Antigenicity of the pollen proteins of various cultivars of Olea europaea

Assessment of heterogeneity of two cultivars of Olea europaea based on the study of their Ole e 1 protein content

Olive pollen is one of the main causes of allergic disease in the Mediterranean area. Ten different proteins with allergenic activity have been described in olive pollen, with major allergen Ole e 1. Olea europaea L. may cause allergenic effects of different severity depending on the Ole e 1 content of cultivars. In this paper, we aimed to assess the heterogeneity of two olive cultivars concerning concentrations of the major allergen Ole e 1 during a period of 2 years. Pollens from two most common olive cultivars, known as "Gemlik" and "Celebi," were analyzed on regular basis. Ole e 1 amounts were measured by double-sandwich enzyme-linked immunosorbent assay (ELISA). The results were expressed as μg of Ole e 1 per μg of total freeze-dried extract. Comparisons of Ole e 1 levels were made both between individual trees and between cultivars. It was analyzed the influence of some meteorological parameters on pollen counts/allergenic content on a local scale, for 2 years. Pollen sampling was carried out continuously for 2 years, using a Hirst-type volumetric trap. "Gemlik" had the higher value (mean ± standard deviation) of Ole e 1 content (2.44 ±0.70 and 1.87 ±1.03 μg/μg, respectively) when compared to "Celebi" (2.16 ±0.86 and 0.20 ±0.30 μg/μg, respectively) in the years 2013 and 2015. In our research, daily variations were observed in pollen samples of two olive cultivars and even different trees of the same cultivar. Furthermore, during certain sampling days, discrepancies between airborne pollen counts and Ole e 1 concentrations were detected for both cultivars. It was found that meteorological changes, especially temperature and precipitation fluctuations, could affect airborne pollen and Ole e 1 allergen levels in the atmosphere. Therefore, pollen samples of different O. europaea cultivars demonstrated great differences in Ole e 1 content. We believe that these findings were a result of alternate bearing behavior modulated by meteorological factors.

Analysis of olive allergens

Olive pollen is one of the most important causes of seasonal respiratory allergy in Mediterranean countries, where this tree is intensely cultivated. Besides this, some cases of contact dermatitis and food allergy to the olive fruit and olive oil have been also described. Several scientific studies dealing with olive allergens has been reported, being the information available about them constantly increasing. Up to date, twelve allergens have been identified in olive pollen while just one allergen has been identified in olive fruit. This review article describes considerations about allergen extraction and production, also describing the different methodologies employed in the physicochemical and immunological characterization of olive allergens. Finally, a revision of the most relevant studies in the analysis of both olive pollen and olive fruit allergens is carried out.

Screening of Ole e 1 polymorphism among olive cultivars by peptide mapping and N-glycopeptide analysis

In the present paper, we have used 2-DE coupled to MS analysis to examine the molecular variability of the Ole e 1 allergen in three olive cultivars (cvs). Our results confirmed that the predicted polymorphism of Ole e 1 at cDNA level is extended to the expressed protein. The profiles of both the Ole e 1 peptides and the N-glycan variants significantly changed among cvs. We observed that Picual and Arbequina cvs presented the highest and lowest degree of Ole e 1 polymorphism, respectively. Some of these peptides and N-glycans were distributed in a cv-specific manner. The putative implications of this molecular polymorphism in the development of the allergy symptoms are discussed.

Olive cultivar origin is a major cause of polymorphism for Ole e 1 pollen allergen

BACKGROUND

Pollens from different olive (Olea europaea L.) cultivars have been shown to differ significantly in their content in Ole e 1 and in their overall allergenicity. This allergen is, in addition, characterized by a high degree of polymorphism in its sequence. The purpose of this study is to evaluate the putative presence of divergences in Ole e 1 sequences from different olive cultivars.

RESULTS

RNA from pollen individually collected from 10 olive cultivars was used to amplify Ole e 1 sequences by RT-PCR, and the sequences were analyzed by using different bioinformatics tools. Numerous nucleotide substitutions were detected throughout the sequences, many of which resulted in amino acid substitutions in the deduced protein sequences. In most cases variability within a single variety was much lower than among varieties. Key amino acid changes in comparison with "canonical" sequences previously described in the literature included: a) the substitution of C19-relevant to the disulphide bond structure of the protein-, b) the presence of an additional N-glycosylation motif, and c) point substitutions affecting regions of Ole e 1 already described like relevant for the immunogenicity/allergenicity of the protein.

CONCLUSION

Varietal origin of olive pollen is a major factor determining the diversity of Ole e 1 variants. We consider this information of capital importance for the optimal design of efficient and safe allergen formulations, and useful for the genetic engineering of modified forms of the allergen among other applications.

Comparison of the allergenicity and Ole e 1 content of 6 varieties of Olea europaea pollen collected during 5 consecutive years

BACKGROUND

Numerous varieties of Olea europaea have been described in Mediterranean countries.

OBJECTIVE

To investigate the immunochemical characteristics of 6 varieties of Olea europaea collected during 5 consecutive years.

METHODS

The varieties Carrasquefio, Manzanillo, Acebuche (wild olive), Hojiblanco, Picual, and Nevado were analyzed. Pollen samples from each variety were collected for 5 consecutive years from the same cultivars by trained personnel. The antigenic and allergenic profiles of these extracts were evaluated by means of sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot using the serum of 29 O. europaea-allergic individuals. Ole e 1 was measured using enzyme-linked immunosorbent assay and purified Ole e 1 and rabbit polyclonal antibodies. Allergenic potency was determined using enzyme-linked immunosorbent assay inhibition and is expressed in histamine equivalent prick units per gram of raw material.

RESULTS

Hojiblanco and Acebuche had the lowest mean +/- SD Ole e 1 content in the 5 years (0.045 +/- 0.029 and 0.059 +/-0.031 microg/microg of freeze-dried material, respectively). The variety with the highest mean +/- SD Ole e 1 content was Picual (0.19 +/-0.075 microg/microg). Hojiblanco had the lowest total biological potency throughout the study. A positive correlation was obtained between rainfall in the winter months and total allergenicity of the 6 varieties.

CONCLUSIONS

The different varieties of O. europaea pollen demonstrated great differences in allergenic potency and Ole e 1 content. These differences were maintained throughout the study, suggesting that they are due to genetic differences intrinsic to the varieties, although certain climatic effects may also play a role.

Allergenic diversity of the olive pollen

A great number of allergenic proteins have been detected in olive pollen extracts. To date, nine allergens have been isolated and characterized, which have been called Ole e 1 to Ole e 9. The most prevalent olive allergen is Ole e 1, which affects more than 70% of patients hypersensitive to olive pollen, but others, such as Ole e 2, Ole e 8, and Ole e 9, have been demonstrated to be major allergens, and Ole e 6 or Ole e 7 reach high values of clinical incidence. Many of these allergens, such as Ole e 2 (profilin) and Ole e 3 (polcalcin), are involved in cross-reactivities, which agrees with their adscription to panallergenic families. Among the many olive allergens of high molecular mass, only Ole e 9 (46 kDa) has been characterized. The allergen is a polymorphic and glycosylated beta-1,3-glucanase, which belongs to a pathogenesis-related (PR-2) protein family. In addition to the polypeptide epitopes, Ole e 1 also exhibits IgE-binding determinants in the carbohydrate, which are recognized by more than 60% of the sera from patients sensitive to the whole allergen, although the level of such glycan-specific IgE seems not to be clinically relevant in the overall content of the sera. Recent advances in the elucidation of the structure of the Ole e 1-oligosaccharide component allows us to explain the antigenicity of the molecule. Finally, the recombinant production of several allergens from olive pollen in both bacterial and eukaryotic cells has allowed us to resolve problems derived from the polymorphism and scarcity of the natural forms of these allergens. The biological equivalence between the natural and recombinant forms lets us initiate studies on the design of mixtures for clinical purposes, in which hypoallergenic derivatives of these allergens could play a definitive role.

Monoclonal antibody-based method for measuring olive pollen major allergen Ole e 1

BACKGROUND

Olive tree pollen is an important cause of inhalant allergy in Mediterranean countries. The major allergen of this pollen, Ole e 1, has caused reactions in the sera of >80% of olive-sensitive patients. Accurate standardization of allergenic products for diagnosis and immunotherapy is essential to guarantee their quality, and measurement of the major allergen content is becoming an important aspect of standardization procedures.

OBJECTIVE

To develop a two-site enzyme-linked immunoadsorbent assay (ELISA) for the quantification of Ole e 1.

METHODS

BALB/c mice were immunized with purified natural Ole e 1. After fusion and screening by direct ELISA, one of the monoclonal antibodies (5A3) was selected as the capture antibody in an ELISA for Ole e 1 quantification. Bound allergens were detected by a combination of biotinylated Ole e 1-specific polyclonal rabbit antibody and peroxidase-conjugated streptavidin. This ELISA was subsequently evaluated and compared with other techniques.

RESULTS

The developed ELISA was highly reproducible and sensitive, with a detection limit of 0.5 ng/mL and a practical range of 1 to 10 ng/mL. The Ole e 1 content ranged from 3 to 50% of the total protein among the nine Olea europaea pollen extracts studied. The assay also detected Ole e 1-like proteins in pollen from other Oleaceae. Correlation was good between the Ole e 1 content determined by ELISA and scanning densitometry and the immunoglobulin E-binding activity of the extracts.

CONCLUSION

The described Ole e 1 ELISA is sensitive, reproducible, specific, and reliable, and therefore, can be helpful for standardization of olive pollen extracts intended for clinical use.

Allergenicity and immunochemical characterization of six varieties of Olea europaea

BACKGROUND

The inhalation of Olea europaea pollen is one of the most important causes of allergic respiratory diseases in the Mediterranean basin. The objective of this study was to investigate the antigenic and allergenic composition of six different O. europaea varieties collected in southern Spain.

METHODS

The varieties included in the study were: Acebuche (wild olive), Carrasqueño, Nevado, Hojiblanco, Manzanillo and Picual. Extracts of these six varieties were prepared. Twenty-nine olive individuals with an immunoglobulin(Ig)E-mediated allergy to olive pollen were skin tested with these extracts. The antigenic profile of these extracts was evaluated by SDS-PAGE; the allergenic profile was investigated by immunoblotting using the serum of these 29 individuals. The Ole e 1 content was established by ELISA inhibition using purified Ole e 1 and rabbit polyclonal antibodies and by scanning densitometry.

RESULTS

The extracts that induced the smallest wheal size were Acebuche and Hojiblanco, being significantly different from the rest of the extracts. The antigenic and allergenic profiles of the extracts also varied. The Ole e 1 content ranged from 0.050 in Hojiblanco to 0.232 in Manzanillo, measured by ELISA inhibition and from 0.153 in Hojiblanco to 0.677 in Nevado, measured by scanning densitometry.

CONCLUSIONS

The different varieties of O. europaea pollen studied demonstrated great differences in the in vivo and in vitro potency of the extracts. There were significant differences in the Ole e 1 content, while the protein content remained very similar in these extracts. This study confirms previous observations of a great variability in the antigenic and allergenic composition of O. europaea pollen extracts and establishes significant differences in Ole e 1 content.

Preliminary assessment of the immune response to Olea europaea pollen extracts encapsulated into PLGA microspheres

In this study, poly (D,L-lactide-co-glycolide) (PLGA) microspheres encapsulating Olea europaea pollen extracts were prepared by using the double emulsion (w/o/w) based on a solvent evaporation/extraction method. The resulting microspheres were 1.93 microns in size. The total allergen loading and surface-associated allergen were 8 and 0.64%, respectively. The release of the allergen from the microspheres showed a biphasic profile with an initial burst release followed by a sustained release phase. Finally, the polyacrylamide gel electrophoresis (SDS-PAGE) results showed that the encapsulation process does not affect the stability of the protein. We describe here some preliminary observations concerning the use of these microspheres as parenteral antigen delivery systems for immunization with O. europaea pollen extracts, in a small animal model, the mouse.

Determination of Ole e 1 by enzyme immunoassay and scanning densitometry. Validation by skin-prick testing

Ole e 1 is an important allergen in Olea europaea pollen extracts. This study describes the development of two new methods that can be used to estimate the Ole e 1 content in olive tree pollen extracts. They are based on (1) an enzyme immunoassay that uses rabbit polyclonal, monospecific antibodies and purified Ole e 1, and (2) scanning densitometry of SDS-PAGE gels. Twelve extracts were evaluated by in vivo and in vitro methods. The in vivo biological potency was estimated by prick skin testing 17 allergic individuals; the in vitro allergenic potency by direct IgE and IgE inhibition assays. The enzyme immunoassay showed an operative range of 0.03-100 microg/ml and demonstrated to be specific for Ole e 1. The Ole e 1 content ranged from 1% to 5% of the total protein in the 12 extracts. The amount of Ole e 1, assessed by gel scanning densitometry significantly correlated with the Ole e 1 content obtained by the immunoassay (r = 0.92; p < 0.001). The Ole e 1 content showed a significant correlation with the total allergenic potency of the extracts, evaluated by direct IgE, specific IgE inhibition and skin-prick testing. These two methods can be used to determine the Ole e 1 content in olive pollen extracts. The content of Ole e 1 can vary from 1% to 5% of the total protein in the extracts.

Allergic responses to pollen of ornamental plants: high incidence in the general atopic population and especially among flower growers

BACKGROUND

The incidence of allergy to pollen of ornamental plants has not been deeply investigated, and its extent has remained obscure. Most of such studies have concentrated only on pollen of ornamental plants from the Asteraceae family (Compositae). In this study an attempt was made to clarify whether various other ornamental plants may also cause skin responses and allergic symptoms among allergic urban dwellers and among rural flower growers.

METHODS

Two hundred ninety-two patients were referred for allergic evaluation by their primary physicians; 75 flower growers and 44 university students were evaluated. For all participants, a detailed health record was obtained, and skin prick tests (SPTs) were performed. Extracts for SPTs included commercial common airborne allergens and autochthonous pollen extracts of 11 species of plants belonging to the Asteraceae, Ranunculaceae, Liliaceae, Scrophulariaceae, and Genetianaceae families.

RESULTS

Fifty-one of the 292 patients (17%) referred for allergic evaluation had positive SPT responses to pollen of various ornamental plants. A similar incidence was found among the students (23%). However, the incidence among flower growers was significantly higher, reaching 52%. Higher incidence (83%) of positive SPT responses to ornamental plants was found among flower growers also sensitive to the common allergens. All the tested plants, not only those belonging to the Asteraceae family, provoked positive SPT responses in all 3 groups of participants. None of the participants from the general population or the group of students reported exacerbation of allergic symptoms on exposure to the tested plants. In contrast, almost half of the flower growers (45%) described nasal, ocular, or respiratory symptoms associated with occupational exposure to the tested plants. Some 15% of the growers were eventually compelled to change their profession.

CONCLUSIONS

The incidence of positive SPT responses to ornamental plants was 17% to 23% among the general public but 52% among flower growers. Thus the effects of ornamental plant pollen on atopic patients should be seriously contemplated.