Peripheral Cd4(+) T Cell Subsets And Antibody Response In Covid-19 Convalescent Individuals

BACKGROUND. Marked progress is achieved in understanding the physiopathology of coronavirus disease 2019 (COVID-19), which caused a global pandemic. However, the CD4(+) T cell population critical for antibody response in COVID-19 is poorly understood.METHODS. In this study, we provided a comprehensive analysis of peripheral CD4(+) T cells from 13 COVID-19 convalescent patients, defined as confirmed free of SARS-CoV-2 for 2 to 4 weeks, using flow cytometry and magnetic chemiluminescence enzyme antibody immunoassay. The data were correlated with clinical characteristics.RESULTS. We observed that, relative to healthy individuals, convalescent patients displayed an altered peripheral CD4(+) T cell spectrum. Specifically, consistent with other viral infections, cTfh1 cells associated with SARS-CoV-2-targeting antibodies were found in COVID-19 covalescent patients. Individuals with severe disease showed higher frequencies of Tern and Tfh-em cells but lower frequencies of Tcm, Tfh-cm, Tfr, and Tnaive cells, compared with healthy individuals and patients with mild and moderate disease. Interestingly, a higher frequency of cTfh-em cells correlated with a lower blood oxygen level, recorded at the time of admission, in convalescent patients. These observations might constitute residual effects by which COVID-19 can impact the homeostasis of CD4(+) T cells in the long-term and explain the highest ratio of class-switched virus-specific antibody producing individuals found in our severe COVID-19 cohort.CONCLUSION. Our study demonstrated a close connection between CD4(+) T cells and antibody production in COVID-19 convalescent patients.