Platelet-Derived Extracellular Vesicles as Lipid Carriers in Severe Allergic Inflammation.

The resolution of inflammation is a complex process that is critical for removing inflammatory cells and restoring tissue function. The dysregulation of these mechanisms leads to chronic inflammatory disorders. Platelets, essential cells for preserving homeostasis, are thought to play a role in inflammation as they are a source of immunomodulatory factors. Our aim was to identify key metabolites carried by platelet-derived extracellular vesicles (PL-EVs) in a model of allergic inflammation. PL-EVs were isolated by serial ultracentrifugation using platelet-rich plasma samples obtained from platelet apheresis from severely (n = 6) and mildly (n = 6) allergic patients and non-allergic individuals used as controls (n = 8). PL-EVs were analysed by a multiplatform approach using liquid and gas chromatography coupled to mass spectrometry (LC-MS and GC-MS, respectively). PL-EVs obtained from severely and mildly allergic patients and control individuals presented comparable particle concentrations and sizes with similar protein concentrations. Strikingly, PL-EVs differed in their lipid and metabolic content according to the severity of inflammation. L-carnitine, ceramide (Cer (d18:0/24:0)), and several triglycerides, all of which seem to be involved in apoptosis and regulatory T functions, were higher in PL-EVs from patients with mild allergic inflammation than in those with severe inflammation. In contrast, PL-EVs obtained from patients with severe allergic inflammation showed an alteration in the arachidonic acid pathway. This study demonstrates that PL-EVs carry specific lipids and metabolites according to the degree of inflammation in allergic patients and propose novel perspectives for characterising the progression of allergic inflammation.

Transcriptomics reveals a distinct metabolic profile in T cells from severe allergic asthmatic patients.

The reasons behind the onset and continuation of chronic inflammation in individuals with severe allergies are still not understood. Earlier findings indicated that there is a connection between severe allergic inflammation, systemic metabolic alterations and impairment of regulatory functions. Here, we aimed to identify transcriptomic alterations in T cells associated with the degree of severity in allergic asthmatic patients. T cells were isolated from severe (n = 7) and mild (n = 9) allergic asthmatic patients, and control (non-allergic, non-asthmatic healthy) subjects (n = 8) to perform RNA analysis by Affymetrix gene expression. Compromised biological pathways in the severe phenotype were identified using significant transcripts. T cells' transcriptome of severe allergic asthmatic patients was distinct from that of mild and control subjects. A higher count of differentially expressed genes (DEGs) was observed in the group of individuals with severe allergic asthma vs. control (4,924 genes) and vs. mild (4,232 genes) groups. Mild group also had 1,102 DEGs vs. controls. Pathway analysis revealed alterations in metabolism and immune response in the severe phenotype. Severe allergic asthmatic patients presented downregulation in genes related to oxidative phosphorylation, fatty acid oxidation and glycolysis together with increased expression of genes coding inflammatory cytokines (e.g. IL-19, IL-23A and IL-31). Moreover, the downregulation of genes involved in TGFß pathway together with a decreased tendency on the percentage of T regulatory cell (CD4 + CD25+), suggest a compromised regulatory function in severe allergic asthmatic patients. This study demonstrates a transcriptional downregulation of metabolic and cell signalling pathways in T cells of severe allergic asthmatic patients associated with diminished regulatory T cell function. These findings support a link between energy metabolism of T cells and allergic asthmatic inflammation.

Deciphering the role of platelets in severe allergy by an integrative omics approach.

BACKGROUND: Mechanisms causing the onset and perpetuation of inflammation in severe allergic patients remain unknown. Our previous studies suggested that severe allergic inflammation is linked to platelet dysfunction. METHODS: Platelet-rich plasma (PRP) and platelet-poor plasma (PPP) samples were obtained by platelet-apheresis from severe (n = 7) and mild (n = 10) allergic patients and nonallergic subjects (n = 9) to perform platelet lipidomics by liquid chromatography coupled to mass spectrometry (LC-MS) and RNA-seq analysis. Significant metabolites and transcripts were used to identify compromised biological pathways in the severe phenotype. Platelet and inflammation-related proteins were quantified by Luminex. RESULTS: Platelets from severe allergic patients were characterized by high levels of ceramides, phosphoinositols, phosphocholines, and sphingomyelins. In contrast, they showed a decrease in eicosanoid precursor levels. Biological pathway analysis performed with the significant lipids revealed the alteration of phospholipases, calcium-dependent events, and linolenic metabolism. RNAseq confirmed mRNA overexpression of genes related to platelet activation and arachidonic acid metabolism in the severe phenotypes. Pathway analysis indicated the alteration of NOD, MAPK, TLR, TNF, and IL-17 pathways in the severe phenotype. P-Selectin and IL-17AF proteins were increased in the severe phenotype. CONCLUSIONS: This study demonstrates that platelet lipid, mRNA, and protein content is different according to allergy severity. These findings suggest that platelet load is a potential source of biomarkers and a new chance for therapeutic targets in severe inflammatory pathologies.

Risk factors for systemic reactions to allergen immunotherapy.

PURPOSE OF REVIEW: To update safety information regarding allergen-specific immunotherapy (ASIT) in clinical practice and highlight the risk factors associated with the adverse reactions, product and each dose. RECENT FINDINGS: Efforts in recent years have focused on increasing our understanding of the efficacy and safety of ASIT, especially the sublingual variety (SLIT), in multicenter studies. Moreover, new Clinical Practice Guidelines (CPGs) and an international consensus concerning ASIT have been published recently. Although no deaths as a result of subcutaneous immunotherapy or SLIT have been reported in the last 2 years, systemic reactions mainly arising from administration errors still appear. Recent studies support the safety of new forms of specific immunotherapy. SUMMARY: An understanding of the risk factors for each patient, product and dose, and the implementation of CPGs are the main factors that could improve the safety of ASIT. The standardization of all procedures for prescribing and administering ASIT, and the systematic collection of standardized safety data in a multicenter database (postmarketing surveillance), may be required to generate new information on the safety of ASIT.

[Anaphylaxis to hymenoptera sting: study of 113 patients]. / Anafilaxia por picadura de himenóptero: estudio de 113 casos.

BACKGROUND AND OBJECTIVE: The purpose of this study was to describe the clinical and epidemiological features of anaphylactic reactions to hymenoptera stings, with a case-history analysis according to severity. PATIENTS AND METHOD: We conducted an observational descriptive study of patients aged between 10 and 80 years who suffered a systemic reaction after hymenoptera sting. All of them showed specific serum IgE to venoms from Apis, Vespula and/or Polistes. A questionnaire including history of atopy, past reactions and characteristics of the reaction, was performed by individual interview. Anaphylactic reactions were classified into two levels of severity according to Müller's classification. An analysis of independence was carried out in order to relate each level with several factors: age, gender, atopy, type of previous reactions, area of sting and time sequence. RESULTS: 113 patients were included (63 male; mean age [standard deviation]: 40.1 [15.9] years). Reactions were accounted for bee venom in 10.6% of patients, and wasp in 89.4%. Specific IgE was positive to Vespula in 91.9% of subjects, Polistes in 71.4%, and Apis in 28.7%. Furthermore, 50.4% were sensitive to both Vespula and Polistes. Personal history of atopy was found in 20.3%. Among the 106 patients who reminded previous stings, local large reactions were referred by 35.9% and systemic reactions by 16.5%. Upper limb was the most frequent area of sting (38.9%). Most common symptoms were: pruritus (77.8%), hives (57.5%), edema (54.8%), erythema (52.2%), dizziness (51.3%) and dyspnea (49.5%). Severe reactions occurred in 65.5% of patients. Age, gender, atopy, type of previous reactions, area of sting and restoration time were not significantly associated with severity. Time elapsed to first symptom was proportionally shorter in severe cases (p < 0.05). CONCLUSIONS: There is a high frequency of hypersensitivity to wasp venom (Vespula) in the studied population. Except for immediacy, severity-associated data could not be established.