Various types of COVID-19 vaccines, including adenovirus, mRNA, and inactivated ones, have been developed and approved for clinical use worldwide. Inactivated vaccines are produced using a proven technology that is widely used for the production of vaccines for the prevention and control of infectious diseases, including influenza and poliomyelitis. The development of inactivated whole-virion vaccines commonly includes several stages: the production of cellular and viral biomass in cell culture; inactivation of the virus; filtration and ultrafiltration; chromatographic purification of the viral antigen; and formulation with stabilizers and adjuvants. In this study, the suitability of four resins for Size-Exclusion Chromatography was investigated for the purification of a viral antigen for the human COVID-19 vaccine.

BACKGROUND: SARS-CoV-2 vaccine immunogenicity is evaluated in neutralization test with live virus. It is performed in a biosafety level 3 zone because requires live virus stage. Therefore, control laboratories should be certified for this class of work. The development of technology based on enzyme-linked immunosorbent assay as an analogue of the neutralization reaction makes it possible to create an immunobiological product in a shorter time and in conditions without special requirements for control laboratories. AIM: Development of an enzyme-linked immunosorbent assay for assessing SARS-CoV-2 vaccine immunogenicity by measuring neutralizing antibodies production in immunized animals. MATERIALS AND METHODS: Recombinant receptor-binding domain fused to a С-terminal hexahistidine sequence was produced in Escherichia coli cells and purified via metal-affinity chromatography on WorkBeads NiMAC (Bio-Works). Purified protein was used in enzyme-linked immunosorbent assay as an antigen for sorption. The sera of mice immunized with the vaccine preparation were tested for neutralizing activity against the SARS-CoV-2, as well as in the developed enzyme-linked immunosorbent assay. RESULTS: Sera with high neutralizing titers showed a high degree of binding to recombinant receptor-binding domain fused to a С-terminal hexahistidine sequence in enzyme-linked immunosorbent assay, while sera from non-immunized animals or sera with neutralization titers less than 1:8 were not reactive in enzyme-linked immunosorbent assay. The Spearman and Pearson correlation coefficients for neutralization test titers and optical density in enzyme-linked immunosorbent assay were 0.759 and 0.76, respectively. The developed assay can be used as a semi-quantitative method for assessing the immunogenicity of a vaccine against coronavirus infection. CONCLUSIONS: The developed platform makes it possible to reliably assess the immunogenicity of an inactivated coronavirus vaccine under conditions that do not require a high biosafety conditions.