Evaluation of virus-neutralizing antibody level after novel coronavirus infection COVID-19: development of an instant assay assessing protective antibodies using a pseudovirus-based reaction

The continued emergence of SARS-CoV-2 variants with immune evasion properties of concern, such as Delta (B.1.617.2) and Omicron (B.1.1.529), calls into question the extent of the antibody-mediated immune response from the virus. The presence of virus-neutralizing antibodies against SARS-CoV-2 in the blood serum of recovered and immunized volunteers is the most accurate indicator of the level of protective activity. Methods for reliable, sensitive and rapid detection of anti-SARS-CoV-2 nAbs are needed for preclinical and clinical vaccine research. In addition, quantification of virus-neutralizing antibodies in recovered COVID-19 subjects may be useful in identifying potential donors for passive immunization and therapeutic use of class G immunoglobulins. Pseudoviruses are actively used as an alternative to infectious viral isolates of pathogenicity groups III in serological studies to determine the titers of neutralizing antibodies formed in vaccinated or infected volunteers. In addition, using several pseudotypes with different reporter genes, it is possible to simultaneously detect antibodies to different types of viruses in one biological sample. Currently, the pseudolentiviral system is widely used, in which pseudoviral particles are obtained by transfection of producer cells with vectors of a multiplasmid system of 45 plasmids: one for the vector genome, the second for Gag-Pol, the third for Rev, and one or two for protein(s) envelope, or for the co-expression of a labeled viral protein such as GAG-GFP or VPR-GFP, the main advantage of which is safety due to the minimal risk of generating a replication-competent virus. The article discusses the development of a technique that allows to determine the presence of virus-specific neutralizing antibodies to the SARS-CoV-2 antigen in the blood serum of volunteers who have had a new coronavirus infection COVID-19 and/or immunized with specific prophylaxis drugs, healthy volunteers in a neutralization reaction on a HEK 293-cell culture. T-hAce2 using pseudotyped viral constructs based on human immunodeficiency virus. The results of the development and validation of the method, as well as its subsequent prospects for use, are shown.