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-Braesh, 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; 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 The longevity of the immune response against SARS-CoV-2 is currently debated. We thus profiled the serum anti-SARS-CoV-2 antibody levels and virus specific memory B- and T-cell responses over time in convalescent COVID-19 patients. Methods A cohort of COVID-19 patients from the Lombardy region in Italy who experienced mild to critical disease and Swedish volunteers with mild symptoms, were tested for the presence of elevated anti-spike and anti-receptor binding domain antibody levels over a period of eight months. In addition, specific memory B- and T-cell responses were tested in selected patient samples. Results Anti-SARS-CoV-2 antibodies were present in 85% samples collected within 4 weeks after onset of symptoms in COVID-19 patients. Levels of specific IgM or IgA antibodies declined after 1 month while levels of specific IgG antibodies remained stable up to 6 months after diagnosis. Anti-SARS-CoV-2 IgG antibodies were still present, though at a significantly lower level, in 80% samples collected at 6-8 months after symptom onset. SARS-CoV-2-specific memory B- and T-cell responses were developed in vast majority of the patients tested, regardless of disease severity, and remained detectable up to 6-8 months after infection. Conclusions Although the serum levels of anti-SARS-CoV-2 IgG antibodies started to decline, virus-specific T and/or memory B cell responses increased with time and maintained during the study period (6-8 months after infection). Funding European Union’s Horizon 2020 research and innovation programme (ATAC), the Italian Ministry of Health, CIMED, the Swedish Research Council and the China Scholarship Council.