A highly specific and sensitive nanoimmunosensor for the diagnosis of neuromyelitis optica spectrum disorders

Abstract

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 (AQP461–70, AQP4131–140, AQP4141–150, and AQP4201–210) with an atomic force microscopy nanoimmunosensor to develop a diagnostic assay. We obtained the highest reactivity with AQP461–70-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. AQP461–70 sensitivity was 81.25% (95% CI 56.50–99.43), slightly higher than with the CBA method. The results with the AQP461–70-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.

AQP4-DARPin1: A Chimeric Antigen Based on Scaffold Protein DARPin for Efficient Detection of AQP4-IgG in NMOSD

“…In 2016, Son et al standardized a peptide-based carbon nanotube biosensor by fabricating nanotubes with AQP4 extracellular loop peptides and reported that the sensors coated with E loop peptide had high sensitivity in detecting AQP4-IgG up to 1 ng/L . In 2019, de Souza Moraes et al generated a novel peptide-based atomic force microscopy nanoimmunosensor, which had a sensitivity of 81% for detecting AQP4-IgG, slightly higher than CBA (76%). However, Iorio et al reported that peptide-based ELISA had low sensitivity due to the masking of the epitopes .…”

“…Although protein-based AQP4-IgG ELISA is easy to use, allows large-scale analysis, and can potentially be automated, having the potential to solve the criticisms of CBA, the sensitivity of ELISA can be affected by the expression, purification, and preservation strategy of the membrane protein AQP4. ,,, Specifically, surfactants are required to maintain the solubility of AQP4 for antigen and antibody interactions, but these compounds cannot prevent the aggregation of the membrane protein AQP4 during measurements, which accounts for the main reason for the low sensitivity of ELISA. , To address these issues, researchers have been focusing on the development of ELISA with extracellular loop peptides of AQP4 as substrates . However, synthetic peptides are short, rigid, and incapable of forming the tertiary structure with antigenicity, resulting in low sensitivity of peptide-based assays, which so far are not a valid alternative to CBA. ,, …”

Comprehensive Metabolic Fingerprints Characterize Neuromyelitis Optica Spectrum Disorder by Nanoparticle-Enhanced Laser Desorption/Ionization Mass Spectrometry

“…Considering the crucial role played in IPND 2015, several immunoassays were proposed to detect blood AQP4-IgG, such as enzyme-linked immunosorbent assay, tissue-based assay, and cell-based assay (CBA). While the former two assays are limited in clinics due to relatively lower sensitivity (48%–69%) and accuracy (48%–62%), CBA is dominantly employed, providing an enhanced sensitivity of 60%–80% and an accuracy of ∼75%. , …”

Possibilities of therapy for neuromyelitis optica spectrum disorders

“…Анти-В-клеточная терапия занимает все более значительное место в патогенетическом лечении демиелинизирующих заболеваний ЦНС, являясь важным составляющим компонентом препаратов, изменяющих течение рассеянного склероза. Наиболее активно внедряются антитела к CD20-дифференцировочному рецептору на поверхности В-клеток [19,23].…”