Anti-Severe Acute Respiratory Syndrome Coronavirus 2 Hyperimmune Immunoglobulin Demonstrates Potent Neutralization and Antibody-Dependent Cellular Cytotoxicity and Phagocytosis Through N and S Proteins

Abstract

Background Although COVID-19 vaccinations have provided a significant reduction in infections, effective COVID-19 treatments remain an urgent need. Methods Functional characterization of anti-SARS-CoV-2 hyperimmune immunoglobulin (hIG) from human convalescent plasma was performed by different virus neutralization methodologies (plaque reduction, virus induced cytotoxicity, TCID50 reduction and immunofluorimetry) at different laboratories using geographically different SARS-CoV-2 isolates (USA (1), Italy (1), Spain (2): 2 containing the D614G mutation). Neutralization capacity against the original Wuhan SARS-CoV-2 strain and variants (D614G mutant, B.1.1.7, P.1 and B.1.351) was evaluated using a pseudovirus expressing the corresponding spike (S) protein. Antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP) was also evaluated. Results All SARS-CoV-2 isolates were potently neutralized by hIG as shown by all four methodologies. Wild-type SARS-CoV-2 and variants were effectively neutralized using the pseudovirus. hIG induced ADCC and ADCP against SARS-CoV-2 N and S proteins but not E protein. Very low concentrations (25-100 µg IgG/mL) were required. A potent effect was triggered by antibodies in hIG solutions against the SARS-CoV-2 S and N proteins. Conclusions Beyond neutralization, IgG Fc-dependent pathways may play a role in combatting SARS-CoV-2 infections using COVID-19 hIG. This could be especially relevant for the treatment of more neutralization-resistant SARS-CoV-2 variants.

First Detection of SARS-CoV-2 Delta (B.1.617.2) Variant of Concern in a Dog with Clinical Signs in Spain

“…HIV reporter pseudoviruses expressing the SARS-CoV-2 S protein (from different VOCs) and Luciferase were generated. Control pseudoviruses were obtained by replacing the S protein expression plasmid with a VSV-G protein expression plasmid as reported previously [31]. For neutralization assay, 200 TCID50 of pseudovirus supernatant was preincubated with serial dilutions of the heat-inactivated plasma samples and then added onto ACE2 overexpressing HEK293T cells.…”

ORFeome Phage Display Reveals a Major Immunogenic Epitope on the S2 Subdomain of SARS-CoV-2 Spike Protein

“…Other viral proteins, such as ORF3a, that is involved in viral replication and release, or ORF8, which is an Ig-like folded dimer that is poorly conserved among coronaviruses and interacts with many host cell proteins, are currently under investigation to ascertain their suitability as targets for the development of therapeutics [7]. Despite the fact that cell binding relies on RBD, directly neutralizing anti-RBD antibodies may only be one part of anti-viral defenses, as other mechanisms such as CDC, ADCC or ADCP may help to clear the virus without direct interference with the RBD/ACE2 interaction [27]. Along these lines, antibodies targeting the N-terminal domain (NTD) of the spike protein showed neutralizing capacities [28].…”

A Qualitative Comparison of the Abbott SARS-CoV-2 IgG II Quant Assay against Commonly Used Canadian SARS-CoV-2 Enzyme Immunoassays in Blood Donor Retention Specimens, April 2020 to March 2021

“…However, even some anti-RBD antibodies may bind to nonneutralizing faces of the RBD molecule ( 44 ). We now understand that antibodies to SARS-CoV-2 are polyfunctional and undertake neutralizing and antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP) through antibodies to both N and S proteins ( 4 , 45 – 47 ). However, the mechanisms of ADCC and ADCP are still being understood and require further studies in humans ( 48 , 49 ).…”