A highly specific and sensitive nanoimmunosensor for the diagnosis of neuromyelitis optica spectrum disorders
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.
1 Institute of Tropical Medicine of São Paulo, University of São Paulo, São Paulo, São Paulo, 05403000, Brazil.
2 Department of Physics, Chemistry and Mathematics, Federal University of São Carlos, Sorocaba, São Paulo,
18052780, Brazil.
3Nanoneurobiophysics research group (GNN), Federal University of São Carlos, Sorocaba,São Paulo, 18052780, Brazil.
4 Department of Neurology, Psychology and Psychiatry, São Paulo State University,Botucatu, São Paulo, 18618687, Brazil.
5 São Carlos Institute of Physics, University of São Paulo, São Carlos, SãoPaulo, 13560970, Brazil.
6 Rheabiotech Laboratory of Research and Development, Campinas, São Paulo, 13084791,Brazil.
7 Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, 05508000, Brazil.
8 Department of Neurosciences and Behavioural Sciences, Ribeirão Preto Medical School, University of São Paulo,
Ribeirão Preto, São Paulo, Brazil.
9 Amilton Antunes Barreira deceased