Immunological imprint of COVID‐19 on human peripheral blood leukocyte populations

Kratzer, Bernhard; Trapin, Doris; Ettel, Paul; Körmöczi, Ulrike; Rottal, Arno; Tuppy, Friedrich; Feichter, Melanie; Gattinger, Pia; Borochova, Kristina; Dorofeeva, Yulia; Tulaeva, Inna; Weber, Milena; Grabmeier‐Pfistershammer, Katharina; Tauber, Peter A.; Gerdov, Marika; Mühl, Bernhard; Perkmann, Thomas; Fae, Ingrid; Wenda, Sabine; Führer, Harald; Henning, Rainer; Valenta, Rudolf; Pickl, Winfried F.

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.