Rapid and lasting generation of B-cell memory to SARS-CoV-2 spike and nucleocapsid proteins in COVID-19 disease and convalescence

Abstract

BackgroundLasting immunity to SARS-CoV-2 following infection is questioned because serum antibodies decline in convalescence. However, functional immunity is mediated by long-lived memory T and B (Bmem) cells.ObjectiveTo determine the longevity and immunophenotype of SARS-CoV-2-specific Bmem cells in COVID-19 patients.MethodsRecombinant spike receptor binding domain (RBD) and nucleocapsid protein (NCP) were produced for ELISA-based serology, and biotinylated for fluorescent tetramer generation to identify SARS-CoV-2-specific Bmem cells by flow cytometry with a panel of 13 mAbs. 36 blood samples were obtained from 25 COVID-19 patients (11 paired) between 4-242 days post-symptom onset for detection of neutralizing antibodies, IgG serology and flow cytometry.ResultsThe recombinant RBD and NCP were specifically recognized by serum IgG in all patients and reactivity declined >20 days post-symptom onset. All patients had detectable RBD- and NCP-specific Bmem cells at 8.23-267.6 cells/ml of blood (0.004-0.13% of B cells) regardless of sampling time. RBD- and NCP-specific Bmem cells predominantly expressed IgM or IgG1, with the latter formed slightly later than the former. RBD-specific IgG+ Bmem were predominantly CD27+, and numbers significantly correlated with circulating follicular helper T cell numbers.ConclusionRBD- and NCP-specific Bmem cells persisted for 8 months, indicating that the decline in serum antibodies after 1 month does not indicate waning of immunity but a contraction of the immune response. Flowcytometric detection of SARS-CoV-2-specific Bmem cells enables detection of long-term functional immunity following infection or vaccination for COVID-19.

Persistence and baseline determinants of seropositivity in health care workers up to nine months after COVID-19

“…Here, hospitalization was associated with higher immunoglobulin levels many months after convalescence, suggesting that severity does not affect stability of memory B cell and plasma cells producing antibodies 12 .…”

Pattern of circulating SARS‐CoV‐2‐specific antibody‐secreting and memory B‐cell generation in patients with acute COVID‐19

“…In recent studies, Bmem cells have been detected as cells binding fluorescently labelled SARS‐CoV‐2 antigens, and the kinetics of Bmem cell response has been analysed over 6 months 13,14 . These studies were mainly performed with SARS‐CoV‐2 convalescent donors, when Bmem cells are already formed and present in quantities available for determination by flow cytometry.…”

Insights into SARS-CoV-2 evolution, potential antivirals, and vaccines

“…Mildly infected COVID-19 patients demonstrated specific immune memory cells that exhibited protective antiviral functions after 3 months of exposure ( Rodda et al, 2020 ). IgM + memory B-cells dominated in the first 20 days followed by a gradual increase in IgG1+ memory B cells ( Hartley et al, 2020 ). The latter cells express CD27 and positively correlate with the T follicular helper (Tfh) cell number that suggest high robustness ( Hartley et al, 2020 ).…”

“…IgM + memory B-cells dominated in the first 20 days followed by a gradual increase in IgG1+ memory B cells ( Hartley et al, 2020 ). The latter cells express CD27 and positively correlate with the T follicular helper (Tfh) cell number that suggest high robustness ( Hartley et al, 2020 ). In addition, memory B cells showed upregulation of CD80, CD180 and TACI that assumed activation upon re-exposure to the antigen ( Berkowska et al, 2011 , 2015 ).…”

“…It was assumed that B cell memory is durable for up to 8 months, which would probably be protective upon reinfection. Accordingly, re-infection is proposed to be milder than the first exposure ( Hartley et al, 2020 ). Increased neutralising antibodies, IgG + classical memory B cells, Tfh, CD4 + memory T-cells, and IFN-γ CD8 + T cells were detected.…”