ABSTRACT
BACKGROUND: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immune response is crucial for disease management, although diminishing immunity raises the possibility of reinfection. METHODS: We examined the immunological response to SARS-CoV-2 in a cohort of convalescent COVID-19 patients in matched samples collected at 1 and 6-8 months after infection. The peripheral blood mononuclear cells were isolated from enrolled study participants and flow cytometry analysis was done to assess the lymphocyte subsets of naive, effector, central memory, and effector memory CD4+ or CD8+ T cells in COVID-19 patients at 1 and 6-8 months after infection. Immunophenotypic characterization of immune cell subsets was performed on individuals who were followed longitudinally for 1 month (n = 44) and 6-8 months (n = 25) after recovery from COVID infection. RESULTS: We observed that CD4 +T cells in hospitalized SARS-CoV-2 patients tended to decrease, whereas CD8+ T cells steadily recovered after 1 month, while there was a sustained increase in the population of effector T cells and effector memory T cells. Furthermore, COVID-19 patients showed persistently low B cells and a small increase in the NK cell population. CONCLUSION: Our findings show that T cell responses were maintained at 6-8 months after infection. This opens new pathways for further research into the long-term effects in COVID-19 immunopathogenesis.
Subject(s)
CD4-Positive T-Lymphocytes , CD8-Positive T-Lymphocytes , COVID-19 , SARS-CoV-2 , Humans , COVID-19/immunology , Longitudinal Studies , Male , Female , SARS-CoV-2/immunology , Middle Aged , Adult , CD8-Positive T-Lymphocytes/immunology , CD4-Positive T-Lymphocytes/immunology , Survivors , Immunologic Memory/immunology , Cohort Studies , Aged , Killer Cells, Natural/immunologyABSTRACT
The cellular immune cell subsets affecting COVID-19 disease severity are being studied by researchers from many countries. The current study was carried out to investigate the alteration of peripheral blood mononuclear cells (PBMCs) and their subsets in hospitalized COVID-19 patients in a tertiary care center in Pune, India. The PBMCs were isolated from enrolled study participants, and flow cytometry analysis was done to assess peripheral white blood cell alterations. The lymphocyte subsets of naive, effector, central memory, and effector memory CD4+ or CD8+ T cells were then evaluated in COVID-19 patients with different disease categories and compared to healthy controls. The immunophenotypic characterization of the immune cell subset was done for 139 COVID-19 patients and 21 healthy controls. These data were evaluated based on the disease severity. A total of 139 COVID-19 patients were classified as mild (n = 30), moderate (n = 57), or severe (n = 52) cases. The decreased percentages of total lymphocytes, CD3+ T cells, CD4+ T cells, naive T cells, central memory T cells, and Natural Killer (NK) cytotoxic cells were found, and there was increase in effector T (TEf) cells and effector memory T cells in patients with severe COVID-19 compared to healthy controls. The severity of SARS-CoV-2 infection has an effect on lymphocyte subsets, resulting in reduced T memory cells and NK cells but increased TEf cells in severe cases. Clinical Trial Registration: CTRI ID-CTRI/2021/03/032028.
