RADIOLABELED CHEMOTACTIC PEPTIDES FOR IMAGING INFECTION

隐匿性炎性病灶的定位通常是重要的， 危重病人的治疗管理。 当前成像 程序，包括：CT，超声和MRI主要依赖于变化 在组织密度或组成中， 炎症过程。 已被用于 局部早期炎症过程需要至少12小时， 通常为从注射到成像的24-48小时。 显然， 一种快速定位急性炎症部位的方法将是非常 有助于患者管理。 最近，我们开发了一种方法， 制备白细胞化学引诱肽For-MLF的类似物， 可以放射性标记用于外部成像。 在体外，这些化合物具有 生物活性和中性粒细胞For-MLF受体结合与 天然肽 动物的初步研究表明， 这些试剂在体内结合白细胞，从循环中清除 快速定位于E.大肠杆菌感染程度 足以在注射后早期产生外部图像。 通过标记 具有非常高比活度的99 mTc的肽，成像可以 以不诱导大鼠中性粒细胞减少症的肽剂量进行， 兔子或猴子。 对照实验旨在确定， 感染定位由肽-For-MLF受体介导 相互作用，证明：1）当与定位的试剂相比， 通过非特异性机制（放射性标记的DTPA，RBC和 99 mTc标记肽的T/B比值明显高于IgG; 2） 高亲和力激动剂，低亲和力激动剂 拮抗剂和受体拮抗剂证明T/B明显 与受体亲和力有关。 这些研究还证实， 受体拮抗剂定位于感染部位， 不良反应的可能性;和3） 99 mTc标记肽可被受体阻断 拮抗剂 拟议研究的目标是开发一种 用于快速检测的最佳趋化肽试剂， 确定感染的病灶部位。 这些研究将涉及 合成一系列趋化肽类似物，重点是： 高亲和力拮抗剂或部分激动剂的设计;不复杂， 快速、高效、高比活度的99 mTc标记， 生物分布良好，定位速度加快， 病变和背景之间的对比。 每种试剂将在 体外测定其对白细胞上For-MLF受体的亲和力 以及它刺激超氧化物产生的能力， 粒细胞 将在动物中测定生物分布， 感染/炎症。 研究中心定位的速率和强度 的炎症将与体外For-MLF受体相关 亲和力和生物活性数据。 组织和细胞分级 技术将用于确定分布的动力学， 肽和代谢物的代谢。

Localization of occult inflammatory foci is frequently essential to the therapeutic management of critically ill patients. Current imaging procedures, including: CT, Ultrasound and MRI rely primarily on changes in tissue density or composition that occur late changes in the inflammatory process. Radionuclide procedures that have been used to localize early inflammatory processes require a minimum of 12 hours, and typically 24-48 hours from the time of injection to imaging. Clearly, a method of rapidly localizing sites of acute inflammation would be very helpful for patient management. Recently, we developed methods for preparing analogs of the leukocyte chemoattractant peptide, For-MLF, that can be radiolabeled for external imaging. In vitro, these compounds have bioactivity and neutrophil For-MLF receptor binding comparable to the native peptide. Preliminary studies in animals have demonstrated that these agents bind to leucocytes in vivo, clear from the circulation rapidly and localize at sites of E. coli infection to an extent sufficient to yield external images early after injection. By labeling the peptides with 99mTc at very high specific activity, imaging can be performed at doses of peptide that do not induce neutropenia in rats, rabbits or monkeys. Control experiments designed to establish that infection localization is mediated by peptide-For-MLF receptor interaction, demonstrated: 1) When compared with reagents that localize at inflammation by non-specific mechanisms (radiolabeled DTPA, RBC's and IgG), T/B ratios for 99mTc-labeled peptide were much greater; 2) Comparisons between a high affinity agonist, a very low affinity antagonist and a receptor antagonist demonstrated that T/B is clearly related to receptor affinity. These studies also established that receptor antagonists localize at sites of infection without the possibility of adverse effects; and 3) The infection localization of 99mTc labeled peptide could be blocked by coinjection of a receptor antagonist. The objective of the proposed research is to develop an optimal chemotactic peptide reagent for the rapid detection and localization of focal sites of infection. These studies will involve the synthesis of a series chemotactic peptide analogs with emphasis on: design of a high affinity antagonists or partial agonist; uncomplicated, rapid, efficient and high specific activity labeling with 99mTc, favorable biodistribution, and enhanced speed of localization and contrast between lesion and background. Each reagent will be studied in vitro to determine its affinity for the For-MLF receptor on leukocytes and its ability to stimulate the production of superoxide by granulocytes. Biodistribution will be determined in animals with infection/inflammation. The rate and intensity of localization at sites of inflammation will be correlated with the in vitro For-MLF receptor affinity and biological activity data. Tissue and cell fractionation techniques will be used to determine the kinetics of distribution and metabolism of the peptides and metabolites.