Interference of cross-reactive carbohydrates in the determination of specific IgE in alcohol drinkers and strategies to minimize it: the example of latex

Comparative Analysis of the Immune Response and the Clinical Allergic Reaction to Papain-like Cysteine Proteases from Fig, Kiwifruit, Papaya, Pineapple and Mites in an Italian Population

Several plant papain-like cysteine proteases are exploited by the food, cosmetic, pharmaceutical and textile industries. However, some of these enzymes can cause allergic reactions. In this context, we investigated the frequency of sensitization and allergic reactions to some fruit and/or latex cysteine proteases, which are used as additives by the food industry to improve and modify the quality of their products. The FABER test was used to analyse the patients' sensitization towards five plants and, for comparison, two homologous mite cysteine proteases. In an Italian population of 341 allergic patients, 133 (39%) had IgE specific for at least one of the seven cysteine proteases under investigation. Most of the patients were IgE positive for Der p 1 and/or Der f 1 (96.38%) reported a clinical history suggestive of respiratory allergy to mites, whereas none of the subjects sensitized to the homologs from papaya, pineapple and fig reported allergy symptoms following ingestion of these foods. Only one patient referred symptoms from ingesting kiwifruit. Therefore, the obtained results showed that sensitization to the fruit enzymes was only rarely concomitant with allergic reactions. These observations, together with the literature reports, suggest that the allergy to plant papain-like cysteine proteases might mainly be an occupational disease.

Sex difference in IgE sensitization associated with alcohol consumption in the general population

The association of alcohol consumption and immunoglobulin E (IgE) sensitization is debated. Few population-based studies have investigated whether such associations differ by sex. We explored the association of alcohol consumption with IgE sensitization in the general population, stratified by sex. We analyzed data for 1,723 adults from the 2010 Korean National Health and Nutrition Examination Survey. We divided subjects into three groups according to their self-reported alcohol consumption or serum level of gamma-glutamyltransferase (GGT), an objective marker of alcohol consumption. After adjustments, the odds ratios (ORs) of male high-risk drinkers were 2.09 (95% confidence interval [CI], 1.34–3.28) for total IgE and 1.71 (95% CI, 1.03–2.83) for Dermatophagoides farinae (DF)-specific IgE compared with male low-risk drinkers. In females, the dog-specific IgE level was associated with high-risk drinking (OR, 11.74; 95% CI, 2.04–67.24). The ORs of males in the high-serum-GGT group were 2.73 (95% CI, 1.72–4.33) for total IgE and 2.17 (95% CI, 1.35–3.47) for DF-specific IgE compared with those in the low-serum-GGT group. This study suggests a possible link between alcohol consumption and IgE sensitization, moreover, the risk of IgE sensitization was significantly higher in male high-risk drinkers. Therefore, clinicians should consider the risk of IgE sensitization possibly afflicting male high-risk drinkers.

ImmunoCAP cellulose displays cross-reactive carbohydrate determinant (CCD) epitopes and can cause false-positive test results in patients with high anti-CCD IgE antibody levels

BACKGROUND

Cross-reactive carbohydrate determinants (CCDs) in plants and insect venoms are a common cause of irrelevant positive test results during in vitro allergy diagnosis. We observed that some CCD-positive sera show nonspecific IgE binding even with CCD-free recombinant allergens when using the Phadia ImmunoCAP platform.

OBJECTIVE

We investigated whether cellulose used as an allergen carrier in ImmunoCAP harbors residual N-glycans, causing nonspecific background binding in CCD-positive sera.

METHODS

IgE binding to 6 samples of blank ImmunoCAPs coupled to either streptavidin (SA-CAP-1 or 2) or nonallergenic maltose-binding protein (MBP; MBP-CAP-1 to 4) and binding to a panel of 4 recombinant allergens were compared in CCD-positive sera before and after inhibition with a CCD inhibitor (MUXF³-human serum albumin).

RESULTS

Of 52 CCD-positive sera (bromelain, 1.01-59.6 kilounits of antigen per liter [kU_A/L]) tested on SA-CAP-1, 35 (67%) showed IgE binding of greater than 0.35 kU_A/L (0.41-4.22 kU_A/L). Among those with anti-CCD IgE levels of greater than 7.0 kU_A/L, 90% (26/29) were positive. IgE binding to SA-CAP-1 correlated with IgE binding to bromelain (r = 0.68) and was completely abolished by serum preincubation with the CCD inhibitor (n = 15). Binding scores with SA-CAP-2 and MBP-CAP-1 to MBP-CAP-4 were generally lower but strongly correlated with those of SA-CAP-1 and bromelain. IgE reactivity of 10 CCD-positive sera (14.0-52.5 kU_A/L) with the recombinant allergens rPhl p 12, rFel d 1, rAra h 2, and rPru p 3 was positive to at least 1 allergen in 8 of 10 (0.36-1.63 kU_A/L) and borderline in 2 of 10 (0.21-0.25 kU_A/L). Binding correlated with antibody binding to bromelain (r = 0.61) and to all blank ImmunoCAPs (r > 0.90) and could be completely blocked by the CCD inhibitor. Overall, mean background binding to cellulose CCDs corresponded to 2% to 3% of the reactivity seen with bromelain.

CONCLUSIONS

Cellulose used as a solid-phase allergen carrier can contain varying amounts of CCDs sufficient to cause false-positive test results up to 2 kU_A/L with nonglycosylated recombinant allergens in patients with high levels of anti-CCD IgE antibodies.

Carbohydrates as food allergens

The literature supports the notion that carbohydrate epitopes, on their own, do not contribute significantly to the induction of allergic reactions. They bind weakly to IgE antibodies and have been termed as cross reactive carbohydrate determinants. These epitopes cause confusion in in vitro IgE testing through nonspecific cross-reactivity. Coincident with the rising trends in food allergy prevalence, there has recently been reports of anaphylaxis induced by carbohydrate epitopes. There are two distinct groups, each with unique characteristics and geographical distribution. Anaphylaxis and acute allergic reactions related to the carbohydrate galactose-α-1,3-galactose (α-Gal) epitope that are present in the monoclonal antibody, cetuximab and red meat have been described in the United States and Europe populations where tick bites have been found to be the primary sensitizer. Another carbohydrate inducing anaphylaxis is galacto-oligosaccharides in commercial milk formula which has been described in the several Asian populations including Singapore. The latter is unique in that the allergen is a pure carbohydrate. We summarize the current literature on carbohydrate-induced food allergy, and evaluate the two new groups of carbohydrate allergy that have defied previous findings on carbohydrates and their role.

IgE antibodies in occupational asthma: are they causative or an associated phenomenon?

PURPOSE OF REVIEW

To evaluate recent data on the causative role of specific IgE antibodies, as well as the performance of IgE diagnostic tests, in allergic occupational asthma induced by high (HMW) or low-molecular-weight (LMW) agents.

RECENT FINDINGS

Skin prick testing (SPT) and specific IgE assays are useful to document allergy to most HMW allergens and some LMW agents. These tests, however, are limited by the lack of standardized and commercially available reagents. There is a wide variability among the quality of occupational allergen extracts used for SPT and the sensitivity of several SPT solutions is low. In addition, many individuals with allergen-specific serum IgE and/or positive SPT to specific HMW allergens do not have clinical symptoms. Sensitization or allergenic cross-reactivity to allergens or epitopes from unrelated sources may interfere in the diagnosis of IgE-mediated allergy, giving rise to false-positive results, particularly when cross-reactive carbohydrate determinants (CCDs) are involved. The immune responses to these ubiquitous structures may interfere with the diagnosis of occupational allergy. Component-resolved diagnosis of IgE-mediated allergic diseases (occupational and nonoccupational) using panels of native or recombinant allergens, or micro-arrayed allergens, have been proposed to identify specific molecules responsible for these disorders and to overcome false-positive in-vitro test results.

SUMMARY

Improvement and standardization of SPT solutions for occupational allergens are highly recommended. More refined diagnostic tools than specific IgE measurements are being developed, such as inhibition assays of IgE binding to CCDs with specific carbohydrate molecules, and component-resolved diagnosis.

Minor interference of cross-reactive carbohydrates with the diagnosis of respiratory allergy in standard clinical conditions

BACKGROUND

Immunoglobulin E (IgE) to N-glycans from plant and invertebrate glycoproteins induces extensive in vitro cross-reactivity. This study investigates the prevalence and diagnostic relevance of IgE to these N-glycans [cross-reactive carbohydrate determinants (CCDs)] in patients with suspicion of respiratory allergy.

METHODS

A total of 1,025 adult subjects with symptoms of rhinitis and/or asthma from a reference allergy clinic were studied. Determinations included a structured questionnaire, skin prick tests (SPT), total IgE, a multiallergen IgE test and specific IgE (sIgE) to bromelain, MUXF (the bromelain-type N-glycan) and honeybee phospholipase-A2. Inhibition studies with CCDs were performed in selected cases.

RESULTS

The prevalence of CCD sensitization (MUXF sIgE and/or bromelain-sIgE ≥0.1 kU(A)/l) was 18.0%. Male sex and atopy (SPT positivity) were associated with CCD sensitization. Sensitization was more frequent in patients sensitized to pollens than in those sensitized to mites, the most common inhalant allergens in the area. A history of Hymenoptera stings was associated with CCD sensitization and multiallergen IgE test positivity. CCD sensitization was not significantly associated with age, rural residence, alcohol consumption or smoking. Only 58 patients (5.6%) showed CCD-sIgE levels ≥0.35 kU(A)/l. CCD-induced inhibition of pollen-sIgE or mite-sIgE in patients with respective positive SPT was minimal or absent in most cases.

CONCLUSIONS

In this population of predominantly mite-allergic patients, CCD sensitization is relatively rare and CCD-sIgE levels are low. Thus, CCDs do not represent a major obstacle for the diagnosis of respiratory allergy in a specialized setting. Hymenoptera stings are associated with CCD sensitization.

Immunoglobulin-E reactivity to wine glycoproteins in heavy drinkers

N-glycans from plant and invertebrate allergens can induce extensive immunoglobulin-E (IgE) cross-reactivity in vitro. IgE antibodies against these N-glycans, also termed cross-reactive carbohydrate determinants or CCDs, are prevalent in alcohol drinkers. This study investigated the prevalence and biological significance of IgE antibodies to N-glycans from wine glycoproteins in heavy drinkers. A structured questionnaire, skin prick tests, serum IgE levels, IgE-immunoblotting to wine extracts, and basophil activation tests were used to characterize 20 heavy drinkers and 10 control subjects. Eleven heavy drinkers (55%) showed IgE binding to proteins in wine extracts. The proteins were identified by mass spectrometry as grape-derived vacuolar invertase and thaumatin-like protein. Immunoblot reactivity was closely associated with the presence of IgE to CCDs and was inhibited by preincubation with a glycoconjugate containing bromelain-type N-glycans. The same conjugate, CCD-bearing allergens, and wine extracts activated basophils in patients with high-titer CCD-specific IgE but not in healthy controls. There was no relationship between immunoblot reactivity and consumption of any specific type of wine. No patient reported symptoms of hypersensitivity to Hymenoptera venom, food, or wine. In conclusion, heavy drinkers frequently show IgE reactivity to the N-glycans of wine glycoproteins. Glycans and wine glycoprotein extracts can induce basophil activation in sensitized alcoholics. The clinical significance of these findings remains to be elucidated.