Toll-like receptor control of endocytic antigen cross-presentation

提案摘要 存在关键的疫苗屏障来引发针对细胞内病原体的细胞毒性CD 8 T细胞。电流 疫苗技术在防止细胞内病原体感染方面取得的成功有限 如结核病、疟疾和艾滋病，其中CD 8 T细胞预防和控制感染。许可疫苗产生 大多数是中和或调理抗体，并且它们的效力取决于稳定的抗原谱。一些 佐剂如明矾可诱导辅助2型CD 4 T细胞，但CD 8 T细胞免疫难以实现。CD8 T细胞可以靶向保守的内部微生物成分，这些成分对病原体来说更难突变。的 无与伦比的效力、交叉保护性免疫和由CD 8 T细胞介导的免疫记忆 强调了开发CD 8 T细胞疫苗的紧迫性。为了引发CD 8 T细胞免疫，佐剂需要 通过树突状细胞（DC）诱导疫苗制剂中存在的抗原的MHC呈递， 抗原提呈细胞，引发幼稚的CD 8 T细胞。MHC I类分子呈递外源性抗原， 因为DC通过交叉呈递发生疫苗组分。了解这些机制， 因此，调节DC交叉呈递对于设计引发强CD 8 T细胞免疫的佐剂至关重要。我们 已发表和未发表的工作表明，Toll样受体（TLR），检测微生物和警报， 免疫系统，积极调节DC交叉呈递。在研究交叉呈递的调节时， 重要的是考虑抗原内化到DC中的途径。取决于内部化的 抗原，内化可以通过吞噬作用（对于直径>1µm的颗粒）或内吞作用 （直径<1µm）。我们发现TLR依赖的交叉呈递调节与内吞作用不同， 和吞噬细胞抗原。决定CD 8 T交叉呈递效率的共同成分 细胞是正确的亚细胞运输MHC-I分子的网站内化抗原。对于吞噬抗原， TLR信号控制DC中MHC-I分子从内体再循环隔室（ERC）的运输 特异性地针对吞噬抗原，例如来自细菌或感染的垂死细胞的吞噬抗原。对于内吞抗原，我们发现 一个独特的TLR信号机制参与其中，它控制内吞抗原交叉呈递给CD 8 T细胞并将MHC-I分子从ERC以外的细胞来源运输至内吞抗原。使用 各种验证和补充的方法，我们将研究TLR调节的内吞机制， 抗原交叉呈递和亚细胞MHC-I向内吞抗原的运输。我们将阐明 调节内吞抗原交叉呈递的不同TLR机制影响保护性循环， 免疫接种引起的组织驻留CD 8 T细胞记忆。我们将使用亚单位疫苗的原型 与佐剂/TLR配体组合，其参与并促进DC内吞抗原交叉呈递。 解读内吞抗原交叉呈递的调节机制将直接影响免疫调节剂的设计。 有效的CD 8 T细胞疫苗用于临床相关的旧的和新的病原体，包括具有大流行潜力的病原体。

PROPOSAL SUMMARY There are critical vaccine barriers to eliciting cytotoxic CD8 T cells against intracellular pathogens. Current vaccine technologies have yielded limited success for protection against infections with intracellular pathogens like tuberculosis, malaria, and HIV where CD8 T cells prevent and control infection. Licensed vaccines generate mostly neutralizing or opsonizing antibodies, and their efficacy is contingent on a stable antigenic profile. Some adjuvants like alum elicit helper type 2 CD4 T cells, but CD8 T cell immunity has been difficult to achieve. CD8 T cells can target conserved internal microbial components that are more difficult for pathogens to mutate. The unparalleled potency, cross-protective immunity, and immunological memory mediated by CD8 T cells underscores the urgency of developing CD8 T cell vaccines. To elicit CD8 T cell immunity, an adjuvant needs to induce MHC presentation of the antigens present in the vaccine formulation by dendritic cells (DC), potent antigen-presenting cells that prime naïve CD8 T cells. The MHC class I presentation of exogenous antigens such as vaccine components by DC takes place through cross-presentation. Understanding the mechanisms that regulate DC cross-presentation is thus critical for designing adjuvants that elicit strong CD8 T cell immunity. Our published and unpublished work has shown that Toll-like receptors (TLR), which detect microbes and alert the immune system, positively regulate DC cross-presentation. When studying the regulation of cross-presentation, it is important to consider the route of antigen internalization into DC. Depending on the size of the internalized antigen, internalization can be through phagocytosis (for particles that are >1µm in diameter) or endocytosis (<1µm in diameter). We found that the TLR-dependent regulation of cross-presentation is different for endocytic and phagocytic antigens. The common component that dictates the efficiency of cross-presentation to CD8 T cells is correct subcellular trafficking of MHC-I molecules to sites of internalized antigen. For phagocytic antigens, TLR signals control the traffic of MHC-I molecules from endosomal recycling compartments (ERC) in DC specifically to phagocytic antigens such as from bacteria or infected dying cells. For endocytic antigens, we found that a distinct TLR signaling machinery is involved, which controls endocytic antigen cross-presentation to CD8 T cells and traffics MHC-I molecules to endocytosed antigen from a cellular source other than the ERC. Using a variety of validated and complementary approaches, we will investigate TLR-regulated mechanisms of endocytic antigen cross-presentation and subcellular MHC-I trafficking to endocytosed antigens. We will elucidate how the distinct TLR mechanisms that regulate endocytic antigen cross-presentation impact protective circulating and tissue-resident CD8 T cell memory elicited by vaccination. We will use prototype subunit vaccines formulated with adjuvant/TLR ligand combinations that engage and boost DC endocytic antigen cross-presentation. Deciphering regulatory mechanisms of endocytic antigen cross-presentation will directly impact the design of effective CD8 T cell vaccines to clinically relevant old and new pathogens including those with pandemic potential.