Department of Animal Health, Institute of Tropical Medicine Antwerp, Antwerp, Belgium.
Br J Pharmacol. 2012 Apr;165(7):2341-53. doi: 10.1111/j.1476-5381.2011.01723.x.
Nanobodies are promising antigen-binding moieties for molecular imaging and therapeutic purposes because of their favourable pharmacological and pharmacokinetic properties. However, the capability of monovalent nanobodies to reach targets in the CNS remains to be demonstrated.
We have assessed the blood-brain barrier permeability of Nb_An33, a nanobody against the Trypanosoma brucei brucei variant-specific surface glycoprotein (VSG). This analysis was performed in healthy rats and in rats that were in the encephalitic stage of African trypanosomiasis using intracerebral microdialysis, single photon emission computed tomography (SPECT) or a combination of both methodologies. This enabled the quantification of unlabelled and (99m) Tc-labelled nanobodies using, respectively, a sensitive VSG-based nanobody-detection elisa, radioactivity measurement in collected microdialysates and SPECT image analysis.
The combined read-out methodologies showed that Nb_An33 was detected in the brain of healthy rats following i.v. injection, inflammation-induced damage to the blood-brain barrier, as in the late encephalitic stage of trypanosomiasis, significantly increased the efficiency of passage of the nanobody through this barrier. Complementing SPECT analyses with intracerebral microdialysis improved analysis of brain disposition. There is clear value in assessing penetration of the blood-brain barrier by monovalent nanobodies in models of CNS inflammation. Our data also suggest that rapid clearance from blood might hamper efficient targeting of specific nanobodies to the CNS.
Nanobodies can enter the brain parenchyma from the systemic circulation, especially in pathological conditions where the blood-brain barrier integrity is compromised.
纳米抗体具有有利的药理学和药代动力学特性，是用于分子成像和治疗目的的有前途的抗原结合片段。然而，单价纳米抗体到达中枢神经系统（CNS）靶点的能力仍有待证明。
我们评估了针对锥虫布鲁斯氏菌布鲁斯氏变体特异性表面糖蛋白（VSG）的纳米抗体 Nb_An33 的血脑屏障通透性。这项分析是在健康大鼠和患有非洲锥虫病脑炎阶段的大鼠中通过脑内微透析、单光子发射计算机断层扫描（SPECT）或两种方法的组合进行的。这使得可以使用分别基于敏感 VSG 的纳米抗体检测 ELISA、收集的微透析液中的放射性测量和 SPECT 图像分析来定量未标记和（99m）Tc 标记的纳米抗体。
联合读出方法表明，Nb_An33 在静脉注射后可在健康大鼠的大脑中检测到，炎症引起的血脑屏障损伤，如在锥虫病的晚期脑炎阶段，显著增加了纳米抗体通过该屏障的传递效率。用脑内微透析术补充 SPECT 分析可改善对大脑分布的分析。在中枢神经系统炎症模型中评估单价纳米抗体对血脑屏障的穿透性具有明显的价值。我们的数据还表明，从血液中快速清除可能会阻碍特定纳米抗体对 CNS 的有效靶向。
纳米抗体可以从体循环进入脑实质，特别是在血脑屏障完整性受损的病理情况下。
