Fatal COVID-19 is Associated with Reduced HLA-DR, CD123 or CD11c Expression on Circulating Dendritic Cells

Purpose: Severe coronavirus disease 2019 (COVID-19) is linked to insufficient control of viral replication and excessive inflamma-tion driven by an unbalanced immune response. Plasmacytoid dendritic cells (pDCs) are specialized in the rapid production of interferons in response to viral infections, and can also prime and activate T-cells. Conventional DCs (cDCs) are critical for the elimination of viral infections owing to their specialized ability to prime and activate T cells. We assessed the frequency and phenotype of pDCs and cDCs in survivors and non-survivors of COVID-19.Patients and methods: Patients with COVID-19 were enrolled, and 22 were included in this study. Peripheral whole blood was obtained during the 2nd week of illness, stained with antibodies specific for lineage markers, human leukocyte antigen-DR isotype (HLA-DR), CD11c, and CD123, and analyzed by flow cytometry. Patients were followed-up during hospital admission and grouped into survivors (n=17) and non-survivors (n=5) of COVID-19.Results: The ratio of pDCs to pre-cDCs was significantly lower (P=0.0005) in non-survivors compared to survivors. The frequency of pDCs was significantly higher than cDC2-like cells (P=0.0002) and pre-cDCs (P<0.0001) in survivors but not in non-survivors. HLA-DR expression level on pDCs and cDC2-like cells was lower in non-survivors compared to survivors (P=0.02 and P=0.058, respectively), and HLA-DR was inversely correlated with disease severity rating (pDCs: r= -0.47, P=0.027; cDC2-like cells: r= -0.45, P=0.037). CD123 expression level on pDCs was significantly lower (P=0.038) in non-survivors compared to survivors, and CD123 was inversely correlated with disease severity rating (r=-0.5, P=0.016). CD11c expression level on cDC2-like cells was significantly lower (P=0.03) in non -survivors compared to survivors, and CD11c was inversely correlated with disease severity rating (r=-0.47, P=0.025).Conclusion: A lower frequency of pDCs compared to other circulating DCs, and lower expression levels of HLA-DR, CD123 or CD11c on DCs is associated with fatal COVID-19.

Automated summary

Severe COVID-19 is associated with a lower frequency of pDCs compared to other circulating DCs, and lower expression levels of HLA-DR, CD123, or CD11c on DCs.