Restoration of dendritic cell homeostasis and Type I/Type III interferon levels in convalescent COVID-19 individuals.

Background: Plasmacytoid and myeloid dendritic cells play a vital role in the protection against viral infections. In COVID-19, there is an impairment of dendritic cell (DC) function and interferon secretion which has been correlated with disease severity.

Results: In this study, we described the frequency of DC subsets and the plasma levels of Type I (IFNα, IFNβ) and Type III Interferons (IFNλ1), IFNλ2) and IFNλ3) in seven groups of COVID-19 individuals, classified based on days since RT-PCR confirmation of SARS-CoV2 infection. Our data shows that the frequencies of pDC and mDC increase from Days 15-30 to Days 61-90 and plateau thereafter. Similarly, the levels of IFNα, IFNβ, IFNλ1, IFNλ2 and IFNλ3 increase from Days 15-30 to Days 61-90 and plateau thereafter. COVID-19 patients with severe disease exhibit diminished frequencies of pDC and mDC and decreased levels of IFNα, IFNβ, IFNλ1, IFNλ2 and IFNλ3. Finally, the percentages of DC subsets positively correlated with the levels of Type I and Type III IFNs.

Conclusion: Thus, our study provides evidence of restoration of homeostatic levels in DC subset frequencies and circulating levels of Type I and Type III IFNs in convalescent COVID-19 individuals.