Pathogen specific imaging of endocarditis

心内膜炎的病原体特异性成像

• 批准号: 8857237
• 负责人: Matthias Nahrendorf
• 金额: $ 41.53万
• 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 2016-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8857237
• 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; Health; 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 agent; imaging platform; imaging probe; improved; killings; mortality; mouse model; novel; pathogen; 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(申请人提供)：急性心内膜炎是心脏瓣膜的一种频繁和致命的感染(死亡率高达47%)，临床治疗仍然具有高度的挑战性，往往不成功1.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)为选择抗生素提供信息的病原体的具体识别；以及(Iii)获取定量数据以指导手术干预。在这里，我们的目标是开发一种临床可行的、新的方法来对金黄色葡萄球菌心内膜炎进行病原体特异性成像。我们的策略是基于细菌分泌的毒力因子葡萄球菌凝固酶对凝血酶原(PROT)的超高亲和力(17 PM)5，并利用这种相互作用来开发特定的成像探针6。葡萄球菌凝固酶的NH2末端d1和d2区域与凝血酶(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，葡萄球菌凝固酶在心内膜赘生物中牢固地锚定了成像探针。我们的初步数据表明，利用Prot和葡萄球菌凝固酶之间的高亲和力用于工程显像剂是可行的(自然医学。6.我们使用凝血酶原的激活口袋作为亲和配体，这种激活口袋通过一种被称为“分子性行为”(Bode和Huber 1976)7的机制与葡萄球菌凝固酶紧密结合。用荧光染料标记Prot的丝氨酸蛋白酶活性部位，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。此外，我们合成了金黄色葡萄球菌的PET报告基因(64Cu-iProT)，发现灵敏的葡萄球菌凝固酶的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，但也将继续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点击化学开发具有优化药代动力学的18F化合物，这是我们最近采用的用于PET试剂8，9的简易合成。两个先导化合物将在G�丁字根小型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触发的PET/CT和PET/MRI对小鼠心内膜炎进行成像，从而将一种敏感的分子模式(PET)与评估左心功能的领先模式相结合，该模式还可以检测瓣膜功能不全(MRI)。试剂开发将侧重于满足上述紧急医疗需求的临床可行性，最终目标是使用PET/MRI检测瓣膜病变中的细菌来诊断患者的急性心内膜炎。