SARS-CoV-2 has mutated during the global pandemic leading to viral adaptation to medications and vaccinations. Here we describe an engineered human virus receptor, ACE2, by mutagenesis and screening for binding to the receptor binding domain (RBD). Three cycles of random mutagenesis and cell sorting achieved sub-nanomolar affinity to RBD. Our structural data show that the enhanced affinity comes from better hydrophobic packing and hydrogen-bonding geometry at the interface. Additional disulfide mutations caused the fixing of a closed ACE2 conformation to avoid off-target effects of protease activity, and also improved structural stability. Our engineered ACE2 neutralized SARS-CoV-2 at a 100-fold lower concentration than wild type; we also report that no escape mutants emerged in the co-incubation after 15 passages. Therapeutic administration of engineered ACE2 protected hamsters from SARS-CoV-2 infection, decreased lung virus titers and pathology. Our results provide evidence of a therapeutic potential of engineered ACE2.

Potential effects of tea and its constituents on SARS-CoV-2 infection were assessed in vitro. Infectivity of SARS-CoV-2 was decreased to 1/100 to undetectable levels after a treatment with black tea, green tea, roasted green tea, or oolong tea for 1 min. An addition of (−) epigallocatechin gallate (EGCG) significantly inactivated SARS-CoV-2, while the same concentration of theasinensin A (TSA) and galloylated theaflavins including theaflavin 3,3′-di-O-gallate (TFDG) had more remarkable anti-viral activities. EGCG, TSA, and TFDG at 1 mM, 40 µM, and 60 µM, respectively, which are comparable to the concentrations of these compounds in tea beverages, significantly reduced infectivity of the virus, viral RNA replication in cells, and secondary virus production from the cells. EGCG, TSA, and TFDG significantly inhibited interaction between recombinant ACE2 and RBD of S protein. These results suggest potential usefulness of tea in prevention of person-to-person transmission of the novel coronavirus.

The multiple mutations of the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) virus have created variants with structural differences in both their spike and nucleocapsid proteins. While the functional relevance of these mutations is under continuous scrutiny, current findings have documented their detrimental impact in terms of affinity with host receptors, antibody resistance, and diagnostic sensitivity. Raman spectra collected on two British variant sub‐types found in Japan (QK002 and QHN001) are compared with that of the original Japanese isolate (JPN/TY/WK‐521), and found bold vibrational differences. These included: i) fractions of sulfur‐containing amino acid rotamers, ii) hydrophobic interactions of tyrosine phenol ring, iii) apparent fractions of RNA purines and pyrimidines, and iv) protein secondary structures. Building upon molecular scale results and their statistical validations, the authors propose to represent virus variants with a barcode specially tailored on Raman spectrum. Raman spectroscopy enables fast identification of virus variants, while the Raman barcode facilitates electronic recordkeeping and translates molecular characteristics into information rapidly accessible by users.

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The SARS-CoV-2 spike protein binds to the human angiotensin-converting enzyme 2 (ACE2) receptor via receptor binding domain (RBD) to enter into the cell. Inhibiting this interaction is a main approach to block SARS-CoV-2 infection and it is required to have high affinity to RBD independently of viral mutation for effective protection. To this end, we engineered ACE2 to enhance the affinity with directed evolution in human cells. Three cycles of random mutation and cell sorting achieved more than 100-fold higher affinity to RBD than wild-type ACE2. The extracellular domain of modified ACE2 fused to the Fc region of the human immunoglobulin IgG1 had stable structure and neutralized SARS-CoV-2 pseudotyped lentivirus and authentic virus with more than 100-fold lower concentration than wild-type. Engineering ACE2 decoy receptors with directed evolution is a promising approach to develop a SARS-CoV-2 neutralizing drug that has affinity comparable to monoclonal antibodies yet displaying resistance to escape mutations of virus.