Isolation, cloning, and characterization of the 2S albumin: a new allergen from hazelnut.

SCOPE: 2S albumins are the major allergens involved in severe food allergy to nuts, seeds, and legumes. We aimed to isolate, clone, and express 2S albumin from hazelnut and determine its allergenicity. METHODS: 2S albumin from hazelnut extract was purified using size exclusion chromatography and RP-HPLC. After N-terminal sequencing, degenerated and poly-d(T) primers were used to clone the 2S albumin sequence from hazelnut cDNA. After expression in Escherichia coli and affinity purification, IgE reactivity was evaluated by Immunoblot/ImmunoCAP (inhibition) analyses using sera of nut-allergic patients. RESULTS: N-terminal sequencing of a approximately 10 kDa peak from size exclusion chromatography/RP-HPLC gave two sequences highly homologous to pecan 2S albumin, an 11 amino acid (aa) N-terminal and a 10 aa internal peptide. The obtained clone (441 bp) encoded a 147 aa hazelnut 2S albumin consisting of a putative signal peptide (22 aa), a linker peptide (20 aa), and the mature protein sequence (105 aa). The latter was successfully expressed in E. coli. Both recombinant and natural 2S albumin demonstrated similar IgE reactivity in Immunoblot/ImmunoCAP (inhibition) analyses. CONCLUSION: We confirmed the postulated role of hazelnut 2S albumin as an allergen. The availability of recombinant molecules will allow establishing the importance of hazelnut 2S albumin for hazelnut allergy.

Diminished response to grass pollen allergen challenge in subjects with concurrent house dust mite allergy.

INTRODUCTION: The clinical manifestation of allergic rhinitis is influenced by many factors; while different subpopulations are not well defined. Different combinations of allergic sensitization may lead to different clinical manifestations of allergic disease. METHODS: In a nasal allergen challenge model we compared allergic rhinitis symptoms between subjects mono-sensitized to grass pollen or house dust mite, poly-sensitized subjects, and healthy controls. We measured visual analogue scales of symptoms and peak nasal inspiratory flow. We also compared serum total IgE, allergen-specific IgE and IgG4, and basophil histamine release. RESULTS: Nasal challenge with grass pollen extract led to a significantly larger increase in subjective (p = 0.031) and objective (p = 0.001) nasal symptoms in grass pollen mono-sensitized subjects than in poly-sensitized subjects. No differences were found in serum levels of allergen-specific IgE and IgG4 or in biological activity of IgE (basophil histamine release) between mono-sensitized and poly-sensitized subjects. We found a strong inverse correlation between serum allergen-specific IgE and basophil histamine release (-0.789, p = 0.001). CONCLUSIONS: Grass pollen mono-sensitized subjects have a more severe clinical response to nasal challenge than poly-sensitized subjects. This cannot be explained by serum levels of IgE or its biological activity. The continuous allergen exposure in poly-sensitized subjects may alter local immuno-regulatory processes, leading to a reduced clinical response to allergen challenge.

Lipid transfer protein allergy: primary food allergy or pollen/food syndrome in some cases.

PURPOSE OF REVIEW: To summarize recent findings on non-specific lipid transfer proteins in food allergy, with a specific focus on the localization, stability and route of sensitization. RECENT FINDINGS: Plant non-specific lipid transfer proteins are major food allergens, especially in the Mediterranean area. They have been identified as allergens in a number of foods and the list grows ever longer. As non-specific lipid transfer proteins are considered to be "true" food allergens that sensitize directly via the gastrointestinal tract their stability during food processing and gastric digestion has been studied in more detail. In addition, several groups have tried to determine the sensitization patterns of lipid transfer protein-reactive patients, to determine and possibly clarify the observed geographical differences in sensitization. Different sensitization routes (via the respiratory tract or even transdermally) have been suggested. SUMMARY: As the structure and molecular properties of non-specific lipid transfer proteins are resolved and more purified non-specific lipid transfer proteins become available for diagnostic purposes, detailed studies on the sensitization pattern and route are becoming feasible. Continuing studies on the pattern of lipid transfer protein sensitization will give more insight into the development and possible treatment of lipid transfer protein-related food allergy.