Circulating myeloid-derived suppressor cells may be a useful biomarker in the follow-up of unvaccinated COVID-19 patients after hospitalization

Abstract

SARS-CoV-2 infection is the cause of the disease named COVID-19, a major public health challenge worldwide. Differences in the severity, complications and outcomes of the COVID-19 are intriguing and, patients with similar baseline clinical conditions may have very different evolution. Myeloid-derived suppressor cells (MDSCs) have been previously found to be recruited by the SARS-CoV-2 infection and may be a marker of clinical evolution in these patients. We have studied 90 consecutive patients admitted in the hospital before the vaccination program started in the general population, to measure MDSCs and lymphocyte subpopulations at admission and one week after to assess the possible association with unfavorable outcomes (dead or Intensive Care Unit admission). We analyzed MDSCs and lymphocyte subpopulations by flow cytometry. In the 72 patients discharged from the hospital, there were significant decreases in the monocytic and total MDSC populations measured in peripheral blood after one week but, most importantly, the number of MDSCs (total and both monocytic and granulocytic subsets) were much higher in the 18 patients with unfavorable outcome. In conclusion, the number of circulating MDSCs may be a good marker of evolution in the follow-up of unvaccinated patients admitted in the hospital with the diagnosis of COVID-19.

Keywords: SARS-CoV-2; COVID-19; MDSCs; T lymphocytes; biomarker.

Figure 1

(A) Monocytic myeloid-derived suppressor cells (MDSCs); (B) Granulocytic MDSCs; (C) Total MDSCs, in COVID-19 patients discharged from the hospital (blue) and died after hospitalization or admitted at Intensive Care Unit (ICU; orange) during the one-week follow-up. Cell concentrations are represented as median and 95% confidence intervals (CI) of cells per microliter. *p ≤ 0.05 and **p ≤ 0.01, comparing determinations at hospitalization vs. one week later in every group of patients; ^###p ≤ 0.001 comparing opposite groups in every determination. N.S., No significant.

Figure 2

Activated OX40+PD-1- T cells, (A) CD4+; (B) CD8+; and (C) Total, in COVID-19 patients discharged from the hospital (blue) and passed away after hospitalization or admitted at Intensive Care Unit (ICU; orange) during the one-week follow-up. Cell concentrations are represented as median and 95% confidence intervals of cells per microliter. *p≤0.05, comparing determinations at hospitalization vs. one week later in every group of patients; ^#p ≤ 0.05, comparing opposite groups in every determination. N.S., No significant.

Figure 3

Activated HLA-DR+ T cells, (A) CD4+; (B) CD8+; and (C) Total, in COVID-19 patients discharged from the hospital (blue) and passed away after hospitalization or admitted at Intensive Care Unit (ICU; orange) during the one-week follow-up. Cell concentrations are represented as median and 95% confidence intervals of cells per microliter. *p ≤ 0.05 and ***p ≤ 0.001, comparing determinations at hospitalization vs. one week later in every group of patients; ^#p ≤ 0.05 and ^##p ≤ 0.01, comparing opposite groups in every determination. N.S., No significant.