First pseudovirus-based assay to measure virus-elicited neutralizing antibodies in Mexico: proof-of-concept with SARS-CoV-2

Abstract The gold-standard method to evaluate a functional antiviral immune response is to titer neutralizing antibodies (NAbs) against a viral pathogen. This is historically performed using an in vitro assay of virus-mediated infection, which requires BSL-3 facilities. As these are insufficient in Latin America, including Mexico, scant information is obtained locally about viral pathogens NAb, using a functional assay. An alternative solution is to use a BSL-2-safe assay with non-replicative viral particles engineered to display a selected pathogen’s entry protein on their surface, that deliver a reporter gene into target cells upon entry protein-mediated transduction. Here we comprehensively describe the first development of a BSL-2 safe NAb-measuring functional assay in Mexico, based on the production of pseudotyped lentiviral particles. As proof-of-concept, the assay is based on Nanoluc-mediated luminescence measurements from target cells transduced with SARS-CoV-2 Spike-pseudotyped lentiviral particles. We applied the optimized assay in a BSL-2 facility to measure SARS-CoV-2 Spike NAbs in 65 serum samples, which evidenced the assay with 100% sensitivity, 86.6% specificity and 96% accuracy. Overall, this is the first report of a BSL-2 safe pseudovirus-based functional assay developed in Mexico to measure NAbs, and a cornerstone methodology necessary to measure NAbs with a functional assay in limited resources settings.