Shrimp allergy in Italian adults: a multicenter study showing a high prevalence of sensitivity to novel high molecular weight allergens.

BACKGROUND: Shrimp is a frequent cause of food allergy worldwide. Besides tropomyosin, several allergens have been described recently. OBJECTIVE: We investigated which allergens are involved in Italian shrimp-allergic adults. METHODS: Sera from 116 shrimp-allergic patients selected in 14 Italian allergy centers were studied. Skin prick tests with house dust mite (HDM) as well as measurements of IgE to Pen a 1 (shrimp tropomyosin) and whole shrimp extract were performed. All sera underwent shrimp immunoblot analysis, and inhibition experiments using HDM extract as inhibitor were carried out on some Pen a 1-negative sera. RESULTS: Immunoblots showed much variability. IgE reactivity at about 30 kDa (tropomyosin) was found in <50% of cases, and reactivity at about 67 kDa and >90 kDa was frequent. Further reactivities at 14-18, 25, 43-50, about 60 and about 80 kDa were detected. Most subjects had a history of shrimp-induced systemic symptoms irrespective of the relevant allergen protein. IgE to Pen a 1 were detected in sera from 46 (41%) patients. Skin reactivity to HDM was found in 43/61 (70%) Pen 1-negative subjects and inhibition studies showed that pre-adsorption of sera with HDM extract induced a marked weakening of the signal at >67 kDa. CONCLUSIONS: Several allergens other than tropomyosin are involved in shrimp allergy in adult Italian patients. Some hitherto not described high molecular weight allergens seem particularly relevant in this population and their cross-reactivity with HDM allergens makes them novel potential panallergens of invertebrates.

Are IgE levels to foods other than rosaceae predictive of allergy in lipid transfer protein-hypersensitive patients?

BACKGROUND: Lipid transfer protein (LTP), the most frequent cause of primary food allergy in Italy, is a cross-reacting plant pan-allergen. Markers able to predict whether a patient sensitized to a certain food but not yet clinically allergic will develop allergy would be extremely helpful. OBJECTIVE: It was the aim of this study to investigate the relevance of IgE levels to some plant foods other than Rosaceae as predictors of either local or systemic allergic reaction in LTP-allergic subjects. METHODS: One hundred (40 males, 60 females , mean age 29 years) peach-allergic patients monosensitized to LTP seen at 14 Italian centres in 2009 were studied. Walnut, hazelnut, peanut, tomato, rice and/or maize allergy was ascertained by interview and confirmed by positive skin prick test. IgE levels to these foods and to rPru p 3 were measured. RESULTS: Higher levels of IgE to Pru p 3 were associated with a higher prevalence of allergy to hazelnut, peanut and walnut. For all study foods, except rice, median IgE levels in allergic subjects significantly exceeded those in tolerant subjects, though within single allergic groups, the differences between patients reporting systemic or local (oral) symptoms were not significant. Ninety-five percent cut-off IgE levels predictive of clinical allergy were established for study foods although the marked overlaps between allergic and tolerant subjects made them of limited usefulness. CONCLUSION: Specific IgE levels are only partially predictive of clinical allergy. The reasons why some individuals showing low specific IgE levels develop clinical allergy whereas others showing high IgE levels do not, despite similar exposure to the allergen, remain unclear.