Biology subjects

Liu, S.-L.

Publications and source records attributed to Liu, S.-L..

At least 37 records · Page 2Linked to original sources

bioRxiv2022

Distinct Neutralizing Antibody Escape of SARS-CoV-2 Omicron Subvariants BQ.1, BQ.1.1, BA.4.6, BF.7 and BA.2.75.2

Continued evolution of SARS-CoV-2 has led to the emergence of several new Omicron subvariants, including BQ.1, BQ. 1.1, BA.4.6, BF.7 and BA.2.75.2. Here we examine the neutralization resistance of these subvariants, as well as their ancestral BA.4/5, BA.2.75 and D614G variants, against sera from 3-dose vaccinated health care workers, hospitalized BA.1-wave patients, and BA.5-wave patients. We found enhanced neutralization resistance in all new subvariants, especially the BQ.1 and BQ.1.1 subvariants driven by a key N460K mutation, and to a lesser extent, R346T and K444T mutations, as well as the BA.2.75.2 subvariant driven largely by its F486S mutation. The BQ.1 and BQ.1.1 subvariants also exhibited enhanced fusogenicity and S processing dictated by the N460K mutation. Interestingly, the BA.2.75.2 subvariant saw an enhancement by the F486S mutation and a reduction by the D1199N mutation to its fusogenicity and S processing, resulting in minimal overall change. Molecular modelling revealed the mechanisms of receptor-binding and non-receptor binding monoclonal antibody-mediated immune evasion by R346T, K444T, F486S and D1199N mutations. Altogether, these findings shed light on the concerning evolution of newly emerging SARS-CoV-2 Omicron subvariants.

microbiology↗

bioRxiv2022

Determinants and Mechanisms of the Low Fusogenicity and Endosomal Entry of Omicron Subvariants

The rapid spread and strong immune evasion of the SARS-CoV-2 Omicron subvariants has raised serious concerns for the global COVID-19 pandemic. These new variants exhibit reduced fusogenicity and increased endosomal entry pathway utilization compared to the ancestral D614G variant, the underlying mechanisms of which remain elusive. Here we show that the C-terminal S1 mutations of the BA.1.1 subvariant, H655Y and T547K, critically govern the low fusogenicity of Omicron. Notably, H655Y also dictates the enhanced endosome entry pathway utilization. Mechanistically, T547K and H655Y likely stabilize the spike trimer conformation, as shown by increased molecular interactions in structural modeling as well as reduced S1 shedding. Importantly, the H655Y mutation also determines the low fusogenicity and high dependence on the endosomal entry pathway of other Omicron subvariants, including BA.2, BA.2.12.1, BA.4/5 and BA.2.75. These results uncover mechanisms governing Omicron subvariant entry and provide insights into altered Omicron tissue tropism and pathogenesis.

microbiology↗

bioRxiv2022

Evasion of Neutralizing Antibody Response by the SARS-CoV-2 BA.2.75 Variant

The newly emerged BA.2.75 SARS-CoV-2 variant exhibits an alarming 9 additional mutations in its spike (S) protein compared to the ancestral BA.2 variant. Here we examine the neutralizing antibody escape of BA.2.75 in mRNA-vaccinated and BA.1-infected individuals, as well as the molecular basis underlying functional changes in the S protein. Notably, BA.2.75 exhibits enhanced neutralization resistance over BA.2, but less than the BA.4/5 variant. The G446S and N460K mutations of BA.2.75 are primarily responsible for its enhanced resistance to neutralizing antibodies. The R493Q mutation, a reversion to the prototype sequence, reduces BA.2.75 neutralization resistance. The mutational impact is consistent with their locations in common neutralizing antibody epitopes. Further, the BA.2.75 variant shows enhanced cell-cell fusion over BA.2, driven largely by the N460K mutation, which enhances S processing. Structural modeling revealed a new receptor contact introduced by N460K, supporting a mechanism of potentiated receptor utilization and syncytia formation.

microbiology↗

bioRxiv2022

Plasmodesmata-located proteins regulate plasmodesmal function at specific cell interfaces in Arabidopsis

Plasmodesmata (PD) are membrane-lined channels connecting adjoining plant cells. PD control symplasmic intercellular communication by allowing molecules to move between cells. Plant polysaccharide callose ({beta}-1,3-glucan) is deposited at PD, affecting plasmodesmal function; however, the regulation of PD at different cell interfaces is largely unknown. This study discovered that two PD-located proteins, PDLP5 and PDLP6, are expressed in non-overlapping cell types. The constitutive expression of PDLP5 and PDLP6 results in the overaccumulation of PD callose at different cell interfaces and starch hyperaccumulation in different cell types within mature leaves. Using a proximity labeling approach, we identified sucrose synthase 6 (SUS6) as a functional partner of PDLP6. We further demonstrated that PDLP6 physically and genetically interacts with SUS6. In addition, callose synthase 7 (CalS7) interacts with both SUS6 and PDLP6 and is required for PDLP6s function. We propose that PDLP6-SUS6-CalS7 forms a callose synthase complex in the vasculature to regulate the plasmodesmal function.

plant biology↗

bioRxiv2022

Durability of the Neutralizing Antibody Response to mRNA Booster Vaccination Against SARS-CoV-2 BA.2.12.1 and BA.4/5 Variants

The recent emergence of the SARS-CoV-2 BA.4/5 and BA.2.12.1 variants has led to rising COVID-19 case numbers and concerns over the continued efficacy of mRNA booster vaccination. Here we examine the durability of neutralizing antibody (nAb) responses against these SARS-CoV-2 Omicron subvariants in a cohort of health care workers 1-40 weeks after mRNA booster dose administration. Neutralizing antibody titers fell by [~]1.5-fold 4-6 months and by [~]2.5-fold 7-9 months after booster dose, with average nAb titers falling by 11-15% every 30 days, far more stable than two dose induced immunity. Notably, nAb titers from booster recipients against SARS-CoV-2 BA.1, BA.2.12.1, and BA.4/5 variants were [~]4.7-, 7.6-, and 13.4-fold lower than against the ancestral D614G spike. However, the rate of waning of booster dose immunity was comparable across variants. Importantly, individuals reporting prior infection with SARS-CoV-2 exhibited significantly higher nAb titers compared to those without breakthrough infection. Collectively, these results highlight the broad and stable neutralizing antibody response induced by mRNA booster dose administration, implicating a significant role of virus evolution to evade nAb specificity, versus waning humoral immunity, in increasing rates of breakthrough infection.

microbiology↗

bioRxiv2022

Differential Evasion of Delta and Omicron Immunity and Enhanced Fusogenicity of SARS-CoV-2 Omicron BA.4/5 and BA.2.12.1 Subvariants

The rising case numbers of the SARS-CoV-2 Omicron BA.4, BA.5, and BA.2.12.1 subvariants has generated serious concern about the course of the pandemic. Here we examine the neutralization resistance, infectivity, processing, and fusogenicity of spike from the BA.4/5 and BA.2.12.1 SARS-CoV-2 variants compared with other Omicron subvariants and Delta. Critically, we found that the new Omicron subvariants BA.4/5 and BA.2.12.1 were more resistant to neutralization by mRNA-vaccinated and boosted health care worker sera and Omicron-BA.1-wave patient sera than were the BA.1 and BA.2 variants. Interestingly, Delta-wave patient sera neutralized more efficiently against not only Delta but also BA.4/5 and BA.2.12.1 variants that also contain substitutions at position L452, similar to Delta. The BA.4/5 and BA.2.12.1 variants also exhibited higher fusogenicity, and increased spike processing, dependent on the L452 substitution. These results highlight the key role of the L452R and L452Q mutations in BA.4/5 and BA.2.12.1 subvariants.

microbiology↗

bioRxiv2022

Prime-pull immunization of mice with a BcfA-adjuvanted vaccine elicits mucosal immunity and prevents SARS CoV-2 infection and pathology

Vaccines against SARS-CoV-2 that induce mucosal immunity capable of preventing infection and disease remain urgently needed. We show that intramuscular priming of mice with an alum and BcfA-adjuvanted Spike subunit vaccine, followed by a BcfA-adjuvanted mucosal booster, generated Th17 polarized tissue resident CD4+ T cells, and mucosal and serum antibodies. The serum antibodies efficiently neutralized SARS-CoV-2 and its Delta variant, suggesting cross-protection against a recent variant of concern (VOC). Immunization with this heterologous vaccine prevented weight loss following challenge with mouse-adapted SARS-CoV-2 and reduced viral replication in the nose and lungs. Histopathology showed a strong leukocyte and polymorphonuclear (PMN) cell infiltrate without epithelial damage in mice immunized with BcfA-containing vaccines. In contrast, viral load was not reduced in the upper respiratory tract of IL-17 knockout mice immunized with the same formulation, suggesting that the Th17 polarized T cell responses are critical for protection. We show that vaccines adjuvanted with alum and BcfA, delivered through a heterologous prime-pull regimen, protect against SARS-CoV-2 infection without causing enhanced respiratory disease. SIGNIFICANCEThere remains a need for SARS CoV-2 booster vaccines that generate mucosal immunity and prevent transmission. We show that systemic priming followed by a mucosal booster with a BcfA-adjuvanted subunit vaccine generates neutralizing antibodies and Th17 polarized systemic and tissue-resident immune responses that provide sterilizing immunity against wildtype SARS CoV-2, and a variant of concern. Importantly, in contrast to alum alone, the addition of BcfA prevents respiratory pathology. These results suggest that a BcfA-adjuvanted mucosal booster may elicit mucosal immunity in individuals previously immunized systemically with approved vaccines. This foundational study in mice sets the stage for testing our vaccine regimen in larger animal models as a booster vaccine.

immunology↗

bioRxiv2021

Neutralization and Stability of SARS-CoV-2 Omicron Variant

The SARS-CoV-2 B.1.1.529/Omicron variant was first characterized in South Africa and was swiftly designated a variant of concern1. Of great concern is its high number of mutations, including 30-40 mutations in the virus spike (S) protein compared to 7-10 for other variants. Some of these mutations have been shown to enhance escape from vaccine-induced immunity, while others remain uncharacterized. Additionally, reports of increasing frequencies of the Omicron variant may indicate a higher rate of transmission compared to other variants. However, the transmissibility of Omicron and its degree of resistance to vaccine-induced immunity remain unclear. Here we show that Omicron exhibits significant immune evasion compared to other variants, but antibody neutralization is largely restored by mRNA vaccine booster doses. Additionally, the Omicron spike exhibits reduced receptor binding, cell-cell fusion, S1 subunit shedding, but increased cell-to-cell transmission, and homology modeling indicates a more stable closed S structure. These findings suggest dual immune evasion strategies for Omicron, due to altered epitopes and reduced exposure of the S receptor binding domain, coupled with enhanced transmissibility due to enhanced S protein stability. These results highlight the importance of booster vaccine doses for maintaining protection against the Omicron variant, and provide mechanistic insight into the altered functionality of the Omicron spike protein.

microbiology↗

bioRxiv2021

Loss of Neutralizing Antibody Response to mRNA Vaccination against SARS-CoV-2 Variants: Differing Kinetics and Strong Boosting by Breakthrough Infection

The waning efficacy of SARS-CoV-2 vaccines combined with the continued emergence of variants resistant to vaccine-induced immunity has reignited debate over the need for booster vaccines. To address this, we examined the neutralizing antibody (nAb) response against four major SARS-CoV-2 variants--D614G, Alpha (B.1.1.7), Beta (B.1.351), and Delta (B.1.617.2)--in health care workers (HCWs) at pre-vaccination, post-first and post-second mRNA vaccine dose, and six months post-second mRNA vaccine dose. Neutralizing antibody titers against all variants, especially the Delta variant, declined dramatically from four weeks to six months post-second mRNA vaccine dose. Notably, SARS-CoV-2 infection enhanced vaccine durability, and mRNA-1273 vaccinated HCWs also exhibited ~2-fold higher nAb titers than BNT162b2 vaccinated HCWs. Together these results demonstrate possible waning of protection from infection against SARS-CoV-2 Delta variant based on decreased nAb titers, dependent on COVID-19 status and the mRNA vaccine received.

microbiology↗

bioRxiv2021

A multifaceted ecological assessment reveals the invasion of the freshwater red macroalga Montagnia macrospora (Batrachospermales, Rhodophyta) in Taiwan

Invasive freshwater macroalgae are rarely described. Recently, a freshwater red alga, Montagnia macrospora, was introduced from South America to East Asia via the global aquarium trade. The earliest occurrence record of this alga in Taiwan is dated 2005. To determine whether M. macrospora has become an invasive species in Taiwan and to understand its traits that facilitated its invasion, we took a total-evidence approach that combines examination of ecological background and population genetic analysis. Our island-wide survey showed that M. macrospora alga was widespread in the field across Taiwan, where the climate greatly differs from that of South America. Our population genetic analysis revealed that the cox2-3 sequences of all the specimens of M. macrospora from Taiwan were identical, consistent with the hypothesis that the alga expanded through asexual reproduction. Moreover, during our long-term ecological assessments and field surveys, we observed that M. macrospora is an ecological generalist that can self-sustain for a decade and bloom. Taken together, our data suggest that M. macrospora has successfully invaded the freshwater ecosystems in Taiwan due to its ability to disperse asexually and to grow under broad environmental conditions. We hope that our study brings attention to invasive freshwater algae, which have been overlooked in conservation planning and management.

ecology↗

bioRxiv2021

Lung-selective Cas13d-based nanotherapy inhibits lethal SARS-CoV-2 infection by targeting host protease Ctsl

The COVID-19 pandemic persists as a global health crisis for which curative treatment has been elusive. Development of effective and safe anti-SARS-CoV-2 therapies remains an urgent need. SARS-CoV-2 entry into cells requires specific host proteases including TMPRSS2 and Cathepsin L (Ctsl)1-3, but there has been no reported success in inhibiting host proteases for treatment of SARS-CoV-2 pathogenesis in vivo. Here we have developed a lung Ctsl mRNA-targeted, CRISPR/Cas13d-based nanoparticle therapy to curb fatal SARS-CoV-2 infection in a mouse model. We show that this nanotherapy can decrease lung Ctsl expression in normal mice efficiently, specifically, and safely. Importantly, this lung-selective Ctsl-targeted nanotherapy significantly extended the survival of lethally SARS-CoV-2 infected mice by decreasing lung virus burden, reducing expression of pro-inflammatory cytokines/chemokines, and diminishing the severity of pulmonary interstitial inflammation. Additional in vitro analyses demonstrated that Cas13d-mediated Ctsl knockdown inhibited infection mediated by the spike protein of SARS-CoV-1, SARS-CoV-2, and more importantly, the authentic SARS-CoV-2 B.1.617.2 Delta variant, regardless of TMPRSS2 expression status. Our results demonstrate the efficacy and safety of a lung-selective, Ctsl-targeted nanotherapy against infection by SARS-CoV-2 and likely other emerging coronaviruses, forming a basis for investigation of this approach in clinical trials.

microbiology↗

bioRxiv2021

SARS-CoV-2 Spreads through Cell-to-Cell Transmission

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a highly transmissible coronavirus responsible for the global COVID-19 pandemic. Herein we provide evidence that SARS-CoV-2 spreads through cell-cell contact in cultures, mediated by the spike glycoprotein. SARS-CoV-2 spike is more efficient in facilitating cell-to-cell transmission than SARS-CoV spike, which reflects, in part, their differential cell-cell fusion activity. Interestingly, treatment of cocultured cells with endosomal entry inhibitors impairs cell-to-cell transmission, implicating endosomal membrane fusion as an underlying mechanism. Compared with cell-free infection, cell-to-cell transmission of SARS-CoV-2 is refractory to inhibition by neutralizing antibody or convalescent sera of COVID-19 patients. While ACE2 enhances cell-to-cell transmission, we find that it is not absolutely required. Notably, despite differences in cell-free infectivity, the variants of concern (VOC) B.1.1.7 and B.1.351 have similar cell-to-cell transmission capability. Moreover, B.1.351 is more resistant to neutralization by vaccinee sera in cell-free infection, whereas B.1.1.7 is more resistant to inhibition by vaccine sera in cell-to-cell transmission. Overall, our study reveals critical features of SARS-CoV-2 spike-mediated cell-to-cell transmission, with important implications for a better understanding of SARS-CoV-2 spread and pathogenesis.

microbiology↗

bioRxiv2021

Unsupervised Clustering characterizes the CPG dinucleotides distribution of the Andes hantavirus

Hantaviruses belong to the family of Bunyaviridae, and small mammals host them. Humans are infected either by inhaling virus-containing aerosols or through contact with animal droppings. Even if rodents host the pathogenic species and humans are dead-end hosts, they get accidentally infected. Andes Orthohantavirusus (ANDV) seems to be the only species with documented person-to-person transmission. Hemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS) are both serious syndromes associated with hantavirus infections. For both syndromes, the mortality rate is near 40%. Decades of studies already highlighted the CpG repression in RNA viruses, and both the estimation of the CpG odds ratio and the correlation with their genome polarity were dominant factors to figure out the CpG bias. We conducted the differential analysis of the CpG odds ratio for all the orthohantaviruses on the full segmented genomes (L, M, S). The results suggested the statistical significance of the three groups. The "Small" genomes resulted in the more informative from the CpG odd ratio point of view. We calculated the CpG odds ratio for all the Orthohantaviruses within these segments, and besides, we estimated the correlation coefficient with the relative coding sequences (CDS). Preliminary results firstly confirmed the CpG odds ratio as the lowest among all the nucleotides. Second, highlighted the Andes virus as that whose CpG odds ratio within CDS is highest. The use of these two measures as features for unsupervised clustering algorithms has brought to the identification of four different sub-groups inside of the Orthohantaviridae family. The evidence is that the Andes Hantavirus exhibits a peculiar CpG odds ratio distribution, probably linked to its unique prerogative to pass from human-to-human.

bioinformatics↗

bioRxiv2020

Plasmodesmata-dependent intercellular movement of bacterial effectors

Pathogenic microorganisms deliver protein effectors into host cells to suppress host immune responses. Recent findings reveal that phytopathogens manipulate the function of plant cell-to-cell communication channels plasmodesmata (PD) to promote diseases. Several bacterial and filamentous pathogen effectors have been shown to regulate PD in their host cells. A few effectors of filamentous pathogens have been reported to move from the infected cells to neighboring plant cells through PD; however, it is unclear whether bacterial effectors can traffic through PD in plants. In this study, we systemically determined the intercellular movement of Pseudomonas syringae pv. tomato (Pst) DC3000 effectors between adjoining plant cells in Nicotiana benthamiana. We observed that at least 16 Pst DC3000 effectors move from transformed cells to the surrounding plant cells. The movement of the effectors is largely dependent on their molecular weights. The expression of PD regulators, Arabidopsis PD-located protein PDLP5 and PDLP7, lead to PD closure and inhibits the PD-dependent movement of a bacterial effector in N. benthamiana. Similarly, a 22-amino acid peptide of bacterial flagellin (flg22) treatment induces PD closure and suppresses the movement of a bacterial effector in N. benthamiana. Together, our findings demonstrated that bacterial effectors are able to move intercellularly through PD in plants.

plant biology↗

bioRxiv2020

An evolutionary analysis of the SARS-CoV-2 genomes from the countries in the same meridian

In the current study we analyzed the genomes of SARS-CoV-2 strains isolated from Italy, Sweden, Congo (countries in the same meridian) and Brazil, as outgroup country. Evolutionary analysis revealed codon 9628 under episodic selective pressure for all four countries, suggesting it as a key site for the virus evolution. Belonging to the P0DTD3 (Y14_SARS2) uncharacterized protein 14, further investigation has been conducted showing the codon mutation as responsible for the helical modification in the secondary structure. According to the predictions done, the codon is placed into the more ordered region of the gene (41-59) and close the area acting as transmembrane (54-67), suggesting its involvement into the attachment phase of the virus. The predicted structures of P0DTD3 mutated and not confirmed the importance of the codon to define the protein structure and the ontological analysis of the protein emphasized that the mutation enhances the binding probability.

genomics↗

bioRxiv2020

Hidden introductions of freshwater red algae via the aquarium trade exposed by DNA barcodes

ABSTRACTThe global aquarium trade can introduce alien freshwater invaders, potentially impacting local aquatic ecosystems and their biodiversity. The role of the aquarium trade in spreading freshwater red macroalgae that hitchhike on ornamental aquatic plants and animals is unassessed. We investigated this human-mediated phenomenon via a broad biodiversity survey and genetic analysis of freshwater red algae in the field and aquarium shops in East Asia. Using rbcL-based DNA barcoding, we surveyed 125 samples from 46 field sites and 88 samples from 53 aquarium shops (213 samples in total) mostly across Taiwan – a key hub in the global aquarium trade – as well as in Hong Kong, Okinawa (Japan), the Philippines, and Thailand. We augmented our rbcL sequences with GenBank rbcL sequences that represent 40 additional countries globally. We found 26 molecular operational taxonomic units (mOTUs) in Taiwan, some of which are cryptic. Phylogeographical analysis revealed three potential introduced mOTUs in Taiwan, which exhibit no local genetic variation in Taiwan and are distributed across continents. Also, we posit that some presumably endangered freshwater red algae may be preserved in aquaria, an unintentional ex situ conservation site for these organisms that are vulnerable to water pollution from anthropogenic disturbances. Collectively, these data suggest that freshwater red algae have been hitchhiking and dispersed via the aquarium trade, an important and overlooked mechanism of introduction of these organisms across the globe.Competing Interest StatementThe authors have declared no competing interest.View Full Text

ecology↗

bioRxiv2020

HamHeat: A fast and simple package for calculating Hamming distance from multiple sequence data for heatmap visualization

The problem of fast calculation of Hamming distance inferred from many sequence datasets is still not a trivial task. Here, we present HamHeat, as a new software package to efficiently calculate Hamming distance for hundreds of aligned protein or DNA sequences of a large number of residues or nucleotides, respectively. HamHeat uses a unique algorithm with many advantages, including its ease of use and the execution of fast runs for large amounts of data. The package consists of three consecutive modules. In the first module, the software ranks the sequences from the most to the least frequent variant. The second module uses the most common variant as the reference sequence to calculate the Hamming distance of each additional sequence based on the number of residue or nucleotide changes. A final module formats all the results in a comprehensive table that displays the sequence ranks and Hamming distances. Availability and implementationHamHeat is based on Python 3 and AWK, runs on Linux system and is available under the MIT License at: https://github.com/alexeyrakov/HamHeat. Contactrakovalexey@gmail.com

bioinformatics↗

bioRxiv2020

Short chain fatty acid butyrate promotes virus infection by repressing interferon stimulated genes

Butyrate is an abundant metabolite produced by the gut microbiota and is known to modulate multiple immune system pathways and inflammatory diseases. However, studies of its effects on virus infection of cells are limited and enigmatic. We found that butyrate increases cellular infection and virus replication in influenza virus, reovirus, and human immunodeficiency virus infections. Further exploring this phenomenon, we found that addition of butyrate to cells deficient in type I interferon (IFN) signaling did not increase susceptibility to virus infection. Accordingly, we discovered that butyrate suppressed levels of specific IFN stimulated gene (ISG) products in human and mouse cells. Butyrate did not inhibit IFN-induced phosphorylation of transcription factors STAT1 and STAT2 or their translocation to the nucleus, indicating that IFN signaling was not disrupted. Rather, our data are suggestive of a role for inhibition of histone deacetylase activity by butyrate in limiting ISG induction. Global transcript analysis revealed that butyrate increases expression of more than 800 cellular genes, but represses IFN-induced expression of 60% of ISGs. Overall, we identify a new mechanism by which butyrate promotes virus infection via repression of ISGs. Our findings also add to the growing body of evidence showing that individual ISGs respond differently to type I IFN induction depending on the cellular environment, including the presence of butyrate. ImportanceButyrate is a lipid produced by intestinal bacteria that can regulate inflammation throughout the body. Here we show for the first time that butyrate influences the innate antiviral immune response mediated by type I IFNs. A majority of antiviral genes induced by type I IFNs were repressed in the presence of butyrate, resulting in increased virus infection and replication in cells. This suggests that butyrate could be broadly used as a tool to increase growth of virus stocks for research and for the generation of vaccines. Our research also indicates that metabolites produced by the gut microbiome can have complex effects on cellular physiology as demonstrated by the dampening of an inflammatory innate immune pathway by butyrate resulting in a pro-viral cellular environment.

microbiology↗