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: 9247795
• 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 2019-01-20
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9247795
• 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; Host Defense; ITGAM gene; Immune response; Impairment; Infection; Influenza; Interferon Type II; Interferon-alpha; LoxP-flanked allele; Lung; Mediating; MicroRNAs; Morbidity - disease rate; Mus; Natural Immunity; Outcome; Patients; Phagocytosis; Pneumococcal Infections; Pneumonia; Production; Recruitment Activity; Regulation; Role; Secondary Prevention; Sirolimus; Staphylococcal Infections; Streptococcus pneumoniae; Testing; Therapeutic; Transgenic Mice; United States; Up-Regulation; Viral; 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; public health relevance; 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(申请人提供)：流感感染是美国和全世界的主要死亡原因，仅在美国每年就有5万人死亡。虽然许多患者死于初级病毒感染，但与流感相关的大量死亡可归因于继发性细菌感染的发展。为什么宿主在流感后更容易受到细菌感染，人们对此知之甚少。为了开发改善结果的治疗方法，有必要更好地了解宿主对连续的流感+细菌感染的反应。使用顺序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，我们发现这些小鼠存活率降低，抗菌反应减弱。我们还表明，宿主对病毒后肺炎的反应特征是巨噬细胞自噬反应受损，巨噬细胞吞噬功能和肺部细菌杀灭能力受损。与单独感染任何一种病原体的小鼠相比，这些发现与干扰素γ的显著上调和miR155的上调有关。因此，我们假设流感后肺炎中对MRSA的天然免疫受损是由于干扰素γ诱导miR155上调，而miR155反过来又阻止保护性自噬反应，防止细菌吞噬和杀伤。我们将以以下具体目标解决这些目标。目的1)研究干扰素γ在单独感染流感、耐甲氧西林金黄色葡萄球菌/肺炎链球菌和连续感染后对miR155的表达、宿主防御、细胞因子产生和巨噬细胞自噬的调节作用。这一目标将在单次和连续感染中表征这些结果，将测试使用野生型和干扰素γ产生的嵌合小鼠的反应。 并将测试一种使用中和单抗阻断干扰素γ的治疗方法。目的2)确定病毒感染后肺炎的宿主防御功能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。这一目的将确定与单一感染相比，肺巨噬细胞的自噬功能是否受损，这是否与miR 155抑制DAPK1有关，以及雷帕霉素/TAT Beclin-1增强自噬功能是否可以通过增加细菌吞噬和杀伤来改善宿主防御。目的3)明确miR-155调节巨噬细胞募集、自噬和破坏抗细菌宿主防御的机制。这一目的将表征miR 155在病毒后肺炎中的表达，并探索由于miR 155抑制DAPK1而对病毒后肺炎期间自噬的抑制。还将探讨miR 155调节细菌吞噬和杀伤的能力。此外，将使用克隆的miR155和CD11b-CRE小鼠产生转基因小鼠，使其能够从巨噬细胞中特定类型地移除miR155，从而进一步提供关于miR 155在巨噬细胞上表达调控自噬的机械性见解。