Sensing living P. aeruginosa using D-alanine derived radiotracers

项目总结： 该应用解决了放射科医生和其他内科医生经常遇到的主要挑战， 即将活动性感染与人体内其他过程区分开来。具体地说，拟议的工作 是由于囊性纤维化患者肺炎的诊断和治疗困难，尤其是那些 由铜绿假单胞菌引起。临床上可用的成像工具或(1)受其背景限制 或者(2)想象宿主对感染的反应，而不是活着的细菌本身。 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 细菌特有的，包括D-氨基酸衍生的探针，最近的D-[3-11C]丙氨酸。 当D-[3-11C]丙氨酸应用于几种引人注目的临床前感染模型时，我们发现它是 对铜绿假单胞菌极其敏感，但已报道的绝大多数放射性示踪剂并非如此。我们 进一步证明D-[3-11C]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)体内良好的放射性合成 稳定性(3)内源底物的适当模拟(4)高掺入率 阴性和革兰氏阳性细菌；(5)背景组织摄取率低。这些研究表明， D-[3-11C]丙氨酸的巨大潜力，以及进一步验证和理解所需的拟议工作 这个示踪剂。我们将首先扩展我们的放射化学方法，合成D-[1-11C]丙氨酸同位素异构体和 结构上相关的18F探针(特定目标1)。然后，我们将进一步研究铅11C同位素异构体 体外，分析其在临床铜绿假单胞菌菌株和验证的生物被膜模型中的性能(特定目标2)。 在具体目标3中，我们将使用急性和慢性肺炎模型在体内扩展这些概念。 铜绿假单胞菌感染。

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.