Background The role of basophils in anaphylaxis is unclear. Objective We sought to investigate whether basophils have an important role in human anaphylaxis. Methods In an emergency department study ...we recruited 31 patients with acute anaphylaxis, predominantly to Hymenoptera venom. We measured expression of basophil activation markers (CD63 and CD203c); the absolute number of circulating basophils; whole-blood FCER1A , carboxypeptidase A3 (CPA3) , and L-histidine decarboxylase (HDC) gene expression; and serum markers (CCL2, CCL5, CCL11, IL-3, and thymic stromal lymphopoietin) at 3 time points (ie, during the anaphylactic episode and in convalescent samples 7 and 30 days later). We recruited 134 patients with Hymenoptera allergy and 76 healthy control subjects for comparison. We then investigated whether the changes observed during venom-related anaphylaxis also occur during allergic reactions to food in 22 patients with peanut allergy undergoing double-blind, placebo-controlled food challenge to peanut. Results The number of circulating basophils was significantly lower during anaphylaxis (median, 3.5 cells/μL) than 7 and 30 days later (17.5 and 24.7 cells/μL, P < .0001) and compared with those in patients with venom allergy and healthy control subjects (21 and 23.4 cells/μL, P < .0001). FCER1A expression during anaphylaxis was also significantly lower than in convalescent samples ( P ≤ .002) and control subjects with venom allergy ( P < .0001). CCL2 levels (but not those of other serum markers) were significantly higher during anaphylaxis (median, 658 pg/mL) than in convalescent samples (314 and 311 pg/mL at 7 and 30 days, P < .001). Peanut-induced allergic reactions resulted in a significant decrease in circulating basophil counts compared with those in prechallenge samples ( P = .016), a decrease in FCER1A expression ( P = .007), and an increase in CCL2 levels ( P = .003). Conclusions Our findings imply an important and specific role for basophils in the pathophysiology of human anaphylaxis.
Food allergy is an increasing public health issue and the most common cause of life-threatening anaphylactic reactions. Conventional allergy tests assess for the presence of allergen-specific IgE, ...significantly overestimating the rate of true clinical allergy and resulting in overdiagnosis and adverse effect on health-related quality of life.
To undertake initial validation and assessment of a novel diagnostic tool, we used the mast cell activation test (MAT).
Primary human blood-derived mast cells (MCs) were generated from peripheral blood precursors, sensitized with patients' sera, and then incubated with allergen. MC degranulation was assessed by means of flow cytometry and mediator release. We compared the diagnostic performance of MATs with that of existing diagnostic tools to assess in a cohort of peanut-sensitized subjects undergoing double-blind, placebo-controlled challenge.
Human blood-derived MCs sensitized with sera from patients with peanut, grass pollen, and Hymenoptera (wasp venom) allergy demonstrated allergen-specific and dose-dependent degranulation, as determined based on both expression of surface activation markers (CD63 and CD107a) and functional assays (prostaglandin D2 and β-hexosaminidase release). In this cohort of peanut-sensitized subjects, the MAT was found to have superior discrimination performance compared with other testing modalities, including component-resolved diagnostics and basophil activation tests. Using functional principle component analysis, we identified 5 clusters or patterns of reactivity in the resulting dose-response curves, which at preliminary analysis corresponded to the reaction phenotypes seen at challenge.
The MAT is a robust tool that can confer superior diagnostic performance compared with existing allergy diagnostics and might be useful to explore differences in effector cell function between basophils and MCs during allergic reactions.
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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.
Our aim was to determine the prevalence and associated impact of tryptase genotypes on anaphylaxis in humans.
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.
Hereditary α-tryptasemia (HαT)—a genetic trait caused by increased α-tryptase–encoding Tryptase-α/β1 (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). HαT 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 HαT 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 α- or β-tryptase homotetramers.
Risk for severe anaphylaxis in humans is associated with inherited differences in α-tryptase–encoding copies at TPSAB1.
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Hymenoptera venom–triggered anaphylaxis (HVA) affects up to 8.9% of the general population and is the most frequent cause of anaphylaxis in adults, accounting for approximately 20% of all fatal ...anaphylaxis cases. Quite often, a fatal reaction is a victim’s first manifestation of HVA. Mastocytosis represents one of the most important risk factors for severe HVA. We analyzed patients with documented fatal HVA for the presence of underlying clonal mast cell disorder (cMCD). Here, we report three cases of fatal HVA, with undiagnosed underlying cMCD identified by the presence of the peripheral blood and/or bone marrow KIT p.D816V missense variant postmortem. In the first case, anaphylaxis was the initial episode and was fatal. In the other two cases, both patients were treated with specific venom immunotherapy (VIT), nevertheless, one died of HVA after VIT discontinuation, and the other during VIT; both patients had cardiovascular comorbidities and were taking beta-blockers and/or ACE inhibitors. Our results point to the importance of screening all high-risk individuals for underlying cMCD using highly sensitive molecular methods for peripheral blood KIT p.D816V variant detection, including severe HVA and possibly beekeepers, for proper management and the need for lifelong VIT to prevent unnecessary deaths. Patients at the highest risk of fatal HVA, with concomitant cardiovascular and cMCD comorbidities, might not be protected from field stings even during regular VIT. Therefore, two adrenaline autoinjectors and lifelong VIT, and possibly cotreatment with omalizumab, should be considered for high-risk patients to prevent fatal HVA episodes.
Hereditary α tryptasemia (HαT) is an autosomal dominant trait characterized by increased TPSAB1 copy number (CN) encoding α-tryptase. The determination of HαT is being discussed as an important ...biomarker to be included in risk assessment models and future diagnostic algorithms for patients with mastocytosis and anaphylaxis. Due to the complex genetic structure at the human tryptase locus, genetic testing for tryptase gene composition is presently notably limited and infrequently pursued. This study aimed to develop, optimise and validate a multiplex droplet digital PCR (ddPCR) assay that can reliably quantify α- and β-tryptase encoding sequences in a single reaction. To optimise the ddPCR conditions and establish an amplitude-based multiplex ddPCR assay, additional primers and probes, a thermal gradient with varying annealing temperatures, different primers/probe concentrations, and various initial DNA quantities were tested. Results obtained from all 114 samples analysed using multiplex ddPCR were identical to those obtained through the use of original duplex assays. Utilizing this multiplex ddPCR assay, in contrast to conducting distinct duplex ddPCRs, presents noteworthy benefits for tryptase genotyping. These advantages encompass a substantial threefold decrease in material costs and considerable time savings. Consequently, this approach exhibits high suitability and particularly captures interest for routine clinical implementation.
Allergy to bee and wasp venom can lead to life-threatening systemic reactions. The identification of the culprit species is important for allergen-specific immunotherapy.
To determine a panel of ...recombinant bee and wasp allergens which is suitable for the identification of bee or wasp as culprit allergen sources and to search for molecular surrogates of clinical severity of sting reactions.
Sera from eighty-seven patients with a detailed documentation of their severity of sting reaction (Mueller grade) and who had been subjected to titrated skin testing with bee and wasp venom were analyzed for bee and wasp-specific IgE levels by ImmunoCAPTM. IgE-reactivity testing was performed using a comprehensive panel of recombinant bee and wasp venom allergens (rApi m 1, 2, 3, 4, 5 and 10; rVes v 1 and 5) by ISAC chip technology, ImmunoCAP and ELISA. IgG4 antibodies to rApi m 1 and rVes v 5 were determined by ELISA and IgE/IgG4 ratios were calculated. Results from skin testing, IgE serology and IgE/IgG4 ratios were compared with severity of sting reactions.
The panel of rApi m 1, rApi m 10, rVes v 1 and rVes v 5 allowed identification of the culprit venom in all but two of the 87 patients with good agreement to skin testing. Severities of sting reactions were not associated with results obtained by skin testing, venom-specific IgE levels or molecular diagnosis. Severe sting reactions were observed in patients showing < 1 ISU and < 2kUA/L of IgE to Api m 1 and/or Ves v 5.
We identified a minimal panel of recombinant bee and wasp allergens for molecular diagnosis which may permit identification of bee and/or wasp as culprit insect in venom-sensitized subjects. The severity of sting reactions was not associated with parameters obtained by molecular diagnosis.
Allergen-specific venom immunotherapy (VIT) is a well-established therapy for
venom allergy (HVA). However, the precise mechanism underlying its clinical effect remains uncertain. Our study aimed to ...identify the molecular mechanisms associated with VIT efficiency. We prospectively included 19 patients with HVA undergoing VIT (sampled before the beginning of VIT, after reaching the maintenance dose, one year after finishing VIT, and after a sting challenge) and 9 healthy controls. RNA sequencing of whole blood was performed on an Illumina sequencing platform. Longitudinal transcriptomic profiling revealed the importance of the inhibition of the NFκB pathway and the downregulation of
transcripts for the early protection and induction of tolerance after finishing VIT. Furthermore, successful treatment was associated with inhibiting Th2, Th17, and macrophage alternative signalling pathways in synergy with the inhibition of the PPAR pathway and further silencing of the Th2 response. The immune system became activated when reaching the maintenance dose and was suppressed after finishing VIT. Finally, successful VIT restores the immune system's balance to a state similar to that of healthy individuals. Our results underline the important role of the inhibition of four pathways in the clinical effect of VIT: Th2, Th17, NFκB, and macrophage signalling. Two biomarkers specific for successful VIT, regardless of the time of sampling, were
and
and should be further tested as potential biomarkers.
Background The identification of the disease-causing insect in venom allergy is often difficult. Objective To establish recombinant allergen-based IgE tests to diagnose bee and yellow jacket wasp ...allergy. Methods Sera from patients with bee and/or wasp allergy (n = 43) and patients with pollen allergy with false-positive IgE serology to venom extracts were tested for IgE reactivity in allergen extract-based tests or with purified allergens, including nonglycosylated Escherichia coli –expressed recombinant (r) Api m 1, rApi m 2, rVes v 5, and insect cell–expressed, glycosylated rApi m 2 as well as 2 natural plant glycoproteins (Phl p 4, bromelain). Results The patients with venom allergy could be diagnosed with a combination of E coli –expressed rApi m 1, rApi m 2, and rVes v 5 whereas patients with pollen allergy remained negative. For a group of 29 patients for whom the sensitizing venom could not be identified with natural allergen extracts, testing with nonglycosylated allergens allowed identification of the sensitizing venom. Recombinant nonglycosylated allergens also allowed definition of the sensitizing venom for those 14 patients who had reacted either with bee or wasp venom extracts. By IgE inhibition studies, it is shown that glycosylated Api m 2 contains carbohydrate epitopes that cross-react with natural Api m 1, Ves v 2, natural Phl p 4, and bromelain, thus identifying cross-reactive structures responsible for serologic false-positive test results or double-positivity to bee and wasp extracts. Conclusion Nonglycosylated recombinant bee and wasp venom allergens allow the identification of patients with bee and wasp allergy and should facilitate accurate prescription of venom immunotherapy.
Clonal mast cell disorders and elevated basal serum tryptase (BST) levels with unknown cause(s) are associated with severe Hymenoptera venom–triggered anaphylaxis (HVA). However, some individuals ...with clonal disease have a normal BST level (<11.4 ng/mL).
Our aim was to evaluate whether screening for KIT p.D816V in the blood is a useful clinical tool to risk-stratify patients with venom allergy.
We prospectively recruited 374 patients with Hymenoptera allergy and no overt signs of mastocytosis who were referred to our center during the years 2018 and 2019. KIT p.D816V was determined in their peripheral blood by quantitative PCR, and tryptase genotyping was performed by droplet digital PCR.
In all, 351 patients (93.9%) had normal levels of BST, and KIT p.D816V was detected in 8% of patients (28 of 351), predominantly in patients with the most severe Mueller grade IV anaphylaxis (18.2% 24 of 132 vs 1.8% in patients with lower grades 4 of 88 with grade III and 0 of 131 with other grades; P < .001). In grade IV patients with a normal BST level, KIT p.D816V was associated with more severe symptoms, including a significantly higher frequency of loss of consciousness (58.3% 14 of 24 vs 34.3% 37 of 108; P = .03) and absence of skin symptoms (41.7% 10 of 24 vs 15.7% 17 of 108; P = .004). Among patients with a normal BST level, KIT p.D816V (OR = 10.25 95% CI = 3.75-36.14; P < .0001) was the major risk factor associated with severe HVA. Hereditary α-tryptasemia (HαT) due to increased germline copies of TPSAB1 encoding α-tryptase was the most common cause (65.2% 15 of 23) of elevated BST level in patients with HVA, and together with KIT p.D816V, it accounted for 90% of BST level elevations (20 of 23) in patients with HVA.
These results indicate that routine KIT p.D816V screening identifies clonal disease in high-risk patients with HVA who are regularly missed when BST level is used alone.
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