Progress on H2B as a multifunctional protein related to pathogens.

Histone H2B is a member of the core histones, which together with other histones form the nucleosome, the basic structural unit of chromosomes. As scientists delve deeper into histones, researchers gradually realize that histone H2B is not only an important part of nucleosomes, but also plays a momentous role in regulating gene transcription, acting as a receptor and antimicrobial action outside the nucleus. There are a variety of epigenetically modified sites in the H2B tail rich in arginine and lysine, which can occur in ubiquitination, phosphorylation, methylation, acetylation, etc. When stimulated by foreign factors such as bacteria, viruses or parasites, histone H2B can act as a receptor for the recognition of these pathogens, and induce an intrinsic immune response to enhance host defense. In addition, the extrachromosomal histone H2B is also an important anti-microorganism agent, which may be the key to the development of antibiotics in the future. This review aims to summarize the interaction between histone H2B and etiological agents and explore the role of H2B in epigenetic modifications, receptors and antimicrobial activity.

Aerobic glycolysis of bronchial epithelial cells rewires Mycoplasma pneumoniae pneumonia and promotes bacterial elimination.

The immune response to Mycoplasma pneumoniae infection plays a key role in clinical symptoms. Previous investigations focused on the pro-inflammatory effects of leukocytes and the pivotal role of epithelial cell metabolic status in finely modulating the inflammatory response have been neglected. Herein, we examined how glycolysis in airway epithelial cells is affected by M. pneumoniae infection in an in vitro model. Additionally, we investigated the contribution of ATP to pulmonary inflammation. Metabolic analysis revealed a marked metabolic shift in bronchial epithelial cells during M. pneumoniae infection, characterized by increased glucose uptake, enhanced aerobic glycolysis, and augmented ATP synthesis. Notably, these metabolic alterations are orchestrated by adaptor proteins, MyD88 and TRAM. The resulting synthesized ATP is released into the extracellular milieu via vesicular exocytosis and pannexin protein channels, leading to a substantial increase in extracellular ATP levels. The conditioned medium supernatant from M. pneumoniae-infected epithelial cells enhances the secretion of both interleukin (IL)-1ß and IL-18 by peripheral blood mononuclear cells, partially mediated by the P2X7 purine receptor (P2X7R). In vivo experiments confirm that addition of a conditioned medium exacerbates pulmonary inflammation, which can be attenuated by pre-treatment with a P2X7R inhibitor. Collectively, these findings highlight the significance of airway epithelial aerobic glycolysis in enhancing the pulmonary inflammatory response and aiding pathogen clearance.

The effects of CypA on apoptosis: potential target for the treatment of diseases.

Cyclophilin A (CypA), the first member of cyclophilins, is distributed extensively in eukaryotic and prokaryotic cells, primarily localized in the cytoplasm. In addition to acting as an intracellular receptor for cyclosporin A (CSA), CypA plays a crucial role in diseases such as aging and tumorigenesis. Apoptosis, a form of programmed cell death, is able to balance the rate of cell viability and death. In this review, we focus on the effects of CypA on apoptosis and the relationship between specific mechanisms of CypA promoting or inhibiting apoptosis and diseases, including tumorigenesis, cardiovascular diseases, organ injury, and microbial infections. Notably, the process of CypA promoting or inhibiting apoptosis is closely related to disease development. Finally, future prospects for the association of CypA and apoptosis are discussed, and a comprehensive understanding of the effects of CypA on apoptosis in relation to diseases is expected to provide new insights into the design of CypA as a therapeutic target for diseases. KEY POINTS: • Understand the effect of CypA on apoptosis. • CypA affects apoptosis through specific pathways. • The effect of CypA on apoptosis is associated with a variety of disease processes.

Mycoplasma genitalium Protein of Adhesion Suppresses T Cell Activation via CypA-CaN-NFAT Pathway.

Mycoplasma genitalium is a prokaryotic microorganism that causes urogenital tract infections. M. genitalium protein of adhesion (MgPa) was essential for M. genitalium attachment and subsequent invasion into host cells. Our prior research confirmed that Cyclophilin A (CypA) was the binding receptor for MgPa and MgPa-CypA interaction can lead to the production of inflammatory cytokines. In this study, we revealed that the recombinant MgPa (rMgPa) could inhibit the CaN-NFAT signaling pathway to reduce the level of IFN-γ, IL-2, CD25, and CD69 in Jurkat cells by binding to the CypA receptor. Moreover, rMgPa inhibited the expressions of IFN-γ, IL-2, CD25, and CD69 in primary mouse T cells. Likewise, the expressions of these T cells activation-related molecules in CypA-siRNA-transfected cells and CypA-/- mouse primary T cell was strengthened by rMgPa. These findings showed that rMgPa suppressed T cell activation by downregulating the CypA-CaN-NFAT pathway, and as a result, acted as an immunosuppressive agent. IMPORTANCE Mycoplasma genitalium is a sexually transmitted bacterium that can co-infect with other infections and causes nongonococcal urethritis in males, cervicitis, pelvic inflammatory disease, premature birth, and ectopic pregnancy in women. The adhesion protein of M. genitalium (MgPa) is the primary virulence factor in the complicated pathogenicity of M. genitalium. This research proved that MgPa could interact with host cell Cyclophilin A (CypA) and prevent T cell activation by inhibiting Calcineurin (CaN) phosphorylation and NFAT nuclear translocation, which clarified the immunosuppression mechanism of M. genitalium to host T cells. Therefore, this study can provide a new idea that CypA can be used for a therapeutic or prophylactic target for M. genitalium infection.

Mycoplasma genitalium infection in the female reproductive system: Diseases and treatment.

Mycoplasma genitalium is a newly emerged sexually transmitted disease pathogen and an independent risk factor for female cervicitis and pelvic inflammatory disease. The clinical symptoms caused by M. genitalium infection are mild and easily ignored. If left untreated, M. genitalium can grow along the reproductive tract and cause salpingitis, leading to infertility and ectopic pregnancy. Additionally, M. genitalium infection in late pregnancy can increase the incidence of preterm birth. M. genitalium infections are often accompanied by co-infection with other sexually transmitted pathogens (Chlamydia trachomatis, Neisseria gonorrhoeae, and Trichomonas vaginalis) and viral infections (Human Papilloma Virus and Human Immunodeficiency Virus). A recent study suggested that M. genitalium plays a role in tumor development in the female reproductive system. However, few studies endorsed this finding. In recent years, M. genitalium has evolved into a new "superbug" due to the emergence of macrolide-and fluoroquinolone-resistant strains leading to frequent therapy failures. This review summarizes the pathogenic characteristics of M. genitalium and the female reproductive diseases caused by M. genitalium (cervicitis, pelvic inflammatory disease, ectopic pregnancy, infertility, premature birth, co-infection, reproductive tumors, etc.), as well as its potential relationship with reproductive tumors and clinical treatment.

Pushing the envelope: Immune mechanism and application landscape of macrophage-activating lipopeptide-2.

Mycoplasma fermentans can cause respiratory diseases, arthritis, genitourinary tract infections, and chronic fatigue syndrome and have been linked to the development of the human immunodeficiency virus. Because mycoplasma lacks a cell wall, its outer membrane lipoproteins are one of the main factors that induce inflammation in the organism and contribute to disease development. Macrophage-activating lipopeptide-2 (MALP-2) modulates the inflammatory response of monocytes/macrophages in a bidirectional fashion, indirectly enhances the cytotoxicity of NK cells, promotes oxidative bursts in neutrophils, upregulates surface markers on lymphocytes, enhances antigen presentation on dendritic cells and induces immune inflammatory responses in sebocytes and mesenchymal cells. MALP-2 is a promising vaccine adjuvant for this application. It also promotes vascular healing and regeneration, accelerates wound and bone healing, suppresses tumors and metastasis, and reduces lung infections and inflammation. MALP-2 has a simple structure, is easy to synthesize, and has promising prospects for clinical application. Therefore, this paper reviews the mechanisms of MALP-2 activation in immune cells, focusing on the application of MALP-2 in animals/humans to provide a basis for the study of pathogenesis in Mycoplasma fermentans and the translation of MALP-2 into clinical applications.

Antibacterial Potential Analysis of Novel α-Helix Peptides in the Chinese Wolf Spider Lycosa sinensis.

The spider Lycosa sinensis represents a burrowing wolf spider (family Lycosidae) widely distributed in the cotton region of northern China, whose venom is rich in various bioactive peptides. In previous study, we used a combination strategy of peptidomic and transcriptomic analyses to systematically screen and identify potential antimicrobial peptides (AMPs) in Lycosa sinensis venom that matched the α-helix structures. In this work, the three peptides (LS-AMP-E1, LS-AMP-F1, and LS-AMP-G1) were subjected to sequence analysis of the physicochemical properties and helical wheel projection, and then six common clinical pathogenic bacteria (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) with multiple drug-resistance were isolated and cultured for the evaluation and analysis of antimicrobial activity of these peptides. The results showed that two peptides (LS-AMP-E1 and LS-AMP-F1) had different inhibitory activity against six clinical drug-resistant bacteria; they can effectively inhibit the formation of biofilm and have no obvious hemolytic effect. Moreover, both LS-AMP-E1 and LS-AMP-F1 exhibited varying degrees of synergistic therapeutic effects with traditional antibiotics (azithromycin, erythromycin, and doxycycline), significantly reducing the working concentration of antibiotics and AMPs. In terms of antimicrobial mechanisms, LS-AMP-E1 and LS-AMP-F1 destroyed the integrity of bacterial cell membranes in a short period of time and completely inhibited bacterial growth within 10 min of action. Meanwhile, high concentrations of Mg2+ effectively reduced the antibacterial activity of LS-AMP-E1 and LS-AMP-F1. Together, it suggested that the two peptides interact directly on bacterial cell membranes. Taken together, bioinformatic and functional analyses in the present work sheds light on the structure-function relationships of LS-AMPs, and facilitates the discovery and clinical application of novel AMPs.

Mycoplasma pneumoniae downregulates RECK to promote matrix metalloproteinase-9 secretion by bronchial epithelial cells.

Airway epithelial cells function as both a physical barrier against harmful substances and pathogenic microorganisms and as an important participant in the innate immune system. Matrix metalloproteinase-9 (MMP-9) plays a crucial role in modulating inflammatory responses during respiratory infections. However, the signalling cascade that induces MMP-9 secretion from epithelial cells infected with Mycoplasma pneumoniae remains poorly understood. In this study, we investigated the mechanism of MMP-9 secretion in airway epithelial cells infected with M. pneumoniae. Our data clearly showed that M. pneumoniae induced the secretion of MMP-9 from bronchial epithelial cells and upregulated its enzymatic activity in a time- and dose-dependent manner. Using specific inhibitors and chromatin co-precipitation experiments, we confirmed that the expression of MMP-9 is reliant on the activation of the Toll-like receptor 2 (TLR2) and TLR6-dependent mitogen-activated protein kinase/nuclear factor- κB/activator protein-1 (MAPK/NF-κB/AP-1) pathways. Additionally, epigenetic modifications such as histone acetylation and the nuclear transcription factor Sp1 also regulate MMP-9 expression. M. pneumoniae infection also decreased the expression of the tumour suppressor reversion-inducing cysteine-rich protein with Kazal motifs (RECK) by inducing Sp1 phosphorylation. Overexpression of RECK significantly impaired the M. pneumoniae-triggered increase in MMP-9 enzymatic activity, although the level of MMP-9 protein remained constant. The study demonstrated that M. pneumoniae-triggered MMP-9 expression is modulated by TLR2 and 6, the MAPK/NF-κB/AP-1 signalling cascade, and histone acetylation, and M. pneumoniae downregulated the expression of RECK, thereby increasing MMP-9 activity to modulate the inflammatory response, which could play a role in airway remodelling.

Two Potential Syphilis Vaccine Candidates Inhibit Dissemination of Treponema pallidum.

Syphilis, caused by the spirochete Treponema pallidum subspecies pallidum, continues to be a major public health problem worldwide. Recent increases in the number of syphilis cases, in addition to the lack of an efficient vaccine against T. pallidum for humans, highlights an urgent need for the design and development of an efficacious syphilis vaccine. Here, we assess the vaccine potential of the adhesion protein Tp0136 and the outer membrane protein Tp0663. Rabbits were subcutaneously immunized with recombinant proteins Tp0136, Tp0663, or control PBS. Immunization with Tp0136 or Tp0663 generated a strong humoral immune response with high titers of IgG, as assessed by ELISA. Moreover, animals immunized with Tp0136 or Tp0663 exhibited attenuated lesion development, increased cellular infiltration at the lesion sites, and inhibition of treponemal dissemination to distant organs compared to the unimmunized animals. These findings indicate that Tp0136 and Tp0663 are promising syphilis vaccine candidates. Furthermore, these results provide novel and important information for not only understanding the pathogenic mechanisms of spirochetes, but also the development of spirochete-specific subunit vaccines.

Community-Acquired Respiratory Distress Syndrome Toxin: Unique Exotoxin for M. pneumoniae.

Mycoplasma pneumoniae infection often causes respiratory diseases in humans, particularly in children and adults with atypical pneumonia and community-acquired pneumonia (CAP), and is often exacerbated by co-infection with other lung diseases, such as asthma, bronchitis, and chronic obstructive pulmonary disorder. Community-acquired respiratory distress syndrome toxin (CARDS TX) is the only exotoxin produced by M. pneumoniae and has been extensively studied for its ADP-ribosyltransferase (ADPRT) activity and cellular vacuolization properties. Additionally, CARDS TX induces inflammatory responses, resulting in cell swelling, nuclear lysis, mucus proliferation, and cell vacuolization. CARDS TX enters host cells by binding to the host receptor and is then reverse transported to the endoplasmic reticulum to exert its pathogenic effects. In this review, we focus on the structural characteristics, functional activity, distribution and receptors, mechanism of cell entry, and inflammatory response of CARDS TX was examined. Overall, the findings of this review provide a theoretical basis for further investigation of the mechanism of M. pneumoniae infection and the development of clinical diagnosis and vaccines.

T-B cell epitope peptides induce protective immunity against Mycoplasma pneumoniae respiratory tract infection in BALB/c mice.

Mycoplasma pneumoniae is the most common pathogen of community-acquired pneumonia in humans. Due to its high rates of antibiotic resistance, vaccination has become the best method to control the dissemination of M. pneumoniae. The recombinant carboxyl terminus of the P1 (P1C) protein is an immunodominant antigen, but it has negative effects such as poor stability and lower purity. In the current study, T-B epitopes of the P1C protein were predicted according to bioinformatics analysis and assessed for efficacy in peptide vaccination. BALB/c mice were subcutaneously inoculated with the T-B epitope peptides four times and then infected with M. pneumoniae through the respiratory tract. The results showed that the T-B epitope peptides of the P1C protein (P1C103-117, P1C155-169, P1C224-238 and P1C244-258) induced strong antigen-specific serum antibody responses and cellular immune responses with high levels of serum IgG, IgA antibodies and Th1-biased (IFN-γ and IL-2) cytokines. Immunization with T-B epitope peptides significantly reduced the M. pneumoniae burden and the degree of inflammation in the challenged mice. Furthermore, the levels of IFN-γ and TNF-α in the supernatants of lung homogenates were observably reduced compared to those in the PBS group. Overall, our findings demonstrate that T-B epitopes (P1C103-117, P1C155-169, P1C224-238 and P1C244-258) play significant roles in the P1C protein and can be used to induce powerful humoral and cellular immune responses to provide significant protection against M. pneumoniae pulmonary infection, which provides new insight into the design of potential multiepitope vaccines to prevent host infection by M. pneumoniae.

Immunogenicity and protective efficacy against Treponema pallidum in New Zealand rabbits immunized with plasmid DNA encoding flagellin.

Plasmid DNA encoding flagellin FlaB3 was used as a vaccination candidate for the evaluation of immunogenicity and protection against Treponema pallidum subsp. pallidum dissemination. First, intramuscular injection of the flagellin encoded by the plasmid DNA into New Zealand rabbits elicited both humoral and cellular immune responses. Total IgG production increased in response to flagellin. In addition, serum IFN-γ secretion and CD8+ cells were substantially greater in the rabbits immunized with the plasmid encoding flagellin FlaB3 than those in the rabbits immunized with recombinant flagellin. The flagellin encoded by the plasmid DNA induced significant upregulation of serum IL-6 and IL-8 compared to that of the control rabbits. Subsequently, intradermal challenge of the vaccinated New Zealand rabbits with 1 × 107T. pallidum resulted in a significant reduction of the bacterial organ burden in the blood, liver, spleen, and testicles in the flagellin plasmid DNA-vaccinated rabbits. Furthermore, the histopathological analysis demonstrated that the rabbits immunized with the plasmid DNA-encoded flagellin (FlaB3) showed better immune protection. These findings provide evidence that plasmid DNA-encoded flagellin (FlaB3) may be useful as a potential immunization route for future development of a vaccine to inhibit T. pallidum dissemination in related animals.