Serological and plasmablast responses and plasmablast-derived IgG monoclonal antibodies (MAbs) have been analysed in three COVID-19 patients with different clinical severities. Potent humoral responses were detected within 3 weeks of onset of illness in all patients and the serological titre was elicited soon after or concomitantly with peripheral plasmablast response. An average of 13.7% and 3.5% of plasmablast-derived MAbs were reactive with virus spike glycoprotein or nucleocapsid, respectively. A subset of anti-spike (10 of 32) antibodies cross-reacted with other betacoronaviruses tested and harboured extensive somatic mutations, indicative of an expansion of memory B cells upon SARS-CoV-2 infection. Fourteen of 32 anti-spike MAbs, including five anti-receptor-binding domain (RBD), three anti-non-RBD S1 and six anti-S2, neutralised wild-type SARS-CoV-2 in independent assays. Anti-RBD MAbs were further grouped into four cross-inhibiting clusters, of which six antibodies from three separate clusters blocked the binding of RBD to ACE2 and five were neutralising. All ACE2-blocking anti-RBD antibodies were isolated from two recovered patients with prolonged fever, which is compatible with substantial ACE2-blocking response in their sera. Finally, the identification of non-competing pairs of neutralising antibodies would offer potential templates for the development of prophylactic and therapeutic agents against SARS-CoV-2. Author summary The global COVID-19 outbreak poses a serious threat to human health and antibody-mediated immunity plays a key role in controlling acute viral infection in humans. We report the complete mapping of antibody responses, from serology through to single plasmablast-derived antibody clone, in three COVID-19 patients with different severities. The data show that a subset of anti-spike plasmablast-derived antibodies cross-react with other betacoronaviruses including human coronavirus OC43, which suggests an expansion of memory B cells upon SARS-CoV-2 infection. Anti-SARS-CoV-2 spike antibody clones target a diverse spectrum of epitopes on the receptor-binding domain (RBD), non-RBD S1 and S2 regions of the spike glycoprotein, 40% of them neutralise wild-type SARS-CoV-2. Anti-RBD antibodies constitute a major part of neutralising antibody response. Potent antibodies target three non-overlapping epitopes on the RBD, and the neutralising activity is linked to ACE2-binding blockade. Combinations of multiple antibody clones targeting non-overlapping epitopes offer a potential avenue to combat the global outbreak.
【초록키워드】 SARS-CoV-2, IgG, viral infection, ACE2, Immunity, serology, antibody, SARS-COV-2 infection, Neutralising Antibodies, monoclonal antibody, spike glycoprotein, memory B cells, Prophylactic, Human coronavirus, Epitopes, Antibody responses, Region, Health, Viral, Receptor-binding domain, Humoral response, COVID-19 outbreak, outbreak, nucleocapsid, RBD, humans, neutralising antibody, sera, Fever, Patient, Clusters, therapeutic agent, therapeutic agents, glycoprotein, expansion, human coronavirus OC43, epitope, serological, potent, mAbs, Anti-spike, memory B cell, binding, Neutralising activity, COVID-19 patient, Antibody-mediated immunity, Anti-RBD antibody, somatic mutations, Prolonged fever, neutralising antibody response, average, combinations, titre, wild-type SARS-CoV-2, acute viral infection, Anti-RBD antibodies, Anti-RBD MAbs, anti-receptor-binding domain, anti-S2, anti-spike MAbs, independent assays, non-overlapping epitopes, non-RBD S1, peripheral plasmablast response, plasmablast, plasmablast responses, Serological and plasmablast responses, blockade, clone, offer, Virus spike, Complete, responses, FIVE, neutralising, reactive, recovered patient, tested, blocked, analysed, the RBD, the receptor-binding domain, elicited, subset, cross-react, betacoronavirus, ACE2-blocking response, anti-non-RBD S1, Anti-RBD MAb, neutralise, non-overlapping epitope, plasmablast response, separate cluster, 【제목키워드】 Antibody Response, Human, acute SARS-CoV-2 infection,