MHC Class II Activation and Interferon-γ Mediate the Inhibition of Neutrophils and Eosinophils by Staphylococcal Enterotoxin Type A (SEA)

Human HLA prolongs the host inflammatory response in Streptococcus suis serotype 2 infection compared to mouse H2 molecules

Streptococcus suis (S. suis) is widely acknowledged as a significant zoonotic pathogen in Southeast Asia and China, which has led to a substantial number of fatalities in both swine and humans. Despite the prevalent use of mice as the primary animal model to study S. suis pathogenesis, the substantial differences in the major histocompatibility complex (MHC) between humans and mice underscore the ongoing exploration for a more suitable and effective animal model. In this study, humanized transgenic HLA-A11/DR1 genotypes mice were used to evaluate the differences between humanized HLA and murine H2 in S. suis infection. Following intravenous administration of S. suis suspensions, we investigated bacterial load, cytokine profiles, pathological alterations, and immune cell recruitment in both Wild-type (WT) and humanized mice across different post-infection time points. Relative to WT mice, humanized mice exhibited heightened pro-inflammatory cytokines, exacerbated tissue damage, increased granulocyte recruitment with impaired resolution, notably more pronounced during the late infection stage. Additionally, our examination of bacterial clearance rates suggests that HLA-A11/DR1 primarily influences cell recruitment and mitochondrial reactive oxygen species (ROS) production, which affects the bacterial killing capacity of macrophages in the late stage of infection. The reduced IL-10 production and lower levels of regulatory T cells in humanized mice could underlie their compromised resolution ability. Intervention with IL-10 promotes bacterial clearance and inflammatory regression in the late stages of infection in transgenic mice. Our findings underscore the heightened sensitivity of HLA-A11/DR1 mice with impaired resolution to S. suis infection, effectively mirroring the immune response seen in humans during infection. The humanized HLA-A11/DR1 mice could serve as an optimal animal model for investigating the pathogenic and therapeutic mechanisms associated with sepsis and other infectious diseases.

Bioinformatic identification of hub genes and key pathways in neutrophils of patients with acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is characterized as a neutrophil-dominant disorder without effective pharmacological interventions. Knowledge of neutrophils in ARDS patients at the transcriptome level is still limited. We aimed to identify the hub genes and key pathways in neutrophils of patients with ARDS. The transcriptional profiles of neutrophils from ARDS patients and healthy volunteers were obtained from the GSE76293 dataset. The differentially expressed genes (DEGs) between ARDS and healthy samples were screened using the limma R package. Subsequently, functional and pathway enrichment analyses were performed based on the database for annotation, visualization, and integrated discovery (DAVID). The construction of a protein-protein interaction network was carried out using the search tool for the retrieval of interacting genes (STRING) database and the network was visualized by Cytoscape software. The Cytoscape plugins cytoHubba and MCODE were used to identify hub genes and significant modules. Finally, 136 upregulated genes and 95 downregulated genes were identified. Gene ontology analyses revealed MHC class II plays a major role in functional annotations. SLC11A1, ARG1, CHI3L1, HP, LCN2, and MMP8 were identified as hub genes, and they were all involved in the neutrophil degranulation pathway. The MAPK and neutrophil degranulation pathways in neutrophils were considered as key pathways in the pathogenesis of ARDS. This study improves our understanding of the biological characteristics of neutrophils and the mechanisms underlying ARDS, and key pathways and hub genes identified in this work can serve as targets for novel ARDS treatment strategies.

egc Superantigens Impair Monocytes/Macrophages Inducing Cell Death and Inefficient Activation

Bacterial superantigens (SAgs) are enterotoxins that bind to MHC-II and TCR molecules, activating as much as 20% of the T cell population and promoting a cytokine storm which enhances susceptibility to endotoxic shock, causing immunosuppression, and hindering the immune response against bacterial infection. Since monocytes/macrophages are one of the first cells SAgs find in infected host and considering the effect these cells have on directing the immune response, here, we investigated the effect of four non-classical SAgs of the staphylococcal egc operon, namely, SEG, SEI, SEO, and SEM on monocytic-macrophagic cells, in the absence of T cells. We also analyzed the molecular targets on APCs which could mediate SAg effects. We found that egc SAgs depleted the pool of innate immune effector cells and induced an inefficient activation of monocytic-macrophagic cells, driving the immune response to an impaired proinflammatory profile, which could be mediated directly or indirectly by interactions with MHC class II. In addition, performing surface plasmon resonance assays, we demonstrated that non-classical SAgs bind the gp130 molecule, which is also present in the monocytic cell surface, among other cells.

Multiboosting of Cancer Immunotherapy by a Core-Shell Delivery System

The synergy of chemotherapy and antiangiogenesis therapy is a new strategy for cancer treatment. In this paper, a well-developed core-shell nanoparticle loaded with gambogic acid (GA), heparin (HP), and the immunoadjuvant cytosine-phosphate-guanine oligonucleotide (CpG ODN), called GHC NP, was constructed to treat hepatocellular carcinoma. GHC NPs with liver targeting activity can effectively inhibit tumor cell proliferation and angiogenesis. With the delivery of nanocarriers and the assistance of GA and HP, the GHC NPs can more effectively upregulate cytotoxic T cell (CTL) levels, promote helper T cell (Th cell) differentiation, and induce Th1 immune responses in long-term treatment compared with single CpG ODN. This synergistically enhanced immunotherapy might have universal application in cancer treatments.

Airway exposure to Staphylococcal enterotoxin type B (SEB) enhances the number and activity of bone marrow neutrophils via the release of multiple cytokines

BACKGROUND

The lung infections by Staphylococcus aureus are strongly associated with its ability to produce enterotoxins. However, little is known about the mechanisms underlying trafficking of bone marrow (BM) neutrophils during airway inflammation induced by Staphylococcal enterotoxin B (SEB). We therefore aimed to investigate the effects of mouse airways SEB exposure on BM neutrophil counts and its adhesive properties as well as on the release of cytokines/chemokines that orchestrate BM neutrophils trafficking to lung tissue.

METHODS

Male BALB/c mice were intranasally exposed to SEB (1 µg), and at 4, 16 and 24 h thereafter, BM, circulating blood, bronchoalveolar lavage (BAL) fluid and lung tissue were collected. BM neutrophils adhesion, MAC-1 and LFA1-α expressions (by flow cytometry) as well as measurement of cytokine and/or chemokines levels were assayed after SEB-airway exposure.

RESULTS

Prior exposure to SEB promoted a marked influx of neutrophils to BAL and lung tissue, which was accompanied by increased counts of BM immature neutrophils and blood neutrophilia. BM neutrophil expressions of LFA1-α and MAC-1 were unchanged by SEB exposure whereas a significant enhancement of adhesion properties to VCAM-1 was observed. The early phase of airway SEB exposure was accompanied by high levels of GM-CSF, G-CSF, IFN-γ, TNF-α and KC/CXCL1, while the latter phase by the equilibrated actions of SDF1-α and MIP-2.

CONCLUSION

Mouse airways exposure to SEB induces BM cytokines/chemokines release and their integrated actions enhance the adhesion of BM neutrophils leading to acute lung injury.

Salmonella spv locus affects type I interferon response and the chemotaxis of neutrophils via suppressing autophagy

Salmonella is a facultative intracellular pathogen that can cause significant morbidity and mortality in humans and animals. Salmonella plasmid virulence (spv) gene sequence is a highly conserved 6.8 kb region which exists in the plasmid of most pathogenic Salmonella. Autophagy is a degradation process of unnecessary and dysfunctional cytoplasm components to maintain cellular homeostasis, which could affect host inflammatory responses, such as type I interferon response. Type I interferon response can promote the antibacterial activity of macrophage as well as the secretion of cytokines and neutrophil chemokines. We previously reported that spv locus could suppress autophagy and the aggregation of neutrophils in zebrafish larvae. To explore the influence of spv locus on Salmonella escaping from the innate immune responses and the underlying mechanism, the models of Salmonella enterica serovar Typhimurium infected macrophages in vitro and zebrafish larvae in vivo were used in this study. The interactions among spv locus, autophagy, type I interferon response and the chemotaxis of neutrophils were investigated. Western blot was used to detect the expression levels of autophagy related proteins and RT-qPCR was used to measure the mRNA levels of type I interferon response and the neutrophil chemokines. The chemotaxis of neutrophils were observed by Laser Scanning confocal microscopy. Autophagy agonist Torin 1 was also involved to interfere the autophagy influx. Results showed that spv locus could restrain type I interferon response and the chemotaxis of neutrophils via suppressing autophagy, which provided substantial foundation to study the mechanism of Salmonella escaping the innate immunity.