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.
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.
