Characterization of the SARS-CoV-2 Neutralization Potential of COVID-19–Convalescent Donors

Abstract

The current SARS-CoV-2 pandemic has triggered the development of various SARS-CoV-2 neutralization tests. A wild-type virus (using African green monkey VeroE6 cells), a pseudovirus (using human Caco-2 cells), and a surrogate neutralization test platform were applied to characterize the SARS-CoV-2 neutralization potential of a cohort of 111 convalescent plasma donors over a period of seven months after diagnosis. This allowed an in-depth validation and assay performance analysis of these platforms. More importantly, we found that SARS-CoV-2 neutralization titers were stable or even increased within the observation period, which contradicts earlier studies reporting a rapid waning of Ab titers after three to four months. Moreover, we observed a positive correlation of neutralization titers with increasing age, number of symptoms reported, and the presence of the Rhesus Ag RhD. Validation of the platforms revealed that highest assay performances were obtained with the wild-type virus and the surrogate neutralization platforms. However, our data also suggested that selection of cutoff titers had a strong impact on the evaluation of neutralization potency. When taking strong neutralization potency, as demonstrated by the wild-type virus platform as the gold standard, up to 55% of plasma products had low neutralization titers. However, a significant portion of these products were overrated in their potency when using the surrogate assay with the recommended cutoff titer. In summary, our study demonstrates that SARS-CoV-2 neutralization titers are stable for at least seven months after diagnosis and offers a testing strategy for rapid selection of high-titer convalescent plasma products in a biosafety level 1 environment.

BNT162b2 Vaccination Elicits Strong Serological Immune Responses Against SARS-CoV-2 Including Variants of Concern in Elderly Convalescents

“…Nevertheless, additional 1:20 predilution of serum samples revealed that individuals in subcohort CC still had a highly significant advantage regarding neutralization capacity over subcohort CN. As in unvaccinated convalescent individuals (18,19), we could confirm that in BNT162b2-vaccinated individuals anti-spike IgG titers strongly correlated with SARS-CoV-2 neutralization capacity, although 3 weeks after 1 st vaccination in a small number of individuals with high neutralization capacity (2%) anti-spike IgG and IgA titers still ranged below the cutoff value (Supplementary Figure 2B).…”

“…Meanwhile, we know that neutralizing antibody levels are highly predictive of immune protection from symptomatic SARS-CoV-2 infection, disease severity and survival (20,21). Despite long-term memory of both neutralizing serological and cellular immunity to SARS-CoV-2 infection after COVID-19 (18,(22)(23)(24), large observational cohort studies have demonstrated that also in COVID-19-convalescent individuals, vaccination can efficiently prevent reinfections (13,14). Furthermore, several studies have shown that in individuals with previous SARS-CoV-2 infections even a single dose vaccination elicits robust and efficient antibody responses (1)(2)(3)(4)(5)(6) and may even boost cross-variant neutralizing antibodies as shown for the mutation B.1.351 (25).…”

“…13 individuals dropped out, so that for 190 individuals (93.6%) relevant data were available for analysis. For analyses regarding neutralization capacity against VOCs we included an additional "historic" (2020) reference cohort of unvaccinated COVID-19-convalescent donors (18,19). For age and gender characteristics of all vaccinated and unvaccinated individuals included see Table 1.…”

B and T cell responses after a third dose of SARS-CoV-2 vaccine in Kidney Transplant Recipients

“…An OD ratio value was determined by calculating the ratio of the OD of the respective test sample over the OD of the internal calibrator provided with the ELISA kit. Virus neutralization capacity of sera was analyzed using a surrogate SARS-CoV-2 neutralization test (GenScript) with more than 30 % being defined as a positive response as described previously 14,23 .…”

Nachweis von Antikörpern gegen SARS-CoV-2

“…1 zeigt eine mögliche Anwendung am Beispiel der Untersuchung des Serokonversionsverlaufs nach Impfung gegen SARS-CoV-2. Wie der oben bereits erwähnte Wildtyp-Neutralisationstest, der nur in Labors der Sicherheitsstufe S3 durchgeführt werden darf, basieren diese Surrogattests nicht auf einem direkten Nachweis von Antikörpern, sondern auf dem Nachweis virusneutralisierender Aktivität in Serum oder Plasma [12]. Unterschiedliche Firmen bieten inzwischen solche Surrogattests an, deren gemeinsames Testprinzip bereits im letzten Jahr publiziert wurde [13]: Die Haupteintrittspforte für SARS-CoV-2 bildet das auf diversen humanen Zellen exprimierte Angiotensinkonvertierende Enzym 2 (ACE2) [14], an welches das Virus mit der Rezeptorbindungsdomäne (RBD) seines Spike-Proteins andockt [15] keine Neutralisationskapazität ▶ Abb.…”