摘要：SummaryAlthough some COVID-19 patients maintain SARS-CoV-2-specific serum immunoglobulin G (IgG) for more than 6 months postinfection, others eventually lose IgG levels. We assessed the persistence of SARS-CoV-2-specific B cells in 17 patients, 5 of whom had lost specific IgGs after 5–8 months. Differentiation of blood-derived B cellsin vitrorevealed persistent SARS-CoV-2-specific IgG B cells in all patients, whereas IgA B cells were maintained in 11. Antibodies derived from cultured B cells blocked binding of viral receptor-binding domain (RBD) to the cellular receptor ACE-2, had neutralizing activity to authentic virus, and recognized the RBD of the variant of concern Alpha similarly to the wild type, whereas reactivity to Beta and Gamma were decreased. Thus, differentiation of memory B cells could be more sensitive for detecting previous infection than measuring serum antibodies. Understanding the persistence of SARS-CoV-2-specific B cells even in the absence of specific serum IgG will help to promote long-term immunity.Graphical abstractDisplay OmittedHighlights•Memory B cells persist in blood of COVID-19 patients despite loss of specific Ig•Differentiating B cellsin vitrorobustly reveals previous SARS-CoV-2 infection•Ig derived from memory B cells neutralizes SARS-CoV-2 variants•Persisting memory B cells contribute to protective immunity against SARS-CoV-2Biological sciences; Immunology; Immune response
