Diagnosis of Hymenoptera venom allergy

The purpose of diagnostic procedure is to classify a sting reaction by history, identify the underlying pathogenetic mechanism, and identify the offending insect. Diagnosis of Hymenoptera venom allergy thus forms the basis for the treatment. In the central and northern Europe vespid (mainly Vespula spp.) and honeybee stings are the most prevalent, whereas in the Mediterranean area stings from Polistes and Vespula are more frequent than honeybee stings; bumblebee stings are rare throughout Europe and more of an occupational hazard. Several major allergens, usually glycoproteins with a molecular weight of 10-50 kDa, have been identified in venoms of bees, vespids. and ants. The sequences and structures of the majority of venom allergens have been determined and several have been expressed in recombinant form. A particular problem in the field of cross-reactivity are specific immunoglobulin E (IgE) antibodies directed against carbohydrate epitopes, which may induce multiple positive test results (skin test, in vitro tests) of still unknown clinical significance. Venom hypersensitivity may be mediated by immunologic mechanisms (IgE-mediated or non-IgE-mediated venom allergy) but also by nonimmunologic mechanisms. Reactions to Hymenoptera stings are classified into normal local reactions, large local reactions, systemic toxic reactions, systemic anaphylactic reactions, and unusual reactions. For most venom-allergic patients an anaphylactic reaction after a sting is very traumatic event, resulting in an altered health-related quality of life. Risk factors influencing the outcome of an anaphylactic reaction include the time interval between stings, the number of stings, the severity of the preceding reaction, age, cardiovascular diseases and drug intake, insect type, elevated serum tryptase, and mastocytosis. Diagnostic tests should be carried out in all patients with a history of a systemic sting reaction to detect sensitization. They are not recommended in subjects with a history of large local reaction or no history of a systemic reaction. Testing comprises skin tests with Hymenoptera venoms and analysis of the serum for Hymenoptera venom-specific IgE. Stepwise skin testing with incremental venom concentrations is recommended. If diagnostic tests are negative they should be repeated several weeks later. Serum tryptase should be analyzed in patients with a history of a severe sting reaction.

Prevention and treatment of hymenoptera venom allergy: guidelines for clinical practice

Based on the knowledge of the living conditions and habitat of social Aculeatae a series of recommendations have been formulated which can potentially greatly minimize the risk of field re-sting. After a systemic sting reaction, patients should be referred to an allergy specialist for evaluation of their allergy, and if necessary venom immunotherapy (VIT). An emergency medical kit should be supplied, its use clearly demonstrated and repeatedly practised until perfected. This should be done under the supervision of a doctor or a trained nurse. Epinephrine by intramuscular injection is regarded as the treatment of choice for acute anaphylaxis. H1-antihistamines alone or in combination with corticosteroids may be effective in mild to moderate reactions confined to the skin and may support the value of treatment with epinephrine in full-blown anaphylaxis. Up to 75% of the patients with a history of systemic anaphylactic sting reaction develop systemic symptoms once again when re-stung. Venom immunotherapy is a highly effective treatment for individuals with a history of systemic reaction and who have specific IgE to venom allergens. The efficacy of VIT in yellow jacket venom allergic patients has been demonstrated also by assessing health-related quality of life. If both skin tests and serum venom specific IgE turn negative, VIT may be stopped after 3 years. After VIT lasting 3-5 years, most patients with mild to moderate anaphylactic symptoms remain protected following discontinuation of VIT even with positive skin tests. Longer term or lifelong treatment should be considered in high-risk patients. Because of the small but relevant risk of re-sting reactions, in these patients, emergency kits, including epinephrine auto-injectors, should be discussed with every patient when stopping VIT.

Risk assessment in anaphylaxis: current and future approaches

Risk assessment of individuals with anaphylaxis is currently hampered by lack of (1) an optimal and readily available laboratory test to confirm the clinical diagnosis of an anaphylaxis episode and (2) an optimal method of distinguishing allergen-sensitized individuals who are clinically tolerant from those at risk for anaphylaxis episodes after exposure to the relevant allergen. Our objectives were to review the effector mechanisms involved in the pathophysiology of anaphylaxis; to explore the possibility of developing an optimal laboratory test to confirm the diagnosis of an anaphylaxis episode, and the possibility of improving methods to distinguish allergen sensitization from clinical reactivity; and to develop a research agenda for risk assessment in anaphylaxis. Researchers from the American Academy of Allergy, Asthma & Immunology and the European Academy of Allergology and Clinical Immunology held a PRACTALL (Practical Allergy) meeting to discuss these objectives. New approaches being investigated to support the clinical diagnosis of anaphylaxis include serial measurements of total tryptase in serum during an anaphylaxis episode, and measurement of baseline total tryptase levels after the episode. Greater availability of the test for mature beta-tryptase, a more specific mast cell activation marker for anaphylaxis than total tryptase, is needed. Measurement of chymase, mast cell carboxypeptidase A3, platelet-activating factor, and other mast cell products may prove to be useful. Consideration should be given to measuring a panel of mediators from mast cells and basophils. New approaches being investigated to help distinguish sensitized individuals at minimum or no risk from those at increased risk of developing anaphylaxis include measurement of the ratio of allergen-specific IgE to total IgE, determination of IgE directed at specific allergenic epitopes, measurement of basophil activation markers by using flow cytometry, and assessment of allergen-specific cytokine responses. Algorithms have been developed for risk assessment of individuals with anaphylaxis, along with a research agenda for studies that could lead to an improved ability to confirm the clinical diagnosis of anaphylaxis and to identify allergen-sensitized individuals who are at increased risk of anaphylaxis.

Social Immunity: Emergence and Evolution of Colony-Level Disease Protection

Social insect colonies have evolved many collectively performed adaptations that reduce the impact of infectious disease and that are expected to maximize their fitness. This colony-level protection is termed social immunity, and it enhances the health and survival of the colony. In this review, we address how social immunity emerges from its mechanistic components to produce colony-level disease avoidance, resistance, and tolerance. To understand the evolutionary causes and consequences of social immunity, we highlight the need for studies that evaluate the effects of social immunity on colony fitness. We discuss the roles that host life history and ecology have on predicted eco-evolutionary dynamics, which differ among the social insect lineages. Throughout the review, we highlight current gaps in our knowledge and promising avenues for future research, which we hope will bring us closer to an integrated understanding of socio-eco-evo-immunology.

Clinical relevance of the venom-specific immunoglobulin G antibody level during immunotherapy

Parameters associated with successful venom immunotherapy in insect allergy were sought by comparison of treatment failures with successes. Half-dose treatment was completely protective in 32 patients (successes) but was only partially effective in eight (failures). The outcome of treatment was not related to the severity of pretreatment sting reactions, to the degree of skin-test sensitivity, to an atopic personal history, or to age or gender. The mean yellow jacket venom-specific IgG antibody level (by the Staph-A solid-phase radioimmunoassay) was significantly less in the failures (3.9 +/- 0.6 microgram/ml) than in the successes (7.3 +/- 1.1 microgram/ml) (p less than 0.01). When the failures were successfully treated, their mean IgG level (6.1 +/- 1.3 microgram/ml) was significantly greater than that associated with treatment failure (p less than 0.025). Patients with an IgG antibody level above 5.0 microgram/ml were significantly more likely to be fully protected (p less than 0.02). Those whose IgG levels were less than 5 microgram/ml had a risk of reaction similar to that in untreated patients. We conclude that early in the maintenance phase of low-dose venom immunotherapy, the risk of a reaction to a challenge sting is significantly greater for those patients with low levels of venom-specific IgG antibodies.

Elevated basal serum tryptase and hymenoptera venom allergy: relation to severity of sting reactions and to safety and efficacy of venom immunotherapy

BACKGROUND

Mastocytosis and/or elevated basal serum tryptase may be associated with severe anaphylaxis.

OBJECTIVE

To analyse Hymenoptera venom-allergic patients with regard to basal tryptase in relation to the severity of sting reactions and the safety and efficacy of venom immunotherapy.

METHODS

Basal serum tryptase was measured in 259 Hymenoptera venom-allergic patients (158 honey bee, 101 Vespula). In 161 of these (104 honey bee, 57 Vespula), a sting challenge was performed during venom immunotherapy.

RESULTS

Nineteen of the 259 patients had an elevated basal serum tryptase. Evidence of cutaneous mastocytosis as documented by skin biopsy was present in 3 of 16 patients (18.8%). There was a clear correlation of basal serum tryptase to the grade of the initial allergic reaction (P<0.0005). Forty-one of the 161 sting challenged patients reacted to the challenge, 34 to a bee sting and 7 to a Vespula sting. Thereof, 10 had an elevated basal serum tryptase, i.e. 1 (2.9%) of the reacting and 2 (2.9%) of the non-reacting bee venom (BV) allergic individuals, as compared to 3 (42.9%) of the reacting and 4 (8%) of the non-reacting Vespula venom-allergic patients. Thus, there was a significant association between a reaction to the sting challenge and an elevated basal serum tryptase in Vespula (chi2=6.926, P<0.01), but not in BV-allergic patients. Systemic allergic side-effects to venom immunotherapy were observed in 13.9% of patients with normal and in 10% of those with elevated basal serum tryptase.

CONCLUSIONS

An elevated basal serum tryptase as well as mastocytosis are risk factors for severe or even fatal shock reactions to Hymenoptera stings. Although the efficacy of venom immunotherapy in these patients is slightly reduced, most of them can be treated successfully. Based on currently available data, lifelong treatment has to be discussed in this situation.

The Hymenoptera venom study. III: Safety of venom immunotherapy

One thousand four hundred ten (44%) of the 3236 subjects in the Hymenoptera venom study accepted venom immunotherapy (VIT). Time to maintenance averaged 95 days, and the largest number achieved maintenance (147 subjects, 10.4%) at day 56. Ninety-two percent of the treated subjects achieved maintenance, and 84% continued therapy, most subjects (91%) until the study was terminated. One hundred seventy-one subjects (12%) experienced 327 treatment systemic reactions (Srs). The incidence of pruritus and angioedema/urticaria was similar with mild, moderate, or severe SRs. The SR severity did not correlate with the severity of the most recent sting before entry into the Hymenoptera-venom study, the most severe historical sting SR, the most severe SR during venom skin tests, the total dose of venom, the degree of skin test reactivity, or the lowest concentration yielding a positive skin test. Most SRs occurred between 1 and 50 micrograms and at maintenance; honeybee or wasp venoms were most likely to produce SR. This study, the largest of its kind with the use of standardized extracts, demonstrates (1) that there was good compliance, (2) that various historical and diagnostic criteria did not predict SRs to VIT, (3) that SRs to VIT were most likely to occur between 1 and 50 micrograms and at maintenance, (4) that honeybee or wasp venoms were most likely to produce an SR, and (5) that VIT is relatively safe.

Insect sting allergy and venom immunotherapy: a model and a mystery

Whole-body extracts of Hymenoptera were used for diagnosis and treatment until controlled clinical trials proved them no better than placebo, whereas venom is 85% to 98% effective. Studies of natural history reveal why whole-body extracts were thought to work. The chance of future systemic reactions is low in large local reactors and in most children and varies between 20% and 70% in adults. Venom skin tests are most accurate, but RAST is an important complementary test. The degree of sensitivity on skin tests or RASTs does not reliably predict the severity of a sting reaction. Venom immunotherapy is recommended for patients at high risk for sting reactions. Rapid regimens are as safe as slower regimens. The recommended dose is 100 microg, but some patients require higher doses for full protection. Venom immunotherapy is continued every 4 to 8 weeks for at least 5 years in most cases. Skin test results become negative in only 25% after 5 years of therapy but in 60% to 70% after 7 to 10 years. When treatment is stopped after 5 years or more, there is a 10% chance of systemic reaction to each future sting, but most reactions are mild. Some patients have a higher risk of relapse and should continue treatment for an extended period.

Efficacy of antihistamine pretreatment in the prevention of adverse reactions to Hymenoptera immunotherapy: a prospective, randomized, placebo-controlled trial

BACKGROUND

Some clinical studies suggest that a combination of an H1- and H2-antagonist may be effective in the prophylaxis of allergic reactions.

OBJECTIVE

The efficacy of pretreatment with an H1/H2-antagonist combination, H1-antagonist alone, or placebo in the prophylaxis of local and systemic adverse reactions to specific immunotherapy with Hymenoptera venom was compared.

METHODS

In a prospective, randomized, double-blind, placebo-controlled study, 121 patients with Hymenoptera venom allergy were treated with rush immunotherapy and pretreatment with one of the following: 120 mg of terfenadine plus 300 mg of ranitidine, 120 mg of terfenadine alone, or placebo. The incidence of unwanted systemic adverse and local reactions was recorded for up to 50 weeks.

RESULTS

In seven patients (6%), six in the placebo group and one in the terfenadine group, systemic side effects required cessation of therapy (p = 0.005). Subjective symptoms occurred in four patients (10%) in the terfenadine plus ranitidine group and in three patients (7%) in the terfenadine group. Regarding local reactions, significantly fewer patients treated with a combination of terfenadine and ranitidine and with terfenadine alone as compared with placebo had severe local symptoms of erythema (29%, 29%, and 49%), edema (24%, 18%, and 41%), and pruritus (13%, 11%, and 31%) at week 1 (p < 0.05). This therapeutic benefit was limited to the first 4 weeks of treatment. Treatment with a combination of terfenadine and ranitidine was not superior to treatment with terfenadine alone.

CONCLUSIONS

Pretreatment with H1-antihistamines with or without H2-antihistamines significantly reduced local and systemic adverse reactions to immunotherapy with Hymenoptera venom and may therefore be helpful in the management of immunotherapy.

Hymenoptera venom allergens

Hymenoptera venoms each contain a variety of protein allergens. The major components have all been characterized, and most of the amino acid sequences are known. This article concentrates on the use of contemporary techniques including cloning, mass spectrometry and genomics in the characterization of venom allergens, and newer separation techniques for protein isolation. Examples of the use of these techniques with venom proteins are presented.

Insect sting allergy with negative venom skin test responses

BACKGROUND

In our 1976 controlled venom immuno rapy trial, 33% of 182 patients with a history of systemic reactions to insect stings were excluded because of negative venom skin test responses. There have been reports of patients with negative skin test responses who have had severe reactions to subsequent stings.

OBJECTIVE

Our aim is to increase awareness about the patient with a negative skin test response and insect sting allergy and to determine the frequency and significance of negative skin test responses in patients with a history of systemic reactions to insect stings.

METHODS

We prospectively examined the prevalence of negative venom skin test responses in patients with a history of systemic reactions to stings. In patients who gave informed consent, we analyzed the outcome of retesting and sting challenge.

RESULTS

Of 307 patients with positive histories screened for our sting challenge study, 208 (68%) had positive venom skin test responses (up to 1 microg/mL concentration), and 99 (32%) had negative venom skin test responses. In 36 (36%) of the 99 patients with negative skin test responses, the venom RAST result was a low positive (1-3 ng/mL), or repeat venom skin test responses were positive; another 7 (7%) patients had high venom-specific IgE antibody levels (4-243 ng/mL). Notably, 56 (57%) of 99 patients with positive histories and negative skin test responses had negative RAST results. In patients with positive skin test responses, sting challenges were performed in 141 of 196 patients, with 30 systemic reactions. Sting challenges were performed on 37 of 43 patients with negative skin test responses and positive venom-specific IgE and in 14 of 56 patients with negative skin test responses and negative RAST results. There were 11 patients with negative skin test responses who had systemic reactions to the challenge sting: 2 had negative RAST results, and 9 had positive RAST results at 1 ng/mL. The frequency of systemic reaction was 21% in patients with positive skin test responses and 22% in patients with negative skin test responses (24% in those with positive RAST results and 14% in those with negative RAST results).

CONCLUSIONS

Venom skin test responses can be negative in patients who will subsequently experience another systemic sting reaction. Venom skin test responses are negative in many patients with a history of systemic allergic reactions to insect stings and may be associated with positive serologic test responses for venom-specific IgE antibodies (sometimes strongly positive results). Venom skin test responses should be repeated when negative, along with a serologic IgE antivenom test. Better diagnostic skin test reagents are urgently needed.

Hymenoptera sting anaphylaxis and urticaria pigmentosa: clinical findings and results of venom immunotherapy in ten patients

BACKGROUND

Occasional patients with urticaria pigmentosa and anaphylaxis after Hymenoptera stings have been described. In this situation the question arises: Is anaphylaxis IgE-mediated or induced by pharmacologic mediator release from mast cells?

METHODS

We investigated 10 patients with histologically confirmed urticaria pigmentosa and a history of anaphylaxis after honeybee or Vespula stings before and during immunotherapy with the respective venom.

RESULTS

In eight of 10 patients, an elevated serum tryptase level was found. In two of 10 patients, no venom-specific IgE could be detected by either skin tests or RAST. Five patients had no detectable venom-specific serum IgE, and in the remaining patients the level was low (<1 Phadebas RAST unit). Venom immunotherapy was well tolerated and caused only one mild systemic reaction in a patient during the dose increase phase. Six patients were re-stung while receiving venom immunotherapy: only one had a mild systemic reaction (angioedema) after a Vespula sting.

CONCLUSION

Anaphylactic symptoms after Hymenoptera stings in patients with urticaria pigmentosa are most often IgE-mediated but can occasionally be observed in the absence of IgE sensitization to venom allergens. Venom immunotherapy can be safely and successfully used in patients with urticaria pigmentosa and sting anaphylaxis.

Mastocytosis and Hymenoptera venom allergy

PURPOSE OF REVIEW

Mastocytosis is a rare disease characterized by increased mast cells in skin and/or internal organs. We evaluate the impact of mastocytosis on diagnosis and treatment of Hymenoptera venom allergy.

RECENT FINDINGS

Patients with Hymenoptera venom allergy who suffer from mastocytosis develop life-threatening sting reactions more often than those who do not. When patients with Hymenoptera venom allergy were systematically examined for mastocytosis, it was found to be represented to an abnormally high extent. Most patients with mastocytosis tolerate venom immunotherapy with no or only minor systemic symptoms. Venom immunotherapy was found to be marginally less effective in patients with mastocytosis than in those without evidence of mast cell disease (defined as absent cutaneous mastocytosis combined with a serum tryptase concentration of <11.4 microg/l). Several deaths from sting reactions were reported in patients with mastocytosis after venom immunotherapy was stopped. These patients should have venom immunotherapy for the rest of their lives.

SUMMARY

Patients suffering from mastocytosis and Hymenoptera venom allergy are at risk from a particularly severe sting anaphylaxis. They need optimal diagnosis and treatment. In patients presenting with Hymenoptera venom allergy, screening tests by measurement of serum tryptase concentration, and a careful skin examination, are highly recommended.

Discontinuing venom immunotherapy: extended observations

BACKGROUND

Our studies of discontinuing venom immunotherapy after at least 5 years have led to the conclusion that the residual risk of a systemic reaction to a sting was in the range of 5% to 10% in adults, and no severe or life-threatening reaction occurred with 270 challenge stings in 74 patients after 1 to 5 years without venom immunotherapy.

OBJECTIVE

The objective of this study was to extend our observation of patients who discontinue venom immunotherapy over 5 to 10 years and to determine which patients are at higher risk for a reaction.

METHODS

Patients who discontinued venom immunotherapy were surveyed for 3 consecutive years to determine the frequency of systemic reactions to field stings and the fate of venom sensitivity. The evaluation included the 74 patients previously studied (group 1) and 51 additional patients followed after stopping therapy in our clinical center (group 2).

RESULTS

Of the original 74 patients, 11 had field stings again after 3 to 7 years without venom immunotherapy, with one systemic reaction (dyspnea). Of the 51 patients in the other group, 15 were stung, of whom four (26%) had systemic reactions, including respiratory symptoms requiring epinephrine. Review of group 1 and group 2 revealed that half of the patients who had systemic reactions to a sting after stopping venom immunotherapy had a history of a systemic reaction occurring during venom immunotherapy (to an injection or a sting). Systemic reactions occurred in three patients who had negative skin test reactions; all three had very low but detectable venom-specific serum IgE antibody levels as determined by RAST and had a history of systemic reactions during venom immunotherapy. Greater severity of the pretreatment reaction was not associated with higher frequency of reaction to stings after stopping therapy but was associated with greater severity if a reaction did occur.

CONCLUSIONS

Venom immunotherapy (yellow jacket/mixed vespid) in adults can be discontinued after 5 to 6 years with a 5% to 10% residual risk of a systemic reaction. Risk factors may include history of a systemic reaction during venom immunotherapy, persistent strongly positive skin test sensitivity, and the severity of the pretreatment reaction.

The CD63 basophil activation test in Hymenoptera venom allergy: a prospective study

BACKGROUND

The basophil activation test (BAT), which relies on flow cytometric quantitation of the allergen-induced up-regulation of the granule-associated marker CD63 in peripheral blood basophils, has been suggested to be a useful approach in detecting responsiveness to allergens. The purpose of this study was to establish the usefulness of the BAT with regard to the clinical history and current diagnostic tools in Hymenoptera venom allergy using a prospective study design.

METHODS

Fifty-seven consecutive patients allergic to Hymenoptera venom as defined by a systemic reaction after an insect sting, and 30 age- and sex-matched control subjects with a negative history were included. The degree and nature of sensitization was confirmed by skin testing, specific immunoglobulin E (IgE), serum tryptase levels and BAT. In the nonallergic control group only analysis of specific IgE and BAT were performed. Correlation of BAT, skin test and specific IgE, respectively, with the clinical history in the allergic group was termed as sensitivity and in the control group as specificity.

RESULTS

Twenty one of 23 (91.3%) bee venom allergic patients and 29 of 34 (85.3%) patients allergic to wasp and hornet venom tested positive in BAT. The overall sensitivity of BAT, specific IgE and skin tests were 87.7, 91.2 and 93.0%, respectively. The overall specificities were 86.7% for BAT and 66.7% for specific IgE. No correlation between the severity of clinical symptoms and the magnitude of basophil activation was observed.

CONCLUSION

The BAT seems to be an appropriate method to identify patients allergic to bee or wasp venom with a comparable sensitivity to standard diagnostic regimens. The higher specificity of BAT as compared with specific IgE makes this test a useful tool in the diagnosis of Hymenoptera venom allergy.

Diagnosis of allergy to stinging insects by skin testing with Hymenoptera venoms

SKin testing was done on 30 patients with a history of anaphylactic reactions after a Hymenoptera sting and on 30 control subjects. The patients all had positive basophilhistamine release to one or more venoms on challenge with the specific venoms used for skin testing (honey bee, yellow jacket, white-faced hornet, yellow hornet, and Polistes). At 0.1 mug of venom/ml and at 1.0 mug of venom/ml, 75% and 100%, respectively, of the sensitive patients had a positive skin test. There was a significant (P less than 0.001) correlation between skin test and histamine release results. Of the 150 skin tests in control patients, only 1 was positive. Venom skin tests provide, for the first time, a simple, readily available technique to accurately diagnose allergy to stinging insects.

In vitro hymenoptera venom allergy diagnosis: improved by screening for cross-reactive carbohydrate determinants and reciprocal inhibition

BACKGROUND

Immunoglobulin (Ig) E-double positivity for honeybee (HB) and yellow jacket (YJ) venom causes diagnostic difficulties concerning therapeutical strategies. The aim of this study was to clarify the cause and relation of the cross-reactivity in patients with insect venom allergy.

METHODS

For this purpose, 147 patients with suspected stinging insect allergy and CAP-FEIA-double positivity were investigated for specific sIgE to additional cross-reactive carbohydrate determinant (CCD)-containing allergens: timothy grass pollen, rape pollen, natural rubber latex (NRL), bromelain, and horseradish peroxidase (HRP). Sera with sIgE to NRL were further investigated with the commercially available recombinant latex allergens. Reciprocal inhibition assays with both venoms and HRP were performed.

RESULTS

About 36 of 147 (24.5%) patients had sIgE to both venoms only. However, 111 of 147 (75.5%) additionally reacted to CCD-carrying allergens. 89 of 111 CCD-reactive sera had NRL-sIgE. In cases where inhibition experiments were performed, the NRL-sIgE binding was completely abolished in the presence of HRP. Only nine of 61 sera were positive for at least one recombinant latex allergen; all of them were negative in history and NRL-skin prick test. In 43 sera containing sIgE to CCD, HRP inhibition revealed unequivocal results: In 28 of 43 (65%) an HRP-inhibition >70% of sIgE to one venom occurred, pointing out the relevant venom. In three of 43 sIgE proved to be entirely CCD-specific.

CONCLUSIONS

Our data indicate that in cases of IgE positivity to both insect venoms supplementary screening tests with at least one CCD-containing allergen should be performed; HRP being a suitable tool for this test. In addition, subsequent reciprocal inhibition is an essential diagnostic method to specify cross-reacting sIgE results.

Survey of patients after discontinuing venom immunotherapy

BACKGROUND

Venom immunotherapy rapidly reduces the risk of a systemic sting reaction in adults from 30% to 70% to less than 2%. When venom immunotherapy is stopped after 5 years or longer, the risk of a systemic sting reaction is 5% to 15% during the first few years after stopping treatment. It is uncertain whether systemic sting reactions will occur more than 5 years after discontinuing venom immunotherapy and whether treatment can be safely stopped in some patients after less than 5 years.

OBJECTIVE

The purpose of this study is to estimate the risk of systemic reaction to a sting 10 years after discontinuing treatment and the relative risk after 3 years of treatment compared with that after 5 years or more of treatment.

METHODS

Among all patients who had venom immunotherapy at our center, we identified 395 patients who stopped treatment: some had dropped out of therapy early (6-24 months), some stopped after 3 to 4 years, and most completed 5 years or more of venom immunotherapy and were advised to stop by the allergist (many as part of our reported studies of discontinuing venom immunotherapy).

RESULTS

Contact was made with 194 patients, including telephone interviews for sting history and requests to visit the office for skin testing and blood sampling. Of these patients, 74 had been included in our original study of patients who had 5 years or more of venom immunotherapy and had sting challenges after 1 to 5 years off venom immunotherapy, as previously reported. Of the 74 in that original study, 61 were reached for this survey, and 30 reported recent stings, with 5 systemic sting reactions. Another 133 patients who had stopped venom immunotherapy were reached: 82 had 5 or more years of venom immunotherapy, 20 had 3 to 4 years of venom immunotherapy, and 31 had less than 2 years of venom immunotherapy. Of 51 patients stung from this group, 27 had 5 or more years of venom immunotherapy (no systemic sting reactions), and 24 had less than 5 years of venom immunotherapy (3 systemic sting reactions). We have now observed a total of 113 patients who had 5 or more years of venom immunotherapy and were stung after stopping. Sixteen (14%) had systemic sting reactions; most were mild, but 4 were severe. Systemic sting reactions occurred in 12 (10.7%) of 112 patients stung in the first 4 years off venom immunotherapy and 5 (10%) of 50 stung more than 5 years off venom immunotherapy. In 4 of 8 patients with current systemic sting reactions, the skin test response was negative, although the venom-IgE response was positive at the previous encounter. All systemic sting reactions were similar in pattern and severity to prevenom immunotherapy reactions in the same patient.

CONCLUSIONS

We conclude that the risk of systemic sting reactions when venom immunotherapy is stopped after 5 years or longer remains in the reported range of 5% to 15% in the 5 to 10 years after stopping venom immunotherapy. This risk of systemic sting reactions does not seem to decrease over time, unlike the progressive decline in immunologic markers (skin test and venom-IgE responses). To prospectively assess the risk of recurrent systemic sting reactions, there is a need for sting challenge studies of patients who have been off venom immunotherapy for 5 to 10 years and patients who have stopped venom immunotherapy after just 3 to 4 years treatment.

Use of β-blockers during immunotherapy for Hymenoptera venom allergy

BACKGROUND

Beta-blockers may aggravate anaphylactic reactions and interfere with treatment. There is therefore concern about their use in patients who have a history of anaphylaxis or are on allergen immunotherapy. Immunotherapy is the best available treatment for prevention of life-threatening anaphylaxis to Hymenoptera stings, which is often observed in elderly patients who have cardiovascular disease and therefore are on beta-blocker treatment.

OBJECTIVE

To analyze the risk of beta-blocker treatment during venom immunotherapy.

METHODS

We screened all 1682 patients with Hymenoptera venom allergy seen during a period of 34 months for immunotherapy, cardiovascular disease, and treatment with beta-blockers.

RESULTS

Of the 1389 patients in whom immunotherapy was recommended, 11.2% had cardiovascular disease, and 44 of these were on beta-blockers before immunotherapy. In 31 of those, the drug was replaced before starting treatment. In 3 with coronary heart disease and 1 with severe ventricular arrhythmia, the drug was continued throughout immunotherapy. In 9, it was reintroduced after reaching the maintenance dose. In an additional 12 patients, beta-blockers were newly started during immunotherapy. Of 25 patients on beta-blockers during immunotherapy, 3 (12%) developed allergic side effects, compared with 23 (16.7%) of 117 with cardiovascular disease but without beta-blockers. Systemic allergic symptoms after re-exposure by sting challenge or field sting were observed in 1 of 7 (14.3%) with and 4 of 29 (13.8%) without beta-blockade. No severe reactions to treatment or sting reexposure were observed in patients with beta-blockade.

CONCLUSION

Combination of beta-blockers with venom immunotherapy may be indicated in heavily exposed patients with severe cardiovascular disease.

The basophil activation test in the diagnosis of allergy: technical issues and critical factors

BACKGROUND

The basophil activation test (BAT) is a widely validated and reliable tool especially for the diagnosis of hymenoptera venom allergy. Nevertheless, several pitfalls have to be considered and outcomes may differ because of diverse in-house protocols and commercially available kits. We aimed to identify the factors that may influence results of the CD63-based BAT.

METHODS

Basophil responses to monoclonal anti-IgE (clone E124.2.8) and bee and wasp venom were determined by BAT based on CD63. The effect of stimulating factors such as, IL-3, cytochalasin B and prewarming of the samples was investigated. Furthermore, we compared two different flow cytometer systems and evaluated the influence of storage time, different staining protocols and anti-allergic drugs on the test results.

RESULTS

Interleukin-3 enhanced the reactivity of basophils at 300 pM, but not at 75 and 150 pM. Prewarming of samples and reagents did not affect basophil reactivity. CD63 expression assayed after storage time of up to 48 h showed that basophil reactivity already started to decline after 4 h. Basophils stained with HLA-DR-PC5 and CD123-PE antibodies gated as HLA-DR(neg)/CD123(pos) cells showed the highest reactivity. No effect on test outcomes was observed at therapeutic doses of dimetindene and desloratadine. Finally, slight differences in the percentage of activated basophils, depending on the cytometer system used, were found.

CONCLUSION

Basophil activation test should be performed as early as possible after taking the blood sample, preferably within 4 h. In contrast to the skin test, BAT can be performed in patients undergoing treatment with antihistamines. For reasons of multiple influencing factors, BAT should be performed only at validated laboratories.

A prospective study of the natural history of large local reactions after Hymenoptera stings in children

Large local reactions are a frequent occurrence after insect stings. We prospectively studied the demography, immunology, and significance of these reactions in the pediatric age group. Most children (83%) who have had large local reactions have positive skin test results to one or more venoms. Elevated amounts of venom-specific IgE antibody are usually present. Over 3 to 5 years, allergic sensitivity declines, as evidenced by less positive skin test results and lower levels of antivenom IgE antibodies. Most significantly, of 113 repeat stings, only 2% resulted in a systemic reaction.

A calreticulin-like protein from endoparasitoid venom fluid is involved in host hemocyte inactivation

During oviposition, most endoparasitoid wasps inject maternal factors into their hosts to interfere with host immune reactions and ensure successful development of their progeny. Since encapsulation is a major cellular defensive response of insects against intruding parasites, parasitoids have developed numerous mechanisms to suppress the host encapsulation capability by interfering with every step in the process, including recognition, adherence and spreading. In previous studies, components of Cotesia rubecula venom were shown to inhibit melanization of host hemolymph by interfering with the prophenoloxidase activation cascade and facilitate expression of polydnavirus genes. Here we report the isolation and characterization of another venom protein with similarity to calreticulin. Results indicate that C. rubecula calreticulin (CrCRT) inhibits hemocyte spreading behavior, thus preventing encapsulation of the developing parasitoid. It is possible that the protein might function as an antagonist competing for binding sites with the host hemocyte calreticulin, which mediates early-encapsulation reactions.

Costs of resistance in insect-parasite and insect-parasitoid interactions

Most, if not all, organisms face attack by natural enemies and will be selected to evolve some form of defence. Resistance may have costs as well as its obvious benefits. These costs may be associated with actual defence or with the maintenance of the defensive machinery irrespective of whether a challenge occurs. In this paper, the evidence for costs of resistance in insect-parasite and insect-parasitoid systems is reviewed, with emphasis on two host-parasitoid systems, based on Drosophila melanogaster and pea aphids as hosts. Data from true insect-parasite systems mainly concern the costs of actual defence; evidence for the costs of standing defences is mostly circumstantial. In pea aphids, the costs of standing defences have so far proved elusive. Resistance amongst clones is not correlated with life-time fecundity, whether measured on good or poor quality plants. Successful defence by a D. melanogaster larva results in a reduction in adult size and fecundity and an increased susceptibility to pupal parasitoids. Costs of standing defences are a reduction in larval competitive ability though these costs only become important when food is limited. It is concluded that costs of resistance can play a pivotal role in the evolutionary and population dynamic interactions between hosts and their parasites.

A retrospective study of epinephrine administration for anaphylaxis: how many doses are needed?

The precise amount of epinephrine needed to reverse severe symptomatology due to an anaphylactic reaction is unknown. We tried to determine how frequently more than one injection of epinephrine is required to treat an anaphylactic reaction. A retrospective review of patient charts with anaphylactic reactions requiring epinephrine, in response to inhalant allergen and hymenoptera venom immunotherapy as well as live hymenoptera stings, examined type of reaction; number, doses, and timing of epinephrine administered; and ancillary treatment. A total of 105 anaphylactic reaction events of varying severity (Ring's classification) were recorded (54--Grade I, 29--Grade II, 18--Grade III, 0--Grade IV, 4--unknown). The median epinephrine dose administered was 0.3 cc (range 0.1 to 0.8 cc, 1:1000). The timing of the first epinephrine injection was < or = 5 minutes in 27, 6-10 minutes in 13, 11-30 minutes in 16, < or = 30 minutes in 32, 31-60 minutes in 12, and > 60 minutes in five epinephrine treated patients. Overall, 38 patients (35.5%; CI95, 26.4-44.6%) required > 1 epinephrine injection. Of these, 11 experienced Grade I (11/54-20.3%; CI95, 9.6-31.0%), 12--Grade II (12/29-41.5%, CI95, 23.5-59.3%), and 13--Grade III (13/18-72.2%, CI95, 51.5-92.9%); reactivity was unknown in 2 patients. Forty-four patients also received an antihistamine, 10 received corticosteroids, and 30 received both medications and/or other ancillary therapy. A significant number of patients (> 35%) with anaphylactic reactions received greater than one epinephrine dose to manage events for the three classes of severity. Patients at risk for anaphylaxis and their caregivers need to recognize that more than one dose of epinephrine may be required for treatment of anaphylaxis.

Anaphylaxis caused by Hymenoptera stings: from epidemiology to treatment

Hymenoptera venom allergy occasionally causes fatal reactions. The prevalence of systemic reactions (SRs) is 0.3-8.9%, with anaphylaxis in 0.3-42.8% of cases. Factors contributing to reaction severity include older age, insect type, a previous less severe SR, preexisting diseases, concomitant treatments, mast cell diseases and elevated baseline tryptase serum concentration. Venom immunotherapy (VIT) is highly effective, as shown by sting challenge and spontaneous field stings. Indications for VIT are based on history of an SR, positive diagnostic tests, natural history and established risk factors for a severe outcome. Current strategies for reducing adverse reactions include anti-IgE monoclonal antibody pretreatment, and purified aqueous and purified aluminium hydroxide adsorbed preparations. New strategies for VIT, mostly using recombinant allergen, are in development. Further improvements will increase the safety and efficacy of VIT.