Disease severity of otitis media: Biofilms, invasion, and host responses

摘要 中耳炎（OM）是儿童中最常见的疾病，也是导致听力下降的主要原因 损失由NTHI引起的OM和其他上呼吸道和下呼吸道疾病仍然是 严重健康和社会经济问题。尽管如此，我们还没有 了解NTHI在宿主中存活的动力学，既作为人鼻咽的替代物， 特殊解剖部位（即中耳）的机会致病菌。必需营养素的宿主隔离 （称为营养免疫）用于控制细菌生长，特别是在特权部位。然而，在这方面， 病原体必须克服这些生长障碍才能茁壮成长并持续存在，最终导致疾病。我们 中心假设是血红素铁可用性的波动影响疾病的进展和严重程度 从而导致增强NTHI持久性的微环境。我们的长期目标是定义治疗性 这些目标将减弱NTHI持续性，减少组织损伤并减少慢性后遗症。这里我们的 目的是探索必需血红素铁可用性的波动对NTHI生理学的影响， 生物膜发展、侵袭和疾病严重程度。在我们的初步和公布的数据中，我们证明 疾病的严重程度与NTHI在引入时的血红素铁状态直接相关， 中耳我们将通过以下具体目标来检验我们的中心假设：1）确定 表型和DNA甲基化对生物膜发育变化的贡献 2）确定血红素铁限制对持续时间的贡献， OM后遗症的严重程度（即亚临床、症状性）和3）定义OM的亚细胞运输模式 中耳上皮内的NTHI作为血红素铁可用性的结果。我们将进一步扩大我们的 症状性和亚临床OM的新模型，以促进我们对不同表现的理解 疾病。我们的调查将增加我们对NTHI如何适应营养限制的理解， 宿主，这种适应对生物膜发育的影响和对疾病进展的后果。在 此外，拟议的研究将直接评估血红素铁螯合的潜在效用， 使用试剂竞争NTHI持久性上的铁以减少NTHI介导的OM的负担。更好的 了解宿主和微环境中的单个细胞和NTHI群落动态 影响NTHI致病性生活方式的变化可以作为潜在的新疗法， 最终阻止传染病状态，从而显著降低复发感染的可能性 以及导致包括听力损失的不良疾病后遗症的组织损伤。

ABSTRACT Otitis media (OM) is the most frequently diagnosed illness in children and a leading cause of hearing loss. OM and other diseases of the upper and lower respiratory tract caused by NTHI continue to be a significant health and socioeconomic problem in both children and adults. Despite this, we do not yet understand the dynamics of NTHI survival in the host, both as a commensal of the human nasopharynx and opportunistic pathogen of privileged anatomical sites (i.e. middle ear). Host sequestration of essential nutrients (termed nutritional immunity) serves to control bacterial growth, particularly in privileged sites. However, pathogens must overcome these barriers to growth to thrive and persist, ultimately causing disease. Our central hypothesis is that fluctuations in heme-iron availability influence the progression and severity of disease resulting in a microenvironment that potentiates NTHI persistence. Our long-term goal is to define therapeutic targets that will attenuate NTHI persistence, reduce tissue damage and diminish chronic sequelae. Here, our objective is to explore the consequence of fluctuations in essential heme-iron availability on NTHI physiology, biofilm development, invasion and disease severity. In our preliminary and published data we demonstrate that the severity of disease is directly related to the heme-iron status of NTHI at the time of introduction into the middle ear. We will test our central hypothesis through the following specific aims: 1) Determine the contribution of filamentation and DNA methylation on the biofilm developmental changes associated with fluctuations in heme-iron availability 2) Determine the contribution of heme-iron limitation on the duration and severity of OM sequelae (i.e. subclinical, symptomatic) and 3) Define the subcellular trafficking patterns of NTHI within middle ear epithelium as a consequence of heme-iron availability. We will further expand upon our novel models of symptomatic and subclinical OM to advance our understanding of the different manifestations of disease. Our investigations will increase our understanding of how NTHI adapts to nutritional limitation in the host, the influence of this adaptation on biofilm development and consequence on disease progression. In addition, the studies proposed will directly evaluate the potential utility of heme-iron sequestration through the use of agents to compete for iron on NTHI persistence to reduce the burden of NTHI-mediated OM. A better understanding of individual cell and NTHI community dynamics in the host and the microenvironmental changes that affect NTHI pathogenic lifestyles can be harnessed as potential novel therapeutics designed to ultimately thwart infectious disease states and thus significantly reduce the potential for recurrent infections and tissue damage that lead to adverse disease sequelae including hearing loss.