Angiotensin Converting Enzyme 2 (ACE-2), Transmembrane
Serine Protease 2 (TMPRSS-2) and
Neuropilin-1 cellular receptors support the entry of SARS-CoV-2 into susceptible human target cells and are characterized at the molecular level. Some evidence on the expression of entry receptors at
mRNA and
protein levels in brain cells is available, but co-expression of these receptors and confirmatory evidence on brain cells is lacking. SARS-CoV-2 infects some brain cell types, but
infection susceptibility, multiple entry receptor density, and
infection kinetics are rarely reported in specific brain cell types. Highly sensitive Taqman ddPCR, flow-cytometry and immunocytochemistry assays were used to quantitate the expression of ACE-2, TMPRSS-2 and
Neuropilin-1 at
mRNA and
protein levels on human brain-extracted pericytes and astrocytes, which are an integral part of the Blood-Brain-Barrier (BBB). Astrocytes showed moderate ACE-2 (15.9 ± 1.3%, Mean ± SD, n = 2) and TMPRSS-2 (17.6%) positive cells, and in contrast show high
Neuropilin-1 (56.4 ± 39.8%, n = 4)
protein expression. Whereas pericytes showed variable ACE-2 (23.1 ± 20.7%, n = 2),
Neuropilin-1 (30.3 ± 7.5%, n = 4)
protein expression and higher TMPRSS-2
mRNA (667.2 ± 232.3, n = 3) expression. Co-expression of multiple entry receptors on astrocytes and pericytes allows entry of SARS-CoV-2 and progression of
infection. Astrocytes showed roughly four-fold more virus in culture supernatants than pericytes. SARS-CoV-2 cellular entry receptor expression and "in vitro" viral kinetics in astrocytes and pericytes may improve our understanding of
viral infection "in vivo". In addition, this study may facilitate the development of novel strategies to counter the effects of SARS-CoV-2 and inhibit
viral infection in brain tissues to prevent the spread and interference in neuronal functions.