Session topic


Title: Singular ACE2-IgG4-Fc fusion protein efficiently inhibits SARS-CoV-2 entry
ID: O 61
Type: Abstract talk
Talk time: 12 + 3 min
Session: Workshop 11
Antivirals and resistance II

Speaker: Julia Sacherl (München/DE)

Abstract - Text

Abstract text (incl. references and figure legends)

Introduction and aim

The binding of the spike protein of severe acute respiratory syndrome (SARS)-like coronavirus 2 (SARS-CoV-2) and other human pathogenic coronaviruses to angiotensin-converting enzyme 2 (ACE2) is an essential step for virus entry into the host cells. A soluble recombinant human ACE2 ectodomain was shown to bind and neutralize the virus but the short in vivo half-live limits its therapeutic use. The fusion of the fragment crystallizable (Fc) part of a human immunoglobulin G (IgG) to the ACE2 ectodomain increases the half-live, however entails the risk of unwanted disease enhancement related to complement dependent immune activation and antibody dependent cytotoxicity.

To overcome these limitations and as efficient treatment options against COVID-19 are still lacking, we aimed to engineer and characterize optimized ACE2-Fc fusion proteins directly acting against SARS-CoV-2.


Biochemical features of eight newly engineered ACE2-Fc fusion constructs with differences in the amino acid sequence and a stabilized mutation in the IgG-Fc hinge region were characterized by circular dichroism spectroscopy, size-exclusion chromatography coupled to multi-angle light scattering, surface plasmon resonance and ACE2 activity assay. Neutralizing capacity of ACE2-Fc fusion constructs against various SARS-CoV strains were evaluated under biosafety level 3 conditions via neutralization assay followed by an in-cell ELISA.


Our analysis demonstrated favourable biophysical and pharmaceutical characteristics of our engineered ACE2-IgG4-Fc fusion proteins while allowing the preservation of beneficial enzymatic activity of ACE2. Moreover, ACE2-Fc fusion constructs efficiently inhibited infection of Vero E6 cells with a SARS-CoV-2 wildtype virus isolate from the earliest documented COVID-19 cases in Germany. Viral neutralization experiments with a later isolated SARS-CoV-2 strain showed even more efficient inhibition of SARS-CoV-2 entry with half maximal inhibitory concentration values below one nanomolar. In addition, all ACE2-Fc molecules inhibited infection with the original SARS-CoV from 2003 demonstrating their broad antiviral activity.


Our data demonstrate that ACE2-IgG4-Fc fusion proteins are promising antiviral treatment candidates against various human pathogenic coronaviruses. Therefore, they are not only valuable for the current SARS-CoV-2 pandemic but also for future coronavirus infectious diseases.