TMPRSS2 and infection: Finally, the triad of factors required for SARS-CoV-2 entry, (ACE2 as the major receptor and co-factors furin and TMPRSS2) should co-localize simultaneously at the cell membrane of surface epithelial cells in order to permit effective infection of the host cells [11, 25, 28], but this was not the case in the literature [12, 14], neither in our study regarding the expression of ACE2 and furin.