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Frontiers in Microbiology 2024(), a zoonotic pathogen with a broad host range, presents a substantial threat to global public health safety. Vaccination stands as an effective strategy for the...
BACKGROUND
(), a zoonotic pathogen with a broad host range, presents a substantial threat to global public health safety. Vaccination stands as an effective strategy for the prevention and control of infection, highlighting an immediate clinical need for the creation of safe and efficient attenuated live vaccines.
METHODS
In this study, a peptidoglycan-associated lipoprotein () gene deletion strain (Δ), was constructed. To assess its virulence, we conducted experiments on biofilm formation capability, motility, as well as cell and mouse infection. Subsequently, we evaluated the immune-protective effect of Δ.
RESULTS
It was discovered that deletion of the gene reduced the biofilm formation capability and motility of . Cell infection experiments revealed that the Δ strain exhibited significantly decreased abilities in invasion, adhesion, and intracellular survival, with downregulation of virulence gene expression, including , , , , , , , and . Mouse infection experiments showed that the LD of Δ increased by 10 times, and its colonization ability in mouse tissue organs was significantly reduced. The results indicated that the gene severely affected the virulence of . Further, immunogenicity evaluation of Δ showed a significant enhancement in the lymphocyte transformation proliferation capability of immunized mice, producing high titers of specific IgG and IgA, suggesting that Δ possesses good immunogenicity. Challenge protection tests demonstrated that the strain could provide 100% immune protection against wild-type strains in mice.
DISCUSSION
This study proves that the gene influences the virulence of , and Δ could serve as a candidate strain for attenuated live vaccines, laying the foundation for the development of attenuated live vaccines against .
PubMed: 38903796
DOI: 10.3389/fmicb.2024.1422202 -
Inorganic Chemistry Jun 2024Pathogenic bacteria have consistently posed a formidable challenge to human health, creating the critical need for effective antibacterial solutions. In response,...
Pathogenic bacteria have consistently posed a formidable challenge to human health, creating the critical need for effective antibacterial solutions. In response, enzyme-metal-organic framework (MOF) composites have emerged as a promising class of antibacterial agents. This study focuses on the development of an enzyme-MOF composite based on HZIF-8, incorporating the advantages of simple synthesis, ZIF-8 antibacterial properties, lysozyme hydrolysis, and high biological safety. Through a one-pot method, core-shell nanoparticles (HZIF-8) were synthesized. This structure enables efficient immobilization of lysozyme and lactoferrin within the HZIF-8, resulting in the formation of the lysozyme-lactoferrin@HZIF-8 (LYZ-LF@HZIF-8) composite. Upon exposure to light irradiation, HZIF-8 itself possessed antibacterial properties. Lysozyme initiated the degradation of bacterial peptidoglycan and lactoferrin synergistically enhanced the antibacterial effect of lysozyme. All of the above ultimately contributed to comprehensive antibacterial activity. Antibacterial assessments demonstrated the efficacy of the LYZ-LF@HZIF-8 composite, effectively eradicating at a cell density of 1.5 × 10 CFU/mL with a low dosage of 200 μg/mL and completely inactivating at 400 μg/mL with the same cell density. The enzyme-MOF composite exhibited significant and durable antibacterial efficacy, with no apparent cytotoxicity in vitro, thereby unveiling expansive prospects for applications in the medical and food industries.
PubMed: 38902911
DOI: 10.1021/acs.inorgchem.4c02082 -
Infection and Immunity Jun 2024Toll-like receptor 9 (TLR9) is an innate immune receptor that localizes to endosomes in antigen presenting cells and recognizes single stranded unmethylated CpG sites on...
Toll-like receptor 9 (TLR9) is an innate immune receptor that localizes to endosomes in antigen presenting cells and recognizes single stranded unmethylated CpG sites on bacterial genomic DNA (gDNA). Previous bioinformatic studies have demonstrated that the genome of the human pathogen contains TLR9 stimulatory motifs, and correlative studies have implied a link between human TLR9 (hTLR9) genotype variants and susceptibility to infection. Here, we present our evaluation of the stimulatory potential of gDNA and its recognition by hTLR9- and murine TLR9 (mTLR9)-expressing cells. Utilizing reporter cell lines, we demonstrate that purified gDNA from can stimulate hTLR9 signaling, albeit at lower levels than gDNA prepared from other Gram-negative bacteria. Interestingly, we found that while is capable of signaling through hTLR9 and mTLR9 during live infections in HEK293 reporter cell lines, signaling only occurs at later developmental time points. Chlamydia-specific induction of hTLR9 is blocked when protein synthesis is inhibited prior to the RB-to-EB conversion, exacerbated by the inhibition of lipooligosaccharide biosynthesis, and is significantly altered during the induction of aberrance/persistence. Our observations support the hypothesis that chlamydial gDNA is released during the conversion between the pathogen's replicative and infectious forms and during treatment with antibiotics targeting peptidoglycan assembly. Given that inclusions do not co-localize with TLR9-containing vacuoles in the pro-monocytic cell line U937, our findings also hint that chlamydial gDNA is capable of egress from the inclusion, and traffics to TLR9-containing vacuoles via an as yet unknown pathway.
PubMed: 38899879
DOI: 10.1128/iai.00063-24 -
EJNMMI Radiopharmacy and Chemistry Jun 2024Infection remains a major cause of morbidity and mortality, regardless of advances in antimicrobial therapy and improved knowledge of microorganisms. With the major... (Review)
Review
BACKGROUND
Infection remains a major cause of morbidity and mortality, regardless of advances in antimicrobial therapy and improved knowledge of microorganisms. With the major global threat posed by antimicrobial resistance, fast and accurate diagnosis of infections, and the reliable identification of intractable infection, are becoming more crucial for effective treatment and the application of antibiotic stewardship. Molecular imaging with the use of nuclear medicine allows early detection and localisation of infection and inflammatory processes, as well as accurate monitoring of treatment response. There has been a continuous search for more specific radiopharmaceuticals to be utilised for infection imaging. This review summarises the most prominent discoveries in specifically bacterial infection imaging agents over the last five years, since 2019.
MAIN BODY
Some promising new radiopharmaceuticals evaluated in patient studies are reported here, including radiolabelled bacterial siderophores like [Ga]Ga-DFO-B, radiolabelled antimicrobial peptide/peptide fragments like [Ga]Ga-NOTA-UBI29-41, and agents that target bacterial synthesis pathways (folic acid and peptidoglycan) like [C]para-aminobenzoic acid and D-methyl-[C]-methionine, with clinical trials underway for [F]fluorodeoxy-sorbitol, as well as for C- and F-labelled trimethoprim.
CONCLUSION
It is evident that a great deal of effort has gone into the development of new radiopharmaceuticals for infection imaging over the last few years, with remarkable progress in preclinical investigations. However, translation to clinical trials, and eventually clinical Nuclear Medicine practice, is apparently slow. It is the authors' opinion that a more structured and harmonised preclinical setting and well-designed clinical investigations are the key to reliably evaluate the true potential of the newly proposed infection imaging agents.
PubMed: 38896373
DOI: 10.1186/s41181-024-00279-7 -
Scientific Reports Jun 2024Penicillin binding proteins (PBPs) are involved in biosynthesis, remodeling and recycling of peptidoglycan (PG) in bacteria. PBP-A from Thermosynechococcus elongatus...
Penicillin binding proteins (PBPs) are involved in biosynthesis, remodeling and recycling of peptidoglycan (PG) in bacteria. PBP-A from Thermosynechococcus elongatus belongs to a cyanobacterial family of enzymes sharing close structural and phylogenetic proximity to class A β-lactamases. With the long-term aim of converting PBP-A into a β-lactamase by directed evolution, we simulated what may happen when an organism like Escherichia coli acquires such a new PBP and observed growth defect associated with the enzyme activity. To further explore the molecular origins of this harmful effect, we decided to characterize deeper the activity of PBP-A both in vitro and in vivo. We found that PBP-A is an enzyme endowed with DD-carboxypeptidase and DD-endopeptidase activities, featuring high specificity towards muropeptides amidated on the D-iso-glutamyl residue. We also show that a low promiscuous activity on non-amidated peptidoglycan deteriorates E. coli's envelope, which is much higher under acidic conditions where substrate discrimination is mitigated. Besides expanding our knowledge of the biochemical activity of PBP-A, this work also highlights that promiscuity may depend on environmental conditions and how it may hinder rather than promote enzyme evolution in nature or in the laboratory.
Topics: Escherichia coli; Hydrogen-Ion Concentration; Penicillin-Binding Proteins; Peptidoglycan; Substrate Specificity; Cyanobacteria; Bacterial Proteins; Synechococcus
PubMed: 38890528
DOI: 10.1038/s41598-024-64806-x -
Archives of Virology Jun 2024The inflammasome is a multimeric protein complex that plays a vital role in the defence against pathogens and is therefore considered an essential component of the...
In vitro analysis of the expression of inflammasome, antiviral, and immune genes in an Oreochromis niloticus liver cell line following stimulation with bacterial ligands and infection with tilapia lake virus.
The inflammasome is a multimeric protein complex that plays a vital role in the defence against pathogens and is therefore considered an essential component of the innate immune system. In this study, the expression patterns of inflammasome genes (NLRC3, ASC, and CAS-1), antiviral genes (IFNγ and MX), and immune genes (IL-1β and IL-18) were analysed in Oreochromis niloticus liver (ONIL) cells following stimulation with the bacterial ligands peptidoglycan (PGN) and lipopolysaccharide (LPS) and infection with TiLV. The cells were stimulated with PGN and LPS at concentrations of 10, 25, and 50 µg/ml. For viral infection, 10 TCID of TiLV per ml was used. After LPS stimulation, all seven genes were found to be expressed at specific time points at each of the three doses tested. However, at even higher doses of LPS, NLRC3 levels decreased. Following TiLV infection, all of the genes showed significant upregulation, especially at early time points. However, the gene expression pattern was found to be unique in PGN-treated cells. For instance, NLRC3 and ASC did not show any response to PGN stimulation, and the expression of IFNγ was downregulated at 25 and 50 µg of PGN per ml. CAS-1 and IL-18 expression was downregulated at 25 µg of PGN per ml. At a higher dose (50 µg/ml), IL-1β showed downregulation. Overall, our results indicate that these genes are involved in the immune response to viral and bacterial infection and that the degree of response is ligand- and dose-dependent.
Topics: Animals; Cichlids; Inflammasomes; Fish Diseases; Cell Line; Peptidoglycan; Liver; Lipopolysaccharides; Immunity, Innate; Fish Proteins; Interleukin-18; Ligands; DNA Virus Infections; Gene Expression Regulation; Interleukin-1beta
PubMed: 38888759
DOI: 10.1007/s00705-024-06077-5 -
International Journal of Biological... Jun 2024Chronic wound healing is a pressing global public health concern. Abuse and drug resistance of antibiotics are the key problems in the treatment of chronic wounds at... (Review)
Review
Chronic wound healing is a pressing global public health concern. Abuse and drug resistance of antibiotics are the key problems in the treatment of chronic wounds at present. Postbiotics are a novel promising strategy. Previous studies have reported that postbiotics have a wide range of biological activities including antimicrobial, immunomodulatory, antioxidant and anti-inflammatory abilities. However, several aspects related to these postbiotic activities remain unexplored or poorly known. Therefore, this work aims to outline general aspects and emerging trends in the use of postbiotics for wound healing, such as the production, characterization, biological activities and delivery strategies of postbiotics. In this review, a comprehensive overview of the physiological activities and structures of postbiotic biomolecules that contribute to wound healing is provided, such as peptidoglycan, lipoteichoic acid, bacteriocins, exopolysaccharides, surface layer proteins, pili proteins, and secretory proteins (p40 and p75 proteins). Considering the presence of readily degradable components in postbiotics, potential natural polymer delivery materials and delivery systems are emphasized, followed by the potential applications and commercialization prospects of postbiotics. These findings suggest that the treatment of chronic wounds with postbiotic ingredients will help provide new insights into wound healing and better guidance for the development of postbiotic products.
PubMed: 38885869
DOI: 10.1016/j.ijbiomac.2024.133195 -
Antimicrobial Agents and Chemotherapy Jun 2024Peptidoglycan (PG) is an important architectural element that imparts physical toughness and rigidity to the bacterial envelope. It is also a dynamic structure that...
Peptidoglycan (PG) is an important architectural element that imparts physical toughness and rigidity to the bacterial envelope. It is also a dynamic structure that undergoes continuous turnover or autolysis. possesses redundant PG degradation enzymes responsible for PG turnover; however, the advantage afforded by the existence of numerous PG degradation enzymes remains incompletely understood. In this study, we elucidated the physiological roles of MltE and MltC, members of the lytic transglycosylase (LTG) family that catalyze the cleavage of glycosidic bonds between disaccharide subunits within PG strands. MltE and MltC are acidic LTGs that exhibit increased enzymatic activity and protein levels under acidic pH conditions, respectively, and deletion of these two LTGs results in a pronounced growth defect at acidic pH. Furthermore, inactivation of these two LTGs induces increased susceptibility at acidic pH against various antibiotics, particularly vancomycin, which seems to be partially caused by elevated membrane permeability. Intriguingly, inactivation of these LTGs induces a chaining morphology, indicative of daughter cell separation defects, only under acidic pH conditions. Simultaneous deletion of PG amidases, known contributors to daughter cell separation, exacerbates the chaining phenotype at acidic pH. This suggests that the two LTGs may participate in the cleavage of glycan strands between daughter cells under acidic pH conditions. Collectively, our findings highlight the role of LTG repertoire diversity in facilitating bacterial survival and antibiotic resistance under stressful conditions.
PubMed: 38884456
DOI: 10.1128/aac.00372-24 -
Organic & Biomolecular Chemistry Jun 2024Muramyl dipeptide (MDP) is the smallest essential peptidoglycan substructure capable of promoting both innate and adaptive immune responses. Herein, we report on the...
Muramyl dipeptide (MDP) is the smallest essential peptidoglycan substructure capable of promoting both innate and adaptive immune responses. Herein, we report on the design, synthesis, and study of the adjuvant properties of two novel MDP analogs containing an achiral adamantyl moiety attached to the desmuramyl dipeptide (DMP) pharmacophore and additionally modified by one mannosyl subunit (derivative 7) or two mannosyl subunits (derivative 11). Mannose substructures were introduced in order to assess how the degree of mannosylation affects the immune response and nucleotide-binding oligomerization-domain-containing protein 2 (NOD2) binding affinity, compared to the reference compound ManAdDMP. Both mannosylated MDP analogs showed improved immunomodulating properties, while the di-mannosylated derivative 11 displayed the highest, statistically significant increase in anti-OVA IgG production. In this study, for the first time, the di-mannosylated DMP derivative was synthesized and immunologically evaluated. Derivative 11 stimulates a Th-2-polarized type of immune reaction, similar to the reference compound ManAdDMP and MDP. Molecular dynamics (MD) simulations demonstrate that 11 has a higher NOD2 binding affinity than 7, indicating that introducing the second mannose significantly contributes to the binding affinity. Mannose interacts with key amino acid residues from the LRR hydrophobic pocket of the NOD2 receptor and loop 2.
PubMed: 38884368
DOI: 10.1039/d4ob00592a -
Frontiers in Microbiology 2024causes listeriosis, an infectious and potentially fatal disease of animals and humans. A diverse network of transcriptional regulators, including LysR-type catabolite...
causes listeriosis, an infectious and potentially fatal disease of animals and humans. A diverse network of transcriptional regulators, including LysR-type catabolite control protein C (CcpC), is critical for the survival of and its ability to transition into the host environment. In this study, we explored the physiological and genetic consequences of deleting and the effects of such deletion on the ability of to cause disease. We found that deletion did not impact hemolytic activity, whereas it resulted in significant reductions in phospholipase activities. Western blotting revealed that the Δ strain produced significantly reduced levels of the cholesterol-dependent cytolysin LLO relative to the wildtype F2365 strain. However, the Δ mutant displayed no significant intracellular growth defect in macrophages. Furthermore, Δ strain exhibited reduction in plaque numbers in fibroblasts compared to F2365, but plaque size was not significantly affected by deletion. In a murine model system, the Δ strain exhibited a significantly reduced bacterial burden in the liver and spleen compared to the wildtype F2365 strain. Interestingly, the deletion of this gene also enhanced the survival of under conditions of HO-induced oxidative stress. Transcriptomic analyses performed under HO-induced oxidative stress conditions revealed that DNA repair, cellular responses to DNA damage and stress, metalloregulatory proteins, and genes involved in the biosynthesis of peptidoglycan and teichoic acids were significantly induced in the deletion strain relative to F2365. In contrast, genes encoding internalin, 1-phosphatidylinositol phosphodiesterase, and genes associated with sugar-specific phosphotransferase system components, porphyrin, branched-chain amino acids, and pentose phosphate pathway were significantly downregulated in the deletion strain relative to F2365. This finding highlights CcpC as a key factor that regulates physiology and responses to oxidative stress by controlling the expression of important metabolic pathways.
PubMed: 38881664
DOI: 10.3389/fmicb.2024.1403694