Biology subjects

Zhang, J.-R.

Publications and source records attributed to Zhang, J.-R..

9 recordsLinked to original sources

bioRxiv2025

Plasma Ficolins Enable Liver Macrophages to Capture Blood-Borne Bacteria by Recognizing Capsular Polysaccharides

Ficolins are evolutionarily conserved glycan-binding lectins in plasma or on cell membranes of immune cells, yet their physiological functions remain to be defined. Here we demonstrate that plasma ficolins drives the capture of diverse encapsulated bacteria in the blood circulation by the liver resident macrophages (Kupffer cells). Ficolin-activated immunity in the liver sinusoids provides swift and sterilizing immunity in mice. Mice lacking ficolin-A (the only plasma ficolin) became hypersusceptible to the blood infections of the ficolin-A-recognizable bacterial serotypes. Mechanistically, plasma ficolins activate complement C3 on bacterial surfaces by pattern recognition of acetylated monosaccharides on polysaccharide capsules, and thereby deliver the opsonized bacteria to C3 receptors on Kupffer cells for phagocytic elimination. These findings reveal that plasma ficolins serve as pattern-recognition receptors that are essential for maintaining the bloodstream sterile.

microbiology↗

bioRxiv2024

Influenza Virus Enhances Bacterial Growth in the Lungs through Weakening Capsule Receptor-Mediated Bacterial Capture by Neutrophils

Certain serotypes of encapsulated bacteria are more associated with severe pneumonia than others, but the biological reason behind this association has remained largely unknown. This study has uncovered a causal relationship between capsule serotype and virulence phenotype of Streptococcus pneumoniae, a leading cause of community-acquired pneumonia, in mice using isogenic bacteria. Certain high-virulence (HV) serotypes persist in the lungs and lead to severe pneumonia, whereas the low-virulence (LV) serotypes are effectively cleared. The capsule type-dependent difference in virulence is determined by the capsule-binding receptors, which recognize the capsular polysaccharides of the LV serotypes (but not the HV serotypes) and enable pathogen capture by neutrophils through complement activation. The capsule receptor-driven immunity of lung neutrophils is significantly compromised by pre-infection of influenza virus, which enhances the survival and virulence of the LV S. pneumoniae serotypes, and recurs in the heightened pathogenicity of Haemophilus influenzae. This study not only unravels the long-sought mechanistic mystery of serotype-dependent virulence in bacterial lung infections, but also provides an explanation for the well-known pathogenesis synergism between influenza virus and respiratory bacteria. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=160 SRC="FIGDIR/small/622589v1_ufig1.gif" ALT="Figure 1"> View larger version (49K): org.highwire.dtl.DTLVardef@1464164org.highwire.dtl.DTLVardef@16f34e5org.highwire.dtl.DTLVardef@1f9ad46org.highwire.dtl.DTLVardef@df104d_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2024

C-Reactive Protein Drives Potent Clearance of Blood Bacteria in the Liver by Activating the Complement System

Plasma C-reactive protein (CRP) is widely used as a biomarker for bacterial infections due to its massive induction during infections, however, the precise function of CRP in bacterial infections remains undefined. Here we show that CRP enables Kupffer cells (liver macrophages) to capture and eliminate a wide range of encapsulated bacteria from the bloodstream of mice and thereby provides rapid and effective immunity. Mechanistically, CRP binds to the structurally diverse capsular polysaccharides of major Gram-positive and -negative pathogens, and thereby activates complement C3 at the bacterial surface. The C3-opsonized microbes are in turn captured by C3 receptors on the surface of Kupffer cells, and eliminated in the liver sinusoids. Since CRP principally shares the functional features of antibodies in pathogen recognition/execution, CRP-based defense combines the broad spectrum of the innate immunity with the swiftness, potency and specificity of the adaptive immunity, which helps explain massive rise of CRP during systemic bacterial infections.

immunology↗

bioRxiv2024

Calcium Homeostasis Modulator 2 Constitutes an ATP-regulation Pore in Mitochondria

Recent structural analyses showed that the calcium homeostasis modulator-2 (CALHM2) forms a mega channel, but its cellular location and endogenous function are yet unknown. We found that native CALHM2 resides on the mitochondrial inner membrane and constitutes an ATP-regulated ATP release channel. CALHM2 knockdown/knockout decreases cytosolic ATP concentration, and thereby compromises energy-sensitive processes, such as intracellular Ca2+ handling. However, CALHM2 loss-of-function elevates ATP concentration in the mitochondrial matrix, dephosphorylates key enzymes in the mammalian target of rapamycin (mTOR) pathway, and promotes longevity in CALHM2 knockout mice. These findings reveal that CALHM2 constitutes a novel regulator of mitochondrial metabolism, which may have important implications in aging and diseases.

cell biology↗

bioRxiv2024

Splenic red pulp macrophages eliminate the liver-resistant Streptococcus pneumoniae during bloodstream infection

The spleen is well-known for defense against invasive infections of encapsulated bacteria, particularly Streptococcus pneumoniae (pneumococcus). However, the precise mechanism of the splenic anti-bacterial immunity remains elusive. Here we report that red pulp (RP) macrophages execute the splenic defense against S. pneumoniae in mice, with the help of natural antibodies (nAbs) and complement system. The spleen slowly but substantially cleared encapsulated pneumococci from the bloodstream in the early phase of blood infection, especially the serotypes that resist to liver filtration. Among splenic macrophage subpopulations, only the lack of RP macrophages led to the complete loss of the splenic immunity. Intravital microscopy detected direct capture and phagocytic killing of circulating pneumococci by RP macrophages in the absence of neutrophils and inflammatory monocytes. Likewise, plasma nAbs targeting pneumococcal cell wall phosphocholine and complement protein C3 were essential for RP macrophage-mediated immune clearance. Our findings have thus uncovered the long-sought immune pathway against invasive pneumococcal infections in the spleen. Short summaryThe spleen plays a crucial role in defending against invasive infections caused by Streptococcus pneumoniae (pneumococcus) and other encapsulated bacteria in humans, but the mechanisms underlying this organ-specific immunity remain largely elusive. This study has revealed that the spleen eliminates pneumococci through a coordinated interplay among red pulp macrophages, serum nAbs targeting phosphocholine and the complement system.

microbiology↗

bioRxiv2024

Natural antibodies to polysaccharide capsules enable Kupffer cells to capture invading bacteria in the liver sinusoids

The interception of blood-borne bacteria in the liver defines the outcomes of invasive bacterial infections, but the mechanisms of this anti-bacterial immunity are largely speculative. This study shows that natural antibodies (nAbs) to capsules enable liver macrophage Kupffer cells (KCs) to rapidly capture and kill blood-borne encapsulated bacteria in mice. Affinity pulldown with serotype-10A capsular polysaccharides (CPS10A) of S. pneumoniae (Spn10A) led to the identification of CPS10A-binding nAbs in serum. The CPS10A-antibody interaction enabled KCs to capture Spn10A bacteria from the bloodstream, in part through complement receptors on KCs. The nAbs were found to recognize the {beta}1-6-linked galactose branch of CPS10A, and similar moieties of serotype-39 S. pneumoniae and serotype-K50 Klebsiella pneumoniae capsules. More importantly, the nAbs empowered KCs to capture serotype-39 S. pneumoniae and serotype-K50 K. pneumoniae in the liver. Collectively, our data have revealed a highly effective immune function of nAb against encapsulated bacteria, and provided a proof of concept for treating septic bacterial diseases with monoclonal antibodies. Short summaryRapid capture of potentially harmful bacteria in blood by liver macrophages are vital for the blood sterility and health. This work reports how naturally occurring antibodies in the plasma enable macrophages to capture and kill blood-borne bacteria in the liver.

microbiology↗

bioRxiv2022

Pathogen Clearance-based Correlates of Immunoprotection Reveal Insightful Features of Vaccine Immunity

Vaccination has significantly reduced the incidence of invasive infections caused by several bacterial pathogens, including Streptococcus pneumoniae, Haemophilus influenzae and Neisseria meningitidis. However, no vaccines are available for many other invasive pathogens. A major hurdle in vaccine development is the lack of functional markers to quantify vaccine immunity in eliminating pathogens in the process of infection. Based on our recent discovery of the liver as the major organ of vaccine-induced clearance of blood-borne virulent bacteria, we here describe a new vaccine evaluation system that quantitatively characterize important properties of effective vaccines in shuffling virulent bacteria from the blood circulation to the liver resident macrophage Kupffer cells (KCs) and sinusoidal endothelial cells (LSECs) in animal models. This system consists of three related correlates or assays: pathogen clearance from the bloodstream, pathogen trapping in the liver, and pathogen capture by KCs/LSECs. The readouts of these correlates were consistently associated with the serotype-specific immunoprotection levels of the 13-valent pneumococcal polysaccharide conjugate vaccine (PCV13) against lethal infections of S. pneumoniae, a major invasive pathogen of community-acquired infections in humans. Furthermore, the reliability and sensitivity of these correlates in reflecting vaccine efficacy were verified with whole cell vaccines of Klebsiella pneumoniae and Escherichia coli, two major pathogens in hospital-acquired invasive infections. This system may be used as cost effective readouts to evaluate the immunoprotective potential of vaccine candidates in the preclinical phase by filling the current technical gap in vaccine evaluation between the conventional in vitro approaches (e.g., antibody production and pathogen neutralization/opsonophagocytosis) and survival of immunized animals.

immunology↗

bioRxiv2022

Potent Bacterial Vaccines Require FcγRIIB-mediated Pathogen Capture by Liver Sinusoidal Endothelium

Certain vaccines are more effective than others against microbial infections, but the molecular mechanisms separating the two types of vaccines are largely undefined. Here, by comparing two vaccines of Streptococcus pneumoniae with identical antigens but different efficacies (pneumococcal conjugate vaccine - PCV13 and pneumococcal polysaccharide vaccine - PPV23), we reveal that superior vaccine protection against blood-borne bacteria is primarily achieved by activating pathogen capture of the sinusoidal endothelial cells (ECs) in the liver. Consistent with its superior protection in humans, PCV13 confers a more potent protection than PPV23 against pneumococcal infection in mice. In vivo real-time imaging and genetic mutagenesis revealed that PCV13 activates both liver ECs and resident macrophages Kupffer cells (KCs) to capture IgG-coated bacteria via IgG Fc gamma receptor (Fc{gamma}R). In particular, the Fc{gamma}RIIB-mediated capture by ECs is responsible for PCV13-induced superior protection. In contrast, PPV23 only activates KCs (but not ECs) to achieve a less effective pathogen capture and protection through complement receptor-mediated recognition of IgM- and C3-coated bacteria. These liver-based vaccine protection mechanisms are also found with the vaccines of Neisseria meningitidis and Klebsiella pneumoniae, another two important invasive human pathogens. Our findings have uncovered a novel EC- and Fc{gamma}RIIB-mediated mechanism in the liver for more efficacious vaccine protection. These findings can serve as in vivo functional readouts to evaluate vaccine efficacy and guide the future vaccine development. One Sentence SummaryVaccine efficacy is defined by Fc{gamma}RIIB-mediated capture of antibody-coated bacteria via liver sinusoidal endothelial cells.

immunology↗

bioRxiv2016

High-throughput CRISPRi phenotyping in Streptococcus pneumoniae identifies new essential genes involved in cell wall synthesis and competence development

Genome-wide screens have discovered a large set of essential genes in the opportunistic human pathogen Streptococcus pneumoniae. However, the functions of many essential genes are still unknown, hampering vaccine development and drug discovery. Based on results from transposon-sequencing (Tn-Seq), we refined the list of essential genes in S. pneumoniae serotype 2 strain D39. Next, we created a knockdown library targeting 348 potentially essential genes by CRISPR interference (CRISPRi) and show a growth phenotype for 254 of them (73%). Using high-content microscopy screening, we searched for essential genes of unknown function with clear phenotypes in cell morphology upon CRISPRi-based depletion. We show that SPD1416 and SPD1417 (renamed to MurT and GatD, respectively) are essential for peptidoglycan synthesis, and that SPD1198 and SPD1197 (renamed to TarP and TarQ, respectively) are responsible for the polymerization of teichoic acid (TA) precursors. This knowledge enabled us to reconstruct the unique pneumococcal TA biosynthetic pathway. CRISPRi was also employed to unravel the role of the essential Clpproteolytic system in regulation of competence development and we show that ClpX is the essential ATPase responsible for ClpP-dependent repression of competence. The CRISPRi library provides a valuable tool for characterization of pneumococcal genes and pathways and revealed several promising antibiotic targets.

microbiology↗