Tryptophan metabolism in Haemophilus persistence and formation of intracellular communities

摘要 由无法分型的流感嗜血杆菌（NTHI）菌株引起的感染是中耳炎的主要原因 (OM)、慢性阻塞性肺病（COPD）恶化和细菌性鼻窦炎。此外，委员会认为， NTHI部分通过形成细胞内细菌群落（IBC）导致慢性难治性疾病 在上皮细胞内，提供了一个避难所，从宿主免疫系统，并从临床干预。 影响NTHI持续性和OM复发的细菌和宿主因素并不完全 明白因此，描绘宿主-病原体相互作用和代谢影响，导致OM- 衍生的后遗症将为新的治疗方法提供信息。我们之前的研究显示， NTHI的持久分离株的生物膜生长期间的所有色氨酸生物合成途径蛋白。该分离株 也证明了在实验OM期间IBC形成的显著增加。对宿主-病原体至关重要 相互作用是色氨酸水平的调节。色氨酸的生物合成促进细胞内其他 病原体和宿主色氨酸的降解限制了细菌生长。在这项研究中，我们将描述 色氨酸代谢对OM期间NTHI发病机制的贡献。我们的中心假设是NTHI 对营养胁迫的适应增强了入侵、IBC的形成、持续和复发。我们的出版 研究表明，代谢的多个方面有助于NTHI IBC的形成和持久性。我们 方法是确定色氨酸代谢在NTHI持续性和IBC中的贡献 形成（目标1）。我们假设细菌对营养限制的适应调节NTHI色氨酸 生物合成直接影响发病机制和持久性。我们还将评估 干扰色氨酸生物合成作为新的治疗靶点（目的2）。我们假设 阻止NTHI侵入上皮细胞将促进细菌清除，从而减少 OM复发的可能性。我们的研究将揭示色氨酸获得对NTHI行为的机制 与宿主在OM期间的反应相关。利用这些途径来减缓IBC的发展， 提供了一个平台，继续开发针对细胞外和 NTHI的细胞内群体作为治疗临床疾病的先进治疗选择。

Abstract Infections caused by nontypeable Haemophilus influenzae (NTHI) strains represent a major cause of otitis media (OM), exacerbations of chronic obstructive pulmonary disease (COPD), and bacterial sinusitis. Furthermore, NTHI causes chronic, treatment-refractory diseases, in part by forming intracellular bacterial communities (IBCs) within epithelial cells that provide a refuge from both the host immune system, and from clinical interventions. The bacterial and host elements that impact NTHI persistence and recurrence of OM are not completely understood. Therefore, the delineation of host-pathogen interactions and metabolic influences that lead to OM- derived sequelae will inform novel therapeutic approaches. Our prior studies revealed a significant increase in all tryptophan biosynthetic pathway proteins during biofilm growth of a persistent isolate of NTHI. This isolate also demonstrated a significant increase in IBC formation during experimental OM. Critical to host-pathogen interactions is modulation of tryptophan levels. Tryptophan biosynthesis promotes intracellular survival of other pathogens and degradation of host tryptophan limits bacterial growth. In this study, we will delineate the contribution of tryptophan metabolism to NTHI pathogenesis during OM. Our central hypothesis is that NTHI adaptation to nutrient stress enhances invasion, IBC formation, persistence and recurrence. Our published studies indicate that multiple aspects of metabolism contribute to NTHI IBC formation and persistence. Our approach is to Determine the contribution of tryptophan metabolism in NTHI persistence and IBC formation (Aim 1). We hypothesize that bacterial adaptation to nutrient limitation modulates NTHI tryptophan biosynthesis that directly impacts pathogenesis and persistence. We will also evaluate the efficacy of interference with tryptophan biosynthesis as a novel therapeutic target (Aim 2). We hypothesize that prevention of invasion of NTHI into epithelial cells will promote bacterial clearance and thereby reduce the potential for recurrence of OM. Our studies will reveal mechanisms of tryptophan acquisition on NTHI behaviors that correlate with host responses during OM. Exploitation of these pathways to mitigate IBC development will provide a platform to continue to develop combinatorial treatments that target both the extracellular and intracellular populations of NTHI as an advanced therapeutic option to treat clinical disease.