The clinical impact of cross-reactions between allergens on allergic skin diseases.

PURPOSE OF REVIEW: The route of allergen sensing via the skin appears to influence the immune system towards mounting a type 2 response, especially in genetically predisposed individuals. Allergens recognized this way may derive from microbial, animal, food, or other plant sources and trigger atopic dermatitis. Allergens can be grouped into families depending on their structure and function, harboring significant structural and sequence similarities. Cross-reactivity between allergens is believed to arise as a consequence, and to underlie the development of further atopic diseases. RECENT FINDINGS: Especially for the plant allergens of the families of PR10-related proteins and profilins, immune cross-reactions have been described. Actual studies support that food and pollen allergens can aggravate skin lesions in patients suffering from atopic dermatitis. Further on, allergens derived from air-borne or skin-borne fungi belong to common allergen families and bear cross-reactivity potential. Cross-reactivity to human homologous proteins, so-called autoallergens, is discussed to contribute to the chronification of atopic dermatitis. SUMMARY: Due to high evolutionary conservation, allergic reactions can be triggered by highly homologous members of allergen families on the humoral as well as on the cellular level.

Pro j 2 is mesquite profilin: molecular characteristics and specific IgE binding activity.

BACKGROUND: Pollens from mesquite (Prosopis juliflora) are potent allergen responsible in causing immediate hypersensitivity reactions in susceptible people in tropical countries. OBJECTIVE: This study aimed to clone, express and purify the mesquite pollen profilin (Pro j 2) as well as evaluating its nucleotide sequence homology in order to predict allergenic cross-reactivity with profilins of common allergenic plants. METHODS: Immunoblotting assay and specific ELISA were applied to determine the immunoreactivity of sera from 35 patients who were allergic to mesquite pollen. The mesquite profilin-coding sequence was cloned into PTZ57R/T vector and amplified. The cDNA of mesquite pollen profilin was then expressed in Escherichia coli using pET-21b (+) vector and puri?ed by one-step Ni2+ a?nity chromatography. IgE binding capacity of the recombinant mesquite profiling (rPro j 2) was analyzed by specific ELISA, immunoblotting, and inhibition assays. RESULTS: cDNA nucleotide sequencing revealed an open reading frame of 399bp encoding for 133 amino acids which belongs to the profilin family. Seventeen patients (17/35, 48.57%) had significant specific IgE level for rPro j 2. Immunodetection and inhibition assays indicated that puri?ed rPro j 2 might be similar as that in the crude extract. CONCLUSION: Pro j 2, as a new allergen from mesquite pollen, was produced in E. coli with an IgE-reactivity similar to that of its natural counterpart. The amino acid sequences homology analysis of mesquite profilin and several profilin molecules from other plants showed high degree of cross-reactivity among plant-derived profilins from unrelated families.

Profilin May Be a Primary Airborne Sensitizer: ACase Report

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IgE reactivity patterns in patients with allergic rhinoconjunctivitis to ragweed and mugwort pollens.

BACKGROUND: Differential diagnosis between ragweed and mugwort pollen allergy represents a large clinical problem in areas where both plants are present. The aim of this study was to investigate ragweed- and mugwort-sensitized patients to identify specific IgE reactivity profiles. Results were correlated to clinical findings such as medical history and health-related quality of life (HRQL). METHODS: Seventy-four patients with allergic rhinoconjunctivitis between July and October were examined and underwent in vivo tests (skin-prick test [SPT] and nasal provocation). Sera were evaluated for IgE reactivity to mugwort and ragweed pollen extracts, major (Art v 1; Amb a 1) and minor (profilin and calcium-binding protein) allergens. HRQL was evaluated using a standardized questionnaire. RESULTS: Seventy-one patients revealed positive SPT reactivity against mugwort and 60 patients against ragweed extracts. Of these patients, 74 revealed IgE antibodies against mugwort extracts, whereas anti-Art v 1 antibodies were detectable in 50 individuals. Fifty-five patients showed IgE antibodies against natural ragweed extracts; anti-Amb v 1 antibodies were detected in six cases only. Using standardized clinical history and HRQL questionnaires we were not able to detect any differences within different reactivity patterns. CONCLUSION: Within the investigated population of 74 weed-allergic patients the prevalence of true mugwort and ragweed sensitization can be calculated as 68 and 8%. High prevalence of ragweed sensitization when testing with full extracts can be explained by cross-reactivity between other weeds, e.g., mugwort rather than cosensitization. Differences in medical history and HRQL between different reactivity patterns were not detectable.

Profilin sensitization detected in the office by skin prick test: a study of prevalence and clinical relevance of profilin as a plant food allergen.

BACKGROUND: Profilin, a pan-allergen present in all eukaryotic cells, is one of the main causes of cross-sensitization between pollen and plant-derived foods, but its clinical relevance as a food allergen is still debated. OBJECTIVE: To investigate the prevalence of profilin sensitization in a pollen-allergic population and its clinical relevance as a food allergen. METHODS: Two hundred consecutive patients with pollen allergy underwent skin prick tests (SPT) with purified natural date palm profilin (Pho d 2; 50 microg/mL; Alk Abello, Madrid, Spain). Those reporting adverse reactions to foods (confirmed by SPT with either commercial food extracts or fresh foods) underwent SPT with an apple extract containing uniquely Mal d 1 (2 microg/mL; ALK-Abello), and with a commercial peach extract containing uniquely lipid transfer protein (LTP 30 microg/mL; ALK-Abello). RESULTS: Sixty patients (30%) showed skin reactivity to date palm profilin, Pho d 2. All were sensitized to grass pollen, and most of them reacted to birch, mugwort, ragweed and plantain pollen as well. SPT with pellitory and cypress scored negative in a high proportion of profilin reactors [26/60 (43%) and 33/60 (55%), respectively]. More than one half (34/60 [57%]) of profilin reactors had food allergy; 21 of these were monosensitized to profilin, 11 were sensitized to both profilin and Bet v 1 homologous protein, one to both profilin and LTP, and one to all the three allergens. The large majority of profilin-allergic patients reported oral allergy syndrome as the only food-induced symptom and were able to tolerate the offending foods if they were cooked or otherwise processed. Twenty-eight of 34 reported reactivity to two or more plant-derived foods. Rosaceae, tree nuts, melon and watermelon, tomato, pineapple, citrus fruits and banana were the more frequently offending foods. CONCLUSION: Profilin should be considered a clinically relevant food allergen. Allergy to melon, watermelon, tomato, banana, pineapple and orange may be considered as a marker of profilin hypersensitivity. This study underlines the clinical importance of being able to diagnose hypersensitivity to single food allergenic proteins by SPT, particularly when the relevant food allergen sources contain several allergens that show different chemical/physical features and, hence, completely different risk profiles.