Biology subjects

Mok, C. K.-P.

Publications and source records attributed to Mok, C. K.-P..

5 recordsLinked to original sources

bioRxiv2026

Somatic evolution of a cross-reactive germline antibody that expands its breadth to neutralize new SARS-CoV-2 variants

Rapid antigenic drift of the SARS-CoV-2 receptor-binding domain (RBD) underlies immune escape and continues to challenge the durability of antibody-mediated protection. Among the major classes of RBD-directed antibodies, germline-encoded IGHV3-53 responses are highly potent against early SARS-CoV-2 variants but are generally compromised by Omicron-associated mutations. Here, we identify an intrinsically cross-reactive IGHV3-53 germline antibody that recognizes multiple pre-Omicron variants, including SARS-CoV-2 wild-type, Alpha, and Delta. Notably, we demonstrate that targeted somatic evolution can further expand this breadth to overcome the immune escape of different Omicron variants. Guided by integrated structural and sequence analyses, we introduce four somatic mutations (G26E, T28I, S53P, and Y58F) into the germline antibody, resulting in markedly enhanced binding and neutralization of Omicron BA.1, BA.2, and BA.4/5. High-resolution crystal structures reveal that these mutations re-establish critical interactions disrupted by substitutions on Omicron RBD and optimize affinity at a remodeled epitope interface. Collectively, our findings delineate a structural and mechanistic pathway through which an inherently cross-reactive germline antibody lineage can be adaptively refined to counter highly divergent SARS-CoV-2 variants. This work highlights the underappreciated breadth encoded within the naive B-cell repertoire and provides a conceptual framework for engineering and eliciting antibody responses resilient to future antigenic drift.

immunology↗

bioRxiv2025

Evolution of antibody cross-reactivity to influenza H5N1 neuraminidase from an N2-specific germline

The ongoing spread of highly pathogenic avian influenza H5N1 clade 2.3.4.4b virus in animals and its occasional spillover to humans have raised concerns about a potential H5N1 pandemic. Although recent studies have shown that pre-existing human antibodies can recognize H5N1 neuraminidase, the molecular basis of how this cross-reactivity develops remains poorly understood. In this study, we used a phage display antibody library derived from 245 healthy donors to isolate an antibody, HB420, that cross-reacts with neuraminidases of human H3N2 and avian H5N1 clade 2.3.4.4b viruses and confers protection in vivo. Cryo-EM analysis reveals that HB420 targets the neuraminidase active site by mimicking sialic acid binding through a single Asp residue. Furthermore, the inferred germline of HB420 is N2-specific but acquires cross-reactivity to H5N1 neuraminidase through somatic hypermutation. Overall, our findings provide insights into how neuraminidase antibody evolves breadth, which has important implications for the development of broadly protective influenza vaccines.

immunology↗

bioRxiv2023

Predictive evolutionary modelling for influenza virus by site-based dynamics of mutations

A predictive evolutionary model was developed to forecast representative influenza viral strains and select vaccine strains for upcoming epidemic seasons. Influenza virus continuously evolves to escape human adaptive immunity and generates seasonal epidemics. A computational approach beth-1 that models site-wise mutation dynamics demonstrated remarkable matching of predicted strains to the circulating viruses in subsequent seasons for the influenza A(H1N1)pdm09 and A(H3N2) viruses in both retrospective and prospective validations. The method offers a promising and ready-to-use tool to facilitate vaccine strain selection for the influenza virus, achieved by capturing heterogeneous evolutionary dynamics over genome space-time and linking molecular variants to population immune response. One-Sentence SummaryA computational model predicts virus evolution and facilitates vaccine strain selection for the influenza virus

evolutionary biology↗

bioRxiv2023

Mutation nsp6 L232F associated with MERS-CoV zoonotic transmission confers higher viral replication in human respiratory tract cultures ex-vivo

Middle East respiratory syndrome coronavirus (MERS-CoV) causes zoonotic disease. Dromedary camels are the source of zoonotic infection. We identified a mutation of amino acid leucine to phenylalanine in the codon 232 position of the non-structural protein 6 (nsp6) (nsp6 L232F) that is repeatedly associated with zoonotic transmission. We generated a pair of isogenic recombinant MERS-CoV with nsp6 232L and 232F residues, respectively, and showed that the nsp6 L232F mutation confers higher replication competence in ex-vivo culture of human nasal and bronchial tissues and in lungs of mice experimentally infected in-vivo. Mechanistically, the nsp6 L232F mutation appeared to modulate autophagy and was associated with higher exocytic virus egress, while innate immune responses and zippering activity of the endoplasmic reticulum remained unaffected. Our study suggests that MERS-CoV nsp6 may contribute to viral adaptation to humans. This highlights the importance of continued surveillance of MERS-CoV in both camels and humans. ImportanceViral host adaptation plays an important role in zoonotic transmission of coronaviruses. For MERS-CoV that widely circulates in dromedary camels from Arabian Peninsula, camel-to human transmissions are ongoing, raising the possibility of human adaptive evolution for MERS-CoV. Here, we analysed MERS-CoV sequences and identified an amino acid mutation L232F in nsp6 to occur repeatedly in human MERS-CoV over the years since the first outbreak in 2012. We found the nsp6 L232F confers increase viral replication in-vitro, in ex-vivo upper human respiratory tract cultures and in mice, using a reverse genetics approach. Our results showed the nsp6 L232F may be advantageous for MERS-CoV to replicate in humans. This study highlighted a human adaptation of MERS-CoV and a need for continued surveillance of MERS-CoV to identify any further adaptations in humans, which may be relevant to the pandemic potential of MERS-CoV.

microbiology↗

bioRxiv2019

OTUB1 is a key regulator of RIG-I dependent immune signalling and is targeted for proteasomal degradation by influenza A NS1

Deubiquitylases (DUBs) regulate critical signaling pathways at the intersection of host innate immunity and viral pathogenesis. Although RIG-I activation is heavily dependent on ubiquitylation, DUBs that regulate this pathway have not been identified. Using a ubiquitin C-terminal electrophile, we profiled DUBs that function during influenza A virus (IAV) infection, and isolated OTUB1 as a key regulator of RIG-I dependent antiviral responses. OTUB1 was interferon-inducible, and interacted with RIG-I, viral PB2 and NS1. Upon infection, OTUB1 relocalised from the nucleus to mitochondrial membranes, and activated the RIG-I signaling complex via hydrolysis of K48 polyubiquitin chains and by forming a repressive complex with UBCH5c. Using a reconstituted system composed of in vitro translated [35S]IRF3, purified RIG-I, mitochondrial membranes and cytosol expressing OTUB1 variants, we recapitulated the mechanism of OTUB1-dependent RIG-I activation. A wide range of IAV NS1 proteins triggered proteasomal degradation of OTUB1, thereby antagonizing the RIG-I signaling cascade and antiviral responses.\n\nHighlightsO_LIOTUB1 is induced during influenza A virus infections in an IFN-I dependent manner\nC_LIO_LIOTUB1 regulates the RIG-I complex by hydrolysing K48-linked polyubiquitin chains and by sequestering UBCH5c to prevent K48 polyubiquitylation\nC_LIO_LIOptimal K63 versus K48 polyubiquitin chain concentrations determine RIG-I activation\nC_LIO_LIInfluenza NS1 targets OTUB1 for proteasomal degradation\nC_LI

biochemistry↗