A Safe Pseudotyped Lentivirus-Based Assay to Titer SARS-CoV-2 Neutralizing Antibodies
36 Pages Posted: 14 Apr 2022 Publication Status: Review Complete
More...Abstract
Measuring the neutralizing potential of SARS-CoV-2 antigens-exposed sera informs on effective humoral immunity. This is relevant to 1-monitor levels of protection within an asymptomatic population, 2-evaluate the efficacy of existing and novel vaccines against emerging variants, 3-test prospective therapeutic monoclonal neutralizing antibodies (NAbs) and, overall, to contribute to understand SARS-CoV-2 immunity. However, the goldstandard method to titer NAbs is a functional assay of virus-mediated infection, which requires biosafety level 3 (BSL-3) facilities. As these facilities are insufficient in Latin American countries, including Mexico, scant information has been obtained about NAb in these countries during the COVID-19 pandemic. An alternative solution to acquire NAb information locally is to use non-replicative viral particles that display the SARS-CoV-2 Spike (S) protein on their surface, and deliver a reporter gene into target cells upon transduction. Here we present the development of a NAb-measuring assay based on Nanolucmediated luminescence measurements from SARS-CoV-2 S-pseudotyped lentiviral particleinfected cells. The successive steps of development are presented, including lentiviral particles production, target cell selection, and TCID50 determination. We applied the optimized assay in a BSL-2 facility to measure NAbs in 15 pre-pandemic, 18 COVID-19 convalescent and 32 BNT162b2 vaccinated serum samples, which evidenced the assay with 100% sensitivity, 86.6% specificity and 96% accuracy. The assay highlighted heterogeneity in neutralization curves which are relevant in discussing neutralization potency dynamics. This is the first report of a safe functional assay to measure SARS-CoV-2 in Mexico and a cornerstone methodology necessary to measure NAb in the context of limited resources settings.
Funding Information:We acknowledge the financial support received by CONACYT (scholarships 1007842 and 657487), Secretaría de Relaciones Exteriores, Tecnológico de Monterrey and StrainBiotech S.A de C.V, that made this work possible.
Conflict of Interests: None to declare.
Ethical Approval: Protocols for the use of human samples for this work were approved by the IRB of the Instituto Mexicano del Seguro Social (IMSS) with reference number R-2020-785-068 prior to starting this work.
Keywords: Neutralizing antibodies, SARS-CoV-2, humoral immunity
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