Pathogen specific imaging of endocarditis

心内膜炎的病原体特异性成像

• 批准号: 8496960
• 负责人: Matthias Nahrendorf
• 金额: $ 41.97万
• 依托单位: MASSACHUSETTS GENERAL HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-06-15 至 2017-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8496960
• 关键词: Active Sites; Acute Endocarditis; Address; Adopted; Affinity; Anatomy; Antibiotic Therapy; Antibiotics; Bacteremia; Bacteria; Bacterial Endocarditis; Binding; Bioluminescence; Blood; Blood Circulation; Brain; Cardiac; Catheters; Cessation of life; Chemistry; Cine Magnetic Resonance Imaging; Clinical; Clinical Management; Data; Detection; Development; Diagnosis; Dose; Drug Kinetics; Electrocardiogram; Embolism; Endocarditis; Engineering; Exclusion; Fever; Fibrinogen; Fluorochrome; Goals; Half-Life; Heart Valves; Heart murmur; Human; Hybrids; Image; Infection; Infective endocarditis; Injection of therapeutic agent; Isotopes; Label; Lead; Left Ventricular Function; Lesion; Life; Ligands; Lung; Magnetic Resonance Imaging; Medical; Methods; Miniature Swine; Minor; Modality; Modeling; Molecular; Monitor; Mus; N-terminal; Nature; Operative Surgical Procedures; Optics; PET/CT scan; Patients; Plasminogen; Population Dynamics; Positron-Emission Tomography; Prothrombin; Recurrent disease; Reporter; Sensitivity and Specificity; Serine Protease; Sexuality; Signal Transduction; Staphylocoagulase; Staphylococcus aureus; Streptococcus; Streptokinase; Terminal Repeat Sequences; Testing; Thrombin; Time; Translations; Treatment Efficacy; Vancomycin; Virulence Factors; Withdrawal; aortic valve; base; clinical Diagnosis; cycloaddition; diagnostic accuracy; imaging probe; improved; killings; mortality; mouse model; novel; pathogen; public health relevance; sensor; septic; valvular insufficiency

DESCRIPTION (provided by applicant): Clinical management of acute endocarditis, a frequent and deadly infection of the heart valves (mortality of up to 47%), remains highly challenging and often unsuccessful1,2. The most common pathogen in acute endocarditis is Staphylococcus aureus, followed by streptococcus species2,3. Unmet clinical needs include: (i) reliable diagnosis or exclusion of endocarditis, (ii) specific identification of the pathogen informing selection of antibiotics, and (iii) acquisition of quantitative data to guide surgical intervention. Here we aim to develop a clinically viable, novel method for pathogen-specific imaging of Staphylococcus aureus endocarditis. Our strategy is based on the ultrahigh affinity (17pM)5 of the virulence factor staphylocoagulase, which is secreted by the bacteria, to prothrombin (ProT) and the use of this interaction to develop specific imaging probes6. Staphylocoagulase's NH2-terminal D1 and D2-domains bind to thrombin (or the ProT imaging platform), while the COOH-terminal repeats region binds to fibrinogen at the same time. Therefore, staphylocoagulase firmly anchors the imaging probe in endocarditic vegetations. Our preliminary data show that harnessing the high affinity between ProT and staphylocoagulase for engineering imaging agents is feasible (Nature Med. 2011)6. We used prothrombin's activation pocket that tightly binds to staphylocoagulase by a mechanism dubbed "molecular sexuality" (Bode and Huber 1976)7 as an affinity ligand. Labeling ProT's serine protease active site with a fluorochrome allowed us to detect and monitor S. aureus endocarditis in a mouse model with optical imaging6. Furthermore, we synthesized a PET reporter for S. aureus (64Cu-iProT) and found that sensitive PET imaging of staphylocoagulase is also feasible. The studies proposed in the first aim are based on this already-established imaging agent but will also pursue development of alternative imaging agents targeted to other bacterial strains. The second aim describes developing 18F compounds with optimized pharmacokinetics using click chemistry, which we recently adopted for facile synthesis of PET agents8,9. Two lead compounds will be tested in a G¿ttingen minipig model of endocarditis. We will employ these probes to image murine endocarditis by hybrid ECG- triggered PET/CT and PET/MRI, thereby combining a sensitive molecular modality (PET) with a leading modality for assessing left ventricular function which can also detect valvular insufficiency (MRI). Agent development will focus on clinical feasibility to address the aforementioned urgent medical needs, with the ultimate goal of using PET/MRI detection of bacteria in valve lesions for the diagnosis of acute endocarditis in patients.

描述（由申请人提供）：急性心内膜炎是一种常见且致命的心脏瓣膜感染（死亡率高达47%），其临床治疗仍然非常具有挑战性，而且往往不成功1,2。急性心内膜炎最常见的病原体是金黄色葡萄球菌，其次是链球菌2,3。未满足的临床需求包括：(i)心内膜炎的可靠诊断或排除，（ii）病原体的特异性鉴定，为选择抗生素提供信息，以及（iii）获得定量数据以指导手术干预。在这里，我们的目标是发展一种临床可行的，新的方法，病原体特异性成像的金黄色葡萄球菌心内膜炎。我们的策略是基于细菌分泌的毒力因子葡萄凝固酶对凝血酶原（ProT）的超高亲和力（17pM）5，并利用这种相互作用来开发特异性成像探针6。葡萄凝固酶的nh2末端D1和d2结构域与凝血酶（或ProT成像平台）结合，而cooh末端重复区域同时与纤维蛋白原结合。因此，葡萄凝固酶牢固地锚定了心内膜植被的成像探针。我们的初步数据表明，利用ProT和葡萄凝固酶之间的高亲和力作为工程显像剂是可行的（Nature Med. 2011）。我们使用凝血酶原的激活袋，它通过一种被称为“分子性”的机制与葡萄凝固酶紧密结合（Bode和Huber 1976）7作为亲和力配体。用荧光染料标记ProT的丝氨酸蛋白酶活性位点，使我们能够用光学成像检测和监测小鼠模型中的金黄色葡萄球菌心内膜炎6。此外，我们合成了金黄色葡萄球菌（S. aureus）的PET报告基因（64Cu-iProT），发现对葡萄凝固酶的敏感PET成像也是可行的。第一个目标中提出的研究是基于这种已经建立的显像剂，但也将寻求开发针对其他细菌菌株的替代显像剂。第二个目标描述了利用click化学方法开发具有优化药代动力学的18F化合物，我们最近将其用于PET试剂的快速合成8,9。两种先导化合物将在G¿ttingen迷你猪心内膜炎模型中进行测试。我们将使用这些探针通过混合心电图触发的PET/CT和PET/MRI对小鼠心内膜炎进行成像，从而将敏感的分子模式（PET）与评估左心室功能的领先模式（PET）结合起来，该模式也可以检测瓣膜功能不全（MRI）。药物的开发将集中在临床可行性上，以解决上述迫切的医疗需求，最终目标是利用PET/MRI检测瓣膜病变中的细菌来诊断患者的急性心内膜炎。