Oxidative Burst in Influenza and MRSA Co-infection

性状（由申请方提供）：流感并发耐甲氧西林沙门氏菌。金黄色葡萄球菌（MRSA）感染在最近的流感大流行和流行期间已经成为主要的死亡原因。细菌负荷增加和肺部炎症加剧被认为是患者和动物模型中高死亡率的原因。然而，迄今为止对合并感染病理生理学的不完全理解已经减缓了有效治疗策略的发展。NADPH氧化酶2（NOX 2）是主要由吞噬细胞表达的酶复合物。NOX 2产生超氧化物，超氧化物与一氧化氮反应，导致形成高毒性的过氧亚硝酸盐。因此，NOX 2和诱导型一氧化氮合酶（iNOS）的活性都对氧化应激有重要作用，而氧化应激长期以来一直被认为与炎性肺损伤有关。另一方面，由NOX 2活性产生的活性氧（ROS）已被证明会加剧流感病毒诱导的组织炎症，但有助于对S.而iNOS活性在流感感染中起着有害的作用，它对肺S.金黄色葡萄球菌清除率。PI实验室的初步研究显示，流感感染降低了吞噬细胞ROS水平，但增加了IFN-？/ iNOS表达。因此，假设流感感染后氧化爆发的失调导致细菌杀伤缺陷和过度氧化应激，并导致致命的流感和MRSA共感染。检验该假设的方法包括：1）确定流感感染对NOX 2活性的影响及其对流感抑制的吞噬MRSA杀伤的贡献。特别地，将在选定的基因缺陷小鼠中检查流感抑制的N 0X 2依赖性MRSA清除的分子机制，2）确定在致死性流感和MRSA共感染期间氧化应激对肺损伤的贡献。具体而言，NOX 2与IFN-γ/IFN-γ的协同或重叠作用，iNOS活性的氧化组织损伤将在NOX 2，IFN-？R和iNOS基因缺陷小鼠~ 3）改进针对细胞内细菌和氧化应激的联合治疗。支持性数据表明，与单独抗生素治疗相比，抗生素和NOX 2抑制剂联合治疗显著提高了流感和MRSA共感染小鼠的存活率。具体目标3是根据目标1和2中提出的研究结果优化这种联合治疗方法。该项目的最终目标是建立治疗策略，以恢复抗微生物活性，但控制流感和MRSA合并感染期间的炎性肺损伤。从这些拟议的研究中获得的结果不仅将为开发新的治疗方法提供关键信息，而且还将为降低患者的高死亡率提供直接适用的信息。

DESCRIPTION (provided by applicant): Influenza-complicated methicillin-resistant S. aureus (MRSA) infection has emerged as a leading cause of death during recent influenza pandemics and epidemics. Both heightened bacterial burden and exaggerated lung inflammation are believed to be responsible for high mortality in patients and animal models. However, a hitherto incomplete understanding of co-infection pathophysiology has slowed the development of effective treatment strategies. NADPH oxidase 2 (NOX2) is an enzyme complex predominantly expressed by phagocytes. NOX2 produces superoxide which reacts with nitric oxide and results in the formation of highly toxic peroxynitrite. Therefore, both NOX2 and inducible nitric oxide synthase (iNOS) activities critically contribute to oxidative stress which has long been known to be involved in inflammatory lung damage. On the other hand, reactive oxygen species (ROS) generated by NOX2 activity has been shown to exacerbate influenza virus-induced tissue inflammation but to contribute to resistance to S. aureus lung infection~ whereas iNOS activity plays a detrimental role during influenza infection, it is dispensable for pulmonary S. aureus clearance. Preliminary studies in the PI's laboratory revealed that influenza infection reduces phagocyte ROS level but increases IFN-?/iNOS expression. Therefore, it is hypothesized that dysregulation of oxidative burst following influenza infection causes defective bacterial killing s well as excessive oxidative stress, and results in fatal influenza and MRSA co-infection. The approaches to test the hypothesis include: 1) determine the influence of influenza infection on NOX2 activity and its contribution to influenza-suppressed phagocytic MRSA killing. Particularly, the molecular mechanisms for influenza-suppressed NOX2-dependent MRSA clearance will be examined in selected gene- deficient mice~ 2) determine the contribution of oxidative stress to lung injury during lethal influenza and MRSA co-infection. Specifically, the synergistic or overlapping contribution of NOX2 versus IFN-?/iNOS activity to oxidative tissue damage will be examined in NOX2, IFN-?R and iNOS gene-deficient mice~ 3) refine combination treatment targeting both intracellular bacteria and oxidative stress. Supportive data demonstrated that combination treatment with antibiotic and NOX2 inhibitor significantly improved the survival rate of influenza and MRSA co-infected mice compared with antibiotic treatment alone. Specific aim 3 is to optimize this combination therapeutic approach based on the findings from studies proposed in aim 1 &2. The ultimate goal of this project is to establish the treatment strategy to restore antimicrobial activity but to control inflammatory lung damage during influenza and MRSA co-infection. The results achieved from these proposed studies will provide not only pivotal but also directly applicable information for the development of novel therapeutics to reduce the high mortality in patients.