Bhatt Mitra Jyotsna, Chatterjee Saurav, Kumar Anuj, Khatoon Elina, Chandak Ashok, Rakshit Sutapa, Bandyopadhyay Anupam, Mukherjee Archana
Radiopharmaceuticals Division, Bhabha Atomic Research Centre (BARC), Mumbai, India.
Homi Bhabha National Institute, Anushaktinagar, Mumbai, India.
EJNMMI Radiopharm Chem. 2024 Mar 26;9(1):25. doi: 10.1186/s41181-024-00252-4.
The urgent demand for innovative theranostic strategies to combat bacterial resistance to antibiotics is evident, with substantial implications for global health. Rapid diagnosis of life-threatening infections can expedite treatment, improving patient outcomes. Leveraging diagnostic modalities i.e., positron emission tomography (PET) and single photon emission computed tomography (SPECT) for detecting focal infections has yielded promising results. Augmenting the sensitivity of current PET and SPECT tracers could enable effective imaging of pathogenic bacteria, including drug-resistant strains.UBI (29-41), an antimicrobial peptide (AMP) fragment recognizes the S. aureus membrane through electrostatic binding. Radiolabeled UBI (29-41) is a promising SPECT and PET-based tracer for detecting focal infections. 2-APBA (2-acetyl-phenyl-boronic acid), a non-natural amino acid, specifically targets lysyl-phosphatidyl-glycerol (lysyl-PG) on the S. aureus membranes, particularly in AMP-resistant strains. We propose that combining UBI with 2-APBA could enhance the diagnostic potential of radiolabeled UBI.
Present work aimed to compare the diagnostic potential of two radiolabeled peptides, namely UBI (29-41) and 2-APBA modified UBI (29-41), referred to as UBI and UBI-APBA. APBA modification imparted antibacterial activity to the initially non-bactericidal UBI against S. aureus by inducing a loss of membrane potential. The antibacterial activity demonstrated by UBI-APBA can be ascribed to the synergistic interaction of both UBI and UBI-APBA on the bacterial membrane. To enable PET imaging, we attached the chelator 1,4,7-triazacyclononane 1-glutaric acid 4,7-acetic acid (NODAGA) to the peptides for complexation with the positron emitter Gallium-68 (Ga). Both NODAGA conjugates were radiolabeled with Ga with high radiochemical purity. The resultant Ga complexes were stable in phosphate-buffered saline and human serum. Uptake of these complexes was observed in S. aureus but not in mice splenocytes, indicating the selective nature of their interaction. Additionally, the APBA conjugate exhibited superior uptake in S. aureus while preserving the selectivity of the parent peptide. Furthermore, [Ga]Ga-UBI-APBA demonstrated accumulation at the site of infection in rats, with an improved target-to-non-target ratio, as evidenced by ex-vivo biodistribution and PET imaging.
Our findings suggest that linking UBI, as well as AMPs in general, with APBA shows promise as a strategy to augment the theranostic potential of these molecules.
对抗细菌抗生素耐药性的创新诊疗策略的迫切需求显而易见，这对全球健康具有重大影响。对危及生命的感染进行快速诊断可加快治疗速度，改善患者预后。利用正电子发射断层扫描（PET）和单光子发射计算机断层扫描（SPECT）等诊断方式检测局部感染已取得了有前景的结果。提高当前PET和SPECT示踪剂的灵敏度能够实现对包括耐药菌株在内的致病细菌进行有效成像。抗菌肽（AMP）片段UBI（29 - 41）通过静电结合识别金黄色葡萄球菌膜。放射性标记的UBI（29 - 41）是一种有前景的基于SPECT和PET的用于检测局部感染的示踪剂。2 - 乙酰基苯基硼酸（2-APBA），一种非天然氨基酸，特异性靶向金黄色葡萄球菌膜上的赖氨酰磷脂酰甘油（lysyl-PG），尤其是在耐AMP菌株中。我们提出将UBI与2-APBA结合可增强放射性标记的UBI的诊断潜力。
当前工作旨在比较两种放射性标记肽的诊断潜力，即UBI（29 - 41）和2-APBA修饰的UBI（29 - 41），分别称为UBI和UBI - APBA。APBA修饰通过诱导膜电位丧失赋予最初无杀菌活性的UBI对金黄色葡萄球菌的抗菌活性。UBI - APBA表现出的抗菌活性可归因于UBI和UBI - APBA在细菌膜上的协同相互作用。为了实现PET成像，我们将螯合剂1,4,7 - 三氮杂环壬烷 - 1 - 戊二酸 - 4,7 - 乙酸（NODAGA）连接到肽上，以便与正电子发射体镓 - 68（Ga）络合。两种NODAGA偶联物都用Ga进行了放射性标记，放射化学纯度高。所得的Ga络合物在磷酸盐缓冲盐水和人血清中稳定。在金黄色葡萄球菌中观察到这些络合物的摄取，但在小鼠脾细胞中未观察到，表明它们相互作用的选择性。此外，APBA偶联物在金黄色葡萄球菌中表现出更高的摄取，同时保留了亲本肽的选择性。此外，[Ga]Ga - UBI - APBA在大鼠感染部位有聚集，靶非靶比得到改善，体外生物分布和PET成像证明了这一点。
我们的研究结果表明，将UBI以及一般的AMPs与APBA连接作为增强这些分子诊疗潜力的策略具有前景。
