Antimicrobial Peptides & Innate Immunity in Otitis Media

描述（由申请人提供）：抗菌多肽（APs）是粘膜主要防御机制的关键组成部分，为呼吸道、胃肠道和泌尿生殖道上皮表面的细菌、真菌和病毒提供一线失活。这些阳离子多肽的有效抗菌活性通常是协同的，也可以是相加的，为先天免疫系统提供了非常有效的作用机制。最近，人们开始认识到，生活在这些粘膜表面的共生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体内平衡。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是由共生细菌的一个子集引起的，共生细菌通常包括儿童鼻咽（NP）的正常菌群。然而，当宿主气道防御被破坏时，这些细菌可以作为机会性病原体，进入现在防御薄弱的中耳。众所周知，NP的定植是OM病程的第一步。在侵入中耳之前，鼻咽部的细菌负荷显著增加。此外，与非中耳炎易感儿童相比，易患中耳炎的儿童更容易被急性和慢性OM中主要的细菌物种定植，从而加强了在NP中保持相对较低的细菌负荷对中耳健康的重要性，特别是在病毒妥协时期。儿童NP中的细菌负荷维持在非感染性“定植”水平，很可能主要是由先天免疫系统（包括气道分泌物中存在的ap和天然抗体的作用）在日常基础上调节的，而不是由获得性免疫的效应器调节的。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（即由于并发上呼吸道（URT）病毒感染或先天免疫系统不充分或反应低下的遗传易感性）可能会使细菌负荷增加到更“容易感染”的水平。因此，定义和研究包括鼻咽部、咽鼓管和中耳在内的最上层气道的先天免疫系统具有重要意义。为了实现这一目标，在目前的应用中，我们建议对上气道产生的ap进行表征和研究。具体来说，我们希望研究它们在鼻咽部细菌定植中的作用，并确定它们的表达是在响应OM的主要病毒和细菌病原体时上调还是下调。此外，我们建议利用成熟的栗鼠模型来确定它们在诱导和分离实验OM过程中的相对表达水平。最后，我们将把分离的重组或合成的栗鼠ap（包括最近鉴定的栗鼠β防御素-1）递送到栗鼠宿主的最上层气道，试图抑制该模型中发生的OM的发展。

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.