Abstract: This disclosure describes recombinant angiotensin-converting enzyme II (ACE2) polypeptides, fusion proteins, and compositions thereof having improved binding affinity for the SARS-CoV-2 spike protein receptor binding domain relative to wild-type ACE2. Also provided are methods of using the recombinant ACE2 polypeptides, fusion proteins, and compositions thereof for treating subjects infected with a SARS-CoV-2 virus (i.e., subjects with COVID-19), subjects having symptoms suggestive of a SARS-CoV-2 infection, and subjects exposed to or at risk of exposure to SARS-CoV-2 virus. Other virus infections may also be treated.

Abstract: Provided herein are protein biosensors, fusion proteins, compositions, and methods that are useful in detecting SARS-CoV-2 viruses in a sample from a subject. The viral detection assays described herein are solution-based, rapid, and quantitative. The protein biosensors and fusion proteins herein are able to bind to SARS-CoV-2 viral proteins. Use of the fusion proteins in proximity assays (e.g., split reporter assays) allows sensitive detection of SARS-CoV-2 virus in samples.