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

## TL;DR

Researchers created a C. elegans strain expressing human ACE2 to study SARS-CoV-2 entry and test drugs like Raloxifene in a cost-effective model.

## Contribution

A new C. elegans model expressing human ACE2 for in vivo pharmacological studies of SARS-CoV-2 entry and drug efficacy.

## Key findings

- ACE2-expressing worms showed pharyngeal impairment when exposed to SARS-CoV-2 RBD, mimicking viral entry.
- Raloxifene reduced viral entry in vitro and counteracted RBD toxicity in ACE2 worms.
- The model is effective for screening molecules targeting ACE2 interactions across multiple SARS-CoV-2 variants.

## Abstract

Testing medical countermeasures for SARS-CoV-2 transmission using vertebrates can be hindered 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 spike protein, which caused dose-dependent 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 interactions with the ACE2 receptor are essential. The ACE2-expressing worm strain was further used for pharmacological research with Raloxifene. In vitro, 1–3 μM of Raloxifene reduced the entry of lentiviral particles carrying the Wuhan variant and B.1.1.7 UK and B.1.1.529 Omicron strains into HEK293-ACE2, in addition to particles expressing N501Y-mutated 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 with effects involving interactions with the ACE2 receptor.