Impaired T Cell Functions Along with Elevated Activated Tregs at the Early Stage of Asymptomatic SARS-CoV-2 Infection

Background: Limited data are available on the T cell responses for the asymptomatic SARS-CoV-2 infection case. Methods: The first imported SARS-CoV-2 infection case in Wuhan was admitted in hospital for quarantine and observation. The T cell responses were followed up by flow cytometry analysis of the peripheral blood nonnuclear cells (PBMCs) at days 7, 13, 22, and 28 after admission. Findings: We found the first imported SARS-CoV-2 infection in Wuhan is an asymptomatic case. His T cell differentiation, proliferation and activation matched the classical kinetics of T cell responses induced by viral infection, but the activation maintained at a relatively low level. Function analysis indicated frequencies of IFN-γ producing CD4+ and CD8+ T cells were notably lower than that of the healthy controls (HC) at day 7, and then rebound gradually. But IFN-γ+ CD8+ T cells were detained at a significant lower level even at day 28, when the SARS-CoV-2 virus had already become undetectable for 3 weeks. Moreover, percentage of IL-17 producing CD4+ T cells was also detained constantly at a much lower level compared to HC. At day 7, although percentage of Tregs was in normal range, the frequency of activated Treg (aTreg) was remarkably as high as 4·4-fold of that in HC. Interpretation: The T cell activation in the asymptomatic SARS-CoV-2 infection experienced a significant suppression and presented impairment of Th1/Th17 and CD8+ T cell functions. Early elevation of the aTregs might play role in the activation and function of T cells in the asymptomatic SARS-CoV-2 infection. Funding Statement: None. Declaration of Interests: All authors declare no competing interests.Ethics Approval Statement: This study was reviewed and approved by the Medical Ethical Committee of Wuhan Jinyintan hospital (approval number KY-2020-47·01). Written informed consent was obtained from the patient and the healthy controls.