Adjuvant strategies for universal and multiseasonal influenza vaccine candidates in the context of pre-existing immunity

项目总结/摘要 流感的负担仍然很高，季节性流行导致300万至500万例重症病例 全球每年约有650，000人死亡。虽然通过自然感染获得的对流感病毒的免疫力 相对广泛和持久，通过接种现有疫苗诱导的免疫应答是短暂的， 生活和狭窄，需要每年重新制定和重新接种。目前还不清楚是什么原因导致了这种差异 感染和疫苗诱导的免疫之间存在差异，但主要差异包括接触途径 （呼吸道与胃肠外），抗原类型（活病毒/蛋白质与灭活病毒/蛋白质），以及病毒- 在感染期间的特异性先天免疫反应。目前的流感疫苗主要引起免疫应答， 针对病毒血凝素（HA）的高度可变的免疫显性头部结构域中的表位。 虽然针对更保守的HA茎结构域的抗体提供跨菌株保护，但这一点不受限制。 结构域免疫原性差。HA头部优势与抗原漂移的快速步伐严重结合， 限制交叉保护。基础广泛的细胞免疫和粘膜免疫也是异亚型免疫的关键。 保护，然而，目前的肠胃外疫苗不能充分诱导这些。因此，发展更多 显然需要靶向粘膜途径的有效佐剂和疫苗接种策略。自然感染 流感病毒通过激活Toll-、RIG-I-和NOD-， 类受体（TLR、RLR、NLR）。由于诱导适当的先天反应对于持久的 适应性免疫和塑造正确类型的免疫反应，我们将采用合理设计的 鼻内组合佐剂以通过粘膜途径激活所有三种途径， 自然感染，我们假设这将导致更强大和持久的疫苗反应。这种佐剂 由激活TLR和NLRP 3的纳米乳液佐剂（NE）和RIG-I衍生的RNA激动剂组成， 从仙台病毒（IVT）的缺陷干扰RNA。NE/IVT诱导针对以下疾病的协同免疫反应 多种病毒抗原，具有放大的TH 1偏向的细胞免疫和粘膜免疫应答。在这里， 我们将比较该佐剂与两种批准用于流感疫苗肠胃外接种的佐剂（AS 03 和MF 59）以改善对两种不同抗原系统的免疫应答，所述两种不同抗原系统具有加宽的异亚型 在临床前和临床环境中的保护：（1）利用含有嵌合的裂解病毒的序贯方案 具有不同“外来”禽类HA头部结构域的HA都具有相同的茎结构域以引导免疫应答 针对茎中的表位，和（2）重组四聚体神经氨酸酶。人类对流感的免疫反应 疫苗受到通过过去的感染和/或免疫接种获得的预先存在的免疫力的严重影响。 我们将进一步确定通过粘膜给予NE/IVT驱动的免疫应答是否与这些免疫应答相关。 抗原系统可以更好地利用这种预先存在的免疫应答 通过将记忆应答重定向至更保守的表位，使用AS 03进行疫苗接种。

Project Summary/Abstract The burden of influenza remains high, with seasonal epidemics resulting in 3-5 million cases of severe illness globally and ~650,000 fatalities/year. While immunity to influenza virus acquired through natural infection is relatively broad and long-lived, immune responses induced through vaccination with current vaccines are short- lived and narrow, requiring annual reformulation and revaccination. It is unclear what causes such dissimilarities between infection- and vaccine-induced immunity, however major differences include route of exposure (respiratory vs. parenteral), antigen type (live vs. inactivated virus/protein), and the robust activation of viral- specific innate immune responses during infection. Current influenza vaccines elicit immune responses primarily directed towards epitopes in the highly variable immunodominant head domain of the viral hemagglutinin (HA). While antibodies directed towards the more conserved HA stalk domain provide cross-strain protection, this domain is poorly immunogenic. HA head dominance compounded with the rapid pace of antigenic drift severely limits cross-protection. Broad-based cellular immunity and mucosal immunity are also key to heterosubtypic protection, however current parenteral vaccines do not induce these sufficiently. Thus, development of more effective adjuvants and vaccination strategies targeting the mucosal route are clearly needed. Natural infection with influenza virus stimulates strong adaptive immune responses through activation of Toll-, RIG-I-, and NOD- like receptors (TLRs, RLRs, NLRs). As induction of appropriate innate responses is crucial for long-lasting adaptive immunity and for shaping the correct types of immune responses, we will employ a rationally designed intranasal combination adjuvant to activate all three pathways through the mucosal route to more closely mimic natural infection, which we hypothesize will lead to more robust and durable vaccine responses. This adjuvant consists of a nanoemulsion adjuvant (NE) that activates TLRs and NLRP3 and an RNA agonist of RIG-I derived from the defective interfering RNA of Sendai virus (IVT). NE/IVT induces synergistic immune responses against a variety of viral antigens, with magnified TH1-biased cellular immunity and mucosal immune responses. Here, we will compare this adjuvant to two adjuvants licensed for parenteral vaccination with influenza vaccines (AS03 and MF59) to improve immune responses to two different antigen systems that have broadened heterosubtypic protection in preclinical and clinical settings: (1) a sequential regimen utilizing split viruses containing chimeric HAs with different “exotic” avian HA head domains all with the same stalk domain to guide immune responses to epitopes in the stalk, and (2) a recombinant tetrameric neuraminidase. Human immune responses to influenza vaccines are heavily influenced by pre-existing immunity acquired through past infections and/or immunizations. We will further determine whether the immune responses driven by mucosal administration of NE/IVT with these antigen systems can better take advantage of such pre-existing immune responses compared to parenteral vaccination with AS03 by redirecting memory responses to more conserved epitopes.