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Abstract: Hymenoptera venom allergy is one of the most severe allergic diseases, with a considerable prevalence of anaphylactic reaction, making it potentially lethal. In this review, we provide an overview of the current knowledge and recent findings in understanding induced immune mechanisms during different phases of venom immunotherapy. We focus on protection mechanisms that occur early, during the build-up phase, and on the immune tolerance, which occurs later, during and after Hymenoptera venom immunotherapy. The short-term protection seems to be established by the early desensitization of mast cells and basophils, which plays a crucial role in preventing anaphylaxis during the build-up phase of treatment. The early generation of blocking IgG antibodies seems to be one of the main reasons for the lower activation of effector cells. Long-term tolerance is reached after at least three years of venom immunotherapy. A decrease in basophil responsiveness correlates with tolerated sting challenge. Furthermore, the persistent decline in IgE levels and, by monitoring the cytokine profiles, a shift from a Th2 to Th1 immune response, can be observed. In addition, the generation of regulatory T and B cells has proven to be essential for inducing allergen tolerance. Most studies on the mechanisms and effectiveness data have been obtained during venom immunotherapy (VIT). Despite the high success rate of VIT, allergen tolerance may not persist for a prolonged time. There is not much known about immune mechanisms that assure longterm tolerance post-therapy.
Keywords: allergy and immunology, hypersensitivity, immunotherapy, immune tolerance, venoms, Hymenoptera, Hymenoptera venom, short-term protection, long-term tolerance
Published in DiRROS: 16.08.2021; Views: 864; Downloads: 277
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Abstract: Background: An elevated basal serum tryptase level is associated with severe systemic anaphylaxis, most notably caused by Hymenoptera envenomation. Although clonal mast cell disease is the culprit in some individuals, it does not fully explain this clinical association. Objective: Our aim was to determine the prevalence and associated impact of tryptase genotypes on anaphylaxis in humans. Methods: Cohorts with systemic mastocytosis (SM) and venom as well as idiopathic anaphylaxis from referral centers in Italy, Slovenia, and the United States, underwent tryptase genotyping by droplet digital PCR. Associated anaphylaxis severity (Mueller scale) was subsequently examined. Healthy volunteers and controls with nonatopic disease were recruited and tryptase was genotyped by droplet digital PCR and in silico analysis of genome sequence, respectively. The effects of pooled and recombinant human tryptases, protease activated receptor 2 agonist and antagonist peptides, and a tryptase-neutralizing mAb on human umbilical vein endothelial cell permeability were assayed using a Transwell system. Results: Hereditary [alpha]-tryptasemia (H[alpha]T)--a genetic trait caused by increased [alpha]-tryptase-encoding Tryptase-[alpha]/[beta]1 (TPSAB1) copy number resulting in elevated BST level--was common in healthy individuals (5.6% [n = 7 of 125]) and controls with nonatopic disease (5.3% [n = 21 of 398]). H[alpha]T was associated with grade IV venom anaphylaxis (relative risk = 2.0; P < .05) and more prevalent in both idiopathic anaphylaxis (n = 8 of 47; [17%; P = .006]) and SM (n = 10 of 82 [12.2%; P = .03]) relative to the controls. Among patients with SM, concomitant H[alpha]T was associated with increased risk for systemic anaphylaxis (relative risk = 9.5; P = .007). In vitro, protease-activated receptor-2-dependent vascular permeability was induced by pooled mature tryptases but not [alpha]- or [beta]-tryptase homotetramers. Conclusions: Risk for severe anaphylaxis in humans is associated with inherited differences in [alpha]-tryptase-encoding copies at TPSAB1.
Keywords: mastocytosis, venoms, hypersensitivity, anaphylaxis - diagnosis, mast cells, idiopathic anaphylaxis, mast cell activation, hereditary alpha-tryptasemia
Published in DiRROS: 11.09.2020; Views: 1976; Downloads: 367
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