One-Year Sustained Cellular and Humoral Immunities in Coronavirus Disease 2019 (COVID-19) Convalescents

Abstract

Background The longitudinal antigen-specific immunity in COVID-19 convalescents is crucial for long-term protection upon individual re-exposure to SARS-CoV-2, and even more pivotal for ultimately achieving population-level immunity. To better understand the features of immune memory in individuals with different disease severities at one year post-disease onset we conducted this cohort study. Methods We conducted a systematic antigen-specific immune evaluation in 101 COVID-19 convalescents, who had asymptomatic, mild, moderate, or severe disease, through two visits at months 6 and 12 post-disease onset. The SARS-CoV-2-specific antibodies, comprising NAb, IgG, and IgM, were assessed by mutually corroborated assays, i.e. neutralization, enzyme-linked immunosorbent assay (ELISA), and microparticle chemiluminescence immunoassay (MCLIA). Meanwhile, the T-cell memory against SARS-CoV-2 spike, membrane and nucleocapsid proteins was tested through enzyme-linked immunospot assay (ELISpot), intracellular cytokine staining (ICS), and tetramer staining-based flow cytometry, respectively. Results SARS-CoV-2-specific IgG antibodies, and also NAb can persist among over 95% COVID-19 convalescents from 6 months to 12 months after disease onset. At least 19/71 (26%) of COVID-19 convalescents (double positive in ELISA and MCLIA) had detectable circulating IgM antibody against SARS-CoV-2 at 12m post-disease onset. Notably, the percentages of convalescents with positive SARS-CoV-2-specific T-cell responses (at least one of the SARS-CoV-2 antigen S1, S2, M and N protein) were 71/76 (93%) and 67/73 (92%) at 6m and 12m, respectively. Furthermore, both antibody and T-cell memory levels of the convalescents were positively associated with their disease severity. Conclusions SARS-CoV-2-specific cellular and humoral immunities are durable at least until one year after disease onset.

Longitudinal analysis of antibody dynamics in COVID-19 convalescents reveals neutralizing responses up to 16 months after infection

“…Recent data from animal models, therapeutic use of neutralizing monoclonal antibodies, and convalescent plasma in a clinical setting suggest a critical role for nAbs in controlling SARS-CoV-2 infection and re-infection [15][16][17][18][19][20][21][22] , while a key question that has not yet been addressed is whether COVID-19 convalescents could maintain long-lasting antibody-mediated protective immunity. Studies have investigated the dynamic change and longevity of the binding and nAb response in COVID-19 convalescents, and indicated that the nAb response in COVID-19 convalescents could be maintained for up to one year after the onset of symptoms, accompanied by a decrease in nAb titres 14,[23][24][25][26] .…”

Humoral and Cellular Responses to SARS-CoV-2 in Convalescent COVID-19 Patients With Multiple Sclerosis

“…This suggests an increased immune response with higher viral loads and inflammatory mediators during acute infection. 28 …”

A COVID-19 T-Cell Response Detection Method Based on a Newly Identified Human CD8⁺ T Cell Epitope from SARS-CoV-2 — Hubei Province, China, 2021

“…Peptides with a purity of over 95% were synthesized by Beijing Scilight Biotechnology Corporation, and the peptide powders were dissolved in DMSO before use. An HLA-A*1101 tetramer complexed with SARS-CoV-2-specific peptide was generated in our laboratory as described previously for the preparation of other HLA class I tetramers (6).…”

“…CD8 + T cells recognize antigenic peptides presented by major histocompatibility complex I (MHC-I) through T cell receptors (TCRs) and are activated to kill virusinfected target cells (4)(5). Nucleocapsid (N) protein is one of the main structural proteins of SARS-CoV-2 and can trigger broad T-cell responses in humans (6). Herein, an overlapping peptide pool covering the full length of N protein was designed, overlapping peptides with positive T-cell activating potency in COVID-19 convalescents were screened, and CD8 + T cell epitopes in the positive overlapping peptides were further identified.…”