A Novel Soluble ACE2 Variant with Prolonged Duration of Action Neutralizes SARS-CoV-2 Infection in Human Kidney Organoids

Significance Statement The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a pandemic for which currently there are limited preventative and therapeutic approaches. The use of soluble ACE2 protein has been recently proposed as a way to intercept the SARS-CoV-2 S spike from binding to the full-length membrane-bound ACE2 receptor. We have developed a newly bioengineered soluble ACE2 protein of shorter molecular size and modified by fusing it with an albumin binding domain (ABD) tag to extend its duration of action. Here, we demonstrate in studies conducted in a BSL-3 facility that human kidney organoids can be infected by SARS-CoV-2 as they possess the human full-length ACE2 receptor and transmembrane serine protease 2, which are needed for infectivity. Using this model, we demonstrate that our novel soluble ACE2 variant can inhibit SARS-CoV-2 infection, suggesting its potential preventative and therapeutic use. Background There is an urgent need for approaches to prevent and treat SARS-CoV-2 infection. Administration of soluble ACE2 protein acting as a decoy to bind to SARS-CoV-2 should limit viral uptake mediated by binding to membrane-bound full-length ACE2, and further therapeutic benefit should result from ensuring enzymatic ACE2 activity to affected organs in patients with COVID-19. Methods A short variant of human soluble ACE2 protein consisting of 618 amino acids (hACE2 1–618) was generated and fused with an albumin binding domain (ABD) using an artificial gene encoding ABDCon, with improved albumin binding affinity. Human kidney organoids were used for infectivity studies of SARS-CoV-2 in a BSL-3 facility to examine the neutralizing effect of these novel ACE2 variants. Results Whereas plasma ACE2 activity of the naked ACE2 1–618 and ACE2 1–740 lasted about 8 hours, the ACE2 1–618-ABD resulted in substantial activity at 96 hours, and it was still biologically active 3 days after injection. Human kidney organoids express ACE2 and TMPRSS2, and when infected with SARS-CoV-2, our modified long-acting ACE2 variant neutralized infection. Conclusions This novel ACE2 1–618-ABD can neutralize SARS-CoV-2 infectivity in human kidney organoids, and its prolonged duration of action should ensure improved efficacy to prevent viral escape and dosing convenience.