SARS-CoV-2 Entry Can Be Mimicked in C. elegans Expressing Human ACE2: A New Tool for Pharmacological Studies

Testing medical countermeasures for SARS-CoV-2 transmission using vertebrates can be slowed by legislation regulating animal experimentation, high costs, and ethical concerns. To overcome these challenges, we propose a new Caenorhabditis elegans strain that constitutively expresses the human angiotensin-converting enzyme 2 receptor (ACE2). This resulted in significant impairment of reproduction and a defect in pharyngeal function compared to wild-type (WT) worms. SARS-CoV-2 infection was simulated by treating worms with the receptor-binding domain (RBD) of the virus, which caused dose- and time-dependent pharyngeal impairment in ACE2 worms but not in WT worms. The toxicity of RBD was prevented by administering an anti-human ACE2 antibody, demonstrating that interaction with the ACE2 receptor is essential. The ACE2-expressing worm strain was further used for pharmacological research with Raloxifene. In vitro, Raloxifene at 1-3 μM reduced the entry of lentiviral particles carrying the Wuhan variant, B.1.1.7 UK, and B.1.1.529 Omicron strains, into HEK293-ACE2, as well as particles expressing N501Y- or P681H-mutated spike proteins. Raloxifene (0.1-1 μM) completely counteracted RBD toxicity in ACE2 worms, indicating that this strain offers a cost-effective in vivo screening platform for molecules whose effects involve interaction with the ACE2 receptor.