Standardization of Viral Neutralization Assay Used in To the Determination of Neutralizing Antibodies in the Evaluation Studies of the Cuban Vaccines against COVID-19

Abstract

The epidemiological situation created by SARS-CoV-2 imposed the challenge of developing vaccines and demonstrating their efficacy through a test capable of detecting functional neutralizing antibodies. It was proposed to standardize of viral neutralization assay used in the determination of neutralizing antibodies in the evaluation studies of the Cuban vaccines against COVID-19. Serial doubling dilutions of the serum samples were used and mixed with equal volumes of strain D614G at different infective doses an concentrations of Vero E6. The neutralization titer was determined by the colorimetric method and the cytopathic effect. 24 hours were defined as virus harvest time, the fourth day as the optimal time for reading the assay, 2x104  cells/well as cell concentration,
and 100 TCID50 as optimal infective dose. The analytical specificity was 100%, as well as the specificity and diagnostic sensitivity. There was a high correlation between the micro neutralization assay and the UMELISA anti RBD system and a strong association with the molecular neutralization test. There were no differences between the cytopathic effect readings between the two reading methods. It was shown that it is a sensitive, specific and precise method, which guarantees the feasibility of its use in the evaluation of vaccine candidates against COVID-19.