Lasting antibody and T cell responses to SARS-CoV-2 in COVID-19 patients three months after infection

Abstract

The dynamics, duration, and nature of immunity produced during SARS-CoV-2 infection are still unclear. Here, we longitudinally measured virus-neutralising antibody, specific antibodies against the spike (S) protein, receptor-binding domain (RBD), and the nucleoprotein (N) of SARS-CoV-2, as well as T cell responses, in 25 SARS-CoV-2-infected patients up to 121 days post-symptom onset (PSO). All patients seroconvert for IgG against N, S, or RBD, as well as IgM against RBD, and produce neutralising antibodies (NAb) by 14 days PSO, with the peak levels attained by 15-30 days PSO. Anti-SARS-CoV-2 IgG and NAb remain detectable and relatively stable 3-4 months PSO, whereas IgM antibody rapidly decay. Approximately 65% of patients have detectable SARS-CoV-2-specific CD4⁺ or CD8⁺ T cell responses 3-4 months PSO. Our results thus provide critical evidence that IgG, NAb, and T cell responses persist in the majority of patients for at least 3-4 months after infection.

Fig. 1. IgG and IgM antibody response kinetics in the serum of patients with SARS-CoV-2 infection, by days after symptom onset.

a–d The percentages (blue line) of patients (P) with serum samples that were positive for IgG to the nucleocapsid (N) protein (a), IgM to the receptor-binding domain (RBD) of SARS-CoV-2 spike (S) (b), IgG to the S (c) and RBD (d), and the corresponding mean optical density (OD) for anti-N IgG and anti-RBD IgM and log₁₀-transformed geometric mean endpoint titer (GMT) for anti-S and -RBD IgG (red dashed line). Error bars represent the 95% confidence interval. Each circle represents the titer for a serum sample. e–h Individual level for anti-N IgG (e), anti-RBD IgM (f), anti-S IgG (g), and anti-RBD IgG (g) in serum samples collected from patients, and the samples from the same patients are connected by the lines. Black dashed line indicates the threshold for positivity (anti-N IgG = 0.19, anti-S IgG = 439.5, anti-RBD IgG = 33.2, and anti-RBD IgM = 0.105). Source data included as a Source Data File.

Fig. 2. SARS-CoV-2 live-virus neutralisation antibody titre in serum and correlation with IgG and IgM responses.

a The percentages of patients with serum samples that were positive for neutralising antibody (NAb) and log10-transformed geometric mean titer (GMT). Error bars represent 95% confidence interval. Each circle represents the titer for a serum sample. b Individual NAb titer in serum samples collected from patients, and the samples from the same patients are connected by the lines. c Correlations between SARS-CoV-2-specific NAb titer and anti- nucleoprotein (N), -spike (S), and -receptor-binding domain (RBD) IgG levels and anti-RBD IgM, and the correlation between anti-S IgG and anti-S IgG. Statistical comparisons were performed using the two-sided nonparametric Spearman correlation. p value and spearman’s rho are presented. p = 4.79E-16, 9.93E-19, 8.46E-16, and 2.76E-18 for anti-N IgG, anti-RBD IgM, anti-S IgG, and anti-RBD IgG with NAb correlation, respectively, and p = 1.78E-43 for anti-S IgG with anti-RBD IgG correlation. Source data included as a Source Data File.

Fig. 3. SARS-CoV-2-specific T cell responses in recovered COVID-19 patients 3–4 months after infection.

a Fluorescence-activated cell sorting (FACS) plot example for analysing IFN-γ expression in CD4 and CD8 T cells is shown for patient No. 4 (Pt4). b Percentage of CD4⁺ and CD8⁺ T cells producing IFN-γ in response to a recombinant replication-deficient adenovirus type 5 that encodes green fluorescent protein (rAd5-GFP), SARS-CoV-2 spike (rAd5-S), or SARS-CoV-2 nucleocapsid protein (rAd5-N) in PBMCs from recovered patients. c FACS plot examples of IFN-γ and granzyme B (GzmB) or TNF-a co-expression. d–e Functional profile of IFN-γ⁺ CD4⁺ (d) and CD8⁺ (e) T cells producing GzmB, or TNF-a in response to rAd5-S and rAd5-N. Data are expressed as mean ± SD for b, d and e. *p < 0.05, **p < 0.01, and ***p < 0.001 by two-tailed paired t-test for b (p = 0.0001, p = 0.0085, and p = 0.03 for CD4, and p = 0.009 and p = 0.174 for CD8). The two-tailed Mann–Whitney U-test was used for d and e. Gating strategies are in Supplementary Fig. 5. Source data included as a Source Data File.

Fig. 4. Phenotypic memory of SARS-CoV-2-specific T cells in recovered COVID-19 patients 3–4 months after infection.

Phenotypic memory (naive, CD45RA⁺ CCR7⁺; central memory, CD45RA⁻ CCR7⁺; effector memory, CD45RA⁻ CCR7⁻; and late effector, CD45RA⁺ CCR7⁻) analysis of IFN-γ-secreting CD4⁺ and CD8⁺ T cells. a FACS plot examples of CD45RA and CCR7 expression on all CD4 and CD8 T cells and recombinant replication-deficient adenovirus type 5 that encodes nucleocapsid protein (rAd5-N) -specific IFN-γ-secreting CD4⁺ and CD8⁺ T cells. b The constitution ratio of naive, central memory, effector memory, and late effector T cells on virus-specific IFN-γ-secreting CD4⁺ and CD8⁺ T cells of recovered patients 3–4 months after infection. Data on rAd5 that encodes green fluorescent protein (rAd5-GFP) controls are not shown because few virus-specific cytokine-secreting T cells were detected. c–d The percentage of rAd5-S- and rAd5-N-specific memory T cells in CD4⁺ (c) and CD8⁺ (d) T cells in recovered patients 3–4 months after infection. Data are presented as mean ± SD. The two-tailed Mann–Whitney U-test was used for c and d. Source data included as a Source Data File.