Antimicrobial Peptides and Innate Immunity in Otitis Media

描述（由申请人提供）：先天性免疫在维持中耳健康方面起着积极的作用，并且在中耳炎（OM）期间也积极参与。抗微生物肽（AP）是先天免疫系统的关键组成部分，提供对排列在呼吸道、胃肠道和泌尿生殖道的巨大上皮表面上的微生物的一线灭活。这些阳离子多肽的有效抗微生物活性可以是加和的，并且通常是协同的，提供先天免疫系统的高度有效的作用机制。然而，现在清楚的是，AP不仅仅是抗微生物的，事实上，杀死微生物甚至可能不是它们最主要的功能，相反，越来越多的证据表明AP在调节获得性免疫应答中的关键作用。最近，人们也开始认识到，生活在粘膜表面的肠道微生物刺激上皮细胞产生AP，从而有助于宿主维持防御性粘膜屏障和稳态。后一点与我们的更新申请特别相关，因为OM不是由高毒力微生物引起的;相反，OM是由构成儿科鼻咽部（NP）正常植物群的肠道细菌亚群引起的。然而，当宿主气道防御受损时，最典型的是上呼吸道（URT）病毒，这些细菌可以表现为机会致病菌并进入现在防御不良的中耳，这种情况与肠道的情况非常相似，其中已经充分研究了正常微生物群和衬在胃肠道上的上皮细胞之间发生的分子串扰。了解宿主和微生物如何共同进化以在殖民期间和谐地存在（事实上，这些微生物如何帮助塑造最上呼吸道的先天免疫系统，反之亦然）对于我们能够了解OM疾病过程早期的“错误”是至关重要的，以及什么允许恢复稳态和健康。因此，重要的是继续研究最上气道的先天免疫系统，包括NP、咽鼓管和中耳。为了实现这一目标，我们建议研究先天免疫在以下方面的作用：1）健康（即在定殖期间）在不可分型流感嗜血杆菌（NTHI）和NP的粘膜上皮之间发生的分子串扰水平; 2）多微生物病OM（即“正常”OM），特别关注先天免疫效应子的表达失调和树突细胞功能的改变URT病毒诱导的基因突变导致疾病进程; 3）OM疾病极端-倾向性和慢性性，特别关注编码α-和β-防御素家族成员的基因中的拷贝数变异如何导致倾向性。我们还将研究AP如何可能首先通过诱导NTHI形成生物膜而无意中导致慢性化，但随后参与其消退，并利用我们对最上气道先天免疫的增强理解来开发治疗和/或预防OM的新方法。公共卫生相关性：由于持续需要改进的方法来治疗和/或预防中耳炎（OM），对侵入性更小、更有针对性的儿科疫苗的期望，以及认识到我们对急性和慢性OM的微生物学和免疫学的理解是不完整的，我们必须寻求更好地理解身体如何防御最上气道，并且潜在地增强这些防御机制的方法被鉴定并进一步开发为治疗和/或预防OM的新方法。获得这种更好的理解将有可能使我们能够开发出局部限制和位点特异性的治疗方法，并促进疫苗制剂的改进，以提高其疗效。这些方法可以极大地增加我们用于对抗急性和慢性OM的可用武器库，并且重要的是，可以潜在地提供在疾病过程的非常早期状态-NP的定殖-进行干预的机制，从而显著降低与这种高度流行的儿科疾病相关的发病率。

DESCRIPTION (provided by applicant): It has become evident that innate immunity plays an active role in maintenance of the health of the middle ear, and is also actively engaged during otitis media (OM). Antimicrobial peptides (APs) are key components of the innate immune system, providing first-line inactivation of microbes on the vast epithelial surfaces that line the respiratory, gastrointestinal and urogenital tracts. The potent antimicrobial activity of these cationic polypeptides, can be additive and is often synergistic, providing the highly effective mechanism of action of the innate immune system. It is now clear however, that APs are not simply antimicrobial, and in fact, microbial killing may not even be their most primary function, rather there is increasing evidence of the pivotal role of APs in regulation of the acquired immune response. Recently, it has also begun to be appreciated that the commensal microorganisms living on mucosal surfaces stimulate epithelial cells to produce APs, and thus contribute to host maintenance of defensive mucosal barriers and homeostasis. This latter point is particularly relevant to our renewal application, because OM is not caused by highly virulent microorganisms; OM is instead caused by a subset of the commensal bacteria that comprise the normal flora of the pediatric naso- pharynx (NP). However, when host airway defenses are compromised, most typically by upper respiratory tract (URT) viruses, these bacteria can behave as opportunistic pathogens and gain access to the now poorly defended middle ear, a situation that closely parallels that of the gut, wherein the molecular crosstalk that occurs between the normal microbiota and the epithelial cells that line the gastrointestinal tract has been well- studied. Understanding how host and microbe have co-evolved to exist in harmony during colonization (and in fact, how these microbes have likely helped to shape the innate immune system of the uppermost airway and vice versa) is essential to our then being able to understand what goes `wrong' early in the disease course of OM, as well as what allows return to homeostasis and health. It is thereby important to continue to study the innate immune system of the uppermost airway, which includes the NP, Eustachian tube and middle ear. Toward this goal, we propose to investigate the role of innate immunity in: 1) health (i.e. during colonization) at the level of the molecular crosstalk that occurs between nontypeable Haemophilus influenzae (NTHI) and the mucosal epithelium of the NP; 2) the polymicrobial disease OM (i.e. `normal' OM), with a particular focus on how dysregulated expression of effectors of innate immunity and altered dendritic cell function(s) induced by the URT viruses contributes to the disease process; 3) the OM disease extremes - proneness and chronicity, with a particular focus on how copy number variations in genes that encode alpha- and beta-defensin family members contribute to proneness. We will also study how APs might first inadvertently contribute to chronicity by inducing NTHI to form a biofilm, but later participate in its resolution and 4 to utilize our enhanced under- standing of innate immunity in the uppermost airway to develop novel methods to treat and/or prevent OM. PUBLIC HEALTH RELEVANCE: Due to the continuing need for improved methods to treat and/or prevent otitis media (OM), the desire for less invasive, more targeted pediatric vaccines and the realization that our understanding of both the microbiology and immunology of acute and chronic OM is incomplete, it is imperative that we seek a greater understanding of how the body defends the uppermost airway, and that methods to potentially augment these defense mechanisms be identified and developed further as a novel approach for the treatment and/or prevention of OM. Gaining this improved understanding will potentially allow us to develop therapeutic approaches that are locally restricted and site-specific, as well as facilitate the refinement of vaccine formulations so as to enhance their efficacy. These approaches could add tremendously to our available arsenal for fighting acute and chronic OM and importantly, could potentially provide a mechanism to intervene at a very early state in disease process- colonization of the NP, thereby significantly reducing the morbidity associated with this highly prevalent pediatric disease.