SARS2 and infection: Based on the reported ELISA assay that involved pre-treatment of the spike protein with angiotensin peptides to assess the enhancement of spike protein interactions with ACE2 [31,32], we applied a similar approach in the infection assay by pre-incubating SARS2-VLP with angiotensins for one hour at 37 °C prior to infecting HEK293T-ACE2 target cells.