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. 2023 Aug 3;13(8):784.
doi: 10.3390/bios13080784.

Study of SARS-CoV-2 Spike Protein Wild-Type and the Variants of Concern Real-Time Interactions with Monoclonal Antibodies and Convalescent Human Serum

Ieva Plikusiene  1   2 , Vincentas Maciulis  1   2 , Silvija Juciute  1 , Arunas Ramanavicius  1 , Almira Ramanaviciene  1
Affiliations

Study of SARS-CoV-2 Spike Protein Wild-Type and the Variants of Concern Real-Time Interactions with Monoclonal Antibodies and Convalescent Human Serum

Ieva Plikusiene et al. Biosensors (Basel). .

Abstract

The spike (S) protein and its receptor-binding domain (RBD) of the coronavirus SARS-CoV-2 have been continually evolving, yielding the majority of significant missense mutations and new variants of concern. In this study, we examined how monoclonal antibodies against RBD (mAbs-SCoV2-RBD) and polyclonal antibodies present in convalescent human serum specifically interact with the S protein of wild-type and SARS-CoV-2 variants of concern (VOCs) in real time and how this can be reflected through surface mass density. Moreover, we combined two distinct, label-free measurement techniques: one based on changes in surface electromagnetic waves after reflection from the surface, and the other on changes in acoustic waves. The results demonstrated that dry surface mass density (ΓSE) of mAbs-SCoV2-RBD attached to the RBD of the S protein decreases three-fold, from 148 ng/cm2 to 46 ng/cm2, due to the B.1.351 or so-called beta mutation of coronavirus and its S protein (SCoV2-β). Consequently, the obtained wet mass ΓQCM-D resulted in values two times lower, from 319 ng/cm2 to 158 ng/cm2, and the hydration of mAbs-SCoV2-RBD/SCoV2-β immune complex was 70.88%. Conversely, when polyclonal antibodies present in convalescent human serum form immune complexes with the S protein of SARS-CoV-2 variants of concern, the ΓSE decreased from 279 ng/cm2 to 249 ng/cm2, and ΓQCM-D from 1545 ng/cm2 to 1366 ng/cm2. These results can give insights into the differences between the interaction of monoclonal and polyclonal antibodies with SARS-CoV-2 VOCs.

Keywords: SARS-CoV-2; immunosensor; kinetics; quartz crystal microbalance with dissipation; spectroscopic ellipsometry.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Time-resolved QCM-D kinetics of ΔF and ΔD for: SCoV2-WTS covalent immobilization on functionalized gold-coated sensor disk surface (A,D); SCoV2-WTS interaction with mAb-SCoV2-RBD antibodies (B,E), and with convalescent human serum containing pAbs-SCoV2-S antibodies (C,F).
Figure 2
Figure 2
Time-resolved QCM-D kinetics of ΔF and ΔD for: SCoV2-αS covalent immobilization on functionalized gold-coated sensor disk surface (A,D); SCoV2-αS interaction with mAb-SCoV2-RBD antibodies (B,E), and with convalescent human serum containing pAbs-SCoV2-S antibodies (C,F).
Figure 3
Figure 3
Time-resolved QCM-D kinetics of ΔF and ΔD for: SCoV2-βS covalent immobilization on functionalized gold-coated sensor disk surface (A,D); SCoV2-S interaction with monoclonal mAb-SCoV2-RBD antibodies (B,E), and with convalescent human serum containing pAbs-SCoV2-S antibodies (C,F).
Figure 4
Figure 4
QCM-D ΔF7 and ΔD7 response to covalent SCoV-2-S proteins of different mutations immobilization on 11-MUA functionalized gold-coated sensor disk surface (A), followed by the immune complex formation with mAbs-SCoV2-RBD (B) and pAbs-SCoV2-S (C) antibodies.
Figure 5
Figure 5
Kinetics of ellipsometric parameter δΔ: during SCoV2-WTS (A), SCoV2-αS (D), SCoV2-βS (G) covalent immobilization on functionalized gold-coated sensor disk surface; after immune complex formation of SCoV2-WTS (B), SCoV2-αS (E), and SCoV2-βS (H) with mAb-SCoV2-RBD, and pAbs-SCoV2-S antibodies (C,F,I), respectively.
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