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. 2022 Jun 20:10:885180.
doi: 10.3389/fchem.2022.885180. eCollection 2022.

Role of Helical Structure in MBP Immunodominant Peptides for Efficient IgM Antibody Recognition in Multiple Sclerosis

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Role of Helical Structure in MBP Immunodominant Peptides for Efficient IgM Antibody Recognition in Multiple Sclerosis

Agnieszka Staśkiewicz et al. Front Chem. .

Abstract

The involvement of Myelin Basic Protein (MBP) in Multiple Sclerosis (MS) has been widely discussed in the literature. This intrinsically disordered protein has an interesting α-helix motif, which can be considered as a conformational epitope. In this work we investigate the importance of the helical structure in antibody recognition by MBP peptides of different lengths. Firstly, we synthesized the peptide MBP (81-106) (1) and observed that its elongation at both N- and C-termini, to obtain the peptide MBP (76-116) (2) improves IgM antibody recognition in SP-ELISA, but destabilizes the helical structure. Conversely, in competitive ELISA, MBP (81-106) (1) is recognized more efficiently by IgM antibodies than MBP (76-116) (2), possibly thanks to its more stable helical structure observed in CD and NMR conformational experiments. These results are discussed in terms of different performances of peptide antigens in the two ELISA formats tested.

Keywords: NMR; circular dichroism; immune response; multiple sclerosis; myelin basic protein antigen; peptide-antigen based ELISA; synthetic helical peptides.

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Conflict of interest statement

Author HR is employed by Fischer Analytics GmbH. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Mean antibody titers to MBP peptide antigens for IgGs (A) and IgMs (B) of MS patient sera. IgM antibody responses of the MS serum to the coated peptides MBP (81–106) (1) and MBP (76–106) (2) are plotted in red.
FIGURE 2
FIGURE 2
Competitive ELISA obtained coating the peptide antigen MBP (76–116) (2) (A) or the MBP protein (B). Inhibition curve of IgMs using peptides and protein as inhibitors at different concentrations. Results show the inhibition activity % (ordinate axis) of the reference MS serum for IgMs vs. antigen concentrations on a logarithmic scale (abscissas axis). Antibody titer values were calculated as (mean Abs of serum triplicate)—(mean Abs of blank triplicate) representing graphically the calculated mean values ± the standard deviation.
FIGURE 3
FIGURE 3
CD spectra of peptides MBP (81–106) (1) (blue line) and MBP (76–116) (2) (red line) measured in water (A) and mixture of H2O:TFE (50:50, v:v) (B) at 25°C.
FIGURE 4
FIGURE 4
CD spectra of peptides MBP (81–106) (1) (blue line) and MBP (76–116) (2) (red line) in PBS at 25°C.
FIGURE 5
FIGURE 5
CD spectra of peptide MBP (81–106) (1) in PBS at various temperatures.
FIGURE 6
FIGURE 6
CD spectra of peptide MBP (76–116) (2) in PBS at various temperatures.

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