Substantial efforts have been made to understand the interactions between immune checkpoint receptors and their ligands targeted in immunotherapies against cancer. To carefully characterize the complete network of interactions involved and the binding affinities between their extracellular domains, an improved kinetic assay is needed to overcome limitations with surface plasmon resonance (SPR). Here, we present a magneto-nanosensor platform integrated with a microfluidic chip that allows measurement of dissociation constants in the micromolar-range. High-density conjugation of magnetic nanoparticles with prey proteins allows multivalent receptor interactions with sensor-immobilized bait proteins, more closely mimicking natural-receptor clustering on cells. The platform has advantages over traditional SPR in terms of insensitivity of signal responses to pH and salinity, less consumption of proteins and better sensitivities. Using this platform, we characterized the binding affinities of the PD-1-PD-L1/PD-L2 co-inhibitory receptor system, and discovered an unexpected interaction between the two known PD-1 ligands, PD-L1 and PD-L2.

中文翻译：

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磁纳米传感器平台，用于探测低亲和力的蛋白质-蛋白质相互作用和鉴定低亲和力的PD-L1 / PD-L2相互作用。

为了理解免疫检查点受体及其靶向癌症的免疫疗法中的配体之间的相互作用，已经做出了巨大的努力。为了仔细地表征所涉及的相互作用的完整网络及其胞外域之间的结合亲和力，需要改进的动力学测定法来克服表面等离振子共振（SPR）的局限性。在这里，我们介绍了一种集成了微流控芯片的磁纳米传感器平台，该平台可以测量微摩尔范围内的解离常数。磁性纳米粒子与猎物蛋白的高密度共轭使传感器固定的诱饵蛋白与多价受体相互作用，从而更紧密地模拟细胞上的天然受体簇集。该平台相对于传统的SPR而言，在信号响应对pH和盐度的不敏感性，更少的蛋白质消耗以及更好的敏感性方面具有优势。使用该平台，我们表征了PD-1-PD-L1 / PD-L2共抑制受体系统的结合亲和力，并发现了两个已知PD-1配体PD-L1和PD-L2之间的意外相互作用。