Immunogenicity of mRNA encoding RBD SARS-CoV-2 in complex with a polycationic carrier

BACKGROUND: RBD, receptor-binding domain, a key region of the SARS-CoV-2 surface glycoprotein for virus binding to host cell receptors and one of the targets of virus-neutralizing antibodies. That is why RBD is a promising immunogen for the development of vaccines that can provide protection against COVID-19. Vaccine mRNA is one of the new and rapidly developing vaccine platforms, and the delivery system is a very important component of it. AIM: The aim of this work was to present the results of a study of the antigenic properties of mRNA encoding the receptor-binding domain of SARS-CoV-2 when administered in combination with a polycationic carrier. MATERIALS AND METHODS: Dynamic and electrophoretic light scattering were used to characterize mRNA complexes with a polyglucin-spermidine conjugate. To assess the immunogenicity of mRNA were immunized BALB/c mice. The specific activity of the sera was assessed using enzyme immunoassay. RESULTS: As a result, the sizes and surface charge of the RBD-encoding mRNA complexes with the polyglucin-spermidine conjugate were determined. It has been shown that wrapping mRNA in a polyglucin-spermidine conjugate shell leads to an increase in the induction of RBD-specific antibodies in BALB/c mice compared to naked mRNA. CONCLUSIONS: An mRNA encoding the receptor-binding domain of SARS-CoV-2 has been obtained. It has been shown that the packaging of mRNA into the polyglucin-spermidine conjugate shell leads to an increase in immunogenic properties.