Institute of Tropical Medicine of São Paulo, University of São Paulo, São Paulo, São Paulo, 05403000, Brazil.
Department of Physics, Chemistry and Mathematics, Federal University of São Carlos, Sorocaba, São Paulo, 18052780, Brazil.
Sci Rep. 2019 Nov 6;9(1):16136. doi: 10.1038/s41598-019-52506-w.
A precise diagnosis for neuromyelitis optica spectrum disorders (NMOSD) is crucial to improve patients' prognostic, which requires highly specific and sensitive tests. The cell-based assay with a sensitivity of 76% and specificity of 100% is the most recommended test to detect anti-aquaporin-4 antibodies (AQP4-Ab). Here, we tested four AQP4 external loop peptides (AQP4, AQP4, AQP4, and AQP4) with an atomic force microscopy nanoimmunosensor to develop a diagnostic assay. We obtained the highest reactivity with AQP4-nanoimunosensor. This assay was effective in detecting AQP4-Ab in sera of NMOSD patients with 100% specificity (95% CI 63.06-100), determined by the cut-off adhesion force value of 241.3 pN. NMOSD patients were successfully discriminated from a set of healthy volunteers, patients with multiple sclerosis, and AQP4-Ab-negative patients. AQP4 sensitivity was 81.25% (95% CI 56.50-99.43), slightly higher than with the CBA method. The results with the AQP4-nanoimmunosensor indicate that the differences between NMOSD seropositive and seronegative phenotypes are related to disease-specific epitopes. The absence of AQP4-Ab in sera of NMOSD AQP4-Ab-negative patients may be interpreted by assuming the existence of another potential AQP4 peptide sequence or non-AQP4 antigens as the antibody target.
视神经脊髓炎谱系疾病（NMOSD）的精确诊断对于改善患者预后至关重要，这需要高度特异性和敏感性的检测。细胞检测法的敏感性为 76%，特异性为 100%，是最推荐用于检测抗水通道蛋白 4 抗体（AQP4-Ab）的检测方法。在此，我们使用原子力显微镜纳米免疫传感器测试了四种 AQP4 外环肽（AQP4、AQP4、AQP4 和 AQP4），以开发一种诊断检测方法。我们发现 AQP4 与纳米免疫传感器的反应性最高。该检测方法在检测 NMOSD 患者血清中的 AQP4-Ab 时具有 100%的特异性（95%CI 63.06-100），其截断粘附力值为 241.3 pN。NMOSD 患者与一组健康志愿者、多发性硬化症患者和 AQP4-Ab 阴性患者成功区分开来。AQP4 敏感性为 81.25%（95%CI 56.50-99.43），略高于 CBA 方法。AQP4 纳米免疫传感器的结果表明，NMOSD 血清阳性和血清阴性表型之间的差异与疾病特异性表位有关。NMOSD AQP4-Ab 阴性患者血清中缺乏 AQP4-Ab 可能是由于假设存在另一种潜在的 AQP4 肽序列或非 AQP4 抗原作为抗体靶标。
