Advancements in organs-on-chips technology for viral disease and anti-viral research

Disease models that can accurately recapitulate human pathophysiology during infection and clinical response to antiviral therapeutics are still lacking, which represents a major barrier in drug development. The emergence of human Organs-on-a-Chip that integrated microfluidics with three-dimensional (3D) cell culture, may become the potential solution for this urgent need. Human Organs-on-a-Chip aims to recapitulate human pathophysiology by incorporating tissue-relevant cell types and their microenvironment, such as dynamic fluid flow, mechanical cues, tissue–tissue interfaces, and immune cells to increase the predictive validity of in vitro experimental models. Human Organs-on-a-Chip has a broad range of potential applications in basic biomedical research, preclinical drug development, and personalized medicine. This review focuses on its use in the fields of virology and infectious diseases. We reviewed various types of human Organs-on-a-Chip-based viral infection models and their application in studying viral life cycle, pathogenesis, virus-host interaction, and drug responses to virus- and host-targeted therapies. We conclude by proposing challenges and future research avenues for leveraging this promising technology to prepare for future pandemics.

Cross-reaction of current available SARS-CoV-2 MAbs against the pangolin-origin coronavirus GX/P2V/2017.

Since the identification of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiological agent of COVID-19, multiple SARS-CoV-2-related viruses have been characterized, including pangolin-origin GD/1/2019 and GX/P2V/2017. Our previous study indicated that both viruses have the potential to infect humans. Here, we find that CB6 (commercial name etesevimab), a COVID-19 therapeutic monoclonal antibody (MAb) developed by our group, efficiently inhibits GD/1/2019 but not GX/P2V/2017. A total of 50 SARS-CoV-2 MAbs divided into seven groups based on their receptor-binding domain (RBD) epitopes, together with the COVID-19 convalescent sera, are systematically screened for their cross-binding and cross-neutralizing properties against GX/P2V/2017. We find that GX/P2V/2017 displays substantial immune difference from SARS-CoV-2. Furthermore, we solve two complex structures of the GX/P2V/2017 RBD with MAbs belonging to RBD-1 and RBD-5, providing a structural basis for their different antigenicity. These results highlight the necessity for broad anti-coronavirus countermeasures and shed light on potential therapeutic targets.

Molecular basis of cross-species ACE2 interactions with SARS-CoV-2-like viruses of pangolin origin.

Pangolins have been suggested as potential reservoir of zoonotic viruses, including SARS-CoV-2 causing the global COVID-19 outbreak. Here, we study the binding of two SARS-CoV-2-like viruses isolated from pangolins, GX/P2V/2017 and GD/1/2019, to human angiotensin-converting enzyme 2 (hACE2), the receptor of SARS-CoV-2. We find that the spike protein receptor-binding domain (RBD) of pangolin CoVs binds to hACE2 as efficiently as the SARS-CoV-2 RBD in vitro. Furthermore, incorporation of pangolin CoV RBDs allows entry of pseudotyped VSV particles into hACE2-expressing cells. A screen for binding of pangolin CoV RBDs to ACE2 orthologs from various species suggests a broader host range than that of SARS-CoV-2. Additionally, cryo-EM structures of GX/P2V/2017 and GD/1/2019 RBDs in complex with hACE2 show their molecular binding in modes similar to SARS-CoV-2 RBD. Introducing the Q498H substitution found in pangolin CoVs into the SARS-CoV-2 RBD expands its binding capacity to ACE2 homologs of mouse, rat, and European hedgehog. These findings suggest that these two pangolin CoVs may infect humans, highlighting the necessity of further surveillance of pangolin CoVs.