[Occupational asthma caused by organic substances]

Identification of Dioscorea batatas (sanyak) allergen as an inhalant and oral allergen

Dioscorea batatas is widely used in Asia as a herbal medicine or food product with potential health benefits. There have been several reports of occupational asthma caused by inhalation of D. batatas dust. However, there has been no report of systemic allergic reactions after oral administration of D. batatas. Two patients with D. batatas allergy were enrolled. One had experienced severe urticaria and angioedema after indigestion, and the other had been exposed to D. batatas dust and was diagnosed as having occupational asthma. Both patients had high serum-specific IgE and IgG4 antibodies to D. batatas. And IgE immunoblot demonstrated that both sera bound to a 27-kDa protein with an IgE-binding motif, which was revealed by 2-D-electrophoresis to have the sequence Asn-Val-Glu-Asp-Glu-Phe-Ser-X-Ile- Glu-Gly-Asn-Pro-X-X-Pro-Glu-Asn-X-Gly (pI 6.40, 6.04). In conclusion, discorin from D. batatas (DB3S) was identified as the major allergen of D. batatas in patients sensitized via an oral or inhalant route.

Allergenicity of some isoforms of white sesame proteins

BACKGROUND

Allergy to sesame seeds is often associated with particularly severe reactions, with a high risk of anaphylaxis. The increase in reports of allergic reactions to sesame is probably due to the growing use of sesame seeds or sesame oil in food.

OBJECTIVE

To determine the molecular weights of the proteins in three variety of sesame seeds and to study the isoelectric points and the allergenicity of white sesame proteins.

METHODS

Extracts of white, brown and black sesame seeds were prepared. The white sesame extract, mostly used in bakery, was run on SDS-PAGE and two dimensional electrophoresis. Six sera from patients sensitized or symptomatic to sesame seed were used for Western blotting.

RESULTS

The protein patterns of the white, brown and black sesame extracts showed major quantitative differences. The white extract had the higher protein concentration and contained 15 proteins of 12-79 kDa, some of them having several acidic isoelectric points. The lowest isoelectric point was 4.9 and the highest was 6.4, giving 35 isoforms. Ten of the 15 proteins (12-57.5 kDa) were recognized by specific IgE. The 12-13 kDa and 22-33 kDa proteins could correspond to the main allergens.

CONCLUSION

White sesame seeds contain at least 10 allergenic proteins with acidic isoelectric points. In accordance with previous results, two of them seem to contain the major allergens.

[Asthma caused by food allergy]

Food allergy (FA) induced asthma is less common than FA induced atopic dermatitis, or angioedema. The incidence reaches 8.5%. Occupational asthma due to the inhalation of various food proteins is increasingly described. Egg proteins could be peculiarly at risk. In the childhood, all the kinds of foods can be incriminated. In adults, FA are predominantly due to vegetal allergens, included in the following botanical families: rosaceae, umbelliferae, and exotic fruits. Bronchi are sensitized either by inhalation of food allergens or by inhalation of cross-reactive pneumoallergens, such as pollens, feathers, latex. The fact that FA might create a bronchial hyperreactivity is controversial. Bronchial challenges induce late-phase reactions and document the acquisition of an inflammatory state. The quantity of allergens gaining access to bronchi plays a major part in the triggering of asthma. It can be modulated by variations of intestinal permeability which are related to viral infections, aspirin, alcohol, etc. The chemical characteristics of proteins, such as hydrophobicity might interfere with the passage through the gut mucosa. The diagnosis is based upon skin tests and the detection of specific IgE, identifying the state of hypersensitivity. Provocation tests are mandatory to establish FA. The pharmacological approach of the treatment is less important than the eviction insofar as the specific immunotherapy is not yet currently performed.