Abstract Background SARS‐CoV‐2 has triggered a pandemic that is now claiming many lives. Several studies have investigated cellular immune responses in COVID‐19‐infected patients during disease but little is known regarding a possible protracted impact of COVID‐19 on the adaptive and innate immune system in COVID‐19 convalescent patients. Methods We used multiparametric flow cytometry to analyze whole peripheral blood samples and determined SARS‐CoV‐2‐specific antibody levels against the S‐protein, its RBD‐subunit, and viral nucleocapsid in a cohort of COVID‐19 convalescent patients who had mild disease ~10 weeks after infection (n = 109) and healthy control subjects (n = 98). Furthermore, we correlated immunological changes with clinical and demographic parameters. Results Even ten weeks after disease COVID‐19 convalescent patients had fewer neutrophils, while their cytotoxic CD8 + T cells were activated, reflected as higher HLA‐DR and CD38 expression. Multiparametric regression analyses showed that in COVID‐19‐infected patients both CD3 + CD4 + and CD3 + CD8 + effector memory cells were higher, while CD25 + Foxp3 + T regulatory cells were lower. In addition, both transitional B cell and plasmablast levels were significantly elevated in COVID‐19‐infected patients. Fever (duration, level) correlated with numbers of central memory CD4 + T cells and anti‐S and anti‐RBD, but not anti‐NC antibody levels. Moreover, a “young immunological age” as determined by numbers of CD3 + CD45RA + CD62L + CD31 + recent thymic emigrants was associated with a loss of sense of taste and/or smell. Conclusion Acute SARS‐CoV‐2 infection leaves protracted beneficial (ie, activation of T cells) and potentially harmful (ie, reduction of neutrophils) imprints in the cellular immune system in addition to induction of specific antibody responses. Ten weeks after disease, COVID‐19 patients had fewer neutrophils compared to subjects without COVID‐19, while their cytotoxic CD8 + T cells were still activated. In COVID‐19 patients both CD3 + CD4 + and CD3 + CD8 + effector memory cells, transitional B cells and plasmablast levels were higher, while CD25 + Foxp3 + T regulatory cells were lower than in subjects without COVID‐19. Fever duration correlated with higher numbers of central memory CD4 + T cells, anti‐S and anti‐RBD antibody levels, while loss of taste/smell was associated with higher levels of recent thymic emigrants. Abbreviations: COVID‐19, coronavirus disease 2019; ELISA, enzyme‐linked immunosorbent assay; KRECs, kappa‐deleting recombination excision circles; qPCR, quantitative PCR; RBD, receptor‐binding domain of SARS‐CoV2 spike protein; TRECs, T‐cell receptor excision circles; S, spike protein of SARS‐Cov2; SARS‐CoV‐2, severe acute respiratory syndrome coronavirus 2.
【저자키워드】 Coronavirus disease 2019, Lymphocytes, T cells, SARS‐CoV‐2, B cells, flow cytometry, clinical immunology, infections, 【초록키워드】 coronavirus disease, Neutrophils, Coronavirus disease 2019, coronavirus, pandemic, adaptive, antibody, Cellular immune response, T cells, neutrophil, Infection, transitional B cells, immune system, severe acute respiratory syndrome Coronavirus, CD4, CD8, ELISA, Spike protein, COVID‐19, SARS‐CoV‐2, Peripheral blood, innate immune system, Cohort, T cell, Convalescent patients, Viral, cells, nucleocapsid, RBD, qPCR, immune responses, Patient, Recombination, Mild, antibody levels, receptor, Taste, respiratory, disease, expression, Quantitative, quantitative PCR, parameters, patients, CD25, CD38, FOXP3, convalescent patient, Mild disease, cellular, SARS‑CoV2, immunological changes, determined by, sense of taste, regression analysis, reduction, acute respiratory syndrome, Activation, acute respiratory syndrome coronavirus, acute respiratory syndrome coronavirus 2, COVID‐19 patients, subject, healthy control, domain, SARS‐CoV‐2 infection, cellular immune responses, sense, CD45, CD45RA, multiparametric flow cytometry, CD31, HLA‐DR, receptor‐binding domain, T regulatory cells, thymic emigrants, transitional B cell, effector memory, T regulatory cell, responses, CD3, immunological, Cell, Result, significantly, addition, investigated, elevated, activated, reflected, correlated, triggered, immunosorbent, central memory, COVID‐19 patient, immunological change, T‐cell, thymic emigrant, 【제목키워드】 COVID‐19, Peripheral blood, leukocyte population,