Anti–SARS-CoV-2 Antibody Responses in Convalescent Plasma Donors Are Increased in Hospitalized Patients; Subanalyses of a Phase 2 Clinical Study
Evangelos Terpos, Marianna Politou, Theodoros Ν. Sergentanis, Αndreas Mentis, Margherita Rosati, Dimitris Stellas, Jenifer Bear, Xintao Hu, Barbara K. Felber, Vassiliki Pappa, Maria Pagoni, Elisavet Grouzi, Stavroula Labropoulou, Ioanna Charitaki, Ioannis Ntanasis‐Stathopoulos, Dimitra Moschandreou, Anthi Bouhla, Stylianos Saridakis, Eleni Korompoki, Chara Giatra, Tina Bagratuni, Angelos Pefanis, Sotirios G. Papageorgiou, Alexandros Spyridonidis, Anastasia Antoniadou, Αnastasia Kotanidou, Konstantinos Syrigos, Konstantinos Stamoulis, George Panayiotakopoulos, Sotirios Tsiodras, Leonidas G. Alexopoulos, Meletios Α. Dimopoulos, George N. Pavlakis
Abstract
We evaluated the antibody responses in 259 potential convalescent plasma donors for Covid-19 patients. Different assays were used: a commercial ELISA detecting antibodies against the recombinant spike protein (S1); a multiplex assay detecting total and specific antibody isotypes against three SARS-CoV-2 antigens (S1, basic nucleocapsid (N) protein and receptor-binding domain (RBD)); and an in-house ELISA detecting antibodies to complete spike, RBD and N in 60 of these donors. Neutralizing antibodies (NAb) were also evaluated in these 60 donors. Analyzed samples were collected at a median time of 62 (14–104) days from the day of first symptoms or positive PCR (for asymptomatic patients). Anti-SARS-CoV-2 antibodies were detected in 88% and 87.8% of donors using the ELISA and the multiplex assay, respectively. The multivariate analysis showed that age ≥50 years (p < 0.001) and need for hospitalization (p < 0.001) correlated with higher antibody titers, while asymptomatic status (p < 0.001) and testing >60 days after symptom onset (p = 0.001) correlated with lower titers. Interestingly, pseudotype virus-neutralizing antibodies (PsNAbs) significantly correlated with spike and with RBD antibodies by ELISA. Sera with high PsNAb also showed a strong ability to neutralize active SARS-CoV-2 virus, with hospitalized patients showing higher titers. Therefore, convalescent plasma donors can be selected based on the presence of high RBD antibody titers.