An IgM-like Inhalable ACE2 fusion protein broadly neutralizes SARS-CoV-2 (preprint)

Many of the currently available COVID-19 vaccines and therapeutics are not effective against newly emerged SARS-CoV-2 variants. Here, we developed the metallo-enzyme domain of angiotensin converting enzyme 2 (ACE2)—the cellular receptor of SARS-CoV-2—into an IgM-like inhalable molecule (HH-120). HH-120 binds to the SARS-CoV-2 Spike (S) protein with exceptionally high avidity and confers potent and broad-spectrum neutralization activity against all known SARS-CoV-2 variants of concern. HH-120 was successfully developed as an inhaled formulation that achieves appropriate aerodynamic properties for respiratory system delivery, and we found that aerosol inhalation of HH-120 significantly reduced viral loads and lung pathology scores in golden Syrian hamsters infected by the SARS-CoV-2 wild-type strain and the Delta variant. Our study presents a breakthrough for the inhalation delivery of large biologics like HH-120 (molecular weight ~ 1000kDa) and demonstrates that HH-120 can serve as a highly efficacious, safe, and convenient agent against all SARS-CoV-2 variants. Finally, given the known role of ACE2 in viral reception, it is conceivable that HH-120 will be efficacious against additional emergent coronaviruses.

SARS-CoV-2 hijacks neutralizing dimeric IgA for enhanced nasal infection and injury (preprint)

Robust severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection in nasal turbinate (NT) accounts for high viral transmissibility, yet whether neutralizing IgA antibodies can control it remains unknown. Here, we evaluated receptor binding domain (RBD)-specific monomeric B8-mIgA1 and B8-mIgA2, and dimeric B8-dIgA1 and B8-dIgA2 against intranasal SARS-CoV-2 challenge in Syrian hamsters. These antibodies exhibited comparably potent neutralization against authentic virus by competing with human angiotensin converting enzyme-2 (ACE2) receptor for RBD binding. While reducing viruses in lungs, pre-exposure intranasal B8-dIgA1 or B8-dIgA2 led to 81-fold more infectious viruses and severer damage in NT than placebo. Virus-bound B8-dIgA1 and B8-dIgA2 could engage CD209 as an alternative receptor for entry into ACE2-negative cells and allowed viral cell-to-cell transmission. Cryo-EM revealed B8 as a class II neutralizing antibody binding trimeric RBDs in 3-up or 2-up/1-down conformation. Therefore, RBD-specific neutralizing dIgA engages an unexpected action for enhanced SARS-CoV-2 nasal infection and injury in Syrian hamsters.

SARS-CoV-2 hijacks neutralizing dimeric IgA for enhanced nasal infection and injury (preprint)

Robust severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection in nasal turbinate (NT) accounts for high viral transmissibility, yet whether neutralizing IgA antibodies can control it remains unknown. Here, we evaluated receptor binding domain (RBD)-specific monomeric B8-mIgA1 and B8-mIgA2, and dimeric B8-dIgA1 and B8-dIgA2 against intranasal SARS-CoV-2 challenge in Syrian hamsters. These antibodies exhibited comparably potent neutralization against authentic virus by competing with human angiotensin converting enzyme-2 (ACE2) receptor for RBD binding. While reducing viruses in lungs, pre-exposure intranasal B8-dIgA1 or B8-dIgA2 led to 81-fold more infectious viruses and severer damage in NT than placebo. Virus-bound B8-dIgA1 and B8-dIgA2 could engage CD209 as an alternative receptor for entry into ACE2-negative cells and allowed viral cell-to-cell transmission. Cryo-EM revealed B8 as a class II neutralizing antibody binding trimeric RBDs in 3-up or 2-up/1-down conformation. Therefore, RBD-specific neutralizing dIgA engages an unexpected action for enhanced SARS-CoV-2 nasal infection and injury in Syrian hamsters.

A molecularly engineered, broad-spectrum anti-coronavirus lectin inhibits SARS-CoV-2 and MERS-CoV infection in vivo (preprint)

Coronaviruses have repeatedly crossed species barriers to cause epidemics1. “Pan-coronavirus” antivirals targeting conserved viral components involved in coronavirus replication, such as the extensively glycosylated spike protein, can be designed. Here we show that the rationally engineered H84T-banana lectin (H84T-BanLec), which specifically recognizes high-mannose found on viral proteins but seldom on healthy human cells2, potently inhibits the highly virulent MERS-CoV, pandemic SARS-CoV-2 and its variants, and other human-pathogenic coronaviruses at nanomolar concentrations. MERS-CoV-infected human DPP4-transgenic mice treated by H84T-BanLec have significantly higher survival, lower viral burden, and reduced pulmonary damage. Similarly, prophylactic or therapeutic H84T-BanLec is effective against SARS-CoV-2 in hamsters. Importantly, intranasally and intraperitoneally administered H84T-BanLec are comparably effective. Time-of-drug-addition assay shows that H84T-BanLec targets virus entry. Real-time structural analysis with high-speed atomic force microscopy depicts multi-molecular associations of H84T-BanLec dimers with the SARS-CoV-2 spike trimer. Single-molecule force spectroscopy demonstrates binding of H84T-BanLec to multiple SARS-CoV-2 spike mannose sites with high affinity, and that H84T-BanLec competes with SARS-CoV-2 spike for binding to cellular ACE2. Modelling experiments identify distinct high-mannose glycans in spike recognized by H84T-BanLec. The multiple H84T-BanLec binding sites on spike likely account for the activity against SARS-CoV-2 variants and the lack of resistant mutants. The broad-spectrum H84T-BanLec should be clinically evaluated in respiratory viral infections including COVID-19.

Cross-linking peptide and repurposed drugs inhibit both entry pathways of SARS-CoV-2 (preprint)

So far, effective antivirals have not been widely available for treating COVID-19. In this study, we identify a dual-functional cross-linking peptide 8P9R which can inhibit the two entry pathways (endocytic pathway and TMPRSS2-mediated surface pathway) of SARS-CoV-2 in cells. The endosomal acidification inhibitors (8P9R and chloroquine) can synergistically enhance the activity of arbidol, a spike-ACE2 fusion inhibitor, against SARS-CoV-2 and SARS-CoV in cells. In vivo studies indicate that 8P9R or the combination of repurposed drugs (arbidol, chloroquine and camostat which is a TMPRSS2 inhibitor), simultaneously interfering with the two entry pathways of coronavirus, can significantly suppress SARS-CoV-2 replication in hamsters and SARS-CoV in mice. Here, we use drug combination (arbidol, chloroquine, and camostat) and a dual-functional 8P9R to demonstrate that blocking the two entry pathways of coronavirus can be a promising and achievable approach for inhibiting SARS-CoV-2 replication in vivo. Cocktail therapy of these drug combinations should be considered in treatment trials for COVID-19.