Fig. 2.

Characterization of SARS-CoV-2 interaction with human platelets and megakaryocytes. a IFA assays suggesting SARS-CoV-2 infection in platelets and megakaryocytes. Platelets from healthy donors and the megakaryocyte cell line MEG-01 were incubated with SARS-CoV-2 (1 MOI per test). SARS-CoV-2 N expression in platelets and MEG-01 cells were immunostained at 3 h p.i. and 24 h p.i., respectively. b Quantitative analysis of SARS-CoV-2 RNA copies in culture supernatants and in MEG-01 cells. c Immunofluorescence assay of ACE2 expression in MEG-01, platelets (PLT), Calu-3, Huh7, and 293 T cell lines. Bars, 10 μm. d Western blot analyses of ACE2 expression in cell lines including MEG-01, 293 T, HeLa, Huh7, and Calu-3, and platelets (PLT) from three healthy donors (D1, D2, and D3). Expression of β-actin in cells were blotted as inner control. e RNA transcripts of 14 receptors in human platelets and megakaryocytes were evaluated using bioinformatic methods using the RNA-seq data obtained from previous studies. f qRT-PCR detection of CD147, GRP78, KREMEN1, Cathepsin L, NRP1, ASGR1, and ACE2 in cell lines including Calu-3, Huh7, HeLa, 293 T, and MEG-01, and platelets from three healthy donors (D1, D2, and D3). The transcription levels were normalized to those of GAPDH in each of respective cell line or platelet samples and compared to MEG-01 or Calu-3 (shaded bars), as described in Additional file 1: Methods. g Comparison of CD147, KREMEN1, and NRP1 RNA levels in ICU and non-ICU COVID-19 patients with those in healthy persons using the RNA-seq data obtained from previous studies. h qRT-PCR detection of CD147, KREMEN1, and NRP1 transcription in MEG-01 cells after SARS-CoV-2 incubation