The kinetic of SARS-CoV-2 antibody (Ab) decline determines the threshold for Ab persistence up to one year

Abstract

Twelve subjects with positive SARS-CoV-2 neutralization test (NT) titers (>1:10) identified in a seroprevalence study with 1655 working adults were followed up for one year. Here we report that 7 of these 12 individuals (58%) still had NT titers ≥1:50, S1-specific IgG concentrations ≥50 BAU/ml and ≥26% ACE2 receptor binding inhibition, measured with surrogate virus NT one year after mild COVID infection. Furthermore, NT_50 titers >1:10 and S1-specific IgG levels >60 BAU/ml present at three months post-infection persisted at detectable levels for 1 year and correlated with circulating S1-specific memory B-cells. Vaccine-induced SARS-CoV2 immune responses decline at similar rates as those after infection; thus the describes threshold of 60 BAU/ml at three months post infection might also be relevant for assessment of Ab persistence after vaccination.

Functional Trimeric SARS-CoV-2 Envelope Protein Expressed in Stable CHO Cells

“…In summary, this study demonstrates the optimal combination of CHO-K1 host cell line, expression vector, and fed-batch or continuous bioprocesses to produce the complex spike protein in large amounts at the highest quality and is already used successfully in ongoing serological studies or to develop novel anti-SARS-CoV-2 antibody formats (Garner-Spitzer et al, 2021;Kallolimath et al, 2021;Sun et al, 2021). The availability of viral proteins in high quality and sufficient amounts now allows investigating the biological and virologic basics of SARS-CoV-2 to understand the infection and propagation mechanisms, the virus distribution in the body, the docking of the virus, viral immune evasion, and the immune response mechanism of the human body in more detail.…”