Peripheral CD4+ T cell subsets and antibody response in COVID-19 convalescent individuals.

BACKGROUND: Marked progress is achieved in understanding the physiopathology of COVID-19 that caused global pandemics. However, CD4+ T cell population that is critical for antibody response in COVID-19 is poorly understood. METHODS: In this study, we provided a comprehensive analysis of peripheral CD4+ T cells of 13 COVID-19 convalescent patients, as defined as confirmed free of SARS-CoV-2 for 2-4 weeks, using flow cytometry, magnetic chemiluminescence enzyme antibody immunoassay and correlated the data 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 cell associated with SARS-CoV-2 targeting antibodies, which was found to skew with disease severity as more severe individuals showed higher frequency of TEM and TFH-EM cells but a lower frequency of TCM, TFH-CM and TNaive cells, relative to mild and moderate patients. Interestingly, higher frequency of cTFH-EM cells correlated with lower number of recorded admission blood oxygen level 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: Together, our study demonstrated close connection between CD4+ T cells and antibody production in COVID-19 convalescents. FUNDING: This study was supported by Six Talent Peaks Project in Jiangsu Province and the National Natural Science Foundation of China (NSFC) grants 81970759.