Medical Microbiology and Immunology最新文献

Airway epithelial cells play a pivotal role in the early host response to Mycoplasma pneumoniae colonization. Our previous study has revealed that M. pneumoniae infection induces metabolic reprogramming in bronchial epithelial cells. However, the mechanisms underlying these metabolic shifts and their contribution to the pathogenesis of pneumonia remain unclear. Herein, we demonstrate that M. pneumoniae infection activates signal transducer and activator of transcription 3 (STAT3), which drives citrate accumulation in airway epithelial cells. Citrate is metabolized by adenosine triphosphate-citrate lyase (ACLY) into acetyl coenzyme A, which is further converted to malonyl coenzyme A, promoting post-translational modifications such as histone acetylation and glyceraldehyde-3-phosphate dehydrogenase malonylation (GAPDH). In vivo, pharmacological inhibition of STAT3 or ACLY attenuated pulmonary inflammation and pro-inflammatory cytokine expression yet paradoxically delayed pathogen clearance, as evidenced by increased colonyforming units in bronchoalveolar lavage fluid and lung tissue. These findings demonstrate that targeting the STAT3/ACLY axis exerts antiinflammatory potential without direct antibacterial activity. Our work highlights the dual regulatory roles of citrate metabolism in inflammation and pathogen control and suggests that combined use of STAT3/ACLY inhibitors with conventional antibiotics may be necessary to achieve both immunomodulation and effective bacterial eradication.

Bacterial superantigens are potent immune activators that trigger T cell proliferation and intensive release of cytokines, leading to toxic shock syndrome. Also, they impair host immune responses, increasing bacterial carriage and transmission. Several studies proposed that superantigens can induce regulatory T (Treg) cells, which may suppress immune responses against bacterial infection. However, the mechanism of Treg cell induction by superantigens is still elusive. We here demonstrated that streptococcal pyrogenic exotoxin A (SPEA) promoted human CD4⁺CD25⁺Foxp3⁺ T cell induction in a dose- and time-dependent manner and the induction required antigen-presenting cells (APCs). SPEA-induced CD4⁺CD25⁺ T cells could suppress allogeneic T cell proliferation and IL-2 secretion. Flow cytometric analyses demonstrated high expression of TNFR2 on SPEA-induced CD4⁺CD25⁺Foxp3⁺ T cells. Blocking the interaction between TNF-⍺ and TNFR2 reduced SPEA-induced CD25⁺Foxp3⁺ Treg cells. Our present study suggests a mechanism that the TNF-⍺ and TNFR2 axis is required for the induction of human CD4⁺CD25⁺Foxp3⁺ Treg cells by SPEA, which implicates a potential strategy to enhance the clearance of Group A streptococcus infection through reducing Treg cell induction by the inhibition of TNFR2 signaling.

Toll-like receptor (TLR) 9 ligand has been reported to induce the formation of intrahepatic myeloid-cell aggregates for T cell population expansion (iMATEs), which enhances responses of cytotoxic T lymphocytes (CTLs). However, little is known about how the formation of iMATEs is regulated. Previously, various studies have demonstrated that regulatory T cells (Tregs) can suppress CTL responses through soluble cytokines or co-inhibitory molecules. It's unclear whether and how Tregs regulate the formation of iMATEs. In this study, we investigated whether Tregs are involved in regulating TLR9-induced iMATEs formation and the mechanisms behind it by using different gene knockout mice and blocking antibodies. We observed that intravenous injection of TLR9 ligand CpG induced significant iMATEs formation, accompanied by a marked increase in the number of Tregs infiltrating the liver as well as upregulation of IL-10 in both peripheral blood and liver. Importantly, depletion of Tregs either by anti-CD4, anti-CD25 blocking antibodies or diphtheria toxin (DT) in DEREG transgenic mice resulted in enhanced CpG-induced iMATEs formation. Conversely, knocking out IL-10 led to increased intrahepatic Treg infiltration and decreased CpG ODN-induced iMATEs formation. Consistently, depleting Kupffer cells (KCs), one of the main source of IL-10, also resulted in reduced formation of iMATEs. In conclusion, our results suggest that IL-10 suppresses Treg infiltration in the liver and thus promote CpG ODN-induced iMATEs formation. These results fill the gap in our understanding of the intrahepatic regulation mechanism of iMATEs formation.

The pathological basis of many visual disorders involves the abnormal viability and migration of retinal pigment epithelium (RPE) cells. Complement response disorder is a significant pathogenic factor causing some autoimmune and inflammation diseases. The complement activation product anaphylatoxin C5a signaling pathway may be associated with RPE cell dysfunction. This study aimed to analyze the molecular mechanisms by which C5a affects RPE cell viability and migration. Recombinant human complement component C5a protein stimulated RPE cells. Cell biological behavior, including cell viability, invasion, and migration were analyzed with Cell Counting Kit-8 and transwell methods. Bioinformatics analysis identified the differentially expressed genes (DEGs) involved in C5a-treated RPE cells based on RNA sequencing. SLC38A1 was knocked down or overexpressed by vector transfection to investigate its involvement in C5a-stimulated RPE cells. C5a promotes RPE cell viability and migration. C5a-induced DEGs are enriched in migration-associated pathways. C5a increased SLC38A1, and SLC38A1 knockdown or overexpression inhibited or promoted RPE cell viability and migration. Glutaminase inhibition abrogated the promoting effect of C5a and SLC38A1 on cell biological behaviors. METTL3-HNRNPC-mediated m6A modification mediated C5a-induced SLC38A1. C5a, METTL3, and SLC38A1 constituted a signaling axis in regulating cell biological behaviors of C5a-treated RPE cells. C5a promotes RPE cell viability and migration, and SLC38A1-mediated improved glutamine metabolism is the downstream signal pathway of the C5a complement pathway. The C5a complement system may target the SLC38A1 to promote RPE cell migration.

IgG antibodies against terminal galactose-α-1,3-galactose (anti-αGal antibodies) are naturally occurring in humans, but their origins remain poorly understood. These antibodies target various microorganisms including Staphylococcus aureus, a common nasal commensal and the major cause of skin abscesses. This study investigates the impact of S. aureus colonization and abscess events on plasma anti-αGal antibody levels. We measured plasma anti-αGal antibody levels using a quantitative immunoassay in: (i) 101 pairs of healthy individuals with and without nasal S. aureus colonization, (ii) 106 healthy individuals before and after abscess formation, and (iii) 43 patients with recurrent skin abscesses compared with 75 patient controls and 60 healthy controls. We observed a 35% reduction (95%CI: 7-54%) in anti-αGal antibody levels in nasal S. aureus carriers. Conversely, we found a 30% increase (95%CI: 4-66%) in individuals within 187 days post-skin abscess, and patients with recurrent skin abscesses exhibited 81% higher (95%CI: 14-190%) levels than patient controls, and 110% higher (95%CI: 39-230%) than healthy controls. This study suggests that skin abscesses lead to elevated plasma anti-αGal antibody levels and that these antibodies might convey or correlate with mucosal immunity to S. aureus.

Clostridium innocuum, a member of the human gut microbiome with intrinsic resistance to vancomycin, has been increasingly associated with inflammatory bowel diseases (IBD). Clinical observations indicate that co-infection with Clostridioides difficile and C. innocuum could lead to poorer clinical remission in ulcerative colitis; however, the pathogenic mechanism of C. innocuum remains unclear. Here, we investigated the effects of vancomycin and C. difficile on C. innocuum secretomes and the functions of the modified secretomes on C. innocuum pathogenicity. The results indicated that, compared to co-culturing with C. difficile, vancomycin was more effective in stimulating the secretion of proteins without a signal peptide, whereas C. difficile was better at promoting the secretion of classical secretory proteins. Based on these results, we further analyzed the effects of three abundant classical secretory proteins on C. innocuum virulence utilizing recombinant proteins. The results demonstrated that the NlpC/P60-containing protein (NlpC/P60) can enhance C. innocuum biofilm formation and adherence to HT-29 cells. Additionally, NlpC/P60, D-Ala-D-Ala carboxypeptidase, and a polysaccharide deacetylase were able to stimulate IL-8 production of HT-29 cells and TNF-α production of Raw264.7 macrophages. Additionally, recombinant NlpC/P60 and polysaccharide deacetylase exhibited cytotoxicity on Raw264.7 cells at 48 h. As the production of IL-8 and TNF-α is closely associated with IBD development, it is suggested that C. innocuum secretomes, under the influence of vancomycin or C. difficile, could contribute to IBD progression by enhancing inflammation and host-pathogen interactions.

Community-acquired pneumonia (CAP) is a significant health threat for adults. Although conjugate vaccines have reduced pneumococcal CAP incidence in children, Streptococcus pneumoniae-related CAP remains prevalent among older adults. The nasopharynx acts as a reservoir for S. pneumoniae, yet the interplay between this pathogen and the nasopharyngeal microbiome during and after pneumonia remains poorly understood. This study included 61 adult patients diagnosed with pneumococcal CAP and 61 matched healthy controls. An S. pneumoniae-specific PCR, urine antigen tests and bacterial cultures were performed. Nasopharyngeal swabs collected at admission and three months post-infection were analyzed for microbiome dynamics through 16 S rRNA gene amplicon sequencing. 16 S rRNA gene amplicon sequencing revealed Streptococcus spp. in the majority of all nasopharyngeal samples during infection compared to the other diagnostic test performed. While overall bacterial biomass did not differ between groups, patients exhibited higher alpha diversity (p = 0.012) and lower microbiome stability post-infection. Beta diversity analysis distinguished infection from healthy status (p = 0.002). Taxonomic analysis showed similar core microbiota across groups, but Streptococcus spp. was significantly more abundant during infection, particularly in those patients with viral co-infections. Notably, unique significant bacterial interactions were identified both during and after infection, as well as in healthy states. A negative correlation was observed between Corynebacterium and Streptococcus spp. in infected patients, suggesting a potential antagonistic interaction between these taxa. The nasopharyngeal microbiome in patients with pneumococcal CAP demonstrates persistent disruption post-infection, characterized by lower resilience three months after acute illness. Additionally, we identified specific bacterial interplays during and after infection that differed from those in healthy donors. These bacterial dynamics might play critical roles in pathogen colonization resistance and infection prevention. Thus, our findings highlight the need for further investigation into microbial interactions and potential microbiome-based therapies for respiratory infections, particularly in vulnerable populations.

Leishmania donovani is the causative agent of the fatal visceral leishmaniasis (VL) disease in humans in the tropical regions, mainly the Indian Subcontinent and Africa. We have previously described centrin1, a basal body associated cell division specific protein in this parasite important for the parasite's host intracellular stage. In this study, we identified a novel centrin1-binding protein called LdDRP through pull-down and MS/MS analysis, which is a homolog of the XPC protein of humans involved in DNA damage. The protein interaction with LdCen1 was also confirmed through peptide spectrum analysis against the UniProt database. Immunofluorescence analysis confirms that LdDRP is localized within the nucleus, suggesting the protein's possible role in DNA interaction. The overexpression of three LdDRP forms in the parasite, each fused with HA-tag (LdDRPF [full length] LdDRPN [only N-terminal], and LdDRPC [only C-terminal]), revealed that only LdDRPF and LdDRPC were able to support the retention of the parasite's shape and promote rapid division following the UV-damage recovery period. This was also correlated to the elevated expression level of both LdDRPC and LdCen1, by Western blot analysis soon after UV-C exposure in the parasites compared to control. The study emphasizes the role of the LdDRP, and its crucial domains involved in the DNA binding process, DNA damage response, and interaction with centrin, particularly in response to UV-C light-induced DNA damage.