Biology subjects

Mok, C. K.

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

4 recordsLinked to original sources

bioRxiv2025

A conserved long-range RNA interaction in SARS-CoV-2 recruits ADAR1 to enhance virus proliferation

Long-range RNA-RNA pairing impacts the genome structure and function of SARS-CoV-2 variants. To understand the structure and function relationships of different SARS-CoV-2 variants that have emerged during the COVID-19 pandemic, we performed high-throughput structure probing and modelling of the genomic structures of the wildtype (WT), Alpha, Beta, Delta and Omicron variants of SARS-CoV-2. We observed that genomes of SARS-CoV-2 variants are generally structurally conserved, and that single-nucleotide variations and interactions with RNA binding proteins can impact RNA structures across the viruses. Importantly, using proximity ligation sequencing, we identified many conserved ultra-long-range RNA-RNA interactions, including one that spans more than 17 kb in both the WT virus and the Omicron variant. We showed that mutations that disrupt this 17 kb long-range interaction reduce viral fitness at later stages of its infection cycle, while compensatory mutations partially restore virus fitness. Additionally, we showed that this ultra-long-range RNA-RNA interaction structure binds directly to ADAR1 to alter the RNA editing levels on the viral genome. These studies deepen our understanding of RNA structures in the SARS-CoV-2 genome and their ability to interact with host factors to facilitate virus infectivity.

genomics↗

bioRxiv2024

Differential antigenic imprinting effects between influenza H1N1 hemagglutinin and neuraminidase in a mouse model

Understanding how immune history influences influenza immunity is essential for developing effective vaccines and therapeutic strategies. This study investigates the antigenic imprinting of influenza hemagglutinin (HA) and neuraminidase (NA) using a mouse model with sequential infection by four seasonal H1N1 strains. Our findings reveal that, among pre-2009 H1N1 strains, the extent of infection history correlates with the restriction of antibody responses to antigenically drifted HA, but not NA. This suggests the mouse model failed to recapitulate NA imprinting in humans, likely due to the difference in NA immunodominance hierarchy between humans and mice. Nevertheless, pre-existing antibodies induced by infection with pre-2009 influenza virus impeded both functional HA and NA antibody responses against a 2009 pandemic H1N1 strain. Overall, this study provides insights into antigenic imprinting for influenza virus, as well as the limitations of using mouse models for studying antigenic imprinting. ImportanceInfluenza viruses continue to pose a significant threat to human health, with vaccine effectiveness being a persistent concern. One important factor is the individual immune history can influence subsequent antibody responses. While many studies have focused on how pre-existing antibodies influence the induction of anti-HA antibodies after influenza virus infections or vaccinations, the impact on anti-NA antibodies has been less extensively investigated. In this study, using a mouse model, we highlighted within the pre-2009 H1N1 strains, a greater extent of immune history negatively affected anti-HA antibodies but positively influenced anti-NA antibody responses. However, for the 2009 pandemic H1N1 strain, which underwent with antigenic shift, both anti-HA and anti-NA antibody responses have been impeded by the antibodies induced by pre-2009 H1N1 virus infection. These findings have important implications for enhancing our understanding of antigenic imprinting on anti-HA and anti-NA antibody response and for developing more effective vaccination strategies.

immunology↗

bioRxiv2022

Age-related seroprevalence trajectories of seasonal coronaviruses in children

Four seasonal coronaviruses, including HCoV-NL63 and HCoV-229E, HCoV-OC43 and HCoV-HKU1 cause approximately 15-30% of common colds in adults. However, the frequency and timing of early infection with four seasonal coronaviruses in the infant are still not well studied. Here, we evaluated the serological response to four seasonal coronaviruses in 1886 children under 18-year-old to construct the viral infection rates. The antibody levels were also determined from the plasma samples of 485 pairs postpartum women and their newborn babies. This passive immunity waned at one year after birth and the resurgence of the IgGs were found thereafter with the increase of the age. Taken together, our results show the age-related seroprevalence trajectories of seasonal coronaviruses in children and provide useful information for deciding vaccine strategy for coronaviruses in the future.

immunology↗

bioRxiv2020

Calcitriol, the active form of vitamin D, is a promising candidate for COVID-19 prophylaxis

COVID-19, the disease caused by SARS-CoV-2 (1), was declared a pandemic by the World Health Organization (WHO) in March 2020 (2). While awaiting a vaccine, several antivirals are being used to manage the disease with limited success (3, 4). To expand this arsenal, we screened 4 compound libraries: a United States Food and Drug Administration (FDA) approved drug library, an angiotensin converting enzyme-2 (ACE2) targeted compound library, a flavonoid compound library as well as a natural product library. Of the 121 compounds identified with activity against SARS-CoV-2, 7 were shortlisted for validation. We show for the first time that the active form of Vitamin D, calcitriol, exhibits significant potent activity against SARS-CoV-2. This finding paves the way for consideration of host-directed therapies for ring prophylaxis of contacts of SARS-CoV-2 patients.

microbiology↗