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The fire ant is an aggressive invasive species whose venom frequently triggers hypersensitivity reactions, including severe anaphylaxis. In endemic regions, its stings represent a significant cause of Hymenoptera-related allergy. Four venom allergens have been identified - phospholipase A1 (Sol i 1), antigen 2 (Sol i 2), antigen 3 (Sol i 3), and antigen 4 (Sol i 4) - with Sol i 3 recognized as the predominant sensitizer. However, the molecular determinants that drive Sol i 3 allergenicity and its potential cross-reactivity with other Hymenoptera venoms remain insufficiently understood. This study identified the linear immunoglobulin E (IgE) epitopes of Sol i 3 and examined their recognition by sera from yellow jacket venom (YJV) - and wasp-allergic patients. Two linear epitopes were mapped: Sol i 3_e1 (ELRQRVASGKEMRG) and Sol i 3_e2 (WAKTTKIGCGRIMF). Although Sol i 3 exhibits limited sequence and structural similarity to other antigen 5 proteins, it contains a conserved immunoreactive core (WAKTTK), analogous to the WAKTKE motif described for the allergen Poly p 5 from . This conserved region may represent a shared epitope contributing to cross-reactivity among Hymenoptera venoms. Consistently, sera from -sensitized patients and YJV-sensitized patients recognized Sol i 3_e2. These findings define key B-cell epitopes of Sol i 3 and reveal a conserved motif that may underlie cross-reactivity, offering implications for improved diagnosis and immunotherapy.

An attack by a parasitic wasp activates a vigorous cellular immune response in Drosophila larvae. This response is manifested by an increased number of circulating cells, the hemocytes, and by the appearance of a specialized class of hemocyte, the lamellocytes, which participate in the encapsulation and killing of the parasite. To study the molecular mechanisms of this response, we have overexpressed different genes in the hemocytes, by using the GAL4-upstream activating sequence system and a hemocyte-specific Hemese-GAL4 driver. Multiple transgenes were tested, representing several important signaling pathways. We found that the proliferation response and the activation of lamellocyte formation are independent phenomena. A drastic increase in the number of circulating hemocytes is caused by receptor tyrosine kinases, such as Egfr, Pvr, and Alk, as well as by the downstream signaling components Ras85D and pointed, supporting the notion that the Ras-mitogen-activated protein kinase pathway regulates hemocyte numbers. In the case of Pvr and Alk, this phenotype also is accompanied by lamellocyte formation. By contrast, constitutively active hopscotch and hemipterous give massive activation of lamellocyte formation with little or no increase in total hemocyte numbers. This finding indicates that both the Jak/Stat and the Jun kinase pathways affect lamellocyte formation. Still other signals, mediated by aopACT, Toll10b, and Rac1 expression, cause a simultaneous increase in lamellocyte and total cell numbers, and the same effect is seen when WNT signaling is suppressed. We conclude that the activation of a cellular response is complex and affected by multiple signaling pathways.

Sensitization to cross-reactive allergens complicates identifying the culprit insect in Hymenoptera venom allergy via diagnostic tests. This study evaluates sensitization to hyaluronidases (Api m 2 from honey bee (Apis mellifera) venom, HBV; Pol d 2 from European paper wasp (Polistes dominula) venom, PDV; and Ves v 2.0101 and Ves v 2.0201 from yellow jacket (Vespula vulgaris) venom, YJV) and their cross-reactivity in allergic patients from Italy, Spain, and Germany using ImmunoCAPs, ELISA, and basophil activation tests. Sensitization rates were 45% for Api m 2 in HBV-allergic subjects, 25% for Pol d 2 in PDV-allergic individuals, and 20% and 10% for Ves v 2.0201 and Ves v 2.0101 in YJV-allergic patients, respectively. Patients primarily sensitized to Api m 2 showed minimal cross-reactivity to vespid hyaluronidases, whereas those primarily sensitized to Pol d 2 or Ves v 2.0201 exhibited IgE reactivity to Api m 2. Neither Pol d 2 nor Ves v 2.0201 triggered basophil activation. Cross-reactivity of Api m 2, Pol d 2, and Ves v 2.0201 depends on the primary sensitizing venom. Sensitization to Pol d 2 and Ves v 2.0201 remains below 25%, yet these patients may exhibit cross-reactivity to Api m 2. Conversely, HBV-allergic patients sensitized to Api m 2 show minimal reactivity to Pol d 2 or Ves v 2.0201.

Background: Hymenoptera venom allergy is a potentially severe allergic reaction in the general population. The only preventative approach in these cases is venom immunotherapy (VIT), which follows different protocols. The recommended initial dose is 0.001–0.1 mcg of venom extract. However, few reports have declared the safety of 1 mcg venom as the starting dose. Methods: The study was conducted on Iranian patients with a history of anaphylaxis to venom. Skin tests confirmed hypersensitivity to honeybee, yellow jacket, and/or paper wasp from subfamily Polistes using Apis melifera, Vespula spp, and Polistes spp venom extracts, respectively. Subsequently, the patients were treated with the cluster protocol. Results: Twenty-two patients (17 males and 5 females, aged 28.3±11.8 years) were enrolled in the study. Skin prick tests and intradermal tests showed positive results for yellow jacket in 17 (77.3%) and 21 (95.4%) patients, honeybee in 14 (63.6%) and 17 (77.3%) patients, and wasp in 14 (63.6%) and 17 (77.3%) patients, respectively. Upon administering the initial dose of 1 mcg/mL, 40.9% (9 cases) of patients presented mild local reactions, including 7 with yellow jacket allergy, 5 with honeybee allergy, and 3 with wasp allergy. One patient with yellow jacket allergy had a mild systemic reaction. Patients with a positive skin test for wasp had significantly lower rate of reactions after the first dose of venom (p=0.026). Throughout the entire build-up phase, more than 90% (20 of 22) of patients experienced mild local reactions, followed by large local reactions (3 cases, 13.6%), mild systemic reactions (1 case at 1 mcg/mL dose), and moderate-to-severe systemic reactions (3 cases, 13.6%). Large local and moderate-to-severe systemic reactions were detected after injecting 50 mcg (each one case) and 100 mcg (each 2 cases) of venom extracts. Conclusion: This study recommends 1 mcg/mL of the venom extract as a safe starting dose for VIT. This accelerated protocol could successfully reduce the time and costs of therapy for patients undergoing out-patient cluster VIT.

Wasp parasitoids use a variety of methods to commandeer their insect hosts in order to create an environment that will support and promote their own development, usually to the detriment of the host insect. Parasitized insects typically undergo developmental arrest and die sometime after the parasitoid has become independent of its host. Parasitoids can deactivate their host's immune system and effect changes in host hormone titers and behavior. Often, host tissues or organs become refractory to stimulation by tropic hormones. Here we present an overview of the manipulative capabilities of wasp-injected calyx fluid containing polydnaviruses and venom, as well as the parasitoid larva and the teratocytes that originate from the serosal membrane that surrounds the developing embryo of the parasitoid. Possibilities for using regulatory molecules produced by the parasitoid or its products that would be potentially useful in developing new, environmentally safe insect control agents are discussed.

Wasp venom allergy can trigger severe allergic reactions, and predicting these acute responses remains challenging. This study evaluates the utility of immune system indexes, particularly the eosinophil–basophil/lymphocyte (EB/LR) and eosinophil–basophil–platelet/lymphocyte (EBP/LR) ratios, in assessing the severity of allergic reactions in patients with wasp venom allergy. A total of 61 patients with confirmed wasp venom allergy were categorized according to the Mueller scale, which classifies the severity of allergic reactions. Blood samples were analyzed for total and specific IgE levels alongside a range of hematological and biochemical parameters. This study found significant differences in the EB/LR and EBP/LR indexes between patients with mild (Mueller I–II) and severe (Mueller III–IV) allergic reactions, with higher values indicating more severe responses. However, no significant differences were observed in other immune indexes, such as the platelet-to-lymphocyte ratio, neutrophil-to-lymphocyte ratio, systemic immune-inflammation index, and systemic inflammatory response index, as well as in additional blood parameters. These findings suggest that the EB/LR and EBP/LR ratios may serve as useful markers for predicting the severity of allergic reactions in patients with wasp venom allergy. This is the first study to establish such a link, although further research with larger cohorts is necessary to confirm these results and their potential application in clinical settings.

Systemic mastocytosis (SM) is a clonal mast cell disorder that can lead to potentially severe anaphylactic reactions. Hymenoptera sting is one of the most frequent triggers of anaphylaxis in these patients, and diagnosis of indolent SM (ISM) without skin involvement (ISMs) is not rare. In this subgroup of patients, venom immunotherapy (VIT) is an effective treatment decreasing subsequent systemic reactions, and lifelong administration is recommended. An individualized diagnosis is necessary to offer the most adequate VIT, and molecular diagnosis (MD) may be useful to discriminate between primary sensitization and cross-reactivity. Nevertheless, other techniques such as ImmunoCAP inhibition assays may be necessary to identify the genuine sensitization to offer the most suitable VIT. We present a male patient with an anaphylactic reaction following several wasp stings. The patient was diagnosed with ISM, and allergy to both Polistes dominula and Vespula sp venom was confirmed. In this scenario, MD did not discriminate between a genuine double sensitization and venom cross-reactivity between both vespids. Thus, CAP-inhibition assay was performed. This case indicated the importance of an accurate diagnosis of hymenoptera venom allergy (HVA). It also highlights the usefulness of CAP-inhibition assays when MD fails to distinguish between genuine double Polistes-Vespula sensitization and cross-reactivity.

Venom immunotherapy (VIT) is highly effective in preventing allergic reactions to insect stings, but the appropriate venom must be used to achieve clinical protection. In patients with multiple positive results to venoms, molecular allergy diagnostics or CAP-inhibition may identify the causative venom. Concerning allergy to venom from Polistes spp. it has been proposed that only the European species P. dominulus should be used for VIT. However, this recommendation is not present in any international guideline. Using both laboratory and clinical data, we aimed to evaluate the reliability of this proposal. We performed an in vitro study using CAP-inhibition to determine sensitization of 19 patients allergic to Polistes venom. The clinical study included 191 patients with positive tests to Polistes treated with VIT, 102 were treated with P. dominulus and 89 were treated with a mix of American Polistes (mAP). The difference in % of inhibition was significant concerning inhibition of P. dominulus sIgE by P. dominulus venom (79.8%) compared with inhibition by mAP venom (64.2%) and not significant concerning the inhibition of mAP sIgE by P. dominulus venom (80.1%) and by mAP venom (73.6%). Instead, the clinical protection from stings was not statistically different between the two kinds of venom. The data from CAP inhibition would suggest that the choice of either P. dominulus venom or mAP venom for VIT is appropriate in patients with CAP inhibition higher than 70%, but the clinical data show the same odds of protection from stings using for VIT P. dominulus or mAP venom.

Background: Local reactions (LRs) are a very frequent side effect of specific immunotherapy with allergens and can impair patients’ adherence. Antihistamine pretreatment – originally introduced as a safety measure to reduce anaphylactic side effects – has been the only treatment option for LRs so far, although these swellings usually do not appear immediately but after hours. We were interested whether pretreatment with the leukotriene antagonist montelukast would be better suited for preventing those reactions than pretreatment with the antihistamine desloratadine. Methods: Fifteen patients with a history of severe anaphylactic reactions to hymenoptera stings were enrolled into a prospective, double-blind, randomized, placebo-controlled pilot study. We selected a rush immunotherapy protocol consisting of 19 injections of hymenoptera venom administered over 5 consecutive days, where the majority is developing LRs, and counted the number of injections until an LR of >3 cm occurred. The patients were randomized to 3 treatment groups: premedication with placebo, 10 mg montelukast and 5 mg of the antihistamine desloratadine. Results: Compared with placebo, the occurrence of LRs (>3 cm) was significantly delayed by montelukast (p < 0.01, analysis of variance) but not by desloratadine (p = 0.19). The difference between montelukast and desloratadine was close to significant (p = 0.054). Itching, recorded on a scale from 0 to 5, did not differ between the 3 groups. Conclusion: Montelukast can be useful in the prevention of LRs after specific immunotherapy.

Pimecrolimus (Elidel, SDZ ASM 981) is an anti-inflammatory and immunomodulatory 33-epichloro-derivative of macrolactam ascomycin, with low potential for affecting systemic immune responses compared with other calcineurin inhibitors, cyclosporin A and tacrolimus. Despite numerous studies focused on the mechanism of pimecrolimus action on mast cells, only the single report has addressed pimecrolimus effects on other typical FcεRI-expressing cells, the basophils. Patients allergic to birch pollen (n = 20), hymenopteran venoms (n = 23) and 10 non-allergic volunteers were examined. Primary human basophils pre-treated or not with 0.5-50 μMol pimecrolimus were exposed to various concentrations of recombinant Bet v 1a allergen, bee or wasp venom extracts and anti-IgE for 20 min, and then examined for the expression of CD45, CD193, CD203c, CD63 and CD164 using flow cytometry. The externalization of basophil activation markers (CD63 and CD164) was equally inhibited through pimecrolimus in cells activated by recombinant pollen allergen, hymenopteran venom extracts and anti-IgE. Although the individual response rate was subject to strong variation, importantly, pre-treatment with pimecrolimus lowered the number of activated basophils in response to any of the stimuli in the basophils from all patients. The inhibition was concentration-dependent; approximately half of the basophils were inhibited in the presence of 2.5 mMol pimecrolimus. Pimecrolimus is a valuable new tool for the inhibition of hyper-reactive basophils in patients with pollen allergy and a history of anaphylactic reactions to bee or wasp venoms. Further research should address short-term use of pimecrolimus in vivo in a wide spectrum of allergic diseases.