Advances in diagnosis and management of insect sting allergy

Global View on Ant Venom Allergy: from Allergenic Components to Clinical Management

Hymenoptera venom allergy is characterised by systemic anaphylactic reactions that occur in response to stings from members of the Hymenoptera order. Stinging by social Hymenoptera such as ants, honeybees, and vespids is one of the 3 major causes of anaphylaxis; along with food and drug exposure, it accounts for up to 43% of anaphylaxis cases and 20% of anaphylaxis-related fatalities. Despite their recognition as being of considerable public health significance, stinging ant venoms are relatively unexplored in comparison to other animal venoms and may be overlooked as a cause of venom allergy. Indeed, the venoms of stinging ants may be the most common cause of anaphylaxis in ant endemic areas. A better understanding of the natural history of venom allergy caused by stinging ants, their venom components, and the management of ant venom allergy is therefore required. This article provides a global view on allergic reactions to the venoms of stinging ants and the contemporary approach to diagnose and manage ant venom allergy.

Hymenoptera venoms used to produce allergen extracts

OBJECTIVE

To review the methods and materials used for collection, purification, commercial production, and clinical application of Hymenoptera venoms.

DATA SOURCES

Most of the sources for this review are the experience and expertise of the authors. Published reports and review articles on Hymenoptera venom collection and production were identified through database searches (PubMed).

STUDY SELECTIONS

Studies describing the methods for Hymenoptera venom collection and production were selected for review.

RESULTS

Meticulous methods for identification and collection of the insects are required. Collection and purification of the venoms from the insects are based on validated methods and result in a commercial extract that is standardized for the major allergenic proteins required for accurate diagnosis and safe and effective treatment of patients allergic to insect sting. The steps required for mixing, purifying, testing, and standardizing the products are described.

CONCLUSION

Hymenoptera venom extracts were developed using many new methods for the collection, purification, and commercial production of the unique materials required for this product. Clinical applications for diagnosis and treatment are affected by the integrity and stability of the allergens after processing and purification.

Allergy associations with the adult fecal microbiota: Analysis of the American Gut Project

BACKGROUND

Alteration of the gut microbial population (dysbiosis) may increase the risk for allergies and other conditions. This study sought to clarify the relationship of dysbiosis with allergies in adults.

METHODS

Publicly available American Gut Project questionnaire and fecal 16S rRNA sequence data were analyzed. Fecal microbiota richness (number of observed species) and composition (UniFrac) were used to compare adults with versus without allergy to foods (peanuts, tree nuts, shellfish, other) and non-foods (drug, bee sting, dander, asthma, seasonal, eczema). Logistic and Poisson regression models adjusted for potential confounders. Odds ratios and 95% confidence intervals (CI) were calculated for lowest vs highest richness tertile. Taxonomy associations considered 122 non-redundant taxa (of 2379 total taxa) with ≥ 0.1% mean abundance.

RESULTS

Self-reported allergy prevalence among the 1879 participants (mean age, 45.5 years; 46.9% male) was 81.5%, ranging from 2.5% for peanuts to 40.5% for seasonal. Fecal microbiota richness was markedly lower with total allergies (P = 10(-9)) and five particular allergies (P ≤ 10(-4)). Richness odds ratios were 1.7 (CI 1.3-2.2) with seasonal, 1.8 (CI 1.3-2.5) with drug, and 7.8 (CI 2.3-26.5) with peanut allergy. These allergic participants also had markedly altered microbial community composition (unweighted UniFrac, P = 10(-4) to 10(-7)). Total food and non-food allergies were significantly associated with 7 and 9 altered taxa, respectively. The dysbiosis was most marked with nut and seasonal allergies, driven by higher Bacteroidales and reduced Clostridiales taxa.

INTERPRETATION

American adults with allergies, especially to nuts and seasonal pollen, have low diversity, reduced Clostridiales, and increased Bacteroidales in their gut microbiota. This dysbiosis might be targeted to improve treatment or prevention of allergy.

Comparable profiles of serum histamine and IgG4 levels in allergic beekeepers

Growing evidence identifies histamine as a key player in allergic responses, but the reports relating serum histamine to tolerance are scarce and inconclusive. This study investigated the relationship of circulating histamine to the tolerant phenotype in allergic beekeepers. The results showed a positive correlation between the serum levels of histamine and specific immunoglobulin G4 (sIgG4) to honeybee venom, but not with total IgE or sIgE. Interestingly, both sIgG4 and histamine levels were negatively correlated with the time since the last bee sting. In contrast to total IgE and sIgE, serum sIgG4 and histamine levels followed comparable patterns, being higher in tolerant/recently stung individuals and lower in the least frequently stung subgroup. The data obtained in this pilot study associated, for the first time, serum histamine levels with allergen tolerance in allergic individuals and provided the lead for further considering the putative immunomodulatory properties of histamine in allergic responses.

New directions in diagnostic evaluation of insect allergy

PURPOSE OF REVIEW

Diagnosis of insect sting allergy and prediction of risk of sting anaphylaxis are often difficult because tests for venom-specific IgE antibodies have a limited positive predictive value and do not reliably predict the severity of sting reactions.

RECENT FINDINGS

Component-resolved diagnosis using recombinant venom allergens has shown promise in improving the specificity of diagnostic testing for insect sting allergy. Basophil activation tests have been explored as more sensitive assays for identification of patients with insect allergy and for prediction of clinical outcomes. Measurement of mast cell mediators reflects the underlying risk for more severe reactions and limited clinical response to treatment.

SUMMARY

Measurement of IgE to recombinant venom allergens can distinguish cross-sensitization from dual sensitization to honeybee and vespid venoms, thus helping to limit venom immunotherapy to a single venom instead of multiple venoms in many patients. Basophil activation tests can detect venom allergy in patients who show no detectable venom-specific IgE in standard diagnostic tests and can predict increased risk of systemic reactions to venom immunotherapy, and to stings during and after stopping venom immunotherapy. The risk of severe or fatal anaphylaxis to stings can also be predicted by measurement of baseline serum tryptase or other mast cell mediators.

Venom immunotherapy: an updated review

Venom immunotherapy (VIT) is the most effective form of specific immunotherapy to date. Hitherto, several relevant queries remain unanswered, namely optimal doses, duration, and means of assessment. Important progress has been lately made in terms of diagnosis by means of component-resolved diagnosis. Moreover, basophil activation test results in patients with negative serum immunoglobulin E (IgE) and skin prick test confer this technique a promising future, although these outcomes shall be considered with caution. This review aims to unravel the important advances made on diagnosis, management, and prognosis and also focuses on several undetermined aspects of VIT.