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BackgroundDespite the fact of ongoing worldwide vaccination programs for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), understanding longevity, breadth, and type of immune response to coronavirus disease-19 (COVID-19) is still important to optimize the vaccination strategy and estimate the risk of reinfection. Therefore, we performed thorough immunological assessments 1 year post-COVID-19 with different severity.MethodsWe analyzed peripheral blood mononuclear cells and plasma samples at 1 year post-COVID-19 in patients who experienced asymptomatic, mild, and severe illness to assess titers of various isotypes of antibodies (Abs) against SARS-CoV-2 antigens, phagocytic capability, and memory B- and T-cell responses.FindingsA total of 24 patients (7, 9, and 8 asymptomatic, mild, and severe patients, respectively) and eight healthy volunteers were included in this study. We firstly showed that disease severity is correlated with parameters of immune responses at 1 year post-COVID-19 that play an important role in protecting against reinfection with SARS-CoV-2, namely, the phagocytic capacity of Abs and memory B-cell responses.InterpretationVarious immune responses at 1 year post-COVID-19, particularly the phagocytic capacity and memory B-cell responses, were dependent on the severity of the prior COVID-19. Our data could provide a clue for a tailored vaccination strategy after natural infection according to the severity of COVID-19.

Additional file 5: Figure S4. Cytokine-producing T cells against wild-type SARS-CoV-2 and the Delta variant according to vaccination status after COVID-19. a CD4+ T-cell populations producing specific cytokines. b CD8+ T-cell populations producing specific cytokines. NS, not significant; IFN-γ, interferon- γ; IL, interleukin; TNF-α, tumor necrosis factor-α.

Additional file 1: Supplementary Figure 1. A The pH of the medium was adjusted by HCl or NaOH and stabilized in a 5% CO2 incubator. the medium pH was measured using a pH meter. B The pH of the medium was adjusted by HCl or NaOH, and MDA-MB-231 cells were incubated for 18 h. mRNA levels were analyzed by qPCR. Supplementary Fig. 2. A–C MDA-MB-231 cells were treated with various conditioned media for 18 h. Protein levels were analyzed by western blotting (A), mRNA levels were analyzed by qPCR (B), and the culture medium pH was measured using a pH meter (C). D, E MDA-MB-231 cells were treated with lactic acid, with/without, NaOH for 24 h. Protein levels were analyzed by western blotting (D) and the culture medium pH was measured using a pH meter (E). Supplementary Fig. 3. A MDA-MB-231 cells were treated with lactic acid or sodium lactate, with/without, NaOH for 24 h. Protein levels were analyzed by western blotting. B MDA-MB-231 cells were treated with various conditioned media with/without NaOH for 18 h. Protein levels were analyzed by western blotting. C The summarization of the process by which various conditioned media are prepared. CON: control; fresh media, NCM: normoxic conditioned media, HCM: hypoxic conditioned media, Oxamate pre-treated HCM). D-F The various conditioned media were treated in MDA-MB-231 breast cancer cells for 18 h. Cells were analyzed by westernblotting (D) and qPCR (E), and cultured media pH was measured using a pH meter (F). G MDA-MB-231 cells were treated with a nifuroxazide under acidic conditions for 18 h. Protein levels were analyzed by western blotting. Supplementary Fig. 4. A Acidic media were treated in MDA-MB-231 breast cancer cells for 18 h. Cell lysates were analyzed by westernblotting. Supplementary Fig. 5. Densitometric and statistical analysis of all western blot data in main figures. Supplementary Fig. 6. Densitometric and statistical analysis of all western blot data in supplementary figures. Supplementary Fig. 7. Full-length blots in Figure 1. The red dotted lines are the main figures. Supplementary Fig. 8. Full-length blots in Figure 2. The red dotted lines are the main figures. Supplementary Fig. 9. Full-length blots in Figure 3. The red dotted lines are the main figures. Supplementary Fig. 10. Full-length blots in Figure 4. The red dotted lines are the main figures. Supplementary Fig. 11. Full-length blots in Supplementary Figure 2. The red dotted lines are the main figures. Supplementary Fig. 12. Full-length blots in Supplementary Figure 3.The red dotted lines are the main figures. Supplementary Fig. 13. Full-length blots in Supplementary Fig. 4.The red dotted lines are the main figures.

Additional file 2: Figure S2. Representative gating strategy for the SARS-CoV-2-specific activated and cytokine-producing T cells.

Additional file 3: Table S1. Detailed clinical information of each group in the present study

Additional file 1: Figure S1. Purification of recombinant RBD proteins of SARS-CoV-2 variants. The purity of the purified recombinant protein was determined by non-reducing (left) and reducing (right) 14% SDS-PAGE gels. M, protein ladder. 1. RBD wild-type; 2. RBD Alpha (B.1.1.7, with N501Y mutation); 3. RBD Beta (B.1.351, with K417N, E484K, and N501Y); 4. RBD Gamma (P.1, with K417T, E484K, and N501Y mutations); 5. RBD Delta (B.1.617.2, with L452R and T478K mutations); 6. RBD Omicron (B. 1.1.529, with G339D, S371L, S373P, S375F, K417N, N440K, G446S, S477N, T478K, E484A, Q493R, G496S, Q498R, N501Y, and Y505H).

Additional file 4: Figure S3. Comparisons of humoral and cellular immune responses against different strains of SARS-CoV-2 in individuals who recovered and then received one dose of an mRNA vaccine 18 months later. a IgG-binding activities measured using an enzyme-linked immunosorbent assay. b Neutralization activities measured using a focus reduction neutralization test. c Proportions of activation-induced marker+ T cells measured by flow cytometric analysis. For simplicity, in Figure S3a, statistical significance is shown by the lines. * P < 0.05, ** P < 0.005 NS, not significant; FRNT, focus reduction neutralizing test.