Gabriel Salcedo

Lipid-transfer proteins are relevant allergens in fruit allergy

BACKGROUND Allergy to apple and Prunus fruits is frequently associated with birch pollinosis, with the principal cross-reacting allergens involved being members of the Bet v 1 family. However, a major 13-kd component, nonimmunologically related to Bet v 1, has been implicated as allergen in patients allergic to Prunoideae fruit but not to birch pollen. OBJECTIVE We sought to isolate and characterize the 13-kd allergen present in apple and peach. METHODS Sera from patients allergic to both fruits were selected on the basis of clinical symptoms, skin prick tests responses, and specific IgE levels. Allergens were purified by reverse-phase HPLC and characterized by N-terminal amino acid sequencing, MALDI analysis, specific IgE immunodetection, and immunoblot inhibition assays. RESULTS A 13-kd protein band was recognized in crude apple and peach extracts by 9 of 10 and 10 of 10 sera from patients allergic to fruit, respectively. The isolation and characterization of the corresponding allergens allowed their identification as lipid-transfer proteins, with a molecular mass of 9058 d for the apple protein and 9138 d for the peach protein. Both purified allergens were recognized by sera from patients allergic to fruit and fully inhibited the IgE binding by the 13-kd component present in the 2 crude fruit extracts. CONCLUSION Lipid-transfer proteins are relevant apple and peach allergens and, considering their ubiquitous distribution in tissues of many plant species, could be a novel type of panallergen of fruits and vegetables.

Clinically relevant peach allergy is related to peach lipid transfer protein, Pru p 3, in the spanish population

BACKGROUND Sensitization to peach and related Rosaceae fruits without clinical expression is commonly observed as the result of the extensive cross-reactivity of IgE antibodies directed toward lipid transfer proteins (LTPs), Bet v 1 homologues, profilins, and carbohydrate determinants. OBJECTIVE We aimed to study whether there are any clinical or immunologic differences between patients allergic to peach and those who have a current clinically irrelevant sensitization to this fruit. METHODS One hundred subjects with adverse reactions to peach were evaluated by medical history, skin prick tests with fresh peach and purified peach LTP (Pru p 3), and specific IgE determinations to peach, rBet v 1, and rBet v 2 (birch profilin). Clinical reactivity to peach was established by double-blind, placebo-controlled food challenges. The clinical characteristics and the in vivo and in vitro tests were compared between allergic and nonallergic patients. RESULTS Peach allergy was confirmed in 76 patients and ruled out in 16; 2 patients dropped out, and the study was not conclusive in 6 individuals (placebo reactors). Pollen allergy was found in 76% of the allergic patients and in 100% of the nonallergic patients. Positive responses to Pru p 3, rBet v 1, and rBet v 2 were observed in 62%, 7%, and 34% of patients allergic to peach, respectively. The sensitization rate to Pru p 3 was significantly higher among subjects allergic than nonallergic to peach (62% vs 31%, P =.02). IgE responses to rBet v 2 were more frequent among subjects allergic to pollen, but no difference was observed in the presence or absence of peach allergy. CONCLUSIONS Pru p 3 is the major allergen of peach in our population, and the IgE response to this allergen is related to the clinical expression of peach allergy. Sensitization to profilin is observed in those patients with an associated pollen allergy but does not appear to be related to the clinical reactivity to peach.

Lipid‐transfer proteins as potential plant panallergens: cross‐reactivity among proteins of Artemisia pollen, Castanea nut and Rosaceae fruits, with different IgE‐binding capacities

Lipid‐transfer proteins (LTPs), but not Bet v 1 homologues, have been identified as major allergens of apple and peach in the Rosaceae fruit‐allergic population in the Mediterranean area. Many of these patients show cosensitization to mugwort pollen. LTPs have an ubiquitous distribution in tissues of many plant species, and have been proposed as a novel type of plant panallergens.

Plant non‐specific lipid transfer proteins as food and pollen allergens

Several members of the plant non‐specific lipid transfer protein (LTP) family have been identified as relevant allergens in foods and pollens. These allergens are highly resistant to both heat treatment and proteolytic digestion. These characteristics have been related with the induction of severe systemic reactions in many patients, and with the possibility of being primary sensitizers by the oral route. A specific geographical distribution pattern of sensitization to LTP allergens has been uncovered. This allergen family is particularly important in the Mediterranean area, but shows a very limited incidence in Central and Northern Europe. The potential role in the plant, as well as the biochemical and allergenic properties of the LTP family, are reviewed here.

Biotic and abiotic stress can induce cystatin expression in chestnut.

A cysteine proteinase inhibitor (cystatin) from chestnut (Castanea sativa) seeds, designated CsC, has been previously characterized. Its antifungal, acaricide and inhibitory activities have allowed to involve CsC in defence mechanisms. The CsC transcription levels decreased during seed maturation and increased throughout germination, an opposite behavior to that shown by most phytocystatins. No inhibition of endogenous proteinase activity by purified CsC was found during the seed maturation or germination processes. CsC message accumulation was induced in chestnut leaves after fungal infection, as well as by wounding and jasmonic acid treatment. Induction in roots was also observed by the last two treatments. Furthermore, CsC transcript levels strongly raised, both in roots and leaves, when chestnut plantlets were subjected to cold‐ and saline‐shocks, and also in roots by heat stress. All together, these data suggest that chestnut cystatin is not only involved in defence responses to pests and pathogen invasion, but also in those related to abiotic stress.

Class I chitinases with hevein-like domain, but not class II enzymes, are relevant chestnut and avocado allergens☆☆☆★★★

BACKGROUND Several foods associated with the latex-fruit syndrome present relevant allergens of around 30 kd. Neither these components nor any other responsible for the reported cross-reactions have been identified and purified. OBJECTIVE We sought to isolate and characterize the 30 kd allergens from avocado fruit and chestnut seed, two of the main allergenic foods linked with latex allergy. METHODS Sera from patients allergic to chestnut and avocado were selected according to clinical symptoms, specific IgE levels, and positive skin prick test responses. Class I and II chitinases were purified by affinity and cation-exchange chromatography and characterized by specific IgE and anti-chitinase immunodetection, immunoblot inhibition assays, enzymatic activity tests, and N-terminal sequencing. RESULTS Relevant 32 kd allergens were detected by specific IgE immunodetection in both avocado and chestnut crude extracts. The same bands, together with others of 25 kd, were revealed by a monospecific antiserum against class II chitinases. Purification and characterization of the 32 kd allergens from both plant sources allowed their identification as class I chitinases with an N-terminal hevein-domain. The purified allergens fully inhibited IgE binding by the corresponding crude extract when tested in immunoblot inhibition assays. Highly related 25 kd class II chitinases that lack the hevein-like domain were also isolated from the same protein preparations. No IgE-binding capacity was shown by these class II enzymes. CONCLUSION Class I chitinases are relevant allergens of avocado and chestnut and could be the panallergens responsible for the latex-fruit syndrome. The hevein-like domain seems to be involved in their allergenic reactivity.

Prevalence of sensitization to Artemisia allergens Art v 1, Art v 3 and Art v 60 kDa. Cross‐reactivity among Art v 3 and other relevant lipid‐transfer protein allergens

Background Artemisia vulgaris is a widespread weed in the Mediterranean area and several allergens have been detected in its pollen. One of them, Art v 3, belongs to the lipid‐transfer protein (LTP) family and its prevalence in Artemisia‐sensitized patients or its relationship with other LTP allergens is not clear.

Identification of IgE-binding epitopes of the major peach allergen Pru p 3

BACKGROUND Lipid transfer proteins (LTPs) are clinically relevant plant food panallergens and have been proposed as ideal tools to study true food allergy. Pru p 3, the major peach allergen in the Mediterranean area, is among the best-characterized allergenic members of the LTP family. Its diagnostic value for Rosaceae fruit allergy has been demonstrated both in vivo and in vitro. OBJECTIVE We sought to locate major IgE-binding epitopes of Pru p 3. METHODS A serum pool and individual sera from patients with peach allergy and positive skin prick test results to Pru p 3 were used. Three-dimensional modeling was achieved by using experimentally available structures of Pru p 3 homologues as templates. Theoretical prediction of potential IgE-binding regions was performed by selecting specific residues on the molecular surface displaying prominent electrostatic potential features. Point mutants of Pru p 3 were constructed by standard polymerase chain reaction procedures with the appropriate primers. Mutants were expressed in P pastoris by means of the pPIC 9 vector and purified from the corresponding supernatants by gel-filtration chromatography followed by RP-HPLC. IgE binding by Pru p 3 mutants was tested by immunodetection and quantified by ELISA and ELISA inhibition assays. Synthetic peptides (10 mer; 5 amino acids overlapping) covering the full Pru p 3 sequence were used to detect IgE epitopes by (125)I-anti-IgE immunodetection. RESULTS Pru p 3 showed a 3-dimensional structure comprising 4 alpha-helixes and a nonstructured C-terminal coil (residues 73 to 91). Regions around amino acids in positions 23 to 36, 39 to 44, and 80 to 91, particularly residues R39, T40, and R44, K80 and K91, were predicted as potential antibody recognition sites according to their relevant surface and electrostatic properties. Point mutants K80A and K91A were found to have an IgE-binding capacity similar to that of recombinant Pru p 3, but the triple mutant R39A/T40A/R44A showed a substantial decrease (approximately 5 times) of IgE binding. IgE immunodetection of synthetic peptides led to the identification of Pru p 3 sequence regions 11 to 25, 31 to 45, and 71 to 80 as major IgE epitopes. CONCLUSIONS Main IgE-binding regions of the Pru p 3 amino acid sequence were identified. The three major ones comprised the end of an alpha-helix and some residues of the following interhelix loop. These data can help to search for Pru p 3 hypoallergenic forms.

Wheat flour peroxidase is a prominent allergen associated with baker's asthma

Background Putative wheat allergens with molecular sizes around 35kDa have been repeatedly detected in immunoblots using sera from patients with bakers asthma. However, none of these allergens had been previously isolated.

In vivo allergenic activities of eleven purified members of a major allergen family from wheat and barley flour

Eleven purified members of the α‐amylase/trypsin inhibitor family from wheat and barlcy that showed very different IgE‐binding capacities when previously assayed in vitro. were used in double blind in vivo diagnostic tests to further evaluate their allergenic activity. These tests were carried out in 31 patients who showed allergic scnsilization to wheat flour as veritied by skin test, RAST and challenge test. The three members of the protein family with highest igl; binding in vitro (the glycosylated subunits of tetrameric α‐amylase inhibitors CM16* from wheat and CMb* from barley, and the barley monomeric inhibitor BMAI‐1) were found to be the strongest allergens as indicated by‐skin sensitivity in prick tests.