PROS1 and COVID-19: Single-nucleus gene-expression profiling of frontal cortex and choroid plexus tissues from severe COVID-19 patients showed broad perturbations, with upregulation of genes involved in innate antiviral response and inflammation, microglial activation and neurodegeneration22, but no direct evidence of viral tropism was found; similarly, Fullard et al.20 did not detect viral transcripts and S proteins in different brain regions of COVID-19 subjects.