Severe SARS-CoV-2 alpha variant convalescent patients exhibit worse T cell immune response than those with mild severity disease.

Objectives: This study aimed to assess T cell phenotype and the role of cellular immunity against acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants in alpha variant coronavirus disease 2019 (COVID-19) convalescent patients.

Methods: Thirty-two confirmed SARS-CoV-2 infected patients and ten healthy controls were enrolled. T cell subsets in peripheral blood were classified and quantified using flow cytometry. Additionally, T cell immune responses against SARS-CoV-2 spike peptide pools were assessed. Flow cytometry data were analyzed using Cytobank software. Other analyses involved Student's t-test or chi-square test.

Results: CD127 expression on T helper cells and cytotoxic T cells was lower in the severe disease group than that in the mild disease group. Severe COVID-19 convalescents with SARS-CoV-2 alpha variant exhibited poorer T cell immune responses than those with mild disease upon spike peptide pools stimulation with SARS-CoV-2 wild type, alpha, or omicron variants.

Conclusions: COVID-19 convalescents showed T helper and cytotoxic T cells with lower CD127 expression in the severe disease group than those in the mild disease group. Severe COVID-19 convalescents infected with the alpha variant exhibited poorer T cell immune responses against the SARS-CoV-2 wild type, alpha, or omicron variants. Our study provides insights into the differences in T cell phenotypes and immune responses during the contraction phase following SARS-CoV-2 infection across varying disease severities. These findings offer valuable perspectives for advancing future research on SARS-CoV-2 T cell-related immune responses.