Determination of neutralising anti-SARS-CoV-2 antibody half-life in COVID-19 convalescent donors

Abstract

Despite the burgeoning field of coronavirus disease-19 (COVID-19) research, the persistence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralising antibodies remains unclear. This study validated two high-throughput immunological methods for use as surrogate live virus neutralisation assays and employed them to examine the half-life of SARS-CoV-2 neutralising antibodies in convalescent plasma donations made by 42 repeat donors between April and September 2020. SARS-CoV-2 neutralising antibody titres decreased over time but typically remained above the methods' diagnostic cut-offs. Using this longitudinal data, the average half-life of SARS-CoV-2 neutralising antibodies was determined to be 20.4 days. SARS-CoV-2 neutralising antibody titres appear to persist in the majority of donors for several months. Whether these titres confer protection against re-infection requires further study and is of particular relevance as COVID-19 vaccines become widely available.

Keywords: COVID-19; Convalescent donor; Half-life; Neutralising antibodies; SARS-CoV-2.

Fig. 1

Correlation of the concentration of surrogate nAb titre (assessed by ACE2 receptor binding inhibition assay and EliA S1-IgG methods) against neutralisation titre (assessed by cell-based, live virus neutralisation assay). Each datapoint represents one donation. A linear regression was fitted to each graph. ACE2, angiotensin-converting enzyme 2; Ig, immunoglobulin; IgG, immunoglobulin G; MN, micro-neutralisation; nAb, neutralising antibody; r, Pearson's r correlation coefficient; S1, spike 1.

Fig. 2

Convalescent plasma donation testing for SARS-CoV-2 nAbs using EliA S1-IgG (A) and ACE2 receptor binding inhibition assay (B) methods, plotted against the number of days post-positive PCR test. Each donor is shown in a different colour, and colours are preserved between graphs. Datapoints for each donor (that is, donations) were fitted using a one-phase decay exponential regression, which allowed for the derivation of the half-life of SARS-CoV-2-related antibodies to be calculated in each case. Exceptionally high EliA S1-IgG results were observed for initial donations from donor #24 (pink), and are therefore called out as an inset to A. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) ACE2, angiotensin-converting enzyme 2; Ig, immunoglobulin; IgG, immunoglobulin G; nAb, neutralising antibody; S1, spike 1; SD, standard deviation.