Xuanling Shi

Bio: Xuanling Shi is an academic researcher from Tsinghua University. The author has contributed to research in topics: Antibody & Epitope. The author has an hindex of 20, co-authored 58 publications receiving 5535 citations. Previous affiliations of Xuanling Shi include University of Shanghai for Science and Technology & Center for Infectious Disease Research and Policy.

Structure of the SARS-CoV-2 spike receptor-binding domain bound to the ACE2 receptor.

Abstract: A new and highly pathogenic coronavirus (severe acute respiratory syndrome coronavirus-2, SARS-CoV-2) caused an outbreak in Wuhan city, Hubei province, China, starting from December 2019 that quickly spread nationwide and to other countries around the world1–3. Here, to better understand the initial step of infection at an atomic level, we determined the crystal structure of the receptor-binding domain (RBD) of the spike protein of SARS-CoV-2 bound to the cell receptor ACE2. The overall ACE2-binding mode of the SARS-CoV-2 RBD is nearly identical to that of the SARS-CoV RBD, which also uses ACE2 as the cell receptor4. Structural analysis identified residues in the SARS-CoV-2 RBD that are essential for ACE2 binding, the majority of which either are highly conserved or share similar side chain properties with those in the SARS-CoV RBD. Such similarity in structure and sequence strongly indicate convergent evolution between the SARS-CoV-2 and SARS-CoV RBDs for improved binding to ACE2, although SARS-CoV-2 does not cluster within SARS and SARS-related coronaviruses1–3,5. The epitopes of two SARS-CoV antibodies that target the RBD are also analysed for binding to the SARS-CoV-2 RBD, providing insights into the future identification of cross-reactive antibodies. High-resolution crystal structures of the receptor-binding domain of the spike protein of SARS-CoV-2 and SARS-CoV in complex with ACE2 provide insights into the binding mode of these coronaviruses and highlight essential ACE2-interacting residues.

Human neutralizing antibodies elicited by SARS-CoV-2 infection.

Abstract: The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) presents a global health emergency that is in urgent need of intervention1-3. The entry of SARS-CoV-2 into its target cells depends on binding between the receptor-binding domain (RBD) of the viral spike protein and its cellular receptor, angiotensin-converting enzyme 2 (ACE2)2,4-6. Here we report the isolation and characterization of 206 RBD-specific monoclonal antibodies derived from single B cells from 8 individuals infected with SARS-CoV-2. We identified antibodies that potently neutralize SARS-CoV-2; this activity correlates with competition with ACE2 for binding to RBD. Unexpectedly, the anti-SARS-CoV-2 antibodies and the infected plasma did not cross-react with the RBDs of SARS-CoV or Middle East respiratory syndrome-related coronavirus (MERS-CoV), although there was substantial plasma cross-reactivity to their trimeric spike proteins. Analysis of the crystal structure of RBD-bound antibody revealed that steric hindrance inhibits viral engagement with ACE2, thereby blocking viral entry. These findings suggest that anti-RBD antibodies are largely viral-species-specific inhibitors. The antibodies identified here may be candidates for development of clinical interventions against SARS-CoV-2.

Structure of MERS-CoV spike receptor-binding domain complexed with human receptor DPP4.

Abstract: The spike glycoprotein (S) of recently identified Middle East respiratory syndrome coronavirus (MERS-CoV) targets the cellular receptor, dipeptidyl peptidase 4 (DPP4). Sequence comparison and modeling analysis have revealed a putative receptor-binding domain (RBD) on the viral spike, which mediates this interaction. We report the 3.0 A-resolution crystal structure of MERS-CoV RBD bound to the extracellular domain of human DPP4. Our results show that MERS-CoV RBD consists of a core and a receptor-binding subdomain. The receptor-binding subdomain interacts with DPP4 β-propeller but not its intrinsic hydrolase domain. MERS-CoV RBD and related SARS-CoV RBD share a high degree of structural similarity in their core subdomains, but are notably divergent in the receptor-binding subdomain. Mutagenesis studies have identified several key residues in the receptor-binding subdomain that are critical for viral binding to DPP4 and entry into the target cell. The atomic details at the interface between MERS-CoV RBD and DPP4 provide structural understanding of the virus and receptor interaction, which can guide development of therapeutics and vaccines against MERS-CoV infection.

Potent human neutralizing antibodies elicited by SARS-CoV-2 infection

Abstract: The pandemic caused by emerging coronavirus SARS-CoV-2 presents a serious global public health emergency in urgent need of prophylactic and therapeutic interventions. SARS CoV-2 cellular entry depends on binding between the viral Spike protein receptor-binding domain (RBD) and the angiotensin converting enzyme 2 (ACE2) target cell receptor. Here, we report on the isolation and characterization of 206 RBD-specific monoclonal antibodies (mAbs) derived from single B cells of eight SARS-CoV-2 infected individuals. These mAbs come from diverse families of antibody heavy and light chains without apparent enrichment for particular families in the repertoire. In samples from one patient selected for further analyses, we found coexistence of germline and germline divergent clones. Both clone types demonstrated impressive binding and neutralizing activity against pseudovirus and live SARS-CoV-2. However, the antibody neutralizing potency is determined by competition with ACE2 receptor for RBD binding. Surprisingly, none of the SARS CoV 2 antibodies nor the infected plasma cross-reacted with RBDs from either SARS CoV or MERS CoV although substantial plasma cross reactivity to the trimeric Spike proteins from SARS-CoV and MERS-CoV was found. These results suggest that antibody response to RBDs is viral species-specific while that cross-recognition target regions outside the RBD. The specificity and neutralizing characteristics of this plasma cross-reactivity requires further investigation. Nevertheless, the diverse and potent neutralizing antibodies identified here are promising candidates for prophylactic and therapeutic SARS-CoV-2 interventions.

Potent neutralization of MERS-CoV by human neutralizing monoclonal antibodies to the viral spike glycoprotein.

Abstract: The recently identified Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe and fatal acute respiratory illness in humans. However, no prophylactic and therapeutic agents specifically against MERS-CoV are currently available. Entry of MERS-CoV into target cells depends on binding of the receptor binding domain (RBD) of the viral envelope spike glycoprotein to the cellular receptor dipeptidyl peptidase 4 (DPP4). We report the isolation and characterization of two potent human RBD-specific neutralizing monoclonal antibodies (MERS-4 and MERS-27) derived from single-chain variable region fragments of a nonimmune human antibody library. MERS-4 and MERS-27 inhibited infection of both pseudotyped and live MERS-CoV with IC50 (half-maximal inhibitory concentration) at nanomolar concentrations. MERS-4 also showed inhibitory activity against syncytia formation mediated by interaction between MERS-CoV spike glycoprotein and DPP4. Combination of MERS-4 and MERS-27 demonstrated a synergistic effect in neutralization against pseudotyped MERS-CoV. Biochemical analysis indicated that MERS-4 and MERS-27 blocked RBD interaction with DPP4 on the cell surface. MERS-4, in particular, bound soluble RBD with an about 45-fold higher affinity than DPP4. Mutagenesis analysis suggested that MERS-4 and MERS-27 recognized distinct regions in RBD. These results suggest that MERS-4 and MERS-27 are RBD-specific potent inhibitors and could serve as promising candidates for prophylactic and therapeutic interventions against MERS-CoV infection.

Origin and evolution of pathogenic coronaviruses

Abstract: Severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) are two highly transmissible and pathogenic viruses that emerged in humans at the beginning of the 21st century. Both viruses likely originated in bats, and genetically diverse coronaviruses that are related to SARS-CoV and MERS-CoV were discovered in bats worldwide. In this Review, we summarize the current knowledge on the origin and evolution of these two pathogenic coronaviruses and discuss their receptor usage; we also highlight the diversity and potential of spillover of bat-borne coronaviruses, as evidenced by the recent spillover of swine acute diarrhoea syndrome coronavirus (SADS-CoV) to pigs. Coronaviruses have a broad host range and distribution, and some highly pathogenic lineages have spilled over to humans and animals. Here, Cui, Li and Shi explore the viral factors that enabled the emergence of diseases such as severe acute respiratory syndrome and Middle East respiratory syndrome.

Structural basis of receptor recognition by SARS-CoV-2.

Abstract: A novel severe acute respiratory syndrome (SARS)-like coronavirus (SARS-CoV-2) recently emerged and is rapidly spreading in humans, causing COVID-191,2. A key to tackling this pandemic is to understand the receptor recognition mechanism of the virus, which regulates its infectivity, pathogenesis and host range. SARS-CoV-2 and SARS-CoV recognize the same receptor—angiotensin-converting enzyme 2 (ACE2)—in humans3,4. Here we determined the crystal structure of the receptor-binding domain (RBD) of the spike protein of SARS-CoV-2 (engineered to facilitate crystallization) in complex with ACE2. In comparison with the SARS-CoV RBD, an ACE2-binding ridge in SARS-CoV-2 RBD has a more compact conformation; moreover, several residue changes in the SARS-CoV-2 RBD stabilize two virus-binding hotspots at the RBD–ACE2 interface. These structural features of SARS-CoV-2 RBD increase its ACE2-binding affinity. Additionally, we show that RaTG13, a bat coronavirus that is closely related to SARS-CoV-2, also uses human ACE2 as its receptor. The differences among SARS-CoV-2, SARS-CoV and RaTG13 in ACE2 recognition shed light on the potential animal-to-human transmission of SARS-CoV-2. This study provides guidance for intervention strategies that target receptor recognition by SARS-CoV-2. The crystal structure of the receptor-binding domain of the SARS-CoV-2 spike in complex with human ACE2, compared with the receptor-binding domain of SARS-CoV, sheds light on the structural features that increase its binding affinity to ACE2.

SARS and MERS: recent insights into emerging coronaviruses

Abstract: The emergence of Middle East respiratory syndrome coronavirus (MERS-CoV) in 2012 marked the second introduction of a highly pathogenic coronavirus into the human population in the twenty-first century. The continuing introductions of MERS-CoV from dromedary camels, the subsequent travel-related viral spread, the unprecedented nosocomial outbreaks and the high case-fatality rates highlight the need for prophylactic and therapeutic measures. Scientific advancements since the 2002-2003 severe acute respiratory syndrome coronavirus (SARS-CoV) pandemic allowed for rapid progress in our understanding of the epidemiology and pathogenesis of MERS-CoV and the development of therapeutics. In this Review, we detail our present understanding of the transmission and pathogenesis of SARS-CoV and MERS-CoV, and discuss the current state of development of measures to combat emerging coronaviruses.