Extended Data Fig. 3: Fibrin clot ultrastructure and Spike protein interactions.
From: Fibrin drives thromboinflammation and neuropathology in COVID-19
a, Topographic visualization of fibrin fibre surface in SEM images of fibrin clots in healthy human donor plasma in the presence of Spike. b, SEM of fibrin clots in human plasma in the presence of Spike. x4000 magnification. Images representative of n = 3 independent biological replicates quantified in (c) and Fig. 1f. c, Fibre radius proportion less than 0.05 µm (boxplot) and intersection density (bar plot) in plasma or plasma with Spike. Generalized linear mixed effects model (boxplot) and two-sample two-sided Welch t-test (bar plot). n = 25 (plasma), n = 28 (plasma with Spike) images from n = 3 biologically independent experiments quantified in Fig. 1f. Images from biologically independent experiments are indicated by different colour dots in boxplot. Box indicates the interquartile range (IQR) and whiskers denote the 1.5 × IQR. d, Alanine scan mutagenesis peptide array. Fibrin peptide γ377-395 was subjected to double-alanine scanning mutagenesis and incubated with His-tagged recombinant Spike. Signal intensity bar graph of the binding of Spike to sequential Ala-Ala substituted peptides (red). Control signal is shown in blue. Residues with low signal intensity upon Ala-Ala substitution are required for binding and highlighted in yellow. e. ELISA of 5B8-huFc or huIgG1 isotype control pre-incubated with fibrin versus the Spike for binding to fibrin. Data are mean ± s.e.m from three biologically independent experiments. f. Iba-1 immunoreactivity in brain following stereotaxic co-injection of fibrinogen with PBS or Spike in WT mice. Scale bar, 50 µm. Data are from n = 6 mice per group. One-way ANOVA with Tukey’s multiple comparisons test. All data are mean ± s.e.m.
