Common epitopes of birch pollen and apples--studies by western and northern blot

Technological processes to decrease the allergenicity of peach juice and nectar

Among vegetable foods peach (Prunus persica) has been recognized as a significant cause of allergy. The protein, which is considered to be the major peach allergen, has been named Pru p 1. Because peaches are consumed both as fresh fruits and after processing to obtain peach juice, nectar, jam, syrupy peach, etc., research was carried out to identify a technological process for production of hypo- or nonallergenic peach-based products. SDS-PAGE and immunoblotting analysis of extracts prepared from four commercial peach nectars showed that the Pru p 1 was not removed, and neither was its allergenic activity decreased by technological treatments carried out for nectar production. Some treatments oriented toward a removal of or, at least, a decrease in the allergenic power were assumed and verified at laboratory scale. A variable considered was heat treatment at 121 degrees C for 10 and 30 min: this treatment was not able to decrease the allergenicity of the Pru p 1 protein. Furthermore, the protein band was still present even after 60-min reaction with two different acidic proteases. The two technological treatments that were found to decrease the major allergen of peach were chemical lye peeling of fruits and ultrafiltration of juice through membranes with suitable cutoff. On the basis of the results obtained from this research, a processing flow sheet was defined to obtain hypoallergenic or probably nonallergenic limpid juices and nectars. These products may represent, besides finished foods, intermediates to obtain various products after addition of further ingredients such as pectins, sugars, and fiber.

Quantitative IgE inhibition experiments with purified recombinant allergens indicate pollen-derived allergens as the sensitizing agents responsible for many forms of plant food allergy

BACKGROUND

Type I allergic symptoms in the oropharyngeal mucosa upon contact with plant-derived food in patients with pollen allergies have been termed oral allergy syndrome (OAS). IgE cross-reactivity between pollen and food allergens represents the molecular basis for this phenomenon. The sensitizing allergen source (pollen or plant food) in OAS is a controversial issue.

OBJECTIVE

We sought to determine the primary sensitizing molecules in patients with OAS.

METHODS

We used recombinant birch pollen (rBet v 1 and rBet v 2) and plant food allergens (apple, rMal d 1; celery, rApi g 1; and carrot, rDau c 1), as well as natural pollen (birch and timothy grass) and plant food (apple, peach, kiwi, hazelnut, celery, and carrot) allergens, to identify cross-reactive allergens by using qualitative immunoblot inhibitions. In addition, we determined the percentage of plant food-specific IgE that can be preadsorbed with recombinant and natural pollen allergens by quantitative RAST inhibitions by using sera from 71 patients with OAS.

RESULTS

Preincubation of sera with recombinant and natural pollen allergens led to an almost complete inhibition of IgE binding to plant food allergens in Western blots, as well as in RAST inhibition experiments. In contrast, recombinant plant food allergens poorly inhibited IgE binding to Bet v 1.

CONCLUSION

Most IgE epitopes in plant food recognized by patients with OAS are resembled by pollen allergens. Thus pollen allergens may be responsible for the elicitation and maintenance of OAS.

Skin testing and food challenges in allergy and immunology practice

Skin tests by prick technique offer considerable guidance in the diagnosis of food allergy. Negative prick skin tests are powerful evidence against food allergy. Positive food skin tests are slightly to moderately predictive of reaction to a food on DBPCFC. Oral food challenge is necessary for confirmation of food allergy, except where the history is overwhelmingly convincing. Open, incremental food challenge as described is diagnostic if negative, but only 50% of all positive open challenges are confirmed on blinded challenge. DBPCFC can be designed for any food with simple blinding techniques. The technique of DBPCFC can be modified for investigation of atypical symptoms.

Fruit-pollen-latex cross-reactivity: implication of profilin (Bet v 2)

BACKGROUND

An association between allergy to fruits and latex, and between pollen and plant-derived food has been described. The cross-reactive structures responsible for these associations have not yet been completely elucidated.

METHODS

IgE reactivity to the recombinant allergens Bet v 1 and Bet v 2, different pollens, natural latex, papain, and bromelain was investigated in 29 patients with allergy to fruits or vegetables who lived in an area without birch trees.

RESULTS

Exactly 79.3% of patients were allergic to grass pollen, and two of them had clinical allergy to latex. Serum IgE reactivity (CAP) to birch pollen was found in 65% of patients, to Bet v 2 in 51.7%, to Bet v 1 in 3.4%, to latex in 58.6%, to bromelain in 51.7%, and to papain in 17.2% of patients. All subjects with positive IgE to Bet v 2 had also reactivity to latex, grass, olive tree, birch, and mugwort pollens. The six patients not allergic to pollen did not show IgE reactivity to latex, Bet v 1, or Bet v 2. A significant correlation was found between CAP to latex with Bet v 2 (r=0.86, P<0.001), with birch (r=0.86, P<0.001), and with ryegrass (r=0.81, P<0.001). Immunoblotting using nine sera with positive CAP to birch pollen showed IgE-binding to a 15-kDa band that was recognized by antiprofilin monoclonal antibody. Bet v 2 CAP could be inhibited up to 52% by ryegrass and up to 23% by mugwort. CAP to latex was almost completely inhibited by ryegrass pollen with sera from five subjects without symptoms due to latex, whereas no inhibition was observed with serum from one patient with allergy to latex.

CONCLUSIONS

Patients with allergy to plant-derived food and associated pollinosis showed a high frequency of IgE reactivity to Bet v 2, which may cause positive serum IgE determinations to latex and birch pollen due to the presence of cross-reactive epitopes. IgE reactivity to Bet v 2 may serve as an indicator of broad sensitization.

The major allergen of peach (Prunus persica) is a lipid transfer protein

BACKGROUND

Allergy to fresh fruits and vegetables is mostly observed in subjects with pollinosis, especially from birch, because of cross-reacting allergens in vegetable foods and pollens. However, allergic reactions to fruits, specifically Rosaceae fruits, have been reported in subjects without pollinosis.

OBJECTIVE

This study evaluated the pattern of IgE reactivity, identifying the allergen responsible in 2 groups of patients with oral allergy syndrome to peach with or without birch pollinosis.

METHODS

The allergenic components of peach were detected by SDS-PAGE and immunoblotting. The major peach allergen was purified by HPLC with a cation-exchange column followed by gel filtration chromatography. Its IgE-binding capacity and its homology with the protein of the crude extract were demonstrated by immunoblotting inhibition techniques. To better characterize this allergen, periodic acid-Schiff stain and isoelectrofocusing were used. The amino acid sequencing was done with a gas-phase sequencer.

RESULTS

SDS-PAGE and immunoblotting of the 15 patients allergic to peach, 8 without and 7 with birch pollinosis, showed that they all recognized a protein with a molecular weight of 9 kd. This was the only allergen recognized by patients not sensitized to pollen, whereas the birch pollen-sensitive patients had IgE binding to other allergenic proteins at higher molecular weights. The purified 9-kd protein retained its IgE-binding capacity, was negative to periodic acid-Schiff stain, and had an isoelectric point value of greater than 9. A search in the Swiss Prot Bank showed this was a lipid transfer protein, belonging to a group of molecules involved in the defensive system of plants.

CONCLUSIONS

The major allergen of peach is a 9-kd protein belonging to the group of lipid transfer proteins. This is the only allergen recognized by patients allergic to peach but not sensitized to birch pollen.

Cross-reactivity and epitope analysis of Pru a 1, the major cherry allergen

A high percentage of birch pollen allergic patients experiences food hypersensivity after ingestion of fresh fruits and vegetables. The cross-reactivity of the major allergens of sweet cherry (Pru a 1), apple (Mal d 1), pear (Pyr c 1), celery tuber (Api g 1) and carrot (Dau c 1) is due to structural similarities which are reflected by high amino acid sequence identities with Bet v 1a, the major birch pollen allergen. Apart from a strong cross-reactivity to Bet v 1a, IgE inhibition experiments with Mal d 1, Pru a 1 and Api g 1 demonstrated the presence of common and different epitopes among the tested food allergens. Secondary structure prediction of all investigated allergens indicated the presence of almost identical structural elements. In particular, the 'P-loop' region is a common domain of the pollen related food allergens and of pathogenesis related proteins. To identify the IgE binding epitopes, five overlapping recombinant Pru a 1 fragments representing the entire amino acid sequence with lengths of approximately 60-120 residues were investigated. Weak IgE binding capacity was measured exclusively with Pru a IF4 (1-120) by immunoblotting, whereas none of the fragments showed allergenicity in the rat basophil leukaemia cell mediator release assay. Site-directed mutagenesis experiments with Pru a 1 revealed that amino acid S112 is critical for IgE binding of almost all patients sera tested. This reduced IgE binding was also observed with a single point mutant of Bet v 1a (S112P) and thus indicated serine 112 as an essential residue for preserving the structure of a cross-reactive IgE epitope. Moreover, two Pru a 1 mutants with an altered 'P-loop' region, showed a lowered IgE binding capacity for IgE from a subgroup of allergic patients. The investigation of essential features for preserving cross-reactive IgE-epitopes provides the structural basis for understanding the clinically observed cross-allergenicity between pollen and fruits. Moreover, non-anaphylactic allergen fragments or variants derived from the IgE-inducing pollen allergens may serve as useful tools for a new strategy of specific immunotherapy.

Effects of birch pollen-specific immunotherapy on apple allergy in birch pollen-hypersensitive patients

BACKGROUND

Most patients with birch pollen allergy report oral allergy symptoms after eating fresh apples and other vegetable foods. Major birch pollen and apple allergens, Bet v 1 and Mal d 1, are highly homologous; as a consequence, pollen-specific immunotherapy (SIT) might be expected to improve apple hypersensitivity.

OBJECTIVE

To evaluate the clinical and immunological effects of birch pollen SIT on oral allergy syndrome (OAS) induced by apples.

METHODS

A prospective study carried out in 49 birch pollen-sensitive patients with apple-induced OAS who received injection immunotherapy for 12, 24, or 36 months. Twenty-six patients not submitted to SIT and followed up for 12-48 months were used as controls. Both SPT and open oral challenges with fresh golden delicious apple were performed, as well as specific IgE measurements, before and after SIT.

RESULTS

Forty-one patients (84%) vs no control (0%) reported a significant reduction (50-95%) or a total disappearance (100%) of OAS symptoms after SIT (P < 0. 001). Similar responses were observed in patients treated for 12, 24, or 36 months. SIT also induced a marked reduction in skin reactivity against fresh apple in 43 patients (88%). The effect of SIT was inversely related with baseline skin reactivity: 50% and 8% patients with a weakly or strongly positive baseline apple skin prick tests (SPT), respectively, did not report changes in OAS severity after SIT (P < 0.01). In contrast, baseline birch pollen-specific or apple-specific IgE antibodies levels did not influence SIT effectiveness on OAS. SIT induced a marked decrease in birch pollen-specific IgE levels (P < 0.001), whereas apple-specific IgE showed an unexpected variability (reduction in 21%, no change in 43%, increase in 38%). No control subject reported a reduction in OAS severity or showed a decrease in skin reactivity at follow-up (P < 0.001).

CONCLUSIONS

SIT with birch pollen extracts effectively reduces clinical apple sensitivity and skin reactivity in most cases after only 1 year of treatment; these effects are not paralleled by a similar reduction in apple-specific IgE. These findings suggest a decrease in activability of effector cells as the mechanism underlying clinical benefit.

Carica papaya pollen allergy

BACKGROUND

Carica papaya (CP) trees are widely cultivated in tropical and subtropical areas; however, CP pollen allergy has not been previously described.

OBJECTIVE

To study patients with CP pollen hypersensitivity.

METHODS

A CP pollen extract was elaborated. Skin prick tests (SPTs) with this extract, as well as with commercial papaya fruit and papain extracts, were performed. Specific IgE levels to CP pollen, papaya fruit, and papain were determined. Specific conjunctival challenge tests to the CP pollen extract were also performed. RAST inhibition studies among CP pollen, papaya fruit, and papain were carried out. Twenty atopic patients were used as a control group for in vivo and in vitro tests.

RESULTS

Six patients with clinical histories of seasonal rhinoconjunctivitis or bronchial asthma in relation to CP trees exposure, suggestive of IgE-mediated respiratory allergy, were studied. Commercial SPT and specific serum IgE to papaya fruit and papain were positive in our patients. An IgE-mediated hypersensitivity to a CP pollen extract was demonstrated in all patients, by means of SPTs, specific serum IgE determinations, and conjunctival challenge tests. Control atopic subjects showed negative SPTs, specific IgE, and conjunctival challenge tests to the CP pollen extract. On RAST inhibition studies using CP pollen extract in solid phase, a significant crossreactivity was found among CP pollen, papaya fruit, and papain.

CONCLUSIONS

Our study suggests that papaya flower pollen is able to induce respiratory IgE-mediated allergy. The existence of common allergens among papaya flower pollen, papaya fruit, and papain has been demonstrated by RAST inhibition.

Specific IgE to recombinant vegetal panallergen (rBet v 2) and fruit allergy in pollinic patients

The presence of IgE antibodies to the allergens rBet v 1 and rBet v 2 was investigated in patients with known sensitization to ryegrass (Lolium perenne) and/or olive (Olea europaea) pollen, by comparing a group of 10 patients who had allergic symptoms after ingestion of fruits (A) with a group of 17 patients who had only seasonal respiratory symptoms (B). There was no significant difference between the two groups for total IgE. All patients showed specific IgE to both L. perenne and O. europaea. No specific IgE binding to rBet v 1 was detected in any patient. The incidence of the presence of IgE antibodies to rBet v 2 was 90% in the group with fruit allergy (A) and 35% in group B. We found a significant association between presence of IgE antibodies to rBet v 2 and fruit allergy (P = 0.007). Specific IgE values to O. europaea pollen were higher in the fruit-allergy group than the group without fruit allergy (P = 0.032). In conclusion, pollen-allergic patients with specific IgE to birch pollen profilin show a significantly elevated frequency of fruit allergy.

Olive-pollen profilin. Molecular and immunologic properties

Olive-pollen profilin has been isolated and characterized as a significant allergen. Its molecular properties, such as a molecular mass of 15 kDa; amino-acid composition; and secondary repetitive structure percentages of 15% alpha-helix, 33% beta-strand, 20% beta-turn, and 32% random coil, have been determined. Its allergenic capability, a recognition frequency estimated at 24% of olive-hypersensitive patients, and high cross-reactivity with all the pollen used have been found. The presence of conformation epitopes in the olive profilin, as well as a high structural and immunologic similarity to other pollen sources such as birch and ash, can be established from these studies.

Hot spices influence permeability of human intestinal epithelial monolayers

Indirect evidence suggests that hot spices may interact with epithelial cells of the gastrointestinal tract to modulate their transport properties. Using HCT-8 cells, a cell line from a human ileocoecal carcinoma, we studied the effects of spices on transepithelial electrical resistance (TER), permeability for fluorescein isothiocyanate (FITC)-labeled dextrans with graded molecular weight, and morphological alterations of tight junctions by immunofluorescence using an anti-ZO-1 antibody, a marker for tight junction integrity. Two different reactivity patterns were observed: paprika and cayenne pepper significantly decreased the TER and increased permeability for 10-, 20- and 40-kDa dextrans but not for -70 kDa dextrans. Simultaneously, tight junctions exhibited a discontinuous pattern. Applying extracts from black or green pepper, bay leaf or nutmeg increased the TER and macromolecular permeability remained low. Immunofluorescence ZO-1 staining was preserved. In accordance with the above findings, capsaicin transiently reduced resistance and piperine increased resistance, making them candidates for causing the effects seen with crude spice extracts. The observation that Solanaceae spices (paprika, cayenne pepper) increase permeability for ions and macromolecules might be of pathophysiological importance, particularly with respect to food allergy and intolerance.

Effects of adjuvants on the immune response to allergens in a murine model of allergen inhalation: cholera toxin induces a Th1-like response to Bet v 1, the major birch pollen allergen

Based on the fact that type I allergies are frequently elicited by inhalant allergens, we have established a model of aerosol inhalation leading to allergic sensitization in BALB/c mice. Using this model we studied the effects of aluminium hydroxide (Al(OH)3), known to enhance IgE antibody responses, compared with cholera toxin (CT), a potent mucosal adjuvant, on the immune response to birch pollen (BP) and its major allergen Bet v 1. Two groups of BALB/c mice were either systemically immunized with recombinant Bet v 1 in Al(OH)3 and subsequently aerosol exposed to BP allergen, or aerosolized with BP and CT. IgE-mediated skin reactions were only elicited in the mice which had received Bet v 1/Al(OH)3. Allergen-specific serum IgE and IgG1 antibodies dominated in the Al(OH)3 group, IgG2a antibody levels to BP and rBet v 1 were markedly higher in the sera of mice exposed to CT with the allergen. IgA antibodies were only detected in the bronchial lavage of the CT-treated group. Moreover, the latter group displayed consistently higher T cell proliferative responses to BP and interferon-gamma production in vitro. Thus, the systemic immunization with rBet v 1 in Al(OH)3 before inhalation of the BP extract promoted a Th2-like immune response, while CT mixed with the aerosolized BP extract rather induced a Th1-like immune response. In an attempt to reverse these ongoing immune responses we could achieve a shift towards a Th0 response. Immunization with BP extract without adjuvant treatment led to undetectable antibody or cellular immune responses. We conclude from the present study that the induction of an immune response to BP allergen after aerosol inhalation can be directed towards a Th1- or a Th2-like response. Once established, the immune response can be modulated.

Allergens in pepper and paprika. Immunologic investigation of the celery-birch-mugwort-spice syndrome

Mugwort and birch pollen allergy are frequently associated with IgE-mediated hypersensitivity to celery and spices. We analyzed 22 sera from patients with the mugwort-birch-celery-spice syndrome for IgE binding to the spices pepper and paprika by immunoblotting. Immunoblot results revealed two major allergens of 28 and 60 kDa in pepper and a 23-kDa allergen together with allergens of higher molecular weight in paprika. In immunoblot-inhibition studies, crude mugwort, birch pollen, and celery extracts significantly reduced the IgE binding to pepper and paprika allergens. However, no inhibition was achieved with rBet v 1 and rBet v 2, suggesting that no homologs of these birch proteins act as allergens in pepper or paprika extracts. N-terminal sequence analysis of the 14- and 28-kDa pepper and 23-kDa paprika allergens revealed no homology to known allergens. The 28-kDa pepper allergen showed homology to a wheat germin protein, and the 23-kDa paprika allergen was identified as a homolog of a osmotin-like or pathogenesis-related protein in tomato. Therefore, we conclude that the IgE cross-reactivity in the mugwort-birch-celery-spice syndrome to the spices pepper and paprika is not caused by homologs of Bet v 1 and profilin. N-terminal amino acid sequence analysis of the main allergens in pepper and paprika indicate a relation to frequently occurring plant proteins.

Peach allergy pattern: experience in 70 patients

We report the clinical characteristics of peach allergy encountered in a population of peach-allergic patients. We evaluated 165 patients. The 70 peach-allergic patients were diagnosed through clinical history, the skin prick-prick test, and open oral challenge and rub tests to peach. As a pollinic control group, 95 pollen-allergic patients were also evaluated. Some 49% of the patients were male and 51% female. The mean age was 20 +/- 8 years. Oral allergy syndrome (86%) was the most common symptom, followed by contact urticaria (61%) and systemic symptoms (26%). Some 67% of the patients were allergic to peach pulp and 36% reported symptoms related to canned peach. Canned peach and pulp symptoms were statistically associated (P < 0.01), and symptoms to canned peach were more frequently reported by patients with systemic symptoms (P < 0.05). On evaluation of the peach-allergic patients' characteristics, three risk factors--allergy to peach pulp, allergy to canned peach, and peach allergy in non-pollen-allergic patients--were found, indicating development of systemic symptoms on eating peach. Most of the peach-allergic patients (81%) also had pollen allergy, which was linked to a higher prevalence of asthma (73%) than in the pollen-allergic patients of the control group (48%); this difference was statistically significant (P < 0.01). Finally, two groups were clearly defined by the seriousness of the peach allergy--the non-pollen-allergic patients were more predisposed to the occurrence of systemic symptoms (> 50%), and the pollen-allergic patients to asthma (> 70%).

Allergenic cross-reactivity, food allergy and pollen

Pollen-allergic patients frequently present oral allergy-like symptoms after ingestion of several kinds of plant foods. The majority of these reactions are due to three distinct cross-reactive structures that are present in birch pollen. Proteins that share common epitopes with Bet v 1, the major birch pollen allergen, occur in other kinds of tree pollen, apples, stone fruits, celery, carrots and nuts. Approximately 70% of patients who are allergic to birch pollen may experience symptoms after consumption of foods from these groups. In contrast to Bet v 1, two minor allergenic structures which sensitise ≈10-20% of all pollen-allergic patients are also present in grass and weed pollen, namely profilin and cross-reactive carbohydrate determinants. Profilins can induce symptoms to almost all kinds of plant foods, whereas the clinical relevance of IgE binding to ubiquitous carbohydrates of N-glycans from plants remains in doubt. The paper summarises the knowledge pertaining to the molecular features of these cross-reactive structures and the characteristics of the cross-reactivity patterns and discusses aspects of diagnosis, management and routes of sensitisation.

Nonspecific binding of IgE to allergens

Nonspecific IgE binding to allergens was observed in testing myeloma IgEs, namely, IgE-VL and IgE-PS, chimeric IgE (IgE-JW8), and the recombinant IgE Fc epsilon peptide CH1-CH4, in two different immunoassays. This binding was concentration-dependent but detectable only at higher IgE concentration. In RAST inhibition, IgE-allergen interactions could be reduced by using either matching or nonmatching allergens. In order to test whether the nonspecific binding of IgE to allergens was due to carbohydrate interaction, myeloma IgEs and the chimeric IgE were desialized with neuraminidase. Desialized samples were equally well recognized by xenogenic antibodies as native IgEs, but binding of IgE to Fc epsilon receptors on basophils was affected by the treatment, as shown in the histamine-release assay. Desialization of IgE affected also its binding capacity to allergens in RAST: binding of chimeric IgE was reduced, but nonspecific binding of myeloma IgE-VL was enhanced. Hence, nonspecific allergen-IgE binding may be partly due to a lectin-like interaction, but may depend mostly on the tertiary structure of IgE. Thus, nonspecific IgE-allergen interactions might present a problem 1) at high IgE concentration, and 2) depend on the grade of sialization of IgE, which might affect its conformation. This may explain why patients with elevated total IgE levels often have multiple weak positive RASTs with non-cross-reactive allergens.

Molecular cloning, expression and characterization of Pru a 1, the major cherry allergen

A high percentage of birch pollen allergic patients experiences food hypersensitivity reactions after ingestion of several fruits and vegetables. Previous work demonstrated common epitopes on an allergen of Mr 18,000 from sweet cherry (Prunus avium) and Bet v 1, the major allergen from birch pollen. N-terminal amino acid sequencing showed a sequence identity of 67% with Bet v 1. Here we report the cloning and cDNA sequencing of this cherry allergen. The entire deduced amino acid sequence described a protein of Mr 17,700 with 59.1% identity to Bet v 1. High degrees of identity in the range of 40 to 60% were also found with related allergens from other kinds of tree pollen and plant foods as well as with stress-induced proteins from food plants such as parsley, potato and soya. The coding DNA of the cherry protein was cloned into vector pET-16b and expressed in E. coli strain BL21(DE3) as a His-tag fusion protein. As shown by SDS-PAGE, the apparent molecular masses of the nonfusion protein and the natural allergen were identical. The fusion protein showed high IgE binding potency when sera from patients allergic to cherry were tested by immunoblotting and enzyme allergosorbent tests. Moreover, it cross-reacted strongly with IgE specific for the natural counterpart and for Bet v 1. The high biological activity of the recombinant fusion protein was further confirmed by the induction of a strong histamine release in basophils from cherry-allergic patients. Since sera from 17/19 of such patients contained IgE against this allergen it was classified as a major allergen and named Pru a 1. Recombinant Pru a 1 mimics most of the allergenic potency of cherry extract and hence could be a useful tool for studying the molecular and immunological properties of pollen related food allergens.

Relevance of pollen-specific IgE levels to the development of Apiaceae hypersensitivity in patients with birch pollen allergy

A large clinical/serologic study was carried out to determine the prevalence of Apiaceae (carrot, celery, and fennel) hypersensitivity in patients with birch pollen allergy, and to investigate its relationship with apple and hazelnut allergy and with birch pollen-specific IgE levels. A total of 196 birch pollen-hypersensitive patients with oral allergy syndrome (OAS) caused by different vegetable foods were examined in the cross-sectional part of the study. Of this total, 195 patients had apple and/or hazelnut allergy, and 103 had Apiaceae sensitivity; only one patient had Apiaceae allergy alone. Apiaceae-positive patients showed significantly higher birch pollen-specific IgE levels than negative ones (median 13 vs 7 AU/ml; P < 0.0001). The prospective part of the study was performed on 103 birch pollen-hypersensitive patients who were OAS-free at the time of the first visit and were periodically followed-up for OAS. Patients who developed Apiaceae sensitivity showed much higher birch-specific IgE levels than patients who developed apple/hazelnut allergy only (median 15.5 vs 8.5 AU/ml; P < 0.05), whereas those who remained OAS-free showed the lowest specific IgE levels (median 5 AU/ml). This study suggests that most Apiaceae determinants cross-react with apple or hazelnut determinants, whereas only some apple or hazelnut determinants cross-react with Apiaceae-allergenic determinants; moreover, it shows that birch-specific IgE levels heavily influence the onset of OAS as a whole, and probably play a critical role in the development of allergies to distinct vegetable foods as well.

Oral allergy syndrome to a jackfruit (Artocarpus integrifolia)

A 30-year-old man from the Philippines with pollen allergy noted the appearance of oral allergy syndrome (OAS) after eating raw apple, raw peach, raw celery, and recently, jackfruit (Artocarpus integrifolia), a tropical fruit which belongs to the Moraceae family (mulberry) and to the genus Artocarpus (breadfruit tree). Despite the patient's multiple sensitization in skin prick tests and in the Pharmacia CAP System to birch, grass, mugwort pollen, related fruits and vegetables, and jackfruit, in RAST-inhibition studies neither rBet v 1 nor rBet v 2 (profilin), the well-known cross-reacting allergenic components in OAS, could inhibit the specific IgE response to jackfruit. Whether the reaction to jackfruit is specific or whether other pollen-related, cross-reacting allergenic components exist should be investigated further.

IgE binding to a new cross-reactive structure: a 35 kDa protein in birch pollen, exotic fruit and other plant foods

Food allergies in birch pollen allergic patients have been shown to be due to cross-reactivities of specific IgE antibodies which are directed against birch pollen allergens with related proteins in fruit, nuts and vegetables. We identified a new cross-reactive structure of 35 kDa in birch pollen and some plant food extracts by Enzyme Allergosorbent Test (EAST) and immunoblot inhibition studies. The 35 kDa birch pollen protein is a minor allergen to which approximately 10-15% of birch pollen allergic individuals have specific IgE. Our data demonstrate that there is cross-reactivity of this protein with proteins of comparable size from lychee, mango, banana, orange, apple, pear and carrot. While the 35 kDa protein is immunologically independent of the major birch pollen allergen Bet v 1, we also observed IgE binding to a 34 kDa structure which appears to be a Bet v 1 dimer.

Identification of a 60 kd cross-reactive allergen in pollen and plant-derived food

BACKGROUND

Cross-reactive IgE antibodies were found to be responsible for allergic reactions in patients allergic to pollen on ingestion of food (oral allergy syndrome). So far, the major birch pollen allergen Bet v 1 and birch profilin (Bet v 2) were identified as relevant cross-reactive allergens.

OBJECTIVE

In this study we attempted to identify additional cross-reactive plant allergens, which could be responsible for food intolerance in patients allergic to pollen.

METHODS

Monoclonal antibodies specific for the major mugwort pollen allergen, Art v 1, representing a 60 kd glycoprotein, were used to detect cross-reactive allergens in other pollens and plant-derived food. The amino acid compositions of the cross-reactive structures were determined, and their resistance against trypsin treatment was investigated. In addition, IgE immunoblot inhibitions were done with the 60 kd mugwort pollen allergen.

RESULTS

Monoclonal antibodies specific for the major mugwort pollen allergen, Art v 1, cross-reacted with proteins of comparable molecular weight in fruit and vegetables. Preadsorption of patients' sera with the 60 kd mugwort allergen led to a reduction of IgE binding to components of a similar molecular weight present in different pollen (birch, timothy grass), fruit (apple, peanuts), and vegetable (celery) extracts and reduced IgE binding to apple, kiwi, and celery as determined by RAST inhibitions.

CONCLUSION

A cross-reactive plant panallergen, possibly identical to the major mugwort pollen allergen, Art v 1, is described. The allergen represents a protein of approximately 60 kd present in various pollen and plant foods; which is distinct from Bet v 1 and profilin and hence may represent a novel cross-reactive allergen in the oral allergy syndrome.

Ole e 3, an olive-tree allergen, belongs to a widespread family of pollen proteins

An allergen has been isolated from a saline extract of olive tree (Olea europaea) pollen. The protein consists of a single polypeptide chain of 9.2-kDa, as determined by mass spectrometry. It contains neither tryptophan nor tyrosine residues, and displays an acidic isoelectric point. The secondary structure of the protein, estimated from the analysis of the circular-dichroism spectrum in the peptide-bond region, is composed of 52% alpha-helix, 10% beta-strand, 29% beta-turn and 9% non-regular conformation. The N-terminal end of the protein is blocked. Amino-acid-sequence data have been obtained from peptides produced by CNBr treatment of the native allergen. A partial sequence of 36 amino acids has thus been elucidated. The protein exhibits sequence similarity with pollen allergens from Brassica species and contains a Ca(2+)-binding motif. The isolated protein displays IgE-binding activity against sera of patients allergic to olive-tree pollen. It has been named Ole e 3, according to the recommendations of the IUIS Nomenclature Committee. IgG ELISA inhibition assays with polyclonal antibodies specific for Ole e 3 reveal the presence of proteins similar to Ole e 3 in the pollen from non-related plant species, which may explain allergic cross-reactivity processes.

Hypersensitivity to carrot associated with specific IgE to grass and tree pollens

This study deals with a 34-year-old female cook with no previous history of atopy, who was studied because of allergic rhinoconjunctivitis and contact urticaria in both hands associated with severe itching when she handled raw carrot. The patient had had anaphylactic episodes after accidental ingestion of raw carrots, but she tolerated cooked carrots. Skin prick tests with carrot, celery, and olive, and birch, grass, and mugwort pollens were positive. Total IgE was 411 UI/ml. Specific IgE to olive, grass, and weed pollens were 10.92, 6.17, and 2.4 AU/ml, respectively. The histamine release test was positive for carrot, celery, celeriac, and olive pollen up to a dilution of 1/10(6). Immunoblot of raw carrot showed a single IgE-binding 18-kDa band. IgE reactivity for raw carrot immunoblot was completely inhibited by carrot and by celery, but not by olive or grass pollens. Specific IgE to olive pollen was not inhibited by carrot. The existence of monosensitization to an 18-kDa protein in carrot and specific IgE to olive pollen has not been reported in the celery-carrot-mugwort-spice syndrome.

Skin testing with recombinant allergens rBet v 1 and birch profilin, rBet v 2: diagnostic value for birch pollen and associated allergies

OBJECTIVE

This study assesses the value of two recombinant birch allergens for diagnosis of patients sensitized to birch pollen with or without associated food allergy.

METHODS

Fifty-one patients with positive skin test responses to Betulaceae and seven nonallergic control subjects were investigated; specific IgE antibodies were evaluated by specific immunoassay and blot immunodetection.

RESULTS

Among 51 patients, 47 reacted to rBet v 1 and 10 to rBet v 2. Seven patients reacted to both recombinant allergens. In skin prick tests we found a correlation between the wheal produced by the commercial birch extract and the wheal produced by rBet v 1. Among 47 patients with positive test responses to rBet v 1, 83% had IgE binding to the Bet v 1 protein as determined by immunoblotting. Among 10 patients sensitized to rBet v 2, six had IgE binding to Bet v 2. Eleven patients with negative results, as determined by immunoblotting, had low levels of birch IgE in the sera (less than 10 kU/L) and low concentrations of IgE to rBet v 1 or rBet v 2 in ELISA. The nonallergic control subjects (n = 7) did not react to rBet v 1 or rBet v 2 in skin prick tests, nor did they have detectable amounts of specific IgE to rBet v 1 or rBet v 2. Histamine release tests confirmed sensitization to Bet v 1 in two patients with discordant results; for Bet v 2, one patient had positive results only at a high concentration, and one had results that remained negative. Thirty-four patients had birch pollinosis, and all reacted to rBet v 1. Patients who were monosensitized to birch never reacted to rBet v 2. Sensitization to rBet v 2 was only found in patients who reacted to other pollens (mainly grass). Twenty-nine patients demonstrated allergy to apples, cherries, or hazelnuts; and all reacted to rBet v 1. Among 11 patients with allergy to Umbelliferae, only three reacted to rBet v 2.

CONCLUSIONS

Use of the two recombinant allergens (rBet v 1 and rBet v 2) always permits the diagnosis of birch sensitization. Sensitization to rBet v 1 is specific for birch and Rosaceae allergies, whereas sensitization to birch profilin, Bet v 2, is encountered in multisensitized subjects and is not always related to Umbelliferae allergy.

Immunological and structural similarities among allergens: prerequisite for a specific and component-based therapy of allergy

It is known that allergic patients are frequently co-sensitized against different allergen sources. Progress made in the field of allergen characterization by molecular biological techniques has now revealed that sensitization against different allergen sources can be explained as cross-reactivity of IgE antibodies with structurally and immunologically related components present in these allergen sources. This review defines groups of cross-reactive plant allergens with significant sequence homology. The similarities among allergens may facilitate allergy diagnosis by using a few representative cross-reactive allergens to determine the patient's IgE reactivity profile (allergogram). According to that typing, a few cross-reactive allergens, carrying most of the relevant IgE epitopes, may then be selected for patient-tailored specific therapy.

Expression of Zm13, a pollen specific maize protein, in Escherichia coli reveals IgE-binding capacity and allergenic potential

Plant proteins belong to the most frequent elicitors of type I allergic symptoms in industrialized countries. Several relevant plant allergens have been found to be either specifically expressed or highly upregulated in mature pollen. The cDNA coding for a pollen specific maize protein, Zm13, shows significant sequence homology with a number of pollen or anther specific proteins from monocot and dicot plants as well as with recently described allergens from olive and rye grass. To test whether the Zm13 protein might possess IgE-binding capacity, Zm13 was expressed in E. coli. The coding region of Zm13 was PCR amplified from a genomic clone and expressed as a glutathione-S-transferase fusion protein. The recombinant Zm13 fusion protein bound a Zm13 specific rabbit antiserum and reacted with serum IgE from grass pollen allergic patients indicating that Zm13 and homologous proteins represent a family of conserved plant allergens.

Oral allergy syndrome induced by chestnut (Castanea sativa)

BACKGROUND

Oral allergy syndrome is a distinctive type of allergy to food resulting from direct contact between food and the oral mucosa. Normally, it affects patients who are allergic to pollens. It can be challenged by testing for hypersensitivity to fresh fruit or vegetables in well-known associations. Oral allergy syndrome rarely occurs in patients with other types of allergies, or to food not associated with pollens. Only occasionally does chestnut cause hypersensitivity. There are only a few reported cases, depending on cross-reactivity in previously latex-hypersensitive patients. Oral allergy syndrome to chestnut in a patient with respiratory allergy to Dermatophagoides is therefore unusual and worth reporting.

OBJECTIVES

To describe the clinical features and their differences from previously reported cases and to analyze the techniques and methodologic problems related to in vivo and in vitro diagnosis.

METHODS

Case report. Skin tests with commercial and freshly made extracts and by the prick-by-prick method. Challenge test. Specific IgE antibody assay. Prausnitz-Küstner reaction.

RESULTS

The challenge with fresh food confirmed an oral allergy syndrome to chestnut. Clear symptoms of rhinoconjunctivitis and asthma set in as well. Skin tests with several commercial extracts and the prick-by-prick test were negative and so was specific IgE assay in serum by RAST and other immunoenzymatic methods. Skin prick test with a freshly prepared extract of fresh chestnut and the passive transfer reaction were positive.

CONCLUSIONS

The case of oral allergy syndrome to chestnut reported here appears to be a manifestation of immediate IgE-dependent hypersensitivity.

Induction of IgE antibodies with predefined specificity in rhesus monkeys with recombinant birch pollen allergens, Bet v 1 and Bet v 2

BACKGROUND

Recombinant birch pollen allergens Bet v 1 and Bet v 2 (birch profilin) have been characterized in vitro previously.

OBJECTIVE

To establish a close-to-man model of type I allergy, recombinant birch pollen allergens were injected into rhesus monkeys.

METHODS

The allergens were expressed in Escherichia coli, purified to homogeneity and injected into rhesus monkeys with aluminium hydroxide as adjuvans. The development of type I allergy was monitored by measurement of specific IgE, in vitro histamine release tests, cellular proliferation assays, skin testing, and bronchial provocation tests.

RESULTS

Immunized rhesus monkeys displayed symptoms of type I allergy comparable to those of allergic patients, and cross-reactivity of IgE antibodies with Bet v 1 and Bet v 2 homologous allergens was observed. Systemic application of corticosteroids during secondary immunizations suppressed specific antibody responses.

CONCLUSION

Recombinant birch pollen allergens (Bet v 1 and Bet v 2) were effective to establish a close-to-man model of natural type I allergy in rhesus monkeys, allowing study of specific IgE regulation in vivo.