Search

Background: Allergy represents a major health problem of increasing prevalence worldwide with a high socioeconomic impact. Our knowledge on the molecular mechanisms underlying allergic diseases and their treatments has significantly improved over the last years. The generation of allergen-specific regulatory T cells (Tregs) is crucial in the induction of healthy immune responses to allergens, preventing the development and worsening of allergic diseases. Summary: In the last decades, intensive research has focused on the study of the molecular mechanisms involved in Treg development and Treg-mediated suppression. These mechanisms are essential for the induction of sustained tolerance by allergen-specific immunotherapy (AIT) after treatment discontinuation. Compelling experimental evidence demonstrated altered suppressive capacity of Tregs in patients suffering from allergic rhinitis, allergic asthma, food allergy, or atopic dermatitis, as well as the restoration of their numbers and functionality after successful AIT. Key Message: The better understanding of the molecular mechanisms involved in Treg generation during allergen tolerance induction might well contribute to the development of novel strategies for the prevention and treatment of allergic diseases. [ABSTRACT FROM AUTHOR]

Keywords: allergen-specific immunotherapy; allergoid-mannan conjugates; human macrophages; immune regulation; innate immunity EN allergen-specific immunotherapy allergoid-mannan conjugates human macrophages immune regulation innate immunity 320 323 4 12/31/21 20220101 NES 220101 ACKNOWLEDGEMENT None. Allergoid-mannan conjugates imprint tolerogenic features in human macrophages LPS-stimulated Mannan-GM-MØ produced significantly lower levels of the pro-inflammatory cytokines TNF- and IL-6 and significantly higher levels of anti-inflammatory IL-10 than conventional GM-MØ (Figure 2D). [Extracted from the article]

Background: Polymerized allergoids conjugated to mannan (PM) are suitable vaccines for allergen‐specific immunotherapy (AIT). Alum remains the most widely used adjuvant in AIT, but its way of action is not completely elucidated. The better understanding of the mechanisms underlying alum adjuvanticity could help to improve AIT vaccine formulations. Objective: We sought to investigate the potential influence of alum in the tolerogenic properties imprinted by PM at the molecular level. Methods: Flow cytometry, ELISAs, cocultures, intracellular staining and suppression assays were performed to assess alum and PM effects in human dendritic cells (DCs). BALB/c mice were immunized with PM alone or adsorbed to alum. Allergen‐specific antibodies, splenocyte cytokine production and splenic forkhead box P3 (FOXP3)+ regulatory T (Treg) cells were quantified. Metabolic and immune pathways were also studied in human DCs. Results: Alum decreases PD‐L1 expression and IL‐10 production induced by PM in human DCs and increases pro‐inflammatory cytokine production. Alum impairs PM‐induced functional FOXP3+ Treg cells and promotes Th1/Th2/Th17 responses. Subcutaneous immunization of mice with PM plus alum inhibits in vivo induction of Treg cells promoted by PM without altering the capacity to induce functional allergen‐specific blocking antibodies. Alum inhibits mTOR activation and alters metabolic reprogramming by shifting glycolytic pathways and inhibiting reactive oxygen species (ROS) production in PM‐activated DCs, impairing their capacity to generate functional Treg cells. Conclusion: We uncover novel mechanisms by which alum impairs the tolerogenic properties induced by PM, which might well contribute to improve the formulation of novel vaccines for AIT. [ABSTRACT FROM AUTHOR]

Allergoid–mannan conjugates are novel vaccines for allergen-specific immunotherapy being currently assayed in phase 2 clinical trials. Allergoid–mannan conjugates target dendritic cells (DCs) and generate functional forkhead box P3 (FOXP3)-positive Treg cells, but their capacity to reprogram monocyte differentiation remains unknown. We studied whether allergoid–mannan conjugates could reprogram monocyte differentiation into tolerogenic DCs and the underlying molecular mechanisms. Monocytes from nonatopic and allergic subjects were differentiated into DCs under conventional protocols in the absence or presence of allergoid–mannan conjugates. ELISA, real-time quantitative PCR, coculture, flow cytometry, and suppression assay were performed. Metabolic and epigenetic techniques were also used. Monocyte differentiation from nonatopic and allergic subjects into DCs in the presence of allergoid–mannan conjugates yields stable tolerogenic DCs. Lipopolysaccharide-stimulated mannan-tolDCs show a significantly lower cytokine production, lower TNF-α/IL-10 ratio, and higher expression of the tolerogenic molecules PDL1, IDO, SOCS1, SOCS3 , and IL10; and they induce higher numbers of functional FOXP3+ Treg cells than conventional DC counterparts. Mannan-tolDCs shift glucose metabolism from Warburg effect and lactate production to mitochondrial oxidative phosphorylation. They also display epigenetic reprogramming involving specific histone marks within tolerogenic loci and lower expression levels of histone deacetylase genes. Mannan-tolDCs significantly increase the expression of the anti-inflammatory miRNA-146a/b and decrease proinflammatory miRNA-155. Allergoid–mannan conjugates reprogram monocyte differentiation into stable tolerogenic DCs via epigenetic and metabolic reprogramming. Our findings shed light on the novel mechanisms by which allergoid–mannan conjugates might contribute to allergen tolerance induction during allergen-specific immunotherapy. [Display omitted] [ABSTRACT FROM AUTHOR]