Understanding the complexities of immune memory to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is key to gain insights into the durability of protective immunity against reinfection.
Objective
We sought to evaluate the immune memory to SARS-CoV-2 in convalescent patients with longer follow-up time.
Methods
SARS-CoV-2–specific humoral and cellular responses were assessed in convalescent patients with coronavirus disease 2019 (COVID-19) at 1 year postinfection.
Results
A total of 78 convalescent patients with COVID-19 (26 moderate, 43 severe, and 9 critical) were recruited after 1 year of recovery. The positive rates of both anti–receptor-binding domain and antinucleocapsid antibodies were 100%, whereas we did not observe a statistical difference in antibody levels among different severity groups. Accordingly, the prevalence of neutralizing antibodies (nAbs) reached 93.59% in convalescent patients. Although nAb titers displayed an increasing trend in convalescent patients with increased severity, the difference failed to achieve statistical significance. Notably, there was a significant correlation between nAb titers and anti–receptor-binding domain levels. Interestingly, SARS-CoV-2–specific T cells could be robustly maintained in convalescent patients, and their number was positively correlated with both nAb titers and anti–receptor-binding domain levels. Amplified SARS-CoV-2–specific CD4+ T cells mainly produced a single cytokine, accompanying with increased expression of exhaustion markers including PD-1, Tim-3, TIGIT, CTLA-4, and CD39, while the proportion of multifunctional cells was low.
Conclusions
Robust SARS-CoV-2–specific humoral and cellular responses are maintained in convalescent patients with COVID-19 at 1 year postinfection. However, the dysfunction of SARS-CoV-2–specific CD4+ T cells supports the notion that vaccination is needed in convalescent patients for preventing reinfection.
Graphical abstract
Key words
SARS-CoV-2
COVID-19
neutralizing antibodies
CD4+ T-cell responses
immune memory
Abbreviations used
COVID-19
Coronavirus disease 2019
M
Membrane
N
Nucleocapsid
nAb
Neutralizing antibody
ORF
Opening reading frame
RBD
Receptor-binding domain
S
Spike
SARS-CoV-2
Severe acute respiratory syndrome coronavirus 2
Cited by (0)
This study was supported by the National Mega Project on Major Infectious Disease Prevention (grant no. 2017ZX10103005-007) and COVID-19 Emergency Project from Wuhan Science and Technology Bureau (grant no. 2020020401010096).
Disclosure of potential conflict of interest: The authors declare that they have no relevant conflicts of interest.