生成途径的根本缺陷。缓解策略可能包括修改Env(改变蛋白质或多糖结构)，加入细胞因子，或添加TLR7/8激动剂的疫苗配方，所有这些策略都是为了改善Tfh反应和记忆B细胞的形成。几乎没有努力来确定众所周知的对包膜糖蛋白的瞬时抗体反应的潜在机制。我们的工作集中在抗体生成的一个方面，并测试其与疫苗效力的关系。 与公共卫生相关：目前的疫苗预防艾滋病毒感染的时间约为1年，但随后开始失效。提高保护性免疫的持久性是获得将影响公共健康的疫苗的关键。我们的目标是寻找产生长期抗体的基本步骤中的缺陷，这些缺陷在之前的动物或人类疫苗研究中没有得到评估。这项工作的结果可能为疫苗试验期间早期检测保护性抗体反应提供新的方法，并可能指导对艾滋病毒具有长期保护作用的新疫苗的开发。

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. PUBLIC HEALTH RELEVANCE: Current vaccines protect against HIV infection for around 1 year, but then begin to fail. Increasing the durability of protective immunity is key to obtaining vaccines which will impact public health. Our goals are to look for defects in the fundamental steps of generating long-term antibodies that have not been evaluated in previous animal or human vaccine studies. Results from this work may provide new approaches for early detection of protective antibody responses during vaccine trials and may guide the development of new vaccines with longer term protection against HIV.