Törnell A, Grauers Wiktorin H, Ringlander J, Arabpour M, Nilsson MR, Nilsson S, Kiffin R, Lindh M, Lagging M, Hellstrand K, Martner A
The Journal of Infectious Diseases - (-) - [2022-01-12; online 2022-01-12]
Waning of IgG antibodies against SARS-CoV-2 complicates diagnosis of past infection. Durability of T cell memory against SARS-CoV-2 remains unclear, and most current T cell protocols are unsuited for large-scale automation. Whole blood samples from 31 patients with verified past COVID-19 and 46 controls, out of which 40 received SARS-CoV-2 vaccine were stimulated with peptides spanning the nucleocapsid (NC) or spike 1 (S1) regions of SARS-CoV-2 and analyzed for interferon-γ (IFN-γ) in supernatant plasma. Diagnostic accuracy of these assays was evaluated against serum anti-NC and anti-receptor-binding domain S1 IgG. Induction of IFN-γ in whole blood by NC or S1 peptides diagnosed past COVID-19 with high accuracy (AUC=0.93, AUC=0.95, respectively). In accordance with previous studies, NC-IgG levels rapidly waned with only 5/17 patients (29%) remaining seropositive >180 days after infection. By contrast, NC-peptide-induced T cell memory responses remained in 13/17 (76%) subjects >180 days after infection (P=0.012 vs. NC-IgG, McNemar test). After two vaccine doses, 18/18 donors exhibited S1-specific T cell memory. Cytokine release assays for the monitoring of T cell memory in whole blood may be useful for evaluation of complications following unverified past COVID-19 and for long-term assessment of vaccine-induced T cell immunity.