Photodynamic Therapy of Localized Infections

描述（由申请人提供）：本提案的总体目标是探索一种新的光化学方法来杀死局部感染模型中的抗生素耐药致病菌。光动力疗法（PDT）采用一种称为光敏剂（PS）的无毒染料和低强度可见光，在氧气存在下产生细胞毒性物质。PDT具有双重选择性的优点，即PS可以靶向其目标细胞或组织，并且光照可以在空间上定向到病变。PDT以前被用于体外杀死病原微生物，但直到现在还没有在动物感染模型中完成。我们已经开发了一种新的方法，将PS偶联物靶向于革兰氏（+）和革兰氏（-）致病菌，在体外可以产生高达6 log的杀灭效果，而在体内，它增加了对细菌治疗的选择性，同时保留了宿主组织。这是基于PS氯e6与聚阳离子传递载体（如聚l -赖氨酸）的共价附着，这增加了与细菌的选择性结合，并使PS能够穿透革兰氏（-）细菌的细胞壁，进入敏感的细胞内部位。多重抗生素耐药菌株和野生型菌株一样容易被杀死。我们使用发光细菌和低光成像相机获得了初步数据，在早期和已建立感染的动物模型中，PDT将在体内杀死革兰氏（-）种（大肠杆菌和铜绿假单胞菌）和革兰氏（+）种金黄色葡萄球菌。在侵入性铜绿假单胞菌的情况下，小鼠被治愈了一种致命的感染。局部PDT可能还有一个额外的优势，因为它也有可能灭活病原细菌用来建立感染和侵入组织的分泌的细胞外毒力因子。该项目将寻求探索局部感染的PDT决定因素。四个具体目标将侧重于优化不同小鼠模型的早期，急性和慢性感染的治疗，包括切除伤口，已建立的软组织感染，慢性脓肿，烧伤和尿路感染。与传统抗生素治疗相比，PDT的优点之一是快速，因此我们还将研究使用PDT快速减少感染中的细菌负担，然后使用抗生素消除残留细菌。

DESCRIPTION (provided by applicant): The overall goal of this proposal is to explore a novel photochemical method for killing antibiotic resistant pathogenic bacteria in localized models of infection. Photodynamic therapy (PDT) employs a non-toxic dye termed a photosensitizer (PS) and low intensity visible light, which in the presence of oxygen produce cytotoxic species. PDT has the advantage of dual selectivity in that the PS can be targeted to its destination cell or tissue, and in addition the illumination can be spatially directed to the lesion. PDT has previously been used to kill pathogenic microorganisms in vitro, but until now this has not been accomplished in animal models of infection. We have developed a novel method of targeting PS conjugates to both Gram (+) and Gram (-) pathogenic bacteria that can produce up to 6 logs of killing in vitro, while in vivo it increases the selectivity of the treatment for bacteria while sparing host tissue. This is based on the covalent attachment of the PS chlorin e6 to polycationic delivery vehicles such as poly-L-lysine, that increases the selective binding to bacteria and enables the PS to penetrate the cell walls of Gram (-) bacteria to gain access to sensitive intracellular sites. Multi-antibiotic resistant strains are as easily killed as wild-type strains. We have generated preliminary data using luminescent bacteria and a low-light imaging camera, that PDT will kill both Gram (-) species (Escherichia coli and Pseudomonas aeruginosa) and Gram (+) species Staphylococcus aureus) in vivo in animal models of both early and established infections. In the case of the invasive P. aeruginosa mice are cured of an otherwise fatal infection. Localized PDT may have an additional advantage in that it is also possible to inactivate secreted extracellular virulence factors that pathogenic bacteria use to establish infections and invade tissue. This project will seek to explore the determinants of PDT for localized infections. Four specific aims will focus on optimizing the treatment in different mouse models of early, acute and chronic infections, comprising excisional wounds, established soft tissue infection, chronic abscesses, burns and urinary tract infections. Since one of the advantages of PDT is its rapidity compared to traditional antibiotic therapy, we will also study the use of PDT to quickly reduce the bacterial burden in the infection, followed by antibiotics to eliminate the residual bacteria.