Sera of patients infected by earlier lineages of SARS-CoV-2 are capable to neutralize later emerged variants of concern

Biol Methods Protoc. 2022 Aug 22;7(1):bpac021. doi: 10.1093/biomethods/bpac021. eCollection 2022.


Serum samples of 20 hospitalized coronavirus disease 2019 (COVID-19) patients from Brazil who were infected by the earlier severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) lineages B.1.1.28 and B.1.1.33, and by the variant of concern (VOC) Gamma (P.1) were tested by plaque reduction neutralization test (PRNT90) with wild isolates of a panel of SARS-CoV-2 lineages, including B.1, Zeta, N.10, and the VOCs Gamma, Alpha, and Delta that emerged in different timeframes of the pandemic. The main objective of this study was to evaluate if the serum of patients infected by earlier lineages was capable to neutralize later emerged VOCs. We also evaluated if the 4-fold difference in PRNT90 titers is a reliable seropositivity criterion to distinguish infections caused by different SARS-CoV-2 lineages. Sera collected between May 2020 and August 2021 from the day of admittance to the hospital to 21 days after diagnostic of patients infected by the two earlier lineages B.1.1.28 and B.1.1.33 presented neutralizing capacity for all challenged VOCs, including Gamma and Delta. Among all variants tested, Delta and N.10 presented the lowest geometric mean of neutralizing antibody titers, and B.1.1.7, presented the highest titers. Four patients infected with Gamma, that emerged in December 2020, presented neutralizing antibodies for B.1, B.1.1.33, and B.1.1.28, its ancestor lineage. All of them had neutralizing antibodies under the level of detection for the VOC Delta. Patients infected by B.1.1.28 presented very similar geometric mean of neutralizing antibody titers for both B.1.1.33 and B.1.1.28. Findings presented here indicate that most patients infected in early stages of COVID-19 pandemic presented neutralizing antibodies capable to neutralize wild types of all later emerged VOCs in Brazil, and that the 4-fold difference in PRNT90 titers is not reliable to distinguish humoral response among different SARS-CoV-2 lineages.

Keywords: Brazil; PRNT; SARS-CoV-2; humoral; immune; variants.