Biology subjects

Liu, L.

Publications and source records attributed to Liu, L..

At least 505 records · Page 28Linked to original sources

bioRxiv2023

High-throughput screening of functional neo-antigens and their specific TCRs via the Jurkat reporter system combine with droplet microfluidics

T-cell receptor (TCR)-engineered T cells can precisely recognize a broad repertoire of targets derived from both intracellular and surface proteins of tumor cells. TCR-T adoptive cell therapy has shown safety and promising efficacy in solid tumor immunotherapy. However, antigen-specific functional TCR screening is time-consuming and expensive, which limits its application clinically. Here, we developed a novel integrated antigen-TCR screening platform based on droplet microfluidics technology, enabling high-throughput peptide-major histocompatibility complex (pMHC) library-to-TCR library screening with high sensitivity and low background signal. We introduced DNA barcoding technology to label peptide antigen candidate-loaded antigen-presenting cells (APCs) and Jurkat reporter cells to check the specificity of pMHC-TCR candidates. Coupled with the next-generation sequencing pipeline, interpretation of the DNA barcodes and the gene expression level of the Jurkat T-cell activation pathway provided a clear peptide-MHC-TCR recognition relationship. Our proof-of-principle study demonstrates that the platform could achieve unbiased pMHC-TCR library-on-library screening, which is expected to be used in the cross-reactivity and off-target testing of candidate pMHC-TCR libraries in clinical applications.

bioengineering↗

bioRxiv2023

SARS-CoV-2 Neutralizing Antibodies After Bivalent vs. Monovalent Booster

Bivalent mRNA vaccine boosters expressing Omicron BA.5 spike and ancestral D614G spike were introduced to attempt to boost waning antibody titers and broaden coverage against emerging SARS-CoV-2 lineages. Previous reports showed that peak serum neutralizing antibody (NAb) titers against SARS-CoV-2 variants following bivalent booster were similar to peak titers following monovalent booster. It remains unknown whether these antibody responses would diverge over time. We assessed serum virus-neutralizing titers in 41 participants who received three monovalent mRNA vaccine doses followed by bivalent booster, monovalent booster, or BA.5 breakthrough infection at one month and three months after the last vaccine dose or breakthrough infection using pseudovirus neutralization assays against D614G and Omicron subvariants (BA.2, BA.5, BQ.1.1, and XBB.1.5). There was no significant difference at one month and three months post-booster for the two booster cohorts. BA.5 breakthrough patients exhibited significantly higher NAb titers at three months against all Omicron subvariants tested compared against monovalent and bivalent booster cohorts. There was a 2-fold drop in mean NAb titers in the booster cohorts between one and three month time points, but no discernible waning of titers in the BA.5 breakthrough cohort over the same period. Our results suggest that NAb titers after boosting with one dose of bivalent mRNA vaccine are not higher than boosting with monovalent vaccine. Perhaps inclusion of D614G spike in the bivalent booster exacerbates the challenge posed by immunological imprinting. Hope remains that a second bivalent booster could induce superior NAb responses against emerging variants.

microbiology↗

bioRxiv2023

Recruitment of apolipoprotein E facilitates Herpes simplex virus 1 release

Over two decades, epidemiological studies have revealed that interactions between human polymorphic apolipoprotein 4 (ApoE, isoform 4) and herpes simplex virus type 1 (HSV1) associate with higher risk of Alzheimers disease, a serious and increasing issue among elder populations worldwide. Nevertheless, little is known about the mechanisms behind ApoE-HSV1 interactions at molecular levels. Here, we investigate the effects of ApoE on the HSV1 infectious life cycle in in vitro cell experiments. Analysis of HSV1 growth curves shows that HSV1 production is promoted in presence of any of the three ApoE isoforms, with ApoE 3 or 4 demonstrating more proviral effects than ApoE 2. Quantification by qPCR reveals that the presence of ApoE 2, 3, or 4 leads to an increase of HSV1 extracellular release but unchanged levels of viral genome copies within cells or on the cell surface, indicating that virus replication, assembly, or transport to cell membrane are not affected. Further test of virus release directly demonstrates that HSV1 detachment from the cell surface is promoted by ApoE. Subsequent results reveal that ApoE is both present in purified HSV1 particles produced in ApoE-expressing cells after ultra-centrifugation and able to incorporate into HSV1 particles after purification, suggesting that harbouring ApoE may play a key role in the pro-viral effect of ApoE. Along these lines, we tested the infectious behaviour of ApoE-coated viruses and observed faster attachment kinetics and higher entry efficiencies of ApoE decorated HSV1. Our hypothesis that the association with ApoE leads to modified interactions of the virus with the cell membrane during entry and egress, was further validated in biophysical experiments. In such experiments, HSV1-membrane interaction kinetics and apparent affinity between HSV1 and native supported lipid bilayers (a plasma membrane mimic) were quantified using total internal reflection microscopy. HSV1 particles decorated with ApoE demonstrate both higher association (kon) and dissociation rate constants (koff), as well as less irreversible binding to the membrane, which is in line with the biological experiments. Overall, our results provide new insights into the roles of ApoE during HSV1 infections, which is worth to be considered when studying their involvement during Alzheimers disease development.

microbiology↗

bioRxiv2023

Landscape of IGH germline genes of Chiroptera and the pattern of Rhinolophus affinisbat IGH CDR3 repertoire

The emergence and re-emergence of a number of viruses from bats that impact human and animal health has resulted in a resurgence of interest in bat immunology. Characterizing the immune receptor repertoire is critical to understanding how bats coexist with viruses in the absence of disease and developing new therapeutics to target viruses in humans and susceptible livestock. We annotated IGH germline genes of Rhinolophus ferrumequinum (RF), Phyllostomus discolor (RD) and Pipistrellus pipistrellus (PP), and investigated the evolutionary relationship between bat germline genes and that of human, mouse, cow, and dog. The IGH repertoire characteristics of Rhinolophus affinis bat (RA) were also analyzed. The V gene families of all three bat species can be classified into three Clan, although PD is special with the abnormal length of IGH locus and 22 reverse V genes. Moreover, the bats germline genes are quite differed from those of human, mouse, cow, and dog in evolution, but the three bat species have high homology. The CDR3 repertoire of RA are unique in many aspects including CDR3 subclass, V/J genes access and pairing, CDR3 clones and somatic high-frequency mutation compared with that of human and mouse, which may be the immunologic basis for the asymptomatic nature of viral infection in bats. This study provide immune genome information and extensive reference for the basic research of bat and virus infection mechanism.

immunology↗

bioRxiv2023

Spike substitution T813S increases Sarbecovirus fusogenicity by enhancing the usage of TMPRSS2.

SARS-CoV Spike (S) protein shares considerable homology with SARS-CoV-2 S, especially in the conserved S2 subunit (S2). S protein mediates coronavirus receptor binding and membrane fusion, and the latter activity can greatly influence coronavirus infection. We observed that SARS-CoV S is less effective in inducing membrane fusion compared with SARS-CoV-2 S. We identify that S813T mutation is sufficient in S2 interfering with the cleavage of SARS-CoV-2 S by TMPRSS2, reducing spike fusogenicity and pseudoparticle entry. Conversely, the mutation of T813S in SARS-CoV S increased fusion ability and viral replication. Our data suggested that residue 813 in the S was critical for the proteolytic activation, and the change from threonine to Serine at 813 position might be an evolutionary feature adopted by SARS-2-related viruses. This finding deepened the understanding of Spike fusogenicity and could provide a new perspective for exploring Sarbecovirus evolution. Author SummaryThe Spike strain of SARS-CoV-2 has accumulated many mutations during its time in circulation, most of which have occurred in the S1 region, and more specifically in the RBD, in an effort to either improve the viruss affinity for the receptor ACE2 or to enhance its ability to evade the immune system. Mutations in the Spike S2 region have more far-reaching effects than those in the S1 region because it is more conserved across sarbecoviruses. By comparing SARS and SARS2, we found that an important substitution at amino acid position 813 in the S2 region (T813S) disrupts the utilization of TMPRSS2 and can significantly influence viral entry into cells. This discovery deepens our knowledge of S proteins and provides new prospects for tracing the evolution of Sarbecoviruses.

microbiology↗

bioRxiv2023

Construction of Model Animals to Explore Intestinal Microbiome for Detection of Breast Cancer

Breast cancer ranks first among female cancers and has become a major public health problem in the current society. More studies indicated that these cancers are related to the change in the gut microbiome that can cause metabolic and immune system disorders in the body. However, there are few studies on the changes in gut microbiome caused by the onset of breast cancer, and the relationship between breast cancer and gut microbiome needs to be further clarified. In this study, we inoculated 4T1 breast cancer cells to induce breast cancer tumorigenesis in mice and collected their feces samples at different stages during this process. These intestinal florae were analyzed using 16S rRNA gene amplicon sequencing, and the results showed that at the phylum level, the ratio of Firmicutes/Bacteroidetes decreased with the development of the tumor; at the family level, the intestinal microbiome had obvious variations of Lachnospiraceae, Bacteroidaceae, Erysipelotrichaceae, etc. The Kyoto Encyclopedia of Genes and Genomes (KEGG) and COG annotation demonstrated that decreased abundance of cancer related signaling pathways. This study elucidated the relationship between breast cancer and intestinal microbiome, and the research results can be used as an important biomarker for the diagnosis of breast cancer.

cancer biology↗

bioRxiv2023

Noise improves the association between effects of local stimulation and structural degree of brain networks

Stimulation to local areas remarkably affects brain activity patterns, which can be exploited to investigate neural bases of cognitive function and modify pathological brain statuses. There has been growing interest in exploring the fundamental action mechanisms of local stimulation. Nevertheless, how noise amplitude, an essential element in neural dynamics, influences stimulation-induced brain states remains unknown. Here, we systematically examine the effects of local stimulation by using a large-scale biophysical model under different combinations of noise amplitudes and stimulation sites. We demonstrate that noise amplitude nonlinearly and heterogeneously tunes the stimulation effects from both regional and network perspectives. Furthermore, by incorporating the role of the anatomical network, we show that the peak frequencies of unstimulated areas at different stimulation sites averaged across noise amplitudes are highly positively related to structural connectivity. Crucially, the association between the overall changes in functional connectivity as well as the alterations in the constraints imposed by structural connectivity with the structural degree of stimulation sites is nonmonotonically influenced by the noise amplitude, with the association increasing in specific noise amplitude ranges. Moreover, the impacts of local stimulation of cognitive systems depend on the complex interplay between the noise amplitude and average structural degree. Overall, this work provides theoretical insights into how noise amplitude and network structure jointly modulate brain dynamics during stimulation and introduces possibilities for better predicting and controlling stimulation outcomes. Author summaryDespite the extensive application of local stimulation in cognition research and disease treatments, how regional perturbations alter brain-wide dynamics has not yet been fully understood. Given that noninvasive stimulation is associated with changes in the signal-noise relationship, we assume that noise amplitude is one of the plausible factors modulating the stimulation effects. Using a whole-brain biophysical model under different stimulation sites and noise amplitudes, we explore the influence of noise amplitude on stimulation effects and, more importantly, the interplay between noise amplitude and network structure. From a regional perspective, noise amplitude reduces the peak frequencies in unstimulated areas during stimulation. Moreover, we find a high similarity between the noise-averaged peak frequency matrix and the structural network. From a network perspective, we show that the changes in functional connectivity are decreased by noise amplitude, while the alterations in structural constraints display nonmonotonic trends. Intriguingly, increasing the noise amplitude in specific ranges can improve the association between network-level effects and structural degree, promoting better predicting and controlling therapeutic performance. Finally, the behaviors of cognitive systems quantified by network-level effects are jointly modulated by the noise amplitude and average structural degree.

neuroscience↗

bioRxiv2022

Bovine blastocyst like structures derived from stem cell cultures

Understanding blastocyst formation and implantation is critical for improving farm animal reproduction but is hampered by a limited supply of embryos. We developed an efficient method to generate bovine blastocyst-like structures (termed blastoids) via the assembly of trophoblast stem cells and expanded potential stem cells. Bovine blastoids resemble blastocysts in morphology, cell composition, single-cell transcriptomes, and represent an accessible in vitro model for studying bovine embryogenesis.

developmental biology↗

bioRxiv2022

Coevolutionary dynamics via adaptive feedback in collective-risk social dilemma game

Human society and natural environment form a complex giant ecosystem, where human activities not only lead to the change of environmental states, but also react to them. By using collective-risk social dilemma game, some studies have already revealed that individual contributions and the risk of future losses are inextricably linked. These works, however, often use an idealistic assumption that the risk is constant and not affected by individual behaviors. We here develop a coevolutionary game approach that captures the coupled dynamics of cooperation and risk. In particular, the level of contributions in a population affects the state of risk, while the risk in turn influences individuals behavioral decision-making. Importantly, we explore two representative feedback forms describing the possible effect of strategy on risk, namely, linear and exponential feedbacks. We find that cooperation can be maintained in the population by keeping at a certain fraction or forming an evolutionary oscillation with risk, independently of the feedback type. However, such evolutionary outcome depends on the initial state. Taken together, a two-way coupling between collective actions and risk is essential to avoid the tragedy of the commons. More importantly, a critical starting portion of cooperators and risk level is what we really need for guiding the evolution toward a desired direction.

evolutionary biology↗

bioRxiv2022

Machine learning prediction of cancer cell metabolism from autofluorescence lifetime images

Metabolic reprogramming at a cellular level contributes to many diseases including cancer, yet few assays are capable of measuring metabolic pathway usage by individual cells within living samples. Here, we combine autofluorescence lifetime imaging with single-cell segmentation and machine-learning models to predict the metabolic pathway usage of cancer cells. The metabolic activities of MCF7 breast cancer cells and HepG2 liver cancer cells were controlled by growing the cells in culture media with specific substrates and metabolic inhibitors. Fluorescence lifetime images of two endogenous metabolic coenzymes, reduced nicotinamide adenine dinucleotide (NADH) and oxidized flavin adenine dinucleotide (FAD), were acquired by a multi-photon fluorescence lifetime microscope and analyzed at the cellular level. Quantitative changes of NADH and FAD lifetime components were observed for cells using glycolysis, oxidative phosphorylation, and glutaminolysis. Conventional machine learning models trained with the autofluorescence features classified cells as dependent on glycolytic or oxidative metabolism with 90 - 92% accuracy. Furthermore, adapting convolutional neural networks to predict cancer cell metabolic perturbations from the autofluorescence lifetime images provided improved performance, 95% accuracy, over traditional models trained via extracted features. In summary, autofluorescence lifetime imaging combined with machine learning models can detect metabolic perturbations between glycolysis and oxidative metabolism of living samples at a cellular level, providing a label-free technology to study cellular metabolism and metabolic heterogeneity.

bioengineering↗

bioRxiv2022

Prenatal maternal stress promotes neural stem cell proliferation in the ependymal-subventricular zone of adult male offspring

Perturbations during critical time windows during embryonic development can lead to adverse functional consequences that manifest later in life. Here, we report that prenatal maternal stress (PNS) during the peak of embryonic neurogenesis (E14-delivery) dramatically increased numbers of proliferating neural stem/progenitor cells (NSC/NPCs) in the ependymal-subventricular zone (E-SVZ) and neuroblasts (NBs) in the rostral migratory stream and newborn neurons in the olfactory bulb (OB) of male mouse offspring without causing significant cell death or a deficit in cell migration to the OB. Mechanistically, bulk and single-nucleus transcriptomic analyses showed that PNS affected gene regulatory networks controlling cell cycle progression and stem cell maintenance, maturation of neural circuits, and gliogenesis in prenatally stressed (STR) offspring. More specifically, we found that prenatal exposure to mild maternal restraint-stress sustained MAPK (ERK) activity in the E-SVZ and thus prolonged NSC/NPC/NB proliferation in stressed brains. Moreover, we found PNS disorganized the cytoarchitecture of the glomerular layer of the OB, which may directly relate to the deficit in discriminating different social orders in stressed offspring. Compared to STR males, their female littermates showed less change in the number of proliferating cells in the E-SVZ.

neuroscience↗

bioRxiv2022

Identification of a key genetic factor governing arabinan utilization in the gut microbiome suggests a novel therapeutic target for constipation

Probiotics have been widely used to improve impaired gastro-intestinal motility, yet their efficacy varied substantially across strains. Here, by a large-scale genetic screen plus in vivo measurements, we identified a key genetic factor (abfA cluster governing arabinan utilization) in probiotic Bifidobacterium longum harnessing the treatment efficacy against functional constipation (FC). Intriguingly, it also presents in a range of gut resident microbiota and played a protective role against FC. Next, our longitudinal multi-omics study in humans revealed that the exogenous abfA-cluster- carrying B. longum can well establish itself in the gut, and enrich arabinan-utilization residents and beneficial metabolites (e.g., acetate, butyrate, chenodeoxycholic acid and uracil). Finally, transplantation of abfA-cluster-enriched human microbiota to FC- induced germ-free mice recapitulated the marked gut-motility improvement and elevated production of beneficial metabolites. Collectively, our proof-of-concept study actively demonstrated a critical yet underexplored role of microbial abfA cluster in ameliorating FC, establishing generalizable principles for developing functional-genomics-directed probiotic therapies.

microbiology↗

bioRxiv2022

A Photonic Resonator Interferometric Scattering Microscope for Label-free Detection of Nanometer-Scale Objects with Digital Precision in Point-of-Use Environments

Label-free detection and digital counting of nanometer-scaled objects such as nanoparticles, viruses, extracellular vesicles, and protein molecules enable a wide range of applications in cancer diagnostics, pathogen detection, and life science research. The contrast of interferometric scattering microscopy is amplified through a photonic crystal surface, upon which scattered light from an object combines with illumination from a monochromatic plane wave source. The use of a photonic crystal substrate for interference scattering microscopy results in reduced requirements for high-intensity lasers or oil-immersion objectives, thus opening a pathway toward instruments that are more suitable for environments outside the optics laboratory. Here, we report the design, implementation, and characterization of a compact Photonic Resonator Interferometric Scattering Microscope (PRISM) designed for point-of-use environments and applications. The instrument incorporates two innovative elements that facilitate operation on a desktop in ordinary laboratory environments by users that do not have optics expertise. First, because scattering microscopes are extremely sensitive to vibration, we incorporated an inexpensive but effective solution of suspending the instruments main components from a rigid metal framework using elastic bands, resulting in an average of 28.7 dBV reduction in vibration amplitude compared to an office desk. Second, an automated focusing module based on the principle of total internal reflection maintains the stability of image contrast over time and spatial position, facilitating automated data collection. In this work, we characterize the systems performance by measuring the contrast from gold nanoparticles with diameters in the 10-40 nm range and by observing various biological analytes, including HIV virus, SARS-CoV-2 virus, exosomes, and ferritin protein.

bioengineering↗

bioRxiv2022

Spateo: multidimensional spatiotemporal modeling of single-cell spatial transcriptomics

Cells do not live in a vacuum, but in a milieu defined by cell-cell communication that can be measured via emerging high-resolution spatial transcriptomics approaches. However, analytical tools that fully leverage such data for kinetic modeling remain lacking. Here we present Spateo (aristoteleo/spateo-release), a general framework for quantitative spatiotemporal modeling of single-cell resolution spatial transcriptomics. Spateo delivers novel methods for digitizing spatial layers/columns to identify spatially-polar genes, and develops a comprehensive framework of cell-cell interaction to reveal spatial effects of niche factors and cell type-specific ligand-receptor interactions. Furthermore, Spateo reconstructs 3D models of whole embryos, and performs 3D morphometric analyses. Lastly, Spateo introduces the concept of "morphometric vector field" of cell migrations, and integrates spatial differential geometry to unveil regulatory programs underlying various organogenesis patterns of Drosophila. Thus, Spateo enables the study of the ecology of organs at a molecular level in 3D space, beyond isolated single cells.

systems biology↗

bioRxiv2022

A Host-Harbored Metabolic Susceptibility of Coronavirus Enables Broad-Spectrum Targeting

Host-based antivirals could offer broad-spectrum therapeutics and prophylactics against the constantly-mutating viruses including the currently-ravaging coronavirus, yet must target cellular vulnerabilities of viruses without grossly endangering the host. Here we show that the master lipid regulator SREBP1 couples the phospholipid scramblase TMEM41B to constitute a host "metabolism-to-manufacture" cascade that maximizes membrane supplies to support coronaviral genome replication, harboring biosynthetic enzymes including Lipin1 as druggable viral-specific-essential (VSE) host genes. Moreover, pharmacological inhibition of Lipin1, by a moonlight function of the widely-prescribed beta-blocker Propranolol, metabolically uncouples the SREBP1-TMEM41B cascade and consequently exhibits broad-spectrum antiviral effects against coronaviruses, Zika virus, and Dengue virus. The data implicate a metabolism-based antiviral strategy that is well tolerated by the host, and a potential broad-spectrum medication against current and future coronavirus diseases.

cell biology↗

bioRxiv2022

Alarming antibody evasion properties of rising SARS-CoV-2 BQ and XBB subvariants

The SARS-CoV-2 Omicron variant continues to evolve, with new BQ and XBB subvariants now rapidly expanding in Europe/US and Asia, respectively. As these new subvariants have additional spike mutations, they may possess altered antibody evasion properties. Here, we report that neutralization of BQ.1, BQ.1.1, XBB, and XBB.1 by sera from vaccinees and infected persons was markedly impaired, including sera from individuals who were boosted with a WA1/BA.5 bivalent mRNA vaccine. Compared to the ancestral strain D614G, serum neutralizing titers against BQ and XBB subvariants were lower by 13-81-fold and 66-155-fold, respectively, far beyond what had been observed to date. A panel of monoclonal antibodies capable of neutralizing the original Omicron variant, including those with Emergency Use Authorization, were largely inactive against these new subvariants. The spike mutations that conferred antibody resistance were individually studied and structurally explained. Finally, the ACE2-binding affinities of the spike proteins of these novel subvariants were found to be similar to those of their predecessors. Taken together, our findings indicate that BQ and XBB subvariants present serious threats to the efficacy of current COVID-19 vaccines, render inactive all authorized monoclonal antibodies, and may have gained dominance in the population because of their advantage in evading antibodies.

microbiology↗

bioRxiv2022

NR5A2 connects genome activation to the first lineage segregation in early mouse development

After fertilization, zygotic genome activation (ZGA) marks the beginning of the embryonic program for a totipotent embryo, which further gives rise to the pluripotent embryonic lineages and extraembryonic trophectoderm after the first lineage commitment. While much has been learned about pluripotency regulation, how ZGA is connected to the pluripotency commitment in early embryos remains elusive. Here, we investigated the role of nuclear receptor 1 family transcription factors (TFs) in mouse pre-implantation embryos, whose motifs are highly enriched in accessible chromatin at the 2-cell (2C) to 8-cell (8C) stages after ZGA. We found NR5A2, an NR TF highly induced upon ZGA, is required for early development, as both the knockdown and knockout of Nr5a2 from 1C embryos led to morula arrest. While the zygotic genome was largely activated at the 2C stage, 4-8C-specific gene activation (mid-preimplantation activation) was substantially impaired. Genome-wide chromatin binding and RNA-seq analyses showed NR5A2 preferentially regulates its binding targets including a subset of key pluripotency genes (i.e., Nanog, Pou5f1, and Tdgf1). Finally, NR5A2-occupied sites at the 2C and 8C stages predominantly reside in accessible B1 elements where its motif is embedded. Taken together, these data identify NR5A2 as a key regulator that connects ZGA to the first lineage segregation in early mouse development.

developmental biology↗

bioRxiv2022

Synthetic in vivo compartmentalisation improves metabolic flux and modulates the product profile of promiscuous enzymes

Enzyme spatial organisation and compartmentalisation are naturally evolved mechanisms for facilitating multi-step biocatalysis. We explored the synthetic in vivo co-encapsulation of two different cargo proteins in yeast using a self-assembling virus-like particle. Co-encapsulation was verified using single particle techniques for both end-to-end fusion of the cargo proteins with the encapsulation anchor at one end, and coexpression of each cargo protein with their individual anchors. The co-encapsulation of a bifunctional geranyl diphosphate/farnesyl diphosphate synthase and a bifunctional linalool/nerolidol synthase delivered nerolidol titres up to 30 times that of an unorganised free enzyme control, a remarkable improvement from a single engineering step. Interestingly, striking differences in the ratio of products (linalool and nerolidol) were observed with each spatial organisation approach. This work presents the largest reported titre fold increases from in vivo enzyme compartmentalisation and suggests that enzyme spatial organisation could be used to modulate the product profile of promiscuous enzymes.

synthetic biology↗