Post Viral Bacterial Pneumonia: Role of MicroRNA and Autophagy

病毒性细菌性肺炎后：MicroRNA 和自噬的作用

• 批准号: 9038427
• 负责人: Bethany B. Moore
• 金额: $ 38.75万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-04-01 至 2018-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9038427
• 关键词: Address; Anti-Bacterial Agents; Antibacterial Response; Autophagocytosis; Bacteria; Bacterial Infections; Bacterial Pneumonia; Cause of Death; Cessation of life; Development; Excision; Experimental Models; Failure; Goals; Grant; Health; Host Defense; ITGAM gene; Immune response; Infection; Influenza; Interferon Type II; Interferons; LoxP-flanked allele; Lung; Mediating; MicroRNAs; Morbidity - disease rate; Mus; Natural Immunity; Outcome; Patients; Phagocytosis; Pneumococcal Infections; Pneumonia; Production; Regulation; Role; Secondary Prevention; Sirolimus; Staphylococcal Infections; Streptococcus pneumoniae; Testing; Therapeutic; Transgenic Mice; United States; Up-Regulation; Viral; Viral Pneumonia; Virus Diseases; attributable mortality; cell type; cytokine; improved; improved outcome; inhibition of autophagy; insight; killings; macrophage; methicillin resistant Staphylococcus aureus; mortality; mouse model; neutralizing monoclonal antibodies; pathogen; prevent; receptor; response; superinfection; therapeutic target; therapy development

DESCRIPTION (provided by applicant): Influenza infections are a leading cause of death in the United States and worldwide, with 50 000 of deaths occurring annually in the United states alone. Although many patients succumb to the primary viral infection, a significant number of influenza-related deaths are attributable to the development of secondary bacterial infections. Why the host is more susceptible to bacterial infections post-influenza is poorly understood. A better understanding of how the host responds to sequential influenza + bacterial infection is necessary in order to develop therapies to improve outcomes. Using a murine model of sequential pulmonary influenza and methicillin-resistant Staphylococcus aureus (MRSA) or Streptococcus pneumoniae infection, we have found that these mice have decreased survival and impaired anti-bacterial responses. We also showed that host responses to post-viral pneumonia are characterized by impaired macrophage autophagy responses, and impaired macrophage phagocytosis and killing of bacteria in the lungs. These findings correlate with significant upregulation of interferon (IFN)γ and upregulation of miR 155 when compared to mice infected with either pathogen alone. Thus, we hypothesize that impaired innate immunity against MRSA in the setting of post-influenza pneumonia is due to IFNγ-induced upregulation of miR 155 which in turn blocks protective autophagy responses and prevents bacterial phagocytosis and killing. We will address these goals with the following specific aims. Aim 1) To determine the role of IFNγ in regulating miR 155 expression, host defense, cytokine production, and macrophage autophagy following infection with influenza alone, MRSA/Streptococcus pneumoniae alone or sequential infection. This aim will characterize these outcomes in single and sequential infections, will test responses in chimeric mice generated using wild-type and IFNγ receptor-/- mice and will test a therapeutic approach to block IFNγ using a neutralizing mAb. Aim 2) To determine whether the impaired host defense noted during post-viral pneumonia is due to a failure of lung macrophages to upregulate protective autophagy responses This aim will determine whether autophagy is impaired in lung macrophages post- sequential infection compared to single infection, whether this is correlated with miR 155 inhibition of DAPK1 and whether enhancement of autophagy using rapamycin/Tat Beclin-1 can improve host defense by increasing bacterial phagocytosis and killing. Aim 3) To identify the mechanism that miR-155 uses to regulate macrophage recruitment, autophagy and to impair the anti-bacterial host-defense. This aim will characterize expression of miR 155 during post-viral pneumonia and explore inhibition of autophagy during post-viral pneumonia as a result of miR 155 inhibition of DAPK1. The ability of miR 155 to regulate bacterial phagocytosis and killing also will be explored. Additionally, transgenic mice will be generated using floxed miR155 and CD11b-Cre mice enabling cell type specific removal of miR155 from macrophages further providing mechanistic insight regarding regulation of autophagy by miR 155 expression on macrophages.

描述（由申请人提供）：流感感染是美国和全世界死亡的主要原因，仅在美国每年就有 5 万人死亡。尽管许多患者死于原发性病毒感染，但大量与流感相关的死亡可归因于继发性细菌感染。为什么宿主在流感后更容易受到细菌感染尚不清楚。为了开发改善结果的疗法，有必要更好地了解宿主对连续流感+细菌感染的反应。使用连续性肺部流感和耐甲氧西林金黄色葡萄球菌（MRSA）或肺炎链球菌感染的小鼠模型，我们发现这些小鼠的存活率降低并且抗菌反应受损。我们还表明，宿主对病毒后肺炎的反应的特点是巨噬细胞自噬反应受损，以及巨噬细胞吞噬和杀死肺部细菌的能力受损。与单独感染任一病原体的小鼠相比，这些发现与干扰素 (IFN)γ 的显着上调和 miR 155 的上调相关。因此，我们假设流感后肺炎中针对 MRSA 的先天免疫受损是由于 IFNγ 诱导的 miR 155 上调，进而阻断保护性自噬反应并阻止细菌吞噬和杀灭。我们将通过以下具体目标来实现这些目标。目的 1) 确定单独感染流感、单独感染 MRSA/肺炎链球菌或连续感染后 IFNγ 在调节 miR 155 表达、宿主防御、细胞因子产生和巨噬细胞自噬中的作用。该目标将表征单次和连续感染中的这些结果，并将测试使用野生型和 IFNγ 产生的嵌合小鼠的反应 受体-/-小鼠，并将测试使用中和单克隆抗体阻断 IFNγ 的治疗方法。目标 2) 确定病毒后肺炎期间宿主防御受损是否是由于肺巨噬细胞未能上调保护性自噬反应所致。该目标将确定与单次感染相比，连续感染后肺巨噬细胞的自噬是否受损，这是否与 DAPK1 的 miR 155 抑制相关，以及是否使用雷帕霉素/Tat 增强自噬 Beclin-1可以通过增加细菌的吞噬和杀灭作用来提高宿主的防御能力。目标 3) 确定 miR-155 调节巨噬细胞募集、自噬和损害抗菌宿主防御的机制。该目标将表征病毒后肺炎期间 miR 155 的表达，并探索 miR 155 抑制 DAPK1 导致病毒后肺炎期间自噬的抑制。 miR 155 调节细菌吞噬和杀灭的能力也将被探索。此外，转基因小鼠将使用 floxed miR155 和 CD11b-Cre 小鼠产生，能够从巨噬细胞中特异性去除 miR155，进一步提供有关巨噬细胞上 miR 155 表达调节自噬的机制见解。