Imaging of fungal infections

摘要： 过去一年的变化： 1.放射性标记糖的评价：我们最近通过2-脱氧-2-18FFDG(18FFDG)的酶转化合成了2-脱氧-2-18FFCB(18FFCB)，放化产率为60-70%，放化纯度98%，合成时间1.5h。在霉菌性、细菌性和无菌炎症性肌炎模型中，注射18FFCB 2小时后，仅在活体烟曲霉灶中可见感染小鼠体内的放射性滞留。体外试验证实，α-葡萄糖苷酶是由烟曲霉产生的，而不是细菌产生的，导致18FFCB被分解成葡萄糖和18FFDG，后者被活真菌保留下来。否则，母体分子会迅速通过肾脏排泄，从而在烟曲霉菌感染部位产生非常低的本底放射性和非常高的靶标与非靶标比率。我们得出结论：18FFCB是一种非常有前途的临床可翻译的曲霉菌特异性PET配体。计划进一步应用于其他真菌感染和对人类的翻译。 2.使用针对甲壳素和层粘连蛋白的放射性标记抗体和纳米抗体：我们目前正在评估针对真菌细胞成分层粘连蛋白和Fab片段的全抗体。虽然我们在真菌感染中发现了标记抗体的摄取，但我们也看到了相同程度的同型抗体摄取，这表明抗体太大，最终由于内皮通透性增加而在炎症区域积聚。当我们使用Fab抗体片段时，我们发现感染的动物摄取了Fab，而未感染的动物没有摄取。同型Fab在感染和未感染的动物中均不积聚。我们发现与大肠杆菌肌炎有交叉反应。 3.我们还在评估单链抗体(纳米抗体)，以提高针对真菌感染的特异性。结果待定。

Summary: Changes over the last year: 1. Evaluation of radiolabeled sugars: we have recently synthesized 2-deoxy-2-18Ffluorocellobiose (18FFCB) by enzymatic conversion of 2-deoxy-2-18Ffluoroglucose (18FFDG) with radiochemical yield of 60-70%, radiochemical purity of > 98% and 1.5 h synthesis time. Two hours after 18FFCB injection in fungal, bacterial and sterile inflammation myositis models, retained radioactivity in infected mice was only seen in live A. fumigatus foci. In vitro testing confirmed production of -glucosidase enzyme by A. fumigatus and not by bacteria, resulting in hydrolysis of 18FFCB into glucose and 18FFDG, the latter getting retained by the live fungus. The parent molecule is otherwise promptly excreted through the kidneys resulting in very low background radioactivity and very high target to non-target ratios in A. fumigatus infectious sites. We conclude that 18FFCB is a highly-promising and clinically translatable Aspergillus-specific PET ligand. Further applications in other fungal infections and translation to humans are planned. 2. Using radiolabeled antibodies and nanobodies specific for chitin and laminarin: we are currently evaluating a full antibody against fungal cell component laminarin as well as Fab Fragment. Although we found uptake of labeled antibody in fungal infection, we also saw uptake of an isotype antibody to the same extent suggesting antibodies are too large and end up accumulating nonspecifically in areas of inflammation due to increased endothelial permeability. When we used Fab antibody fragments, we found uptake of the Fab in the infected animals but no uptake in uninfected animals. Isotype Fab did not accumulate neither in infected nor in uninfected animals. We found some cross reactivity with E coli myositis. 3. We are also evaluating single chain antibodies (nanobodies) to improve the specificity of targeting fungal infections. Results pending.