P01: 

Name: Dr Hinson Pak-Hin Cheung

Title: Generation and rescue of live attenuated spike knockout SARS-CoV-2 by transcomplementation reverse genetics

Abstract: Live attenuated vaccine (LAV) is one of the best vaccine types that can elicit close-to-natural immunity and memory. To generate LAV of SARS-CoV-2, one approach is to produce single cycle infectious SARS-CoV-2 mutants. Spike protein plays a critical role for SARS-CoV-2 to enter host cells by binding and recognising receptor protein ACE2. In the current study, we engineered SARS-CoV-2 genome to ablate spike protein expression by deleting spike gene. We found that spike knockout SARS-CoV-2 genome was ineffective in production of viral progeny. Extrinsic trans-complementation of spike protein rescued viral progeny production from spike knockout SARS-CoV-2 genome. We found that the spike reconstituted viral progeny, namely ΔS, cannot further propagate itself. Despite its incomplete viral life cycle, however, ΔS delivered its viral genome, expressed viral proteins properly and delivered its coated spike protein to the infected cells. We found that ΔS can be reconstituted with spike protein of either ancestral strain or the emerging Omicron strains. Therefore, our finding indicates spike knockout SARS- CoV-2 genome can be a versatile platform to produce live attenuated infectious ΔS coating with spike protein of different emerging SARS-CoV-2 strains.

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P02: 

Name: Mr Shaofeng Deng

Title: An intranasal influenza virus-vectored vaccine protects against SARS-CoV-2 variants in mice and Syrian hamsters

Abstract: Vaccination is the most effective means of alleviating COVID-19 disease burden, however, the intramuscular vaccine does not elicit sufficient local mucosal immunity in the respiratory tract, which is important for preventing the transmission of SARS-CoV-2.

This study reports an intranasally-administered virus-vectored SARS-CoV-2 vaccine candidate based on a live attenuated influenza virus with the NS1 gene deleted that expresses the RBD of SARS-CoV-2 spike protein, designated DelNS1-RBD4N-DAF, which induced high levels of neutralizing antibodies against variants and stimulated robust RBD-specific T cell responses in mice and hamsters. It also generally elicited effective cross-protection against challenge with SARS-CoV-2 variants and influenza virus in mice and hamsters, with superior activity to that of intramuscular injection of the BNT162b2 mRNA vaccine.

In conclusion, the DelNS1-RBD4N-DAF vaccine platform can be used to make bivalent vaccines against both influenza and COVID-19 in response to dual circulation of seasonal influenza and SARS-CoV-2 in the future.

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P03: 

Name: Dr Sin-Yee Fung

Title: Exosomal ORF3a induces proinflammatory cytokine release in bystander macrophages

Abstract: Live attenuated vaccine (LAV) is one of the best vaccine types that can elicit close-to-natural immunity and memory. To generate LAV of SARS-CoV-2, one approach is to produce single cycle infectious SARS-CoV-2 mutants. Spike protein plays a critical role for SARS-CoV-2 to enter host cells by binding and recognising receptor protein ACE2. In the current study, we engineered SARS-CoV-2 genome to ablate spike protein expression by deleting spike gene. We found that spike knockout SARS-CoV-2 genome was ineffective in production of viral progeny. Extrinsic trans-complementation of spike protein rescued viral progeny production from spike knockout SARS-CoV-2 genome. We found that the spike reconstituted viral progeny, namely ΔS, cannot further propagate itself. Despite its incomplete viral life cycle, however, ΔS delivered its viral genome, expressed viral proteins properly and delivered its coated spike protein to the infected cells. We found that ΔS can be reconstituted with spike protein of either ancestral strain or the emerging Omicron strains. Therefore, our finding indicates spike knockout SARS- CoV-2 genome can be a versatile platform to produce live attenuated infectious ΔS coating with spike protein of different emerging SARS-CoV-2 strains.

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P04: 

Name: Dr Bodan Hu

Title: The study on spike interaction with cholesterol in spike-mediated membrane fusion and entry of SARS-CoV-2

Abstract: Cholesterol, a major lipid component of host cell membrane, plays an important role in replication of enveloped viruses, such as influenza virus, HIV, HCV and SARS-CoV-2, mainly in virus entry and assembly. Spike protein of coronaviruses mediated receptor binding and membrane fusion. Through amino acid sequence alignment of spike protein of coronaviruses, we identified a conserved cholesterol consensus motif (CCM) in the transmembrane region. The CuAAC click assay with a photoactivable cholesterol revealed that spike, especially S2, indeed interacts with cholesterol. Mutations in the CCM reduced photocholesterol incorporation into S2. Spike-mediated cell-cell fusion and pseudovirus entry are impaired for spikes with double mutations in the CCM. Choelsterol analogues including ergosterol and lanosterol inhibit authentic SARS-CoV-2 entry. In summary, cholesterol interacts with spike, which is critical for spike-mediated fusion and virus entry. 

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P05: 

Name: Mr Chengxi Huang

Title: A transgenic mouse model facilitating the pathogenesis study for Enterovirus D68

Abstract: Enterovirus D68 (EV-D68) is a reemerging pathogen, which causes severe respiratory symptoms globally. Acute flaccid myelitis (AFM), a polio-like condition, can be found in infected children. Although adults can be infected by EV-D68, normally do not develop symptoms or only develop mild symptoms. Currently, there is no specific treatment or vaccine for EV-D68 infection, moreover, its association with neurological diseases is yet explained due to the vacancy of virus-host interaction and EV-D68 pathogenicity. Researchers have developed various animal models to investigate EV- D68, however, there are significant limitations in present models. Current mouse models focus on neonatal mice or immunocompromised mice, which cannot fully represent physiologically relevant infection situations. Thus, a transgenic mouse model was constructed by introducing human tryptophanyl-tRNA synthetase (hWARS) gene into the mouse genome. Limb paralysis could be observed in not only EV-D68-infected neonatal but also adult transgenic mice. Tissue histological stain revealed the inflammation and tissue damages. Viral gene and protein were further detected in mouse tissues by quantitative PCR, western blot and immunofluorescent staining. Our study established a platform to study EV-D68 pathogenesis and evalute candidate treatments or vaccines.

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P06: 

Name: Dr Xiner Huang

Title: Investigation on Broad Spectrum Antiviral Targets through Epigenetic Regulation

Abstract: Epigenetic regulation refers to the manipulation of gene expression patterns through chromatin remodeling including DNA methylation, histone modification, and chromatin looping. In recent years, epigenetic modulators have been revealed to play key regulatory roles in innate immune responses. To identify epigenetic factors that may regulate virus replication through modulating the host immune response, we performed a knockdown screen on ZIKV replication using an epigenetic siRNA library that targeted 835 genes encoding for histone and DNA modification factors. Our siRNA screen identified a number of candidates that simultaneously upregulated type-I antiviral interferon response while limiting ZIKV replication. Downstream experiments using small molecule inhibitors similarly suggested a role of the prioritized candidate, RING1A and its associated complex, polycomb repressive complex 1 (PRC1), in ZIKV replication. We further demonstrated that RING1A and PRC1 inhibition similarly limited the replication of enterovirus (EV-71) and coronaviruses (SARS-CoV-2, SARS-CoV-1, MERS-CoV), highlighting the potential of RING1A/PRC1 inhibition as a novel strategy against the infection of emerging viral pathogens. We further investigated the mechanism of RING1A/PRC1 inhibition on virus replication in vitro and in vivo, which reveals insight into the intersection of epigenetic regulation and virus infection and provides new targets to our current repertoire of antiviral strategies.

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P07: 

Name: Mr Jonathan Daniel Ip

Title: Intrahost SARS-CoV-2 virus evolution during prolonged infection of 3 Omicron patients

Abstract: It is well known that SARS-CoV-2, just like other viruses, can acquire mutations during infection. While many pieces of research have been published regarding the pathological aspect of SARS-CoV-2 prolonged infection. Transient mutations and mutation rates during the infection period were limited, especially for the Omicron variant. In our study, we investigated 3 patients who has been infected for 100 days and collected at least 10 time points each during the whole study. The aim of the study is to understand the evolution of the Omicron strain in the 3 patients in terms of mutation rate and the transient mutations that emerged. The finding of this study can increase our understanding of intrahost variations of Omicron during prolonged infection, for example, mutation rate at different periods of infection, and common mutations emerged in different patients. The findings can provide a detailed description of how different is intrahost evolution is different in Pre-Omicron and Omicron-infected patients and address the question of how to distinguish intrahost variation and prolonged infection.

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P08:

Name: Dr Cun Li

Title: Human Respiratory Organoids Reveal Escalating Replicative Fitness of SARS-CoV-2 Omicron Variants

Abstract: The high transmissibility of SARS-CoV-2 Omicron subvariants was generally ascribed to immune escape. It remained unclear whether the emerging variants have gradually acquired replicative fitness in human respiratory epithelial cells. We sought to evaluate the replicative fitness of BA.5 and earlier variants in physiologically-active respiratory organoids. BA.5 exhibited a dramatically increased replicative capacity and infectivity than B.1.1.529 and an ancestral strain WT in human nasal and airway organoids. BA.5 spike pseudovirus showed a significantly higher entry efficiency than that carrying WT or B.1.1.529 spike. Notably, we observed prominent syncytium formation in BA.5-infected nasal and airway organoids, albeit elusive in WT- and B.1.1.529- infected organoids. BA.5 spike-triggered syncytium formation was verified by lentiviral overexpression of spike in nasal organoids. Moreover, BA.5 replicated modestly in alveolar organoids, with a significantly lower titer than B.1.1.529 and WT. Collectively, the higher entry efficiency and fusogenic activity of BA.5 spike potentiated viral spread through syncytium formation in the human airway epithelium, leading to enhanced replicative fitness and immune evasion, whereas the attenuated replicative capacity of BA.5 in the alveolar organoids may account for its benign clinical manifestation.

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P09:

Name: Ms Mengxian Luo; Dr Runhong Zhou; Prof Zhiwei Chen

Title: Characterization of neutralizing antibody from patients with SARS-CoV-2 breakthrough infectionAbstract: Increasing spread by SARS-CoV-2 Omicron variants challenges existing vaccines and broadly reactive neutralizing antibodies (bNAbs) against COVID-19. Here we determine the diversity, potency, breadth and structural insights of bNAbs derived from memory B cells of BNT162b2-vaccinee after homogeneous Omicron BA.1 breakthrough infection. The infection activates diverse memory B cell clonotypes for generating potent class I/II and III bNAbs with new epitopes mapped to the receptor- binding domain (RBD). The top eight bNAbs neutralize wildtype and BA.1 potently but display divergent IgH/IgL sequences and neuralization profiles against other variants of concern (VOCs). Two of them (P2D9 and P3E6) belonging to class III NAbs display comparable potency against BA.4/BA.5, although structural analysis reveals distinct modes of action. P3E6 neutralizes all variants tested through a unique bivalent interaction with two RBDs. Our findings provide new insights into hybrid immunity on BNT162b2-induced diverse memory B cells in response to Omicron breakthrough infection for generating diverse bNAbs with distinct structural basis.

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P10:

Name: Mr Chon Phin Ong

Title: Combinatorial attenuation strategy against SARS-CoV-2Abstract: Since the declaration of COVID-19, millions of people worldwide have been infected by SARS-CoV-2. Through existing vaccines, severe viral pathogenicity and mortality rate was greatly averted. However, the virus has persisted due to its adaptation mutation capability. Live attenuated vaccines have proved its effectiveness in the eradication of diseases previously, owing to its robust and long-lasting immunogenicity. We have successfully created a 2’-O-methyltransferase-deficient mutant virus, designated d16, that was shown to be attenuated in vitro and in vivo. Besides that, induction of mucosal immunity has hindered viral transmission upon reinfection in d16-vaccinated Syrian hamsters. Thereonafter, we aim to further attenuate d16 to improve its safety. Particularly, we inverted the ORF3a sequence of SARS-CoV-2 through recombineering system, designated d16Δ3a. Our in vitro and in vivo results revealed that d16Δ3a is viable and further attenuated. Intranasal vaccination with d16Δ3a also protected Syrian hamsters against prominent Delta and Omicron variants, BA.1 and XBB.1. With our combinatorial strategy to attenuate the virus, our subsequent phase involves replacing the original to Omicron-specific spike to assure greatest immunogenicity and hopefully putting an end to this disease.

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P11:

Name: Ms Cynthia Cheuk-Ying Shum

Title: A novel broad spectrum antiviral target at the interface between the propeptide and catalytic domain of Cathepsin L which is also active against SARS-CoV-2Abstract: In the past two decades, three human coronaviruses (HCoVs), including severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV) and SARS-like coronavirus (SARS-CoV-2) have emerged. The current pandemic outbreak of SARS-CoV-2 poses a hazard to public health, despite the limited availability of clinically-approved antiviral treatments. To fight against CoV infection, we herein identify three broad-spectrum CoV inhibitors CA- 616, CA-607 and CA-603 through a chemical compound library screening against SARS- CoV and MERS-CoV. We find that the compounds specifically inhibit CoV at low micromolar level, and further confirm their inhibition on the viral entry. Next, through the immunofluorescence assay and the polykaryon formation assay, the compounds inhibit virus-cell fusion in endosomes, which is contributed by inhibiting the host protease cathepsin L (CTSL) to block S protein activation. More specifically, our compounds preferentially target the full-length CTSL to inhibit its autoactivation, in which its N-terminal propeptide is cleaved by itself to become an active protease. Through molecular docking analysis and epitope mapping, we illustrate the potential interacting interfaces between the compounds and the CTSL propeptide. Our research has provided concrete biological and mechanistic insights for the development of a novel class of CTSL inhibitors as potential broad-spectrum CoV entry inhibitors.

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P12:

Name: Mr Xiankun Wang

Title: Cross-linking peptide showing broad antiviral activity against human adenovirusesAbstract: Human adenoviruses (HAdVs) are ubiquitous human pathogens with various tropisms causing numerous outbreaks, especially potentially involved in acute hepatitis of unknown aetiology in children reported in Scotland in April 2022, since the viral identification in 1953 from children adenoids. Mild and self-limiting infection normally occurs in the immunocompetent patients. However, severe and even fatal damages can be life-threatening for the immunocompromised individuals or children with strongly impaired immune responses, especially in patients with Acquired Immunodeficiency Syndrome or organ transplants. Although HAdVs pose a huge threat to the public health, there is no U.S. Food and Drug Administration approved drugs for the HAdVs infection. In this study, a cross-linking antiviral peptide 4P can be a forceful candidate, which has been proved to show significant antiviral effect against different subtype adenoviruses without obvious cytotoxicity in vitro and in vivo through inhibiting viral endosomal escape in endocytic pathway.

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P13:

Name: Dr Jack Chun-Kit Yuen

Title: A pan-Sarbecovirus nasal vaccine composing of a live-attenuated SARS-CoV-2 virusAbstract: Coronaviruses possess a continuous threat to humans. While the SARS-CoV-2 that caused the COVID-19 pandemic continues to circulate globally, novel deadly coronaviruses could emerge at any unpredictable moment. A broadly protective vaccine effective against SARS-CoV-2 and future coronaviruses is therefore desired. In this study, we rationally designed a pan-Sarbecovirus nasal vaccine composing of a live- attenuated SARS-CoV-2 virus. Envelope gene of the virus was deleted to blunt the multiple-round viral replication. A gene coding for interferon beta was further inserted into the viral genome to enhance the immune response elicited. In a lethal mouse infection model, the live vaccine demonstrated complete protection against all tested SARS-CoV-2 variants. In a hamster transmission model, it also protected all animals from transmission-acquired SARS-CoV-2 infection. Importantly, the vaccine protected both mice and hamsters from SARS-CoV-1 infection, demonstrating its effectiveness against Sarbecoviruses other than SARS-CoV-2. Taken together, our vaccine could be a plausible pan-Sarbecovirus vaccine candidate for the preparedness of future coronavirus outbreaks, and therefore warrants further studies and clinical trials.

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P14:

Name: Dr Terrence Tsz-Tai Yuen

Title: Vaccine-induced protection against SARS-CoV-2 requires IFN-γ-driven cellular immune response

Abstract: The overall success of worldwide mass vaccination in limiting the negative effect of the COVID-19 pandemics is inevitable, however, recent SARS-CoV-2 variants of concern, especially Omicron and its sub-lineages, efficiently evade humoral immunity mounted upon vaccination or previous infection. Thus, it is an important question whether these variants, or vaccines against them, induce anti-viral cellular immunity. Here we show that the mRNA vaccine BNT162b2 induces robust protective immunity in K18-hACE2 transgenic B-cell deficient (μMT)mice.We further demonstrate that the protection is attributed to cellular immunity depending on robust IFN-γ production. Viral challenge with SARS-CoV-2 Omicron BA.1 and BA.5.2 sub-variants induce boosted cellular responses in vaccinated μMTmice,which highlights the significance of cellular immunity against the ever-emerging SARS-CoV-2 variants evading antibodymediated immunity. Our work, by providing evidence that BNT162b2 can induce significant protective immunity in mice that are unable to produce antibodies, thus highlights the importance of cellular immunity in the protection against SARS-CoV-2.

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