The role of PMNs and CD73 in host-resistance against S. pneumoniae / influenza A virus co-infection

摘要 甲型流感病毒(IAV)感染后，由以下原因引起的后续肺炎的风险 肺炎链球菌的数量增加了100倍。宿主老化与更严重的后果相关，因此 需要新的方法来提高对感染的抵抗力。我们的目标是阐明IAV感染是如何 改变多形核白细胞(PMN)的反应和胞外腺苷(EAD)途径 在肺炎球菌肺炎期间，跨越宿主年龄。背景：在原发肺炎链球菌感染后， PMN是一种天然免疫细胞，其功能随着年龄的增长而下降，这是控制细菌所必需的 数字。EAD是由CD73分解受损细胞泄漏的ATP而产生的，它控制着PMN 在感染过程中的反应。我们发现CD73在宿主抵抗和PMN肺内流中起关键作用。 以及在原发肺炎球菌肺炎期间的抗微生物功能。重要的是，年长的老鼠有显著的 EAD酶和受体表达的变化及靶向这一途径逆转了年龄驱动的 对原发肺炎球菌感染的易感性。在人类中，鼻咽携带肺炎球菌是一种 侵袭性疾病的先决条件。此外，呼吸道的IAV感染在那里触发上皮细胞 损伤和损害宿主的抗菌反应是混合感染致命性协同的关键。然而，动物 合并肺炎链球菌在IAV合并感染期间从定殖者到病原体的进化的模型 模仿人类所见的严重疾病，是缺乏的。因此，我们建立了一个优化模型 其中小鼠鼻腔内定植肺炎球菌，随后鼻咽感染IAV， 肺部。这种模型导致一半的幼鼠出现明显的疾病和死亡迹象，重要的是， 复制了衰老的易感性，其中显著更多的老年小鼠表现出严重的临床症状和 与年轻的控制组相比，他们死于致命的死亡。使用这个模型，我们惊人地发现CD73的作用 相反，CD73变得不利于年轻宿主对联合感染的抵抗力。这突出显示了 IAV感染引发了宿主与肺炎球菌相互作用的深刻变化。然而， 多菌感染对宿主反应的影响及其背后的机制仍然是该领域的一个空白。 在这里，我们将使用我们改进的模型来检验这样的假设，即IAV感染改变了CD73介导的 PMN对不同宿主年龄肺炎球菌感染的反应有两个特定目的：1)测试年龄的影响 和IAV感染对继发性肺炎时PMN应答的影响；2)检测CD73在肺炎中的作用 肺炎链球菌/IAV混合感染的PMN应答和宿主抵抗力。意义/创新/相关性： 使用这种模拟人类疾病方面的生理相关模型来解释PMN如何 单菌与多菌感染在不同宿主年龄的反应变化以及CD73在其中的作用 有可能发现驱动宿主易受感染的新途径。这项工作可以带来高度的 结合以腺苷为基础的药物的创新方法来对抗这种严重的肺部疾病。

ABSTRACT Following influenza A virus (IAV) infection, the risk for subsequent pneumococcal pneumonia caused by Streptococcus pneumoniae is enhanced 100-fold. Host aging is associated with more severe outcomes, thus novel approaches that boost resistance to infections are needed. Our goal is to elucidate how IAV infection alters the responses of polymorphonuclear leukocytes (PMN) and the extracellular adenosine (EAD) pathway across host age, during pneumococcal pneumonia. Background: Following primary S. pneumoniae infection, PMNs, which are innate immune cells whose function declines with age, are required for controlling bacterial numbers. EAD, which is produced from breakdown of ATP leaking from injured cells by CD73, controls PMN responses during infection. We found that CD73 was crucial for host resistance and PMN pulmonary influx as well as anti-microbial function during primary pneumococcal pneumonia. Importantly, old mice had significant changes in expression of EAD enzymes and receptors and targeting this pathway reversed the age-driven susceptibility to primary pneumococcal infection. In humans, pneumococcal carriage in the nasopharynx is a prerequisite to invasive diseases. Further, IAV infection of the respiratory tract where it triggers epithelial damage and impairs host antibacterial responses is key for the lethal synergy of co-infection. However, animal models incorporating the evolution of S. pneumoniae from colonizer to pathogen during IAV co-infection while mimicking the severe disease seen in humans, are lacking. Therefore, we established an optimized model where mice are intra-nasally colonized with pneumococci followed by IAV infection of the nasopharynx and lungs. This model resulted in obvious signs of illness and lethality in half of the young mice and importantly, reproduced the susceptibility of aging, where significantly more old mice displayed severe clinical signs and succumbed to lethality compared to young controls. Using this model, we strikingly found that the role of CD73 was reversed, where CD73 became detrimental to resistance of young hosts to co-infection. This highlighted that IAV infection triggers profound changes in the interaction of the host with pneumococci. However, the effect of polymicrobial infections on host responses and the mechanisms behind that remain a gap in the field. Here we will use our improved model to test the Hypothesis that IAV infection alters CD73-mediated control of PMN responses to pneumococcal infection across host age using two specific Aims: 1) Test the effect of age and IAV infection on PMN responses during secondary pneumococcal pneumonia; 2) Test the role of CD73 in PMN responses and host resistance to S. pneumoniae/IAV co-infection. Significance/innovation/ relevance: Using this physiologically relevant model that mimics aspects of human disease to elucidate how PMN responses change in mono vs polymicrobial infections across host age and the role of CD73 in that, has the potential to uncover novel pathways that drive host susceptibly to infection. This work can lead to highly innovative approaches incorporating adenosine-based drugs to combat this serious lung disease.