Synthesis of SARS-CoV-2 Spike Glycoprotein Peptide Fragments and Study of Their Binding to Human Blood Cells

Objective: Тhe development of new proteins against COVID-19 is an urgent task. The goal of this work was the synthesis of the peptides Lys-Ile-Ala-Asp-Tyr-Asn-Tyr-Lys-Leu (417–425 aa) and Val-Arg-Gln-Ala-Pro-Asn-Gly- Gln-Thr (407–415 aa) – fragments of the surface glycoprotein Spike of SARS-CoV-2 – as potential components of a vaccine against COVID-19 and the study of their binding to human blood cells. Methods: The compounds were synthesized using peptide chemistry methods in solution. The effect of peptides on leukocytes was studied by flow cytometry using monoclonal antibodies against molecules expressed on leukocytes (CD45), that are responsible for the early activation of lymphocytes (CD69) and basophils (CD203c, CD63). The concentration of IFN-γ, which was secreted by lymphocytes in response to peptides, was determined by ELISA. Results and Discussion: It was established that peptides could bind to leukocytes, which indicates the universality of reactions to peptides, especially in innate immune cells. It was shown that the Lys-Ile-Ala-Asp-Tyr-Asn-Tyr-Lys-Leu peptide contacted the leukocytes activated the lymphocytes and basophils. It was confirmed by an increase in gamma interferon compared to the Val-Arg-Gln-Ala-Pro-Asn-Gly-Gln-Thr. Conclusions: A method that allows to evaluate the effect of short peptides on leukocytes was tested. It was shown that the obtained peptides interact with leukocytes, activating them, which was evidenced by secretion of IFN-γ. Our proposed method for evaluating the effect of short peptides on blood cells is the first step in the development of a new peptide-based vaccine against COVID-19.