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Summary As SARS-CoV-2 infections and death counts continue to rise, it remains unclear why some individuals recover from infection whereas others rapidly progress and die. While the immunological mechanisms that underlie different clinical trajectories remain poorly defined, pathogen-specific antibodies often point to immunological mechanisms of protection. Here, we profiled SARS-CoV-2–specific humoral responses on a cohort of 22 hospitalized individuals. Despite inter-individual heterogeneity, distinct antibody signatures resolved individuals with different outcomes. While no differences in SARS-CoV-2-specific IgG levels were observed, spike–specific humoral responses were enriched among convalescent individuals, whereas functional antibody responses to the nucleocapsid were elevated in deceased individuals. Furthermore, this enriched immunodominant S-specific antibody profile in convalescents was confirmed in a larger validation cohort. These results demonstrate that early antigen-specific and qualitative features of SARS-CoV-2-specific antibodies, point to differences in disease trajectory, highlighting the potential importance of functional antigen-specific humoral immunity to guide patient care and vaccine development., Graphical Abstract, Highlights • Limited early differences across groups were observed in titers and neutralization • Five antibody features collectively could differentiate convalescents and deceased • A shift in the balance of spike versus nucleocapsid immunity separated the groups • Spike-specific phagocytic and complement fixing activity was enriched in convalescents, Although most SARS-CoV-2 infected individuals experience mild disease, a significant fraction of individuals become severely infected. Early biomarkers that predict outcome are urgently needed. Atyeo et al demonstrate that distinct acute SARS-CoV-2 humoral immune responses exist across severely ill individuals that ultimately convalesce or pass away.

Understanding the properties and mechanisms by which antibodies provide protection is essential to defining immunity. Although neutralizing antibodies have been proposed as a potential key mechanism of protection against many viral pathogens, antibodies mediate additional immune functions that may have both protective and pathological consequences. Dissecting these properties against SARS-CoV-2 is likely necessary for defining metrics of immunity that will inform the design of vaccines and therapeutics and improve clinical management., Beyond neutralization, antibodies have immune-modulating functions that can be protective but, in some cases, can enhance pathology. Understanding these functions is critical for the development of safe vaccines and antibody therapies for COVID-19.