Longitudinal Characteristics of Lymphocyte Responses and Cytokine Profiles in the Peripheral Blood of SARS-CoV-2 Infected Patients

Background: The dynamic changes of lymphocyte subsets and cytokines profiles of patients with novel coronavirus disease (COVID-19) and their correlation with the disease severity remain unclear. Method: Peripheral blood samples were longitudinally collected from 40 confirmed COVID-19 patients and examined for lymphocyte subsets by flow cytometry and cytokine profiles by specific immunoassays. Findings: Of the 40 COVID-19 patients enrolled, 13 severe cases showed significant and sustained decreases in lymphocyte counts but increases in neutrophil counts than 27 mild cases. Further analysis demonstrated significant decreases in the counts of T cells, especially CD8 + T cells, as well as increases in IL-6, IL-10, IL-2 and IFN-γ levels in the peripheral blood in the severe cases compared to those in the mild cases. T cell counts and cytokine levels in severe COVID-19 patients who survived the disease gradually recovered at later time points to levels that were comparable to those of the mild cases. Moreover, the neutrophil-to-CD8+ T cell ratio (N8R) were identified as the most powerful prognostic factor affecting the prognosis for severe COVID-19. Interpretation: The degree of lymphopenia and a proinflammatory cytokine storm is higher in severe COVID-19 patients than in mild cases, and is associated with the disease severity. N8R may serve as a useful prognostic factor for early identification of severe COVID-19 cases. Funding Statement: This work is supported by the National Natural Science Foundation of China (81861138044, 91742114 and 91642118), the National Science and Technology Major Project (2018ZX10723203, 2018ZX10302206, 2017ZX10202201, 2017ZX10202202 and 2017ZX10202203), the Innovation Team Project of Health Commission of Hubei Province (WJ2019C003), the Integrated Innovative Team for Major Human Diseases Program of Tongji Medical College and the “Double-First Class” Project for the International Cooperation Center on Infection and Immunity, HUST, and a special joint project of University Hospital Essen, University of Duisburg-Essen. Declaration of Interests: The authors disclose no conflicts of interest. Ethics Approval Statement: A written informed consent was regularly obtained from all patients upon admission into Wuhan Union Hospital, China. The study was approved by the Ethics Committee of Tongji Medical College of Huazhong University of Science and Technology.