Persistence of SARS-CoV-2 specific B- and T-cell responses in convalescent COVID-19 patients 6-8 months after the infection

Sherina, Natalia; Piralla, Antonio; Du, Likun; Wan, Hui; Kumagai-Braesch, Makiko; Andréll, Juni; Braesch-Andersen, Sten; Cassaniti, Irene; Percivalle, Elena; Sarasini, Antonella; Bergami, Federica; Di Martino, Raffaella; Colaneri, Marta; Vecchia, Marco; Sambo, Margherita; Zuccaro, Valentina; Bruno, Raffaele; Sachs, Michele; Oggionni, Tiberio; Meloni, Federica; Abolhassani, Hassan; Bertoglio, Federico; Schubert, Maren; Byrne-Steele, Miranda; Han, Jian; Hust, Michael; Xue, Yintong; Hammarström, Lennart; Baldanti, Fausto; Marcotte, Harold; Pan-Hammarström, Qiang

Background Monitoring the adaptive immune responses during the natural course of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection provides useful information for the development of vaccination strategies against this virus and its emerging variants. We thus profiled the serum anti-SARS-CoV-2 antibody levels and specific memory B- and T-cell responses in convalescent coronavirus disease-2019 (COVID-19) patients. Methods Altogether 119 samples from 88 convalescent donors who experienced mild to critical disease were tested for the presence of elevated anti-spike and anti-receptor binding domain antibody levels over a period of eight months. In addition, level of SARS-CoV-2 neutralizing antibodies, specific memory B- and T-cell responses were tested in a subset of samples. Findings Anti-SARS-CoV-2 antibodies were present in 85% of the samples collected within 4 weeks after onset of symptoms in COVID-19 patients. Levels of specific IgM/IgA antibodies declined after 1 month while levels of specific IgG antibodies and plasma neutralizing activities remained relatively stable up to 6 months after diagnosis. Anti-SARS-CoV-2 IgG antibodies were still present, though at a significantly lower level, in 80% of the samples collected at 6-8 months after symptom onset. SARS-CoV-2-specific memory B- and T-cell responses developed with time and were persistent in all patients followed up till 6-8 months. Conclusions Our data suggest that protective adaptive immunity following natural infection of SARS-CoV-2 might persist for at least 6-8 months, regardless of disease severity. Development of medium or long-term protective immunity through vaccination might thus be possible. Funding EU-ATAC consortium, the Italian Ministry of Health and SciLife/KAW.