mRNA as a mediator of immunological information transfer in vivo

mRNA 作为体内免疫信息传递的介质

• 批准号: 8894191
• 负责人: J. Lindsay Whitton
• 金额: $ 47.38万
• 依托单位: SCRIPPS RESEARCH INSTITUTE, THE
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-01 至 2016-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8894191
• 关键词: Acute; Anti-Bacterial Agents; Antibodies; Antiviral Agents; Bacteria; Bacterial Infections; Biological; CD4 Positive T Lymphocytes; CD8B1 gene; Cancer Vaccines; Cells; Characteristics; Clinical; Code; Complex; Cross Presentation; Cross-Priming; Data; Dendritic Cells; Disease; Enterovirus; Epitopes; Family; Flavivirus; Goals; Grant; Immune; Immune response; Immunity; In Vitro; Infection; Injection of therapeutic agent; Link; MHC Class I Genes; Mediator of activation protein; Messenger RNA; Molecular; Mus; Names; Organism; Pathway interactions; Peptides; Play; Poxviridae; Process; Property; Proteins; RNA; Recombinants; Regulatory Element; Route; Surface; T cell response; T-Lymphocyte; Testing; Transfer RNA; Translating; Translations; Uncertainty; Vaccines; Viral; Viral Proteins; Virus; Virus Diseases; Work; extracellular; immunogenic; in vivo; microbial; pathogen; public health relevance; tumor

DESCRIPTION (provided by applicant): In vivo injection of mRNA triggers immune responses to the encoded proteins, and confers protection against disease. For this and other reasons, outlined below, RNA vaccines have great clinical potential, so it is important that we understand how they induce immunity. I hypothesize that RNA vaccines may be exploiting a biological pathway that has evolved specifically to capture, internalize, and translate mRNA. I propose that this pathway facilitates the transfer of immunological information into uninfected dendritic cells (DCs), thereby playing a key part in regulating CD8+ T cell responses to many viral and bacterial infections. Almost all acute virus infections induce strong CD8+ T cell responses, which are initiated when na�ve CD8+ T cells are activated by contact with an MHC class I / epitope peptide complex on the surface of DCs that express appropriate costimulatory molecules. However, many viruses do not infect DCs; and some viruses that infect DCs also encode proteins that quite effectively inhibit MHC class I presentation. These facts posed a puzzle: how could epitopes encoded by these viruses be effectively presented by DCs? The answer came with the identification of cross-presentation which, if it results in the triggering of naive CD8+ T cells, causes cross-priming. However, two in vivo observations show that cross-presentation/cross-priming (hereinafter, CP) is not always highly-efficient. First, enteroviruses replicate to very high titers and induce CD4+ T cells and antibodies, yet (unique among acute virus infections) they completely avoid triggering na�ve CD8+ T cells. Second, extracellular bacterial infections, in which microbial protein is hugely abundant, do not induce strong CD8+ T cell responses. For reasons described below, I hypothesize that both observations can be explained by proposing that some transfer of immunological information into uninfected DCs may rely on mRNA (rather than protein). So, this proposal has two goals: First, to evaluate how naked RNA induces immunity. Second, to test the hypothesis that, during most microbial infections, mRNA is transferred to uninfected DCs; if it is translated therein, the encoded protein will reach the class I MHC pathway, inducing strong CD8+ T cell responses; I have named this mechanism TATOR (transfer and translation of RNA). Conversely, if the mRNA cannot be translated, the organism is undetectable by CD8+ T cells. Thus, the specific characteristics of their mRNAs renders enteroviruses and extracellular bacteria invisible to CD8+ T cells. Aim 1. To identify and characterize the DC subset that is involved in RNA-triggered immunity. Aim 2. To ask if mRNA coding strategy explains how enteroviruses can almost completely evade naive CD8+ T cells, while most viruses induce strong CD8+ T cell responses. Aim 3. To determine if mRNA regulatory sequences explain why extracellular bacteria fail to induce strong CD8+ T cell responses.

描述（由申请人提供）：体内注射 mRNA 会引发针对编码蛋白质的免疫反应，并提供针对疾病的保护。由于这个原因和其他原因（如下所述），RNA 疫苗具有巨大的临床潜力，因此了解它们如何诱导免疫力非常重要。我推测 RNA 疫苗可能正在利用一种专门进化来捕获、内化和翻译 mRNA 的生物途径。我认为这条途径有助于将免疫信息转移到未感染的树突状细胞 (DC) 中，从而在调节 CD8+ T 细胞对许多病毒和细菌感染的反应中发挥关键作用。几乎所有急性病毒感染都会诱导强烈的 CD8+ T 细胞反应，这种反应是在幼稚 CD8+ T 细胞通过与表达适当共刺激分子的 DC 表面 MHC I 类/表位肽复合物接触而被激活时启动的。然而，许多病毒并不感染树突状细胞；一些感染树突状细胞的病毒也编码能相当有效地抑制 MHC I 类呈递的蛋白质。这些事实提出了一个难题：这些病毒编码的表位如何能有效地由 DC 呈递？答案来自交叉呈现的识别，如果它导致触发 初始 CD8+ T 细胞，导致交叉启动。然而，两项体内观察表明交叉呈递/交叉引发（下文称为CP）并不总是高效的。首先，肠道病毒复制到非常高的滴度并诱导 CD4+ T 细胞和抗体，但（在急性病毒感染中独一无二）它们完全避免触发幼稚 CD8+ T 细胞。其次，细胞外细菌感染（其中微生物蛋白非常丰富）不会诱导强烈的 CD8+ T 细胞反应。由于下述原因，我假设这两种观察结果都可以通过提出免疫学信息向未感染 DC 的某些转移可能依赖于 mRNA（而不是蛋白质）来解释。 因此，该提案有两个目标：首先，评估裸 RNA 如何诱导免疫。其次，检验以下假设：在大多数微生物感染期间，mRNA 会转移到未感染的 DC 中；如果它在其中被翻译，则编码的蛋白质 将到达 I 类 MHC 途径，诱导强烈的 CD8+ T 细胞反应；我把这个机制命名为TATOR（RNA的转移和翻译）。相反，如果 mRNA 无法翻译，则 CD8+ T 细胞无法检测到该生物体。因此，它们的 mRNA 的特定特征使得肠道病毒和细胞外细菌对 CD8+ T 细胞来说是不可见的。目标 1. 鉴定和表征参与 RNA 触发免疫的 DC 亚群。目标 2. 询问 mRNA 编码策略是否解释了肠道病毒如何几乎完全逃避初始 CD8+ T 细胞，而大多数病毒却诱导强烈的 CD8+ T 细胞反应。目标 3. 确定 mRNA 调控序列是否可以解释为什么胞外细菌无法诱导强烈的 CD8+ T 细胞反应。