A Role for Nucleocapsid-Specific Antibody Function in COVID-19 Convalescent Plasma Therapy

COVID-19 convalescent plasma (CCP), a passive polyclonal antibody therapeutic, has exhibited mixed results in the treatment of COVID-19. Given that the therapeutic effect of CCP may extend beyond the ability of SARS-CoV-2-specific antibody binding and neutralization to influence the evolution of the endogenous antibody response, we took a systematic and comprehensive approach to analyze SARS-CoV-2 functional antibody profiles of participants in a randomized controlled trial of CCP treatment of individuals hospitalized with COVID-19 pneumonia where CCP was associated with both decreased mortality and improved clinical severity. Using systems serology, we found that the clinical benefit of CCP is related to a shift towards reduced inflammatory Spike (S) responses and enhanced Nucleocapsid (N) humoral responses. We found CCP had the greatest clinical benefit in participants with low pre-existing anti-SARS-CoV-2 antibody function, rather than S or N antibody levels or participant demographic features. Further, CCP induced immunomodulatory changes to recipient humoral profiles persisted for at least two months, marked by the selective evolution of anti-inflammatory Fc-glycan profiles and persistently expanded nucleocapsid-specific humoral immunity following CCP therapy. Together, our findings identify a novel mechanism of action of CCP, suggest optimal patient characteristics for CCP treatment, identify long-last immunomodulatory effects of CCP, and provide guidance for development of novel N-focused antibody therapeutics for severe COVID-19 hyperinflammation.Funding Information: We thank Nancy Zimmerman, Mark and Lisa Schwartz, an anonymous donor (financial support), Terry and Susan Ragon, and the SAMANA Kay MGH Research Scholars award for their support. We acknowledge support from the Ragon Institute of MGH, MIT and Harvard, the Massachusetts Consortium on Pathogen Readiness (MassCPR), the NIH (3R37AI080289-11S1, R01AI146785, U19AI42790-01, U19AI135995-02, U19AI42790-01, 1U01CA260476 – 01, CIVIC75N93019C00052, T32 AI007061, 3UL1TR002556), the Gates Foundation, the Global Health Vaccine Accelerator Platform funding (OPP1146996 and INV-001650), and the Musk Foundation.Conflict of Interests: G. A. is a founder of SeromYx Systems, Inc. and an equity holder in Leyden Labs. G.A. is a member of the scientific advisory board of Sanofi Pasteur. The other authors declare no competing interests.Ethical Approval: The clinical cohort described in Bar et al.(Bar et al., 2021) was approved by the University of Pennsylvania institutional review board and registered at ClinicalTrials.gov with number NCT04397757. All participants provided informed consent prior to participation in the study. Secondary Use of patient samples and clinical samples was approved by the Mass General Brigham Institutional Review Board.