ACE2 and infection: Human embryonic kidney cells (AD293 cells) transfected to express guinea pig ACE2 (gpACE2) are not rendered susceptible to infection with SARS-CoV-1, likely owing to the low sequence homology (86.8%) between gpACE2 with hACE2, low expression post transfection (≈20% cells), and overall low infection rate (≈20% cells) [42].