Markers of Polyfunctional SARS-CoV-2 Antibodies in Convalescent Plasma

Abstract

Convalescent plasma is a promising therapy for coronavirus disease 2019 (COVID-19), but the antibody characteristics that contribute to efficacy remain poorly understood. This study analyzed plasma samples from 126 eligible convalescent blood donors in addition to 15 naive individuals, as well as an additional 20 convalescent individuals as a validation cohort. Multiplexed Fc Array binding assays and functional antibody response assays were utilized to evaluate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody composition and activity. Donor convalescent plasma samples contained a range of antibody cell- and complement-mediated effector functions, indicating the diverse antiviral activity of humoral responses observed among recovered individuals. In addition to viral neutralization, convalescent plasma samples contained antibodies capable of mediating such Fc-dependent functions as complement activation, phagocytosis, and antibody-dependent cellular cytotoxicity against SARS-CoV-2. Plasma samples from a fraction of eligible donors exhibited high activity across all activities evaluated. These polyfunctional plasma samples could be identified with high accuracy with even single Fc Array features, whose correlation with polyfunctional activity was confirmed in the validation cohort. Collectively, these results expand understanding of the diversity of antibody-mediated antiviral functions associated with convalescent plasma, and the polyfunctional antiviral functions suggest that it could retain activity even when its neutralizing capacity is reduced by mutations in variant SARS-CoV-2. IMPORTANCE Convalescent plasma has been deployed globally as a treatment for COVID-19, but efficacy has been mixed. Better understanding of the antibody characteristics that may contribute to its antiviral effects is important for this intervention as well as offer insights into correlates of vaccine-mediated protection. Here, a survey of convalescent plasma activities, including antibody neutralization and diverse effector functions, was used to define plasma samples with broad activity profiles. These polyfunctional plasma samples could be reliably identified in multiple cohorts by multiplex assay, presenting a widely deployable screening test for plasma selection and investigation of vaccine-elicited responses.

Decay of Fc-dependent antibody functions after mild to moderate COVID-19

“…At present, analyses of Fc-mediated functions of SARS-CoV-2 antibodies within COVID-19 convalescent subjects have focused upon cross-sectional analyses or short-term longitudinal studies up to 1 to 2 months post-symptom onset. 16,19,20 We extend these findings and analyze Fc effector functions mediated by S-specific antibodies in a cohort of 53 convalescent individuals up to 149 days postsymptom onset. We developed functional assays using SARS-CoV-2 S-expressing cells to comprehensively analyze plasma ADCC and ADP activity against SARS-CoV-2 S. Our results show that plasma ADCC and ADP activity decays over the first 4 months post-infection, mirroring the decline in S-specific IgG titers.…”

Antibodies Elicited in Response to a Single Cycle Glycoprotein D Deletion Viral Vaccine Candidate Bind C1q and Activate Complement Mediated Neutralization and Cytolysis

“…This more restrictive functional antibody response failed to protect in clinical trials [ 8 ]. Polyfunctional antibody responses are likely to be important for the prevention and control of other viral infections, including, for example, HIV, Ebolavirus and SARS-CoV-2 [ 32 , 33 , 34 , 35 ]. We speculate that prophylactic and therapeutic vaccines that elicit polyfunctional responses will prove more effective in preventing HSV and other viral infections.…”

Antibody Attributes that Predict the Neutralization and Effector Function of Polyclonal Responses to SARS-CoV-2

“…Antibody functions, including neutralization assessed by either an authentic virus assay or a luciferase-based pseudovirus assay, antibody-dependent cell-mediated phagocytosis (ADCP) mediated by monocytes, deposition of the complement cascade component C3b (ADCD), and FcgRIIIa ligation as a proxy for NK cell mediated antibody dependent cellular cytotoxicity (ADCC) induced by antibodies in response to recombinant antigen were previously reported 26 for a set of convalescent samples collected from a discovery cohort of 126 eligible convalescent plasma donors from the Baltimore/Washington D.C. area (Johns Hopkins Medical Institutions, JHMI) 27 and serum samples from 15 naïve controls and a validation cohort of 20 convalescent subjects from New Hampshire (Dartmouth-Hitchcock Medical Center, DHMC) 43 (Supplemental Table 1). Biophysical antibody features were defined by a customized multiplexed Fc array assay that characterizes both variable fragment (Fv) and Fc domain attributes across a panel of SARS-CoV-2 antigens, consisting of: nucleocapsid (N) protein, stabilized (S-2P) 44 and unstabilized trimeric spike protein, spike subdomains including S1 and S2, the receptor binding domain (RBD), and the fusion peptide (FP) from SARS-CoV-2; in addition, the panel included diverse pathogenic, zoonotic, and endemic coronavirus spike proteins and subdomains.…”