Antimicrobial Peptides & Innate Immunity in Otitis Media

描述（由申请人提供）：抗菌多肽（AP）是粘膜主要防御机制的关键组分，可对呼吸道、胃肠道和泌尿生殖道的大量上皮表面上的细菌、真菌和病毒进行一线灭活。这些阳离子多肽的有效抗微生物活性（其通常是协同的并且可以是加和的）提供了先天免疫系统的高度有效的作用机制。最近，已经开始认识到，生活在这些粘膜表面上的肠道微生物刺激上皮细胞产生这些先天免疫效应物，从而有助于宿主维持防御性粘膜屏障和稳态。后一点与中耳炎（OM）特别相关，因为OM不是由高毒力微生物引起的;相反，OM是由通常包含儿科鼻咽（NP）正常植物群的咽部细菌亚群引起的。然而，当宿主的气道防御受到损害时，这些细菌可以表现为机会致病菌，并进入现在防御薄弱的中耳。众所周知，NP的定殖因此是OM病程中的第一步。就在中耳侵入之前，鼻咽部的细菌负荷显著增加。此外，与其非中耳炎易感性对应物相比，中耳炎易感性儿童被在急性和慢性OM中占优势的细菌物种更重地定殖，从而强化了在NP中保持相对低的细菌载量对中耳的健康是重要的这一概念，特别是在病毒危害时期。儿童NP中的细菌负荷维持在非感染性“定殖”水平很可能主要由先天免疫系统（包括AP和气道分泌物中存在的天然抗体的作用）在日常基础上进行调节，而不是由获得性免疫效应物调节。先天免疫系统在特定个体中的相对有效性也会影响中耳炎的易感性。相反，先天防御机制的失调（即由于并发的上呼吸道（URT）病毒感染或先天免疫系统不充分或低反应的遗传易感性）可能会使细菌负荷增加到更“易感染”的水平。因此，重要的是定义和研究最上气道的先天免疫系统，其包括鼻咽、咽鼓管和中耳。为了这个目标，在本申请中，我们提出表征和研究在最上气道中产生的AP。具体而言，我们希望调查他们的作用，鼻咽部的细菌定植，并确定其表达上调或下调，以应对占主导地位的病毒和细菌病原体的OM。此外，我们建议确定它们的相对表达水平在诱导和分辨率的实验OM使用完善的灰鼠模型。最后，我们将提供分离的重组或合成的灰鼠AP（包括最近确定的灰鼠β防御素-1）的灰鼠主机的最上气道，试图抑制OM的发展，发生在这个模型。

DESCRIPTION (provided by applicant): Antimicrobial polypeptides (APs) are key components of the primary defense mechanisms of mucus membranes, providing first-line inactivation of bacteria, fungi and viruses on the vast epithelial surfaces that line the respiratory, gastrointestinal and urogenital tracts. The potent antimicrobial activity of these cationic polypeptides, which is often synergistic and can be additive, provides the highly effective mechanism of action of the innate immune system. Recently, it has begun to be appreciated that the commensal microorganisms living on these mucosal surfaces stimulate epithelial cells to produce these effectors of innate immunity and thus contribute to host maintenance of defensive mucosal barriers and homeostasis. This latter point is particularly relevant to otitis media (OM) because OM is not caused by highly virulent microorganisms; OM is instead caused by a subset of the commensal bacteria that typically comprise the normal flora of the pediatric nasopharynx (NP). However, when host airway defenses are compromised, these bacteria can behave as opportunistic pathogens and gain access to the now poorly defended middle ear. It is well known that colonization of the NP is thus the very first step in the disease course of OM. Immediately preceding invasion of the middle ear, the bacterial load in the nasopharynx increases significantly. Moreover, otitis prone children are more heavily colonized by the bacterial species that are predominant in acute and chronic OM compared to their non-otitis prone counterparts, thus reinforcing the notion that maintaining a relatively low bacterial load in the NP is important to the health of the middle ear, particularly during times of viral compromise. It is highly likely that maintenance of the bacterial load in a child's NP at a noninfectious "colonizing" level is regulated on a day-to-day basis primarily by the innate immune system, including action of the APs and natural antibodies present in airway secretions, and not by effectors of acquired immunity. The relative effectiveness of the innate immune system in a given individual would then influence otitis proneness as well. Conversely, dysregulation of innate defense mechanisms (i.e. due to concurrent upper respiratory tract (URT) viral infection or genetic predisposition to an inadequate or hypo-responsive innate immune system) may allow an increase in bacterial load to a more 'infectious-prone' level. It is thereby important to define and study the innate immune system of the uppermost airway, which includes the nasopharynx, Eustachian tube and middle ear. Toward this goal, in the present application we propose to characterize and study the APs produced in the uppermost airway. Specifically, we wish to investigate their role in bacterial colonization of the nasopharynx and determine if their expression is up- or down-regulated in response to the predominant viral and bacterial pathogens of OM. Moreover, we propose to determine their relative level of expression during induction and resolution of experimental OM using well-established chinchilla models. Finally, we will deliver isolated recombinant or synthetic chinchilla APs (including the recently identified chinchilla beta defensin-1) to the uppermost airway of the chinchilla host in an attempt to inhibit the development of OM that occurs in this model.