Sensing living P. aeruginosa using D-alanine derived radiotracers

项目概要： 该应用解决了放射科医生和其他医生经常遇到的一个主要挑战， 即区分活动性感染与人体内的其他过程。具体而言，拟议的工作 是由于诊断和治疗囊性纤维化患者肺炎的困难，特别是那些 是由铜绿假单胞菌引起的临床可用的成像工具（1）受到其背景的限制 在肺中的积累或（2）成像宿主对感染的反应，而不是活细菌本身。 为了应对这一挑战，我们开发了几种利用代谢途径的PET放射性示踪剂 细菌特异性探针，包括D-氨基酸衍生的探针，最近是D-[3- 11 C]丙氨酸。 当D-[3- 11 C]丙氨酸应用于几种引人注目的临床前感染模型时，我们发现， 对铜绿假单胞菌非常敏感，而绝大多数报告的放射性示踪剂并非如此。我们 进一步表明，D-[3- 11 C]丙氨酸是一种放射性示踪剂，具有（1）简单，高产率的放射性合成（2）良好的体内 稳定性（3）内源性底物的适当模拟（4）高速率掺入到两种革兰氏阴性菌中。 阴性和革兰氏阳性细菌和（5）背景组织中的低摄取。这些研究表明， D-[3- 11 C]丙氨酸的突出潜力，建议的工作需要进一步验证和了解 这个追踪器我们将首先扩展我们的放射化学方法，合成D-[1- 11 C]丙氨酸同位素异构体， 结构上相关的18F探针（特异性目的1）。然后，我们将进一步研究铅11 C同位素异构体， 体外，分析其在临床铜绿假单胞菌菌株和经验证的生物膜模型中的性能（具体目标2）。 在具体目标3中，我们将扩展这些概念，在体内采用急性和慢性模型的P。 铜绿感染

PROJECT SUMMARY: This application addresses a major challenge that radiologists and other physicians encounter frequently, namely distinguishing active infection from other processes in the human body. Specifically, the proposed work is motivated by the difficulty in diagnosing and treating pneumonias in cystic fibrosis patients, especially those caused by P. aeruginosa. Clinically available imaging tools either (1) are limited by their background accumulation in the lungs or (2) image the host response to infection rather than the living bacteria themselves. To address this challenge, we have developed several PET radiotracers that exploit metabolic pathways specific to bacteria, including D-amino acid derived probes most recently D-[3-11C]alanine. When D-[3-11C]alanine was applied to several compelling preclinical models of infection, we found that it was exquisitely sensitive to P. aeruginosa, which is not the case for the vast majority of reported radiotracers. We further showed that D-[3-11C]alanine is a radiotracer with (1) a simple, high-yield radiosynthesis (2) good in vivo stability (3) appropriate mimicry of the endogenous substrate (4) high rate of incorporation into both gram- negative and gram-positive bacteria and (5) low uptake in background tissues. These studies demonstrate the outstanding potential of D-[3-11C]alanine, with the proposed work necessary to further validate and understand this tracer. We will first expand our radiochemical methods, synthesizing the D-[1-11C]alanine isotopomer and structurally related 18F probes (Specific Aim 1). We will then further investigate the lead 11C isotopomer in vitro, analyzing its performance in clinical P. aeruginosa strains and validated biofilm models (Specific Aim 2). In Specific Aim 3, we will extend these concepts in vivo employing both acute and chronic models of P. aeruginosa infection.