George F. Gao’s research while affiliated with Beijing Film Academy and other places

The continuous evolution of SARS‐CoV‐2 through accumulating mutations, combined with the persistent risk of zoonotic sarbecovirus transmission events, highlights the critical demand for broadly protective vaccines. Building on our previous findings that a heterodimeric receptor‐binding domain (RBD) design substantially improves cross‐reactive immunogenicity in vaccine candidates, we propose this strategy as a foundation for developing pan‐sarbecovirus vaccines with cross‐neutralizing capacity against diverse and emerging variants. In this study, we developed a sarbecovirus immunogen, utilizing a heterodimeric strategy incorporating the RBDs from both SARS‐CoV and SARS‐CoV‐2. Pseudovirus neutralization assays revealed that mice immunized with the SARS‐CoV‐2 prototype (PT)‐SARS‐CoV heterodimer (PT‐SARS) developed 39.9‐ to 305.6‐fold higher neutralizing antibody (NAb) titers against SARS‐CoV‐2 sub‐variants compared to the SARS‐CoV RBD homodimer (SARS‐SARS). Furthermore, PT‐SARS elicited 17.6‐ and 31.2‐fold enhanced neutralization against WIV1 and SARS‐CoV, respectively, relative to the SARS‐CoV‐2 PT homodimer (PT‐PT). To address evolving Omicron sub‐variants, we further updated BA.1‐SARS and BA.2‐SARS immunogens. Notably, BA.2‐SARS exhibited a 6.2‐fold increase in neutralizing potency against BA.2.86 compared to PT‐SARS. Crucially, the heterodimeric immunogen induced balanced and broadly reactive NAbs against multiple sarbecoviruses, including RaTG13, Pangolin GD, SARS‐CoV, and SARS‐CoV‐2 variants/sub‐variants, demonstrating its potential as a sarbecovirus immunogen candidate.

The Mpox virus (MPXV) is an orthopoxvirus that caused a global outbreak in 2022. The poxvirus DNA polymerase complex is responsible for the replication and integrity of the viral genome; however, the molecular mechanisms underlying DNA replication fidelity are still unclear. In this study, we determined the cryoelectron microscopy (cryo-EM) structures of the MPXV F8–A22–E4 polymerase holoenzyme in its editing state, in complex with mismatched primer–template DNA and DNA containing uracil deoxynucleotide. We showed that the MPXV polymerase has a similar replication-to-edit transition mechanism to proofread the mismatched nucleotides like the B-family DNA polymerases of other species. The unique processivity cofactor A22–E4 undergoes conformational changes in different working states and might affect the proofreading process. Moreover, we elucidated the base excision repair (BER) function of E4 as a uracil-DNA glycosylase and the coupling mechanism of genome replication and BER, characteristic of poxviruses. Our findings greatly enhance our molecular understanding of DNA replication fidelity of orthopoxviruses and will stimulate the development of broad-spectrum antiviral drugs.

Impact statement This study identifies avian tuberculosis as a potential cause of mass mortality in wild migratory birds in Inner Mongolia, China. Combining meta‐transcriptomic sequencing and histopathological analysis, it reveals one of the rare instances of tuberculosis‐associated outbreaks in avian populations. These findings underscore the importance of surveillance on wildlife diseases to mitigate the risk of interspecies transmission of the disease associated pathogens and their broader implications for biodiversity and public health.

Recent avian-origin H3N8 influenza A virus (IAV) that have infected humans pose a potential public health concern. Alterations in the viral surface glycoprotein, hemagglutinin (HA), are typically required for IAVs to cross the species barrier for adaptation to a new host, but whether H3N8 has adapted to infect humans remains elusive. The observation of a degenerative codon in position 228 of HA in human H3N8 A/Henan/4-10/2022 protein sequence, which could be residue G or S, suggests a dynamic viral adaptation for human infection. Previously, we found this human-isolated virus has shown the ability to transmit between ferrets via respiratory droplets, with the HA-G228S substitution mutation emerging as a critical determinant for the airborne transmission of the virus in ferrets. Here, we investigated the receptor-binding properties of these two H3N8 HAs. Our results showed H3N8 HAs have dual receptor-binding properties with a preference for avian receptor binding, and G228S slightly increased binding to human receptors. Cryo-electron microscopy structures of the two H3N8 HAs with avian and human receptor analogs revealed the basis for dual receptor binding. Mutagenesis studies reveal that the Q226L mutation shifts H3N8 HA’s receptor preference from avian to human, while the G228S substitution enhances binding to both receptor types. H3N8 exhibits distinct antigenic sites compared to H3N2, prompting concerns regarding vaccine efficacy. These findings suggest that the current H3N8 human isolates are yet to adapt for efficient human-to-human transmission and further continuous surveillance should be implemented. IMPORTANCE Influenza virus transmission remains a public health concern currently. H3N8 subtype influenza A viruses infect humans and their HAs acquire the ability to bind to both human and avian receptors, posing a threat to human health. We have solved and analyzed the structural basis of dual receptor binding of recently human-infecting H3N8 HA, and we demonstrate that the G228S enhances human receptor binding and adaptation. We also found that HN/4-10 H3N8 HA has distinct antigenic sites, which challenges vaccine efficacy. Taken together, our work is critical to the prevention and control of human H3 influenza virus infection.

The genome‐based surveillance of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) in the past nearly 5 years since its emergence has refreshed our understanding of virus evolution, especially on convergent co‐evolution with the host. SARS‐CoV‐2 evolution has been characterized by the emergence of sets of mutations that affect the functional properties of the virus by altering its infectivity, virulence, transmissibility, and interactions with host immunity. This poses a huge challenge to global prevention and control measures based on drug treatment and vaccine application. As one of the key evasion strategies in response to the immune profile of the human population, there are overwhelming amounts of evidence for the reduced antibody neutralization of SARS‐CoV‐2 variants. Additionally, data also suggest that the levels of CD4⁺ and CD8⁺ T‐cell responses against variants or sub‐variants decrease in the populations, although non‐negligible cross‐T‐cell responses are maintained. Herein, from the perspectives of structural immunology, we outline the characteristics and mechanisms of the T cell and antibody responses to SARS‐CoV and its variants/sub‐variants. The molecular bases for the impact of the immune escaping variants on the interaction of the epitopes with the key receptors in adaptive immunity, that is, major histocompatibility complex (MHC), T‐cell receptor (TCR), and antibody are summarized and discussed, the knowledge of which will widen our understanding of this pandemic‐threatening virus and assist the preparedness for Pathogen X in the future.

Although antibody escape is observed in emerging severe acute respiratory syndrome coronavirus 2 variants, T cell escape, especially after the global circulation of BA.2.86/JN.1, is unexplored. Here we demonstrate that T cell evasion exists in epitope hotspots spanning BA.2.86/JN.1 mutations. The newly emerging Q229K at this conserved nucleocapsid protein site impairs HLA-A2 epitope hotspot recognition. The association between HLA-A24 convalescents and T cell immune escape points to the spike (S) protein epitope S448–456NYNYLYRLF, with multiple mutations from Delta to JN.1, including L452Q, L452R, F456L, N450D and L452W, and N450D, L452W and L455S. A cliff drop of immune responses was observed for S448–456NYNYRYRLF (Delta/BA.5.2) and S448–456NYDYWYRSF (JN.1), but with immune preservation of S448–456NYDYWYRLF (BA.2.86). Structural analyses showed that hydrophobicity exposure determines the pronounced escape of L452R and L455S mutants, which was further confirmed by T cell receptor binding. This study highlights the characteristics and molecular mechanisms of the T cell immune escape for JN.1 and provides new insights into understanding the dominant circulation of variants, from the viewpoint of cytotoxic T cell evasion.