Abstract
The current coronavirus disease 2019 (COVID-19) vaccines are used to prevent viral infection by inducing neutralizing antibody in the body, but according to the existing experience of severe acute respiratory syndrome coronavirus (SARS) infection, T-cell immunity could provide a longer durable protection period than antibody. The research on SARS-CoV-2-specific T-cell epitope can provide target antigen for the development and evaluation of COVID-19 vaccines, which is conducive to obtain COVID-19 vaccine that can provide long-term protection. For screening specific T-cell epitopes, a SARS-CoV-2 S protein peptide library with a peptide length of 15 amino acids was synthesized. Through flow cytometry to detect percentage of IFN-γ+ T cells after mixed COVID-19 convalescent patients’ peripheral blood mononuclear cell with peptide library, seven peptides (P77, P14, P24, P38, P48, P74, and P84) that can be recognized by the T cells of COVID-19 convalescent patients were found. After excluding the nonspecific cross-reactions with unexposed population, three SARS-CoV-2-specific T-cell potential epitopes (P38, P48, and P84) were finally screened with the positive reaction rates between 15.4% and 48.0% in COVID-19 convalescent patients. This study also provided the HLA allele information of peptide-positive-response COVID-19 convalescent patients, thus predicting the population coverage of these three potential epitopes. Some HLA alleles showed higher frequency of occurrence in COVID-19 patients than in total Chinese population but no HLA alleles related to the T-cell peptide response and the severity of COVID-19. This research provides three potential T-cell epitopes that are helpful for the design and efficacy evaluation of COVID-19 vaccines. The HLA information provided by this research supplies reference significance for subsequent research such as finding the relation of HLA genotype with disease susceptibility.
Highlights
Coronavirus disease 2019 (COVID-19) that is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to just under 5.4 million deaths and over 278 million cases globally, as of December 26, 2021
We found that some HLA alleles showed higher frequency of occurrence in COVID-19 patients than in Chinese population, but no HLA alleles was related to T-cell response to peptide and the severity of COVID19
The results showed that P14 induced CD4+ IFN-g+ T-cell and CD8+ IFN-g+ T-cell-positive response in one peripheral blood mononuclear cell (PBMC) sample, and P74 induced positive CD8+ IFN-g+ T-cell response in another sample (Supplementary Figure S1), suggesting P14 and P74 had cross-reaction with T cells of unexposed people
Summary
Coronavirus disease 2019 (COVID-19) that is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to just under 5.4 million deaths and over 278 million cases globally, as of December 26, 2021 (https://www.who.int/). SARSCoV-2 is the seventh identified coronavirus that could cause human disease till and it belongs to the same genus of bcoronavirus as severe acute respiratory syndrome coronavirus (SARS-CoV) [1]. Both SARS-CoV and SARS-CoV-2 cause similar clinical symptoms and disease outcome and possess similar transmission pattern. The memory B-cell response could not be detected after 6 years [4], but specific T-cell response remained detectable even after 17 years in some individuals [5] These results indicated that compared with antibody, memory T-cell immunity is more durable and plays a more long-term role in immune clearance of coronavirus infection. Monitoring the intensity and duration of specific Tcell response induced by vaccine is vital for comprehensively evaluating the protective efficacy of COVID-19 vaccine
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