Photodynamic Therapy of Localized Infections

描述(申请人提供)：这项提案的总体目标是探索一种新的光化学方法，在局部感染模型中杀灭耐药病原菌。光动力疗法(PDT)使用一种称为光敏剂(PS)的无毒染料和低强度可见光，在氧气存在的情况下会产生细胞毒性物质。PDT具有双重选择性的优点，即PS可以定向到其目的细胞或组织，此外，照明可以在空间上定向到病变。PDT以前曾被用来在体外杀死致病微生物，但到目前为止，这还没有在动物感染模型中实现。我们开发了一种新的方法，针对革兰氏()和革兰氏(-)致病菌的PS结合物，在体外可以产生高达6个对数的杀伤力，而在体内，它增加了治疗细菌的选择性，同时节省了宿主组织。这是基于PS氯e6与聚阳离子载体(如聚L赖氨酸)的共价结合，这增加了对细菌的选择性结合，并使PS能够穿透革兰氏(-)细菌的细胞壁，获得细胞内敏感部位。多重抗药性菌株和野生型菌株一样容易被杀死。我们已经使用发光细菌和微光成像相机产生了初步数据，在早期和已确定的感染动物模型中，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。在侵袭性铜绿假单胞菌的情况下，小鼠被治愈了否则致命的感染。局部PDT可能还有一个额外的优势，因为它还可以灭活病原菌用来建立感染和入侵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的决定因素。四个具体目标将侧重于优化早期、急性和慢性感染的不同小鼠模型的治疗，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。由于与传统的抗生素疗法相比，光动力疗法的优势之一是它的快速，我们还将研究利用光动力疗法来快速降低感染中的细菌负担，然后再用抗生素来消除残留的细菌。

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.