Host Cell Research Articles

Visualization of giant Mimivirus in a movie for biology classrooms.

We have developed a new observation chamber for Mimivirus-infected Acanthamoeba to create dynamic visual teaching materials for virus education suitable for high school and university biology courses. We conducted experiments and captured a movie showcasing the infection process of Acanthamoeba cells by mimiviruses. In this educational film, we successfully recorded the active movement of healthy Acanthamoeba cells across the surface of a culture flask under an agarose gel. After Mimivirus infection, the movement of the Acanthamoeba cells gradually slowed and eventually stopped. This cessation coincided with the development of the Mimivirus virion factory, which began producing new virions on the surface of the host cells. Moreover, we captured continuous footage of a single cell throughout the viral proliferation process, thereby illustrating the viral proliferation in real time. This educational movie, which visually demonstrates the proliferation of Mimivirus within host cells, acts as an effective teaching tool. Moreover, it enhances students' understanding of virus proliferation mechanisms and highlights the biological significance of viruses, their impact on host cell fate, and their role in ecosystems.

Impact of the elderly lung mucosa on Mycobacterium tuberculosis transcriptional adaptation during infection of alveolar epithelial cells.

Tuberculosis is one of the leading causes of death due to a single infectious agent. Upon infection, Mycobacterium tuberculosis (M.tb) is deposited in the alveoli and encounters the lung mucosa or alveolar lining fluid (ALF). We previously showed that, as we age, ALF presents a higher degree of oxidation and inflammatory mediators, which favors M.tb replication in human macrophages and alveolar epithelial cells (ATs). Here, we define the transcriptional profile of M.tb when exposed to healthy ALF from adult (A-ALF) or elderly (E-ALF) humans before and during infection of ATs. Prior to infection, M.tb exposure to E-ALF upregulated genes essential for bacterial host adaptation directly involved in M.tb pathogenesis. During infection of ATs, E-ALF exposed M.tb further upregulated genes involved in its ability to escape into the AT cytosol bypassing critical host defense mechanisms, as well as genes associated with defense against oxidative stress. These findings demonstrate how alterations in human ALF during the aging process can impact the metabolic status of M.tb, potentially enabling a greater adaptation and survival within host cells. Importantly, we present the first transcriptomic analysis on the impact of the elderly lung mucosa on M.tb pathogenesis during intracellular replication in ATs.IMPORTANCETuberculosis is one of the leading causes of death due to a single infectious agent. Upon infection, Mycobacterium tuberculosis (M.tb) is deposited in the alveoli and comes in contact with the alveolar lining fluid (ALF). We previously showed that elderly ALF favors M.tb replication in human macrophages and alveolar epithelial cells (ATs). Here we define the transcriptional profile of when exposed to healthy ALF from adult (A-ALF) or elderly (E-ALF) humans before and during infection of ATs. Prior to infection, exposure to E-ALF upregulates genes essential for bacterial host adaptation and pathogenesis. During infection of ATs, E-ALF further upregulates M.tb genes involved in its ability to escape into the AT cytosol, as well as genes for defense against oxidative stress. These findings demonstrate how alterations in human ALF during the aging process can impact the metabolic status of M.tb, potentially enabling a greater adaptation and survival within host cells.

A Self-Amplifying Human Papillomavirus 16 Vaccine Candidate Delivered by Tobacco Mosaic Virus-Like Particles.

Virus-like particles (VLPs) are naturally occurring delivery platforms with potential for mRNA vaccines that can be used as an alternative to lipid nanoparticles. Here we describe a self-amplifying mRNA vaccine based on tobacco mosaic virus (TMV) expressing a mutated E7 protein from human papillomavirus 16 (HPV16). E7 is an early gene that plays a central role in viral replication and the oncogenic transformation of host cells, but nononcogenic mutant E7 proteins can suppress this activity. Immunization studies involving the delivery of self-amplifying mutant E7 mRNA packaged with TMV coat proteins confirmed the elicitation of E7-specific IgG antibodies. Additional in vitro splenocyte proliferation and cytokine profiling assays indicated the activation of humoral and cellular immune responses. We conclude that TMV particles are suitable for the delivery of mRNA vaccines and can preserve their integrity and functionality in vitro and in vivo.

Alpha-synuclein expression in neurons modulates Japanese encephalitis virus infection.

Japanese encephalitis virus (JEV) poses a significant threat, particularly to children. Despite extensive research efforts, the development of effective treatments against JEV has been impeded. One of the major setbacks is a lack of comprehensive understanding of neurotropism. The study focuses on alpha-synuclein (α-syn), a neuronal protein, and aims to determine its role in JEV pathogenesis. The present study reveals that the host cell upregulates α-syn in response to JEV infection. α-syn restrains JEV propagation by modulating superoxide dismutase 1 (SOD1) expression which further blocks JEV-induced ROS generation. Endogenous α-syn silencing led to a decrease in SOD1 expression and increased viral titer. α-syn plays a crucial role in counteracting oxidative stress through SOD1, which is essential for limiting JEV replication. This study provides broader implications for antiviral strategies and their possible role in neurodegenerative diseases; however, there is still much to explore, particularly regarding α-syn aggregation kinetics in JEV infection.

Inducible cell lines producing replication-defective human immunodeficiency virus particles containing envelope glycoproteins stabilized in a pretriggered conformation.

During the process by which human immunodeficiency virus (HIV-1) enters cells, the envelope glycoprotein (Env) trimer on the virion surface engages host cell receptors. Binding to the receptor CD4 induces Env to undergo transitions from a pretriggered, "closed" (State-1) conformation to more "open" (State 2/3) conformations. Most broadly neutralizing antibodies (bNAbs), which are difficult to elicit, recognize the pretriggered (State-1) conformation. More open Env conformations are recognized by poorly neutralizing antibodies (pNAbs), which are readily elicited during natural infection and vaccination with current Env immunogens. Env heterogeneity likely contributes to HIV-1 persistence by skewing antibody responses away from the pretriggered conformation. The conformationally flexible gp160 Env precursor on the infected cell or virion surface potentially presents multiple pNAb epitopes to the host immune system. Although proteolytic cleavage to produce the functional, mature Env trimer [(gp120/gp41)3] stabilizes State-1, many primary HIV-1 Envs spontaneously sample more open conformations. Here, we establish inducible cell lines that produce replication-defective HIV-1 particles with Env trimers stabilized in a pretriggered conformation. The mature Env is enriched on virus-like particles (VLPs). Using complementary approaches, we estimate an average of 25-50 Env trimers on each VLP. The stabilizing changes in Env limit the natural conformational heterogeneity of the VLP Env trimers, allowing recognition by bNAbs but not pNAbs. These defective VLPs provide a more homogeneous source of pretriggered Env trimers in a native membrane environment. Thus, these VLPs may facilitate the characterization of this functionally important Env conformation and its interaction with the immune system.IMPORTANCEA major impediment to the development of an effective HIV/AIDS vaccine is the inefficiency with which human immunodeficiency virus (HIV-1) envelope glycoproteins elicit antibodies that neutralize multiple virus strains. Neutralizing antibodies recognize a particular shape of the envelope glycoproteins that resides on the viral membrane before the virus engages the host cell. Here, we report the creation of stable cell lines that inducibly produce non-infectious HIV-like particles. The normally flexible envelope glycoprotein spikes on these virus-like particles have been stabilized in a conformation that is recognized by broadly neutralizing antibodies. These virus-like particles allow the study of the envelope glycoprotein conformation, its modification by sugars, and its ability to elicit desired neutralizing antibodies.

Probing Single-Molecule Dynamics in Self-Assembling Viral Nucleocapsids.

All viruses on Earth rely on host cell machinery for replication, a process that involves a complex self-assembly mechanism. Our aim here is to scrutinize in real time the growth of icosahedral viral nucleocapsids with single-molecule precision. Using total internal reflection fluorescence microscopy, we probed the binding and unbinding dynamics of fluorescently labeled capsid subunits on hundreds of immobilized viral RNA molecules simultaneously at each time point. A step-detection algorithm combined with statistical analysis allowed us to estimate microscopic quantities such as the equilibrium binding rate and mean residence time, which are otherwise inaccessible through traditional ensemble-averaging techniques. Additionally, we could estimate a set of rate constants modeling the growth kinetics from nonequilibrium measurements, and we observed an acceleration in growth caused by the electrostatic screening effect of monovalent salts. Single-molecule fluorescence imaging will be crucial for elucidating virus self-assembly at the molecular level, particularly in crowded, cell-like environments.

Macrophage-derived extracellular vesicles from Ascaris lumbricoides antigen exposure enhance Mycobacterium tuberculosis growth control, reduce IL-1β, and contain miR-342-5p, miR-516b-5p, and miR-570-3p that regulate PI3K/AKT and MAPK signaling pathways

BackgroundHelminth coinfection with tuberculosis (TB) can alter the phenotype and function of macrophages, which are the major host cells responsible for controlling Mycobacterium tuberculosis (Mtb). However, it is not known whether helminth infection stimulates the release of host-derived extracellular vesicles (EVs) to induce or maintain their regulatory network that suppresses TB immunity. We previously showed that pre-exposure of human monocyte-derived macrophages (hMDMs) with Ascaris lumbricoides protein antigens (ASC) results in reduced Mtb infection-driven proinflammation and gained bacterial control. This effect was entirely dependent on the presence of soluble components in the conditioned medium from helminth antigen-pre-exposed macrophages.MethodsOur objective was to investigate the role of EVs released from helminth antigen-exposed hMDMs on Mtb-induced proinflammation and its effect on Mtb growth in hMDMs. Conditioned medium from 48-h pre-exposure with ASC or Schistosoma mansoni antigen (SM) was used to isolate EVs by ultracentrifugation. EVs were characterized by immunoblotting, flow cytometry, nanoparticle tracking assay, transmission electron microscopy, and a total of 377 microRNA (miRNA) from EVs screened by TaqMan array. Luciferase-expressing Mtb H37Rv was used to evaluate the impact of isolated EVs on Mtb growth control in hMDMs.ResultsEV characterization confirmed double-membraned EVs, with a mean size of 140 nm, expressing the classical exosome markers CD63, CD81, CD9, and flotillin-1. Specifically, EVs from the ASC conditioned medium increased the bacterial control in treatment-naïve hMDMs and attenuated Mtb-induced IL-1β at 5 days post-infection. Four miRNAs showed unique upregulation in response to ASC exposure in five donors. Pathway enrichment analysis showed that the MAPK and PI3K-AKT signaling pathways were regulated. Among the mRNA targets, relevant for regulating inflammatory responses and cellular stress pathways, CREB1 and MAPK13 were identified. In contrast, SM exposure showed significant regulation of the TGF-β signaling pathway with SMAD4 as a common target.ConclusionOverall, our findings suggest that miRNAs in EVs released from helminth-exposed macrophages regulate important signaling pathways that influence macrophage control of Mtb and reduce inflammation. Understanding these interactions between helminth-induced EVs, miRNAs, and macrophage responses may inform novel therapeutic strategies for TB management.

Postbiotic Metabolite Derived from Lactiplantibacillus plantarum PD18 Maintains the Integrity of Cell Barriers and Affects Biomarkers Associated with Periodontal Disease

Background/Objectives: Periodontal disease is caused by oral infections, biofilms, persistent inflammation, and degeneration of cell barrier integrity, allowing pathogens to invade host cells. Probiotics have been extensively studied for the treatment of periodontal disease. However, research on the involvement of beneficial substances produced by probiotics, called “postbiotics,” in periodontal diseases remains in its early stages. The present study aimed to evaluate the effect of a postbiotic metabolite (PM) from Lactiplantibacillus plantarum PD18 on immunomodulation and maintenance of cell barrier integrity related to periodontal disease. Method: The main substance in PM PD18 was analyzed by GC-MS. The cytotoxic effect of PM PD18 was performed using the MTT assay, wound healing through the scratch assay, cell permeability through TEER value, modulation of inflammatory cytokines through ELISA, and gene expression of inflammatory cytokines and tight junction protein was determined using qRT-PCR. Results: The main substance found in PM PD18 is 2,3,5,6-tetramethylpyrazine. PM PD18 did not exhibit cytotoxic effects on RAW 264.7 cells but promoted wound healing and had an antiadhesion effect on Porphyromonas gingivalis concerning SF-TY cells. This postbiotic could maintain cell barrier integrity by balancing transepithelial electrical resistance (TEER) and alkaline phosphatase (ALP) activity. In addition, the gene and protein expression levels of zonula occludens-1 (ZO-1) increased. PM PD18 was found to have immunomodulatory properties, as demonstrated by regulated anti- and pro-inflammatory cytokines. Interleukin-10 (IL-10) increased, while IL-6 and IL-8 were reduced. Conclusions: This study demonstrated that PM PD18 is efficient as a natural treatment for maintaining cell barrier integrity and balancing inflammatory responses associated with periodontal disease.

Foreign Body Immune Response to Zwitterionic and Hyaluronic Acid Granular Hydrogels Made with Mechanical Fragmentation.

Granular hydrogels have recently attracted the attention for diverse tissue engineering applications due to their versatility and modularity. Despite previous studies showing enhanced viability and metabolism of cells encapsulated in these hydrogels, the in vitro immune response and long-term fibrotic response of these scaffolds have not been well characterized. Here, bulk and granular hydrogels are studied based on synthetic zwitterionic (ZI) and natural polysaccharide hyaluronic acid (HA) made with mechanical fragmentation. In vitro, immunomodulatory studies show an increased stimulatory effect of HA granular hydrogels compared to bulk, while both bulk and granular ZI hydrogels do not induce an inflammatory response. Subcutaneous implantation in mice shows that both ZI and HA granular hydrogels resulted in less collagen capsule deposition around implants compared to bulk HA hydrogels 10 weeks after implantation. Moreover, the HA granular hydrogels are infiltrated by host cells, including macrophages and mature blood vessels, in a porosity-dependent manner. However, a large number of cells, including multinucleated giant cells as well as blood vessels, surround bulk and granular ZI hydrogels and are not able to infiltrate. Overall, this study provides new insights on the long-term stability and fibrotic response of granular hydrogels, paving the way for future studies and applications.

The long non-coding RNA lncRNA-DRNR enhances infectious bronchitis virus replication by targeting chicken JMJD6 and modulating interferon-stimulated genes expression via the JAK-STAT signalling pathway.

Infectious bronchitis virus (IBV) is the causative agent of infectious bronchitis (IB), a severe disease that primarily affects young chickens and poses a significant challenge to the global poultry industry. Understanding the complex interaction between the virus and its host is vital for developing innovative antiviral strategies. Long non-coding RNA (lncRNA) plays a crucial role in regulating host antiviral immune responses. Our previous studies have shown that IBV infection disrupts the stability of lncRNA in host cells, indicating a potential regulatory role for lncRNA in IBV pathogenesis. It is still not clear how lncRNA precisely modulates IBV replication. In this study, we observed down-regulation ofMSTRG.26120.58 (named lncRNA-DRNR) expression in various chicken cell lines upon IBV infection. We demonstrated that silencing lncRNA-DRNR using siRNA enhances intracellular replication of IBV. Through exploring genes encoding proteins upstream and downstream of lncRNA-DRNR within a 100kb range, we identified chJMJD6 (chicken JMJD6) as a potential target gene negatively regulated by lncRNA-DRNR expression levels. Furthermore, chJMJD6 inhibits STAT1 methylation, thereby affecting the induction of interferon-stimulated genes (ISGs) through the activation of the IFN-β-mediated JAK-STAT signalling pathway, ultimately promoting the intracellular replication of IBV. In summary, our findings reveal the critical role played by lncRNA-DRNR during IBV infection, providing novel insights into mechanisms underlying coronavirus-induced disruption in lncRNA stability.

Architectural dissection of adhesive bacterial cell surface appendages from a "molecular machines" viewpoint.

The ability of bacteria to interact with and respond to their environment is crucial to their lifestyle and survival. Bacterial cells routinely need to engage with extracellular target molecules, in locations spatially separated from their cell surface. Engagement with distant targets allows bacteria to adhere to abiotic surfaces and host cells, sense harmful or friendly molecules in their vicinity, as well as establish symbiotic interactions with neighboring cells in multicellular communities such as biofilms. Binding to extracellular molecules also facilitates transmission of information back to the originating cell, allowing the cell to respond appropriately to external stimuli, which is critical throughout the bacterial life cycle. This requirement of bacteria to bind to spatially separated targets is fulfilled by a myriad of specialized cell surface molecules, which often have an extended, filamentous arrangement. In this review, we compare and contrast such molecules from diverse bacteria, which fulfil a range of binding functions critical for the cell. Our comparison shows that even though these extended molecules have vastly different sequence, biochemical and functional characteristics, they share common architectural principles that underpin bacterial adhesion in a variety of contexts. In this light, we can consider different bacterial adhesins under one umbrella, specifically from the point of view of a modular molecular machine, with each part fulfilling a distinct architectural role. Such a treatise provides an opportunity to discover fundamental molecular principles governing surface sensing, bacterial adhesion, and biofilm formation.

Retinol binding protein 4 restricts PCV2 replication via selective autophagy degradation of viral ORF1 protein.

Autophagy is a highly conserved degradative process that has been linked to various functions, including defending host cells against pathogens. Although the involvement of autophagy in porcine circovirus 2 (PCV2) infection has become apparent, it remains unclear whether selective autophagy plays a critical role in PCV2 restriction. Here we show that retinol-binding protein 4 (RBP4), an adipokine for retinol carrier, initiates the autophagic degradation of PCV2 ORF1 protein. PCV2 infection increases RBP4 protein levels through MAPK-eIF4E axis in living cells. Ectopic expression of RBP4 or recombinant RBP4 treatment promotes the degradation of ORF1 protein. Mechanistically, RBP4 activates TRAF6 to induce K63-linked ubiquitination of ORF1, leading to SQSTM1/p62-mediated selective autophagy for degradation. Consequently, RBP4 deficiency increases viral loads and exacerbates the pathogenicity of PCV2 in vivo. Collectively, these results identify RBP4 as a key host restriction factor of PCV2 and reveal a previously undescribed antiviral mechanism against PCV2 in infected cells.

Leveraging mathematical modeling framework to guide regimen strategy for phage therapy

Bacteriophage (phage) cocktail therapy has been relied upon more and more to treat antibiotic-resistant infections. Understanding of the complex kinetics between phages, target bacteria, and the emergence of phage resistance remain hurdles to successful clinical outcomes. Building upon previous mathematical concepts, we develop biologically-motivated nonlinear ordinary differential equation models to explore single, cocktail, and sequential phage treatment modalities. While the optimal pairwise phage treatment strategy was the double simultaneous administration of two highly potent and asymmetrically binding phage strains, it appears unable to prevent the evolution of resistance. This treatment regimen did have a greater lysis efficiency, promoted higher phage population sizes, reduced bacterial density the most, and suppressed the evolution of resistance the longest compared to all other treatments strategies tested. Conversely, the combination of phages with polar potencies allows the more efficiently replicating phages to monopolize susceptible host cells, thereby quickly negating the intended compounding effect of cocktails. Together, we demonstrate that a biologically-motivated modeling-based framework can be leveraged to quantify the effects of each phage’s properties to more precisely predict treatment responses.

Epigenetic control of T-DNA during transgenesis and pathogenesis.

Mobile elements known as T-DNAs are transferred from pathogenic Agrobacterium to plants and reprogram the host cell to form hairy roots or tumors. Disarmed non-oncogenic T-DNAs are extensively used to deliver transgenes in plant genetic engineering. Such T-DNAs were the first known targets of RNA silencing mechanisms, which detect foreign RNA in plant cells and produce small RNAs that induce transcript degradation. These T-DNAs can also be transcriptionally silenced by the deposition of epigenetic marks such as DNA methylation and the dimethylation of lysine 9 (H3K9me2) in plants. Here, we review the targeting and the roles of RNA silencing and DNA methylation on T-DNAs in transgenic plants as well as during pathogenesis. In addition, we discuss the crosstalk between T-DNAs and genome-wide changes in DNA methylation during pathogenesis. We also cover recently discovered regulatory phenomena, such as T-DNA suppression and RNA silencing-independent and epigenetic-independent mechanisms that can silence T-DNAs. Finally, we discuss the implications of findings on T-DNA silencing for the improvement of plant genetic engineering.

Molecular Dynamics Investigation of the Influenza Hemagglutinin Conformational Changes in Acidic pH.

The surface protein hemagglutinin (HA) of the influenza virus plays a pivotal role in facilitating viral infection by binding to sialic acid receptors on host cells. Its conformational state is pH-sensitive, impacting its receptor-binding ability and evasion of the host immune response. In this study, we conducted extensive equilibrium microsecond-level all-atom molecular dynamics (MD) simulations of the HA protein to explore the influence of low pH on its conformational dynamics. Specifically, we investigated the impact of protonation on conserved histidine residues (H1062) located in the hinge region of HA2. Our analysis encompassed comparisons between nonprotonated (NP), partially protonated (1P, 2P), and fully protonated (3P) conditions. Our findings reveal substantial pH-dependent conformational alterations in the HA protein, affecting its receptor-binding capability and immune evasion potential. Notably, the nonprotonated form exhibits greater stability compared to protonated states. Conformational shifts in the central helices of HA2 involve outward movement, counterclockwise rotation of protonated helices, and fusion peptide release in protonated systems. Disruption of hydrogen bonds between the fusion peptide and central helices of HA2 drives this release. Moreover, HA1 separation is more likely in the fully protonated system (3P) compared to nonprotonated systems (NP), underscoring the influence of protonation. These insights shed light on influenza virus infection mechanisms and may inform the development of novel antiviral drugs targeting HA protein and pH-responsive drug delivery systems for influenza.

Immunopathological markers and cell types linked to COVID-19 symptom manifestation

BackgroundNumerous studies have investigated the molecular properties that contribute to the symptoms of COVID-19, such as the virus’s genetic makeup, its replication mechanisms, and how it interacts with host cells. However, identifying the immunopathological properties, such as the immune system’s response, cytokine levels, and the presence of specific biomarkers, that are associated with the severity of the infection remains crucial for developing effective treatments and preventions.MethodsWe analyzed blood protein factor profiles from 420 individuals to identify features differentiating between test-negative healthy, asymptomatic, and symptomatic individuals using statistical comparison and the least absolute shrinkage and selection operator (i.e., LASSO) algorithm. Additionally, we examined single-cell RNA sequencing data from 141 individuals to identify specific cell types associated with the COVID-19 symptoms.ResultsHealthy individuals who tested negative had distinct blood protein factor levels compared to asymptomatic individuals. We identified two key protein factors, Serpin A10 and Complement C9, that differentiate between asymptomatic and symptomatic patients. Symptomatic patients showed lower levels of CD4+ T naïve, CD4+ T effector & memory, and CD8+ T naïve cells, along with higher levels of CD14+ classical monocytes compared to asymptomatic patients. Additionally, CD16+ non-classical monocytes, major producers of C1QA/B/C, appeared to contribute to the observed Complement C9 levels.ConclusionsThese findings advance our understanding of the immunopathological mechanisms underlying COVID-19 and may inform the development of targeted therapies and preventative measures. Future research should focus on further elucidating these mechanisms and exploring their potential clinical applications in managing COVID-19 severity.

Visualizing the virus world inside the cell by cryo-electron tomography.

Structural studies on purified virus have revealed intricate architectures, but there is little structural information on how viruses interact with host cells in situ. Cryo-focused ion beam (FIB) milling and cryo-electron tomography (cryo-ET) have emerged as revolutionary tools in structural biology to visualize the dynamic conformational of viral particles and their interactions with host factors within infected cells. Here, we review the state-of-the-art cryo-ET technique for in situ viral structure studies and highlight exemplary studies that showcase the remarkable capabilities of cryo-ET in capturing the dynamic virus-host interaction, advancing our understanding of viral infection and pathogenesis.

Deletion of glycosyltransferase galE impairs the InlB anchoring and pathogenicity of Listeria monocytogenes

ABSTRACT Listeria monocytogenes (L. monocytogenes) is a foodborne intracellular pathogen that causes serious disease in both humans and animals. InlB is the major internalin protein of L. monocytogenes, which anchors to the bacterial surface and mediates its invasion into various host cells. Recent studies have shown that galactosylation of the cell wall polymer wall teichoic acid (WTA) is essential for InlB anchoring on the cell surface of L. monocytogenes serotype 4b strains. Galactosylation of WTA is exerted by the coordinated action of several glycosyltransferases, including GalU, GalE, GtcA, GttA, and GttB. Among these glycosyltransferases, GttA and GttB are specific to serotype 4b strains, whereas GalE, GalU, and GtcA are conserved across all serotypes. The role of GalE in InlB anchoring and L. monocytogenes pathogenicity remains unclear. In this study, we deleted the galE gene, which is involved in galactosylation, from L. monocytogenes strain ScottA. We found that galE deletion reduced InlB anchoring, weakened bacterial adhesion and invasion of Caco-2 cells (human colorectal adenocarcinoma cells) and MGC803 cells (human gastric carcinoma cells), increased phagocytosis but decreased proliferation in RAW264.7 cells (mouse mononuclear macrophage leukaemia cells), and decreased bacteria load, mortality, and tissue damage in infected mice. Taken together, galE deletion significantly reduced the anchoring of InlB and weakened the pathogenicity of L. monocytogenes. This finding provides new insights into the correlation between cell wall modification and pathogenicity of L. monocytogenes.

Cell-autonomous targeting of arabinogalactan by host immune factors inhibits mycobacterial growth

Deeper understanding of the crosstalk between host cells and Mycobacterium tuberculosis (Mtb) provides crucial guidelines for the rational design of novel intervention strategies against tuberculosis (TB). Mycobacteria possess a unique complex cell wall with arabinogalactan (AG) as a critical component. AG has been identified as a virulence factor of Mtb which is recognized by host galectin-9. Here, we demonstrate that galectin-9 directly inhibited mycobacterial growth through AG-binding property of carbohydrate-recognition domain 2. Furthermore, IgG antibodies with AG specificity were detected in the serum of TB patients. Based on the interaction between galectin-9 and AG, we developed a monoclonal antibody (mAb) screening assay and identified AG-specific mAbs which profoundly inhibit Mtb growth. Mechanistically, proteomic profiling and morphological characterizations revealed that AG-specific mAbs regulate AG biosynthesis, thereby inducing cell wall swelling. Thus, direct AG-binding by galectin-9 or antibodies contributes to protection against TB. Our findings pave the way for the rational design of novel immunotherapeutic strategies for TB control.

Cell-autonomous targeting of arabinogalactan by host immune factors inhibits mycobacterial growth.

Deeper understanding of the crosstalk between host cells and Mycobacterium tuberculosis (Mtb) provides crucial guidelines for the rational design of novel intervention strategies against tuberculosis (TB). Mycobacteria possess a unique complex cell wall with arabinogalactan (AG) as a critical component. AG has been identified as a virulence factor of Mtb which is recognized by host galectin-9. Here, we demonstrate that galectin-9 directly inhibited mycobacterial growth through AG-binding property of carbohydrate-recognition domain 2. Furthermore, IgG antibodies with AG specificity were detected in the serum of TB patients. Based on the interaction between galectin-9 and AG, we developed a monoclonal antibody (mAb) screening assay and identified AG-specific mAbs which profoundly inhibit Mtb growth. Mechanistically, proteomic profiling and morphological characterizations revealed that AG-specific mAbs regulate AG biosynthesis, thereby inducing cell wall swelling. Thus, direct AG-binding by galectin-9 or antibodies contributes to protection against TB. Our findings pave the way for the rational design of novel immunotherapeutic strategies for TB control.