Varying allergen composition and content affects the in vivo allergenic activity of commercial Dermatophagoides pteronyssinus extracts

Abstract

Background: Diagnosis and immunotherapy of house-dust mite (HDM) allergy is still based on natural allergen extracts. The aim of this study was to analyze commercially available Dermatophagoides pteronyssinus extracts from different manufacturers regarding allergen composition and content and whether variations may affect their allergenic activity.

Methods: Antibodies specific for several D. pteronyssinus allergens (Der p 1, 2, 5, 7, 10 and 21) were used to analyze extracts from 10 different manufacturers by immunoblotting. Sandwich ELISAs were used to quantify Der p 1 and Der p 2 in the extracts. Mite-allergic patients (n = 45) were skin-tested with the extracts and tested for immunoglobulin E (IgE) reactivity to a panel of 10 mite allergens (Der p 1, 2, 4, 5, 7, 8, 10, 14, 20 and 21) by dot blot.

Results: Only Der p 1 and Der p 2 were detected in all extracts but their concentrations and ratios showed high variability (Der p 1: 6.0-40.8 µg ml(-1); Der p 2: 1.7-45.0 µg ml(-1)). At least 1 out of 4 allergens (i.e. Der p 5, 7, 10 and 21) was not detected in 8 of the studied extracts. Mite-allergic subjects showed different IgE reactivity profiles to the individual mite allergens, the extracts showed different allergenic activity in skin-prick tests and false-negative results.

Conclusions: Commercially available D. pteronyssinus extracts lack important allergens, show great variability regarding allergen composition and content and some gave false-negative diagnostic test results in certain patients.

Fig. 1

Silver-stained SDS-PAGE containing D. pteronyssinus extracts from different companies, i.e. lanes 1–9 (a) and A–D (b). Lane M = Molecular mass marker.

Fig. 2

Variability of skin responses to 9 D. pteronyssinus extracts (1–9) in the Italian population and to 4 extracts (A–D) in the French population. Wheal areas of the extracts and of histamine (H), expressed in mm² (y-axes), are presented in box plots (maximum, 3rd quartile, median value, 1st quartile and minimum).

Fig. 3

Wheal areas to 9 D. pteronyssinus extracts (1–9) in mite-allergic subjects (No. 5, 7, 8, 14, 16, 17, 18 and 22) which could not be diagnosed with certain extracts. Wheal areas are expressed in mm² with the cutoff at 7 mm². Φ = Glycerol-saline solution; H = histamine dihydrochloride 10 mg ml⁻¹.