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. 2022 May 18;12(5):351.
doi: 10.3390/bios12050351.

Investigation and Comparison of Specific Antibodies' Affinity Interaction with SARS-CoV-2 Wild-Type, B.1.1.7, and B.1.351 Spike Protein by Total Internal Reflection Ellipsometry

Ieva Plikusiene  1 , Vincentas Maciulis  1   2 , Silvija Juciute  1 , Ruta Maciuleviciene  1 , Saulius Balevicius  1   2 , Arunas Ramanavicius  1 , Almira Ramanaviciene  1
Affiliations

Investigation and Comparison of Specific Antibodies' Affinity Interaction with SARS-CoV-2 Wild-Type, B.1.1.7, and B.1.351 Spike Protein by Total Internal Reflection Ellipsometry

Ieva Plikusiene et al. Biosensors (Basel). .

Abstract

SARS-CoV-2 vaccines provide strong protection against COVID-19. However, the emergence of SARS-CoV-2 variants has raised concerns about the efficacy of vaccines. In this study, we investigated the interactions of specific polyclonal human antibodies (pAb-SCoV2-S) produced after vaccination with the Vaxzevria vaccine with the spike proteins of three SARS-CoV-2 variants of concern: wild-type, B.1.1.7, and B.1.351. Highly sensitive, label-free, and real-time monitoring of these interactions was accomplished using the total internal reflection ellipsometry method. Thermodynamic parameters such as association and dissociation rate constants, the stable immune complex formation rate constant (kr), the equilibrium association and dissociation (KD) constants and steric factors (Ps) were calculated using a two-step irreversible binding mathematical model. The results obtained show that the KD values for the specific antibody interactions with all three types of spike protein are in the same nanomolar range. The KD values for B.1.1.7 and B.1.351 suggest that the antibody produced after vaccination can successfully protect the population from the alpha (B.1.1.7) and beta (B.1.351) SARS-CoV-2 mutations. The steric factors (Ps) obtained for all three types of spike proteins showed a 100-fold lower requirement for the formation of an immune complex when compared with nucleocapsid protein.

Keywords: SARS-CoV-2; antibody–antigen interaction; immune complex; total internal reflection ellipsometry.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(A) Schematic representation of SARS-CoV-2 S protein (SCoV2-S, SCoV2-αS, or SCoV2-βS) covalent immobilization on the gold-coated SPR sensor disc pre-modified with 11-MUA SAM. (B) The principle scheme representing total internal reflection ellipsometry measurements. (C) Schematic representation of SCoV2-S, SCoV2-αS, and SCoV2-βS covalent immobilization and interaction with specific polyclonal antibodies (pAb-SCoV2-S).
Figure 2
Figure 2
Time-resolved TIRE kinetics and ellipsometric parameters of SCoV2-S immobilization and interaction with specific polyclonal antibodies. (A) Kinetics of covalent SCoV2-S immobilization on 11-MUA SAM modified gold-coated SPR sensor disc; (B) kinetics of polyclonal antibody interaction with covalently immobilized ScoV2-S at different serum dilutions (1:4, 1:10, 1:20, 1:30, and 1:40); (C) Δ and (D) Ψ spectral shift after immune complex formation using the same dilutions of polyclonal antibodies.
Figure 3
Figure 3
Time-resolved TIRE kinetics and ellipsometric parameters of SCoV2-αS immobilization and interaction with specific polyclonal antibodies. (A) Kinetics of covalent SCoV2α-S immobilization on 11-MUA SAM modified gold-coated SPR sensor disc; (B) kinetics of polyclonal antibody interaction with covalently immobilized SCoV2-αS at 1:40 dilution of serum; (C) Δ and (D) Ψ spectral shift after immune complex formation using the same dilutions of polyclonal antibodies.
Figure 4
Figure 4
Time-resolved TIRE kinetics and ellipsometric parameters of SCoV2-βS immobilization and interaction with specific polyclonal antibodies. (A) Kinetics of covalent SCoV2β-S immobilization on 11-MUA SAM modified gold-coated SPR sensor disc; (B) kinetics of polyclonal antibody interaction with covalently immobilized SCoV2-βS at 1:40 dilution of serum; (C) Δ and (D) Ψ spectral shift after the formation of immune complexes using the same dilutions of polyclonal antibodies.
Figure 5
Figure 5
Normalized pAb-SCoV2-S antibody surface concentration (f) evolution in time obtained using 1:40 diluted blood serum during the formation of the immune complex with (A) SCoV2-S, (B) SCoV2-αS, (C) SCoV2-βS. Points correspond to experimentally obtained results, while lines for fitting are derived by using two-step irreversible binding immune complex formation mathematical modeling.
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Supplementary concepts