Application of the SARS-CoV-2-S1 ACE-2 receptor interaction as the basis of the fully automated assay to detect neutralizing SARS-CoV-2-S1 antibodies in blood samples.

A quantitative, high throughput, fully automated diagnostic method for the detection of neutralizing anti-SARS-CoV-2 antibodies was developed on the Phadia system based on the interaction of SARS-CoV-2 S1 protein and the human ACE-2 receptor. This method was compared to the current state of the art plaque reduction neutralization test (PRNT) and a high correlation between the two methods was observed. Using a large cohort of blood samples from convalescent patients and controls the method displays very high sensitivity and specificity (99,8% and 99.99%, respectively). Neutralizing antibody titers of mRNA-1273 and BNT162b2-vaccinated persons can also be quantified with this method as well. This fully automated method provides the possibility to determine anti-SARS-CoV-2 neutralizing antibody concentrations in just 2  h.

Modelling the concentration of anti-SARS-CoV-2 immunoglobulin G in intravenous immunoglobulin product batches.

BACKGROUND: Plasma-derived intravenous immunoglobulin (IVIg) products contain a dynamic spectrum of immunoglobulin (Ig) G reactivities reflective of the donor population from which they are derived. We sought to model the concentration of anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgG which could be expected in future plasma pool and final-product batches of CSL Behring's immunoglobulin product Privigen. STUDY DESIGN AND METHODS: Data was extracted from accessible databases, including the incidence of coronavirus disease 2019 and SARS-CoV-2 vaccination status, antibody titre in convalescent and vaccinated groups and antibody half-life. Together, these parameters were used to create an integrated mathematical model that could be used to predict anti-SARS-CoV-2 antibody levels in future IVIg preparations. RESULTS: We predict that anti-SARS-CoV-2 IgG concentration will peak in batches produced in mid-October 2021, containing levels in the vicinity of 190-fold that of the mean convalescent (unvaccinated) plasma concentration. An elevated concentration (approximately 35-fold convalescent plasma) is anticipated to be retained in batches produced well into 2022. Measurement of several Privigen batches using the Phadia™ EliA™ SARS-CoV-2-Sp1 IgG binding assay confirmed the early phase of this model. CONCLUSION: The work presented in this paper may have important implications for physicians and patients who use Privigen for indicated diseases.

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

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.

Comment on Favresse et al. Persistence of Anti-SARS-CoV-2 Antibodies Depends on the Analytical Kit: A Report for Up to 10 Months after Infection. Microorganisms 2021, 9, 556.

We thank the authors of the article [...].