Background A substantial subgroup of asthmatic patients have “nonallergic” or idiopathic asthma, which often takes a severe course and is difficult to treat. The cause might be allergic reactions to ...the gram-positive pathogen Staphylococcus aureus , a frequent colonizer of the upper airways. However, the driving allergens of S aureus have remained elusive. Objective We sought to search for potentially allergenic S aureus proteins and characterize the immune response directed against them. Methods S aureus extracellular proteins targeted by human serum IgG4 were identified by means of immunoblotting to screen for potential bacterial allergens. Candidate antigens were expressed as recombinant proteins and used to analyze the established cellular and humoral immune responses in healthy adults and asthmatic patients. The ability to induce a type 2 immune response in vivo was tested in a mouse asthma model. Results We identified staphylococcal serine protease–like proteins (Spls) as dominant IgG4 -binding S aureus proteins. SplA through SplF are extracellular proteases of unknown function expressed by S aureus in vivo . Spls elicited IgE antibody responses in most asthmatic patients. In healthy S aureus carriers and noncarriers, peripheral blood T cells elaborated TH 2 cytokines after stimulation with Spls, as is typical for allergens. In contrast, TH 1/TH 17 cytokines, which dominated the response to S aureus α-hemolysin, were of low concentration or absent. In mice inhalation of SplD without adjuvant induced lung inflammation characterized by TH 2 cytokines and eosinophil infiltration. Conclusion We identify Spls as triggering allergens released by S aureus , opening prospects for diagnosis and causal therapy of asthma.
Background Chronic airway inflammatory diseases, such as chronic rhinosinusitis with nasal polyps and asthma, show increased nasal Staphylococcus aureus colonization. Staphylococcus aureus –derived ...serine protease–like protein (Spl) D and other closely related proteases secreted by S aureus have recently been identified as inducers of allergic asthma in human subjects and mice, but their mechanism of action is largely unknown. Objective We investigated the role of recombinant SplD in driving TH 2-biased responses and IgE formation in a murine model of allergic asthma. Methods Allergic asthma was induced in C57BL/6 J wild-type mice, Toll-like receptor (TLR) 4 knockout (Tlr4 −/− ) mice, and recombination-activating gene (Rag2) knockout (Rag2 −/− ) mice by means of repeated intratracheal applications of SplD. Inflammatory parameters in the airways were assessed by means of flow cytometry, ELISA, Luminex, and immunohistochemistry. Serum SplD-specific IgE levels were analyzed by using ELISA. Results We observed that repeated intratracheal exposure to SplD led to IL-33 and eotaxin production, eosinophilia, bronchial hyperreactivity, and goblet cell hyperplasia in the airways. Blocking IL-33 activity with a soluble ST2 receptor significantly decreased the numbers of eosinophils, IL-13+ type 2 innate lymphoid cells and IL-13+ CD4+ T cells and IL-5 and IL-13 production by lymph node cells but had no effect on IgE production. SplD-induced airway inflammation and IgE production were largely dependent on the presence of the functional adaptive immune system and independent of TLR4 signaling. Conclusion The S aureus –derived protein SplD is a potent allergen of S aureus and induces a TH 2-biased inflammatory response in the airways in an IL-33–dependent but TRL4-independent manner. The soluble ST2 receptor could be an efficient strategy to interfere with SplD-induced TH 2 inflammation but does not prevent the allergic sensitization.
Pancreatitis starts with primarily sterile local inflammation that induces systemic inflammatory response syndrome, followed by compensatory anti-inflammatory response syndrome (CARS). We ...investigated the mechanisms of these processes in mice and human serum.
We induced severe acute pancreatitis by partial duct ligation with caerulein stimulation or intraperitoneal injection of l-arginine in mice with deletion of interleukin (IL)12B, NLRP3, or IL18 and in mice given MCC950, a small molecule inhibitor of the NLRP3-inflammasome. Pancreata were collected from mice and analyzed by histology, and cytokine levels were measured in serum samples. We measured activation of adaptive immune responses in mice with pancreatitis by flow cytometry analysis of T cells (CD25 and CD69) isolated from the spleen. Differentiation of T-helper (Th1) cells, Th2 cells, and T-regulatory cells was determined by nuclear staining for TBET, GATA3, and FOXP3. We performed transcriptome analysis of mouse lymph nodes and bone marrow–derived macrophages after incubation with acini. We measured levels of cytokines in serum samples from patients with mild and severe acute pancreatitis.
Activation of the adaptive immune response in mice was initiated by macrophage-derived, caspase 1–processed cytokines and required activation of NLRP3 (confirmed in serum samples from patients with pancreatitis). Spleen cells from mice with pancreatitis had increases in Th2 cells but not in Th1 cells. Bone marrow–derived macrophages secreted IL1B and IL18, but not IL12, after co-incubation with pancreatic acini. T-cell activation and severity of acute pancreatitis did not differ significantly between IL12B-deficient and control mice. In contrast, NLRP3- or IL18-deficient mice had reduced activation of T cells and no increase in Th2 cell–mediated responses compared with control mice. The systemic type 2 immune response was mediated by macrophage-derived cytokines of the IL1 family. Specifically, IL18 induced a Th2 cell–mediated response in the absence of IL12. MCC950 significantly reduced neutrophil infiltration, T-cell activation, and disease severity in mice.
In mice with severe pancreatitis, we found systemic inflammatory response syndrome and compensatory anti-inflammatory response syndrome developed in parallel. Infiltrating macrophages promote inflammation and simultaneously induce a Th2 cell–mediated response via IL18. Inhibition of NLRP3 reduces systemic inflammatory response syndrome and compensatory anti-inflammatory response syndrome and might be used to treat patients with severe pancreatitis.
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Recent studies have attributed the increased infection vulnerability of patients with stroke to stroke-induced immunosuppression. We have therefore explored the immunological changes in patients with ...ischemic stroke.
Blood from 46 patients with stroke was analyzed by fluorescent-activated cell sorter to determine leukocyte subsets. To identify changes that represent clinically relevant immunosuppression, we compared patients who developed infection within 14 days after stroke with those who did not.
Stroke induced a dramatic and immediate loss of T-lymphocytes, most pronounced within 12 hours after stroke onset. Only patients with subsequent infection exhibited a delay in the recovery of CD4+ T-lymphocyte counts.
Our data suggest that a loss of CD4+ T cell function contributes to the stroke-induced immunosuppression. The CD4+ T cell count on the day after stroke may emerge as a predictive marker for poststroke infection allowing, early identification of patients at risk.
Vaccination using the adenoviral vector COVID-19 vaccine ChAdOx1 nCoV-19 (AstraZeneca) has been associated with rare vaccine-induced immune thrombotic thrombocytopenia (VITT). Affected patients test ...strongly positive in platelet factor 4 (PF4)/polyanion enzyme immunoassays (EIAs), and serum-induced platelet activation is maximal in the presence of PF4. We determined the frequency of anti-PF4/polyanion antibodies in healthy vaccinees and assessed whether PF4/polyanion EIA+ sera exhibit platelet-activating properties after vaccination with ChAdOx1 nCoV-19 (n = 138) or BNT162b2 (BioNTech/Pfizer; n = 143). In total, 19 of 281 participants tested positive for anti-PF4/polyanion antibodies postvaccination (All: 6.8% 95% confidence interval (CI), 4.4-10.3; BNT162b2: 5.6% 95% CI, 2.9-10.7; ChAdOx1 nCoV-19: 8.0% 95% CI, 4.5% to 13.7%). Optical densities were mostly low (between 0.5 and 1.0 units; reference range, <0.50), and none of the PF4/polyanion EIA+ samples induced platelet activation in the presence of PF4. We conclude that positive PF4/polyanion EIAs can occur after severe acute respiratory syndrome coronavirus 2 vaccination with both messenger RNA- and adenoviral vector-based vaccines, but many of these antibodies likely have minor (if any) clinical relevance. Accordingly, low-titer positive PF4/polyanion EIA results should be interpreted with caution when screening asymptomatic individuals after vaccination against COVID-19. Pathogenic platelet-activating antibodies that cause VITT do not occur commonly following vaccination.
•Low-titer PF4/polyanion antibodies occur after vaccination with ChAdOx1 nCoV-19 and BNT162b2.•These PF4/polyanion antibodies do not activate platelets and may have little relevance for the diagnosis of VITT.
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•S. aureus is a frequent cause of infection and a common human commensal.•The S. aureus pan-genome encodes numerous toxins.•The endowment of clinical S. aureus isolates with toxin genes is highly ...variable.•Toxin gene distribution is not random but coupled to the genetic background.•This has important implications for epidemiological studies of pathogenesis.
The outcome of encounters between Staphylococcus (S.) aureus and its human host ranges from life-threatening infection through allergic reactions to symptom-free colonization. The pan-genome of this bacterial species encodes numerous toxins, known or strongly suspected to cause specific diseases or symptoms. Three toxin families are in the focus of this review, namely (i) pore-forming toxins, (ii) exfoliative toxins and (iii) superantigens. The majority of toxin-encoding genes are located on mobile genetic elements (MGEs), resulting in a pronounced heterogeneity in the endowment with toxin genes of individual S. aureus strains. Recent population genomic analysis have provided a framework for an improved understanding of the temporal and spatial scales of the motility of MGEs and their associated toxin genes. The distribution of toxin genes among clonal lineages within the species S. aureus is not random, and phylogenetic (sub-)lineages within clonal complexes feature characteristic toxin signatures. When studying pathogenesis, this lineage association, which is caused by the clonal nature of S. aureus makes it difficult to discriminate effects of specific toxins from contributions of the genetic background and/or other associated genetic factors.
Abstract
Chronic pancreatitis (CP) is characterized by chronic inflammation and the progressive fibrotic replacement of exocrine and endocrine pancreatic tissue. We identify Treg cells as central ...regulators of the fibroinflammatory reaction by a selective depletion of FOXP3-positive cells in a transgenic mouse model (DEREG-mice) of experimental CP. In Treg-depleted DEREG-mice, the induction of CP results in a significantly increased stroma deposition, the development of exocrine insufficiency and significant weight loss starting from day 14 after disease onset. In CP, FOXP3
+
CD25
+
Treg cells suppress the type-2 immune response by a repression of GATA3
+
T helper cells (Th2), GATA3
+
innate lymphoid cells type 2 (ILC2) and CD206
+
M2-macrophages. A suspected pathomechanism behind the fibrotic tissue replacement may involve an observed dysbalance of Activin A expression in macrophages and of its counter regulator follistatin. Our study identified Treg cells as key regulators of the type-2 immune response and of organ remodeling during CP. The Treg/Th2 axis could be a therapeutic target to prevent fibrosis and preserve functional pancreatic tissue.
Cold physical plasma promotes NETosis in an oxidant–dependent manner, but does not impair other crucial cell effector functions.
Cold physical plasma is an ionized gas with a multitude of components, ...including hydrogen peroxide and other reactive oxygen and nitrogen species. Recent studies suggest that exposure of wounds to cold plasma may accelerate healing. Upon wounding, neutrophils are the first line of defense against invading microorganisms but have also been identified to play a role in delayed healing. In this study, we examined how plasma treatment affects the functions of peripheral blood neutrophils. Plasma treatment induced oxidative stress, as assessed by the oxidation of intracellular fluorescent redox probes; reduced metabolic activity; but did not induce early apoptosis. Neutrophil oxidative burst was only modestly affected after plasma treatment, and the killing of Pseudomonas aeruginosa and Staphylococcus aureus was not significantly affected. Intriguingly, we found that plasma induced profound extracellular trap formation. This was inhibited by the presence of catalase during plasma treatment but was not replicated by adding an equivalent concentration of hydrogen peroxide. Plasma‐induced neutrophil extracellular trap formation was not dependent on the activity of myeloperoxidase or NADPH oxidase 2 but seemed to involve short‐lived molecules. The amount of DNA release and the time course after plasma treatment were similar to that with the common neutrophil extracellular trap inducer PMA. After neutrophil extracellular traps had formed, concentrations of IL‐8 were also significantly increased in supernatants of plasma‐treated neutrophils. Both neutrophil extracellular traps and IL‐8 release may aid antimicrobial activity and spur inflammation at the wound site. Whether this aids or exacerbates wound healing needs to be tested.
Mobile genetic elements (MGEs) encoding virulence and resistance genes are widespread in bacterial pathogens, but it has remained unclear how they occasionally jump to new host species. ...Staphylococcus aureus clones exchange MGEs such as S. aureus pathogenicity islands (SaPIs) with high frequency via helper phages. Here we report that the S. aureus ST395 lineage is refractory to horizontal gene transfer (HGT) with typical S. aureus but exchanges SaPIs with other species and genera including Staphylococcus epidermidis and Listeria monocytogenes. ST395 produces an unusual wall teichoic acid (WTA) resembling that of its HGT partner species. Notably, distantly related bacterial species and genera undergo efficient HGT with typical S. aureus upon ectopic expression of S. aureus WTA. Combined with genomic analyses, these results indicate that a 'glycocode' of WTA structures and WTA-binding helper phages permits HGT even across long phylogenetic distances thereby shaping the evolution of Gram-positive pathogens.
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