SARS-CoV-2 virions associate with ACE2+ exosomes.

(A) TEM of negative stained exosomes and virus alone. Arrowheads: putative exosomes. Scale bars: 200 nm. Red arrows mark the characteristic collapsing of exosomes during TEM imaging. (B) Double immunogold labeling TEM images of SARs-CoV-2 virions mixed with ACE2+ exosomes (right panel, scale bar: 50 nm) or ACE2− exosomes (left panel). Virions are labeled using an antibody for SARS-CoV-2 N, followed by nanogold-conjugated Fab (black triangle outline), which fills the entirety of the virion giving it the appearance of the larger dark mass. Exosomes are labeled using an antibody against CD63, followed by 18-nm colloidal gold-conjugated IgG (filled white triangles). Bottom panels are the same images as the top panels, with exosome membranes marked with dotted yellow outlines denotes to enhance their visibility. (C) Quantification of CD63 structures per virion present in a cluster containing both markers. ACE2+ (n = 68 clusters), ACE2− (n = 57). Error bars represent mean ± SEM from at least 2 independent experiments. Underlying data can be found in S1 Data. Unpaired t test with Welch’s correction. * P ≤ 0.05; ** P ≤ 0.01; *** P ≤ 0.001; **** P ≤ 0.0001. ns, not significant; SARS‑CoV‑2, Severe Acute Respiratory Syndrome Coronavirus 2; TEM, transmission electron microscopy.