CTSL and COVID-19: More recently, neuropilin-1 (NRP1) was identified as a novel mechanism of access to the brain for SARS-CoV-2, which was expressed in brains and olfactory bulbs (OBs) (Table 2), at high levels relative to ACE2 and TMPRSS2.43,44,142 The autopsies of the olfactory epithelium from COVID-19 patients determined that the infected olfactory epithelial cells with high expression of NRP1.43 In addition to NRP1, SARS-CoV-2 invades cells via BASIGIN (GBS) and Cathepsin L (CTSL), which also facilitated SARS-CoV-1 to infect cells45,46,143–147 (Table 2).