Helios negative Regulatory T-cells as a key factor of immune tolerance in non-allergic beekeepers

BACKGROUND AND OBJECTIVE

Background: Although exposure to stings has been identified as the leading risk factor for anaphylaxis due to Hymenoptera venom allergy, professional beekeepers receive hundreds yearly without developing systemic reactions. Objective: This study aims to analyse the mechanisms underlying bee venom tolerance in beekeepers.

METHODS

A cross-sectional study was conducted. Participants were recruited and classified into three groups: allergic patients (AP) experiencing systemic reactions after bee stings, with a positive intradermal test and specific IgE (sIgE) to Apis mellifera venom (AmV); tolerant beekeepers (TBK) receiving ≥50 stings/year; and healthy non-exposed controls (HC). Serum levels of sIgE and specific IgG4 (sIgG4) to AmV, rApi m 1, rApi m 2, rApi m 3, Api m 4, rApi m 5 and rApi m10, as well as AmV-induced basophil degranulation, percentage of T-cell subsets, regulatory T-cells (Treg cells) and IL-10 production, were measured.

RESULTS

APs had high levels of sIgE to AmV and all its allergic components (p<0.001) together with a high basophil activation rate (p<0.001) compared to TBKs. Conversely, compared to APs, TBKs showed higher levels of sIgG4 (p<0.001) and IL-10 (p<0.001) as well as an enhanced CTLA-4+ Treg population (p=0.001), expanded Helios- Treg (p<0.003), and reduced T-helper 1 (p=0.008), T-helper 2 (p=0.004) and T-helper 17 (p=0.007) subsets.

CONCLUSIONS

A different profile, strongly marked by Treg activity, was found in TBKs. This natural tolerance would be led by the expansion of inducible Helios-Treg cells at a peripheral level. Helios-Treg population could be a novel candidate biomarker useful for monitoring tolerance.

Component-resolved diagnosis in hymenoptera allergy

Component-resolved diagnosis based on the use of well-defined, properly characterised and purified natural and recombinant allergens constitutes a new approach in the diagnosis of venom allergy. Prospective readers may benefit from an up-to-date review on the allergens. The best characterised venom is that of Apis mellifera, whose main allergens are phospholipase A2 (Api m1), hyaluronidase (Api m2) and melittin (Api m4). Additionally, in recent years, new allergens of Vespula vulgaris have been identified and include phospholipase A1 (Ves v1), hyaluronidase (Ves v2) and antigen 5 (Ves v5). Polistes species are becoming an increasing cause of allergy in Europe, although only few allergens have been identified in this venom. In this review, we evaluate the current knowledge about molecular diagnosis in hymenoptera venom allergy.

Application of recombinant antigen 5 allergens from seven allergy-relevant Hymenoptera species in diagnostics

BACKGROUND

Hymenoptera stings can cause severe anaphylaxis in untreated venom-allergic patients. A correct diagnosis regarding the relevant species for immunotherapy is often hampered by clinically irrelevant cross-reactivity. In vespid venom allergy, cross-reactivity between venoms of different species can be a diagnostic challenge. To address immunological IgE cross-reactivity on molecular level, seven recombinant antigens 5 of the most important Vespoidea groups were assessed by different diagnostic setups.

METHODS

The antigens 5 of yellow jackets, hornets, European and American paper wasps, fire ants, white-faced hornets, and Polybia wasps were recombinantly produced in insect cells, immunologically and structurally characterized, and their sIgE reactivity assessed by ImmunoCAP, ELISA, cross-inhibition, and basophil activation test (BAT) in patients with yellow jacket or Polistes venom allergy of two European geographical areas.

RESULTS

All recombinant allergens were correctly folded and structural models and patient reactivity profiles suggested the presence of conserved and unique B-cell epitopes. All antigens 5 showed extensive cross-reactivity in sIgE analyses, inhibition assays, and BAT. This cross-reactivity was more pronounced in ImmunoCAP measurements with venom extracts than in sIgE analyses with recombinant antigens 5. Dose-response curves with the allergens in BAT allowed a differentiated individual dissection of relevant sensitization.

CONCLUSIONS

Due to extensive cross-reactivity in various diagnostic settings, antigens 5 are inappropriate markers for differential sIgE diagnostics in vespid venom allergy. However, the newly available antigens 5 from further vespid species and the combination of recombinant allergen-based sIgE measurements with BAT represents a practicable way to diagnose clinically relevant sensitization in vespid venom allergy.

Improving pollen immunotherapy: minor allergens and panallergens

Multiple sensitizations to pollens are common clinical situations in Spain, and alter the efficacy of allergen-specific immunotherapy. We now know that optimization of the diagnosis is required to define the best suited treatment for each patient. All pollen allergens belong to 29 families of proteins - the most abundant being the expansins, prophyllins and polcalcins. The ubiquitous nature of proteins such as the prophyllins and polcalcins defines them as panallergens, and explains the cross-reactivity that is erroneously interpreted by clinicians as constituting multi-sensitization. Other families of allergens, such as the calcium transporting proteins (LTPs) are more restricted, but are associated to severe types of allergic disease - this being particularly useful to decide upon the indication of immunotherapy. Although recombinant allergens can be produced for in vitro diagnostic purposes, current legislation only allows the use of natural proteins for immunotherapy. However, the same technology can be applied to the study of extracts for vaccines, and it seems that allergen quantification by the manufacturers is a no return trip which clinicians are obliged to follow.