Isolation, cDNA cloning and expression of Lig v 1, the major allergen from privet pollen

PbrPOE21 inhibits pear pollen tube growth in vitro by altering apical reactive oxygen species content

Genome-wide identification, tissue-specific expression analysis and functional characterization of selected genes containing the pear Pollen Olea europaea I domain reveal their roles in pollen tube growth. Genes containing the Pollen Olea europaea I (POE) domain play crucial roles in diverse growth and developmental processes. Nevertheless, the specific functions of POE family members in progression of pollen tube growth (PTG) remain uncharacterized. We identified 45 PbrPOE genes in the pear (Pyrus bretschneideri) genome, clustered into seven subclasses. PbrPOE genes contained 1 to 11 exons and 0 to 10 introns, with exon/intron structure mostly conserved within each subclass. Whole-genome duplication has mainly contributed to the duplication pattern of PbrPOE genes in pear. Expression profiles of 45 PbrPOE genes in 12 different pear tissues revealed that six PbrPOE genes (PbrPOE6, 12, 21, 29, 35 and 41) of subclass B were highly expressed during the growth of the pear pollen tube in vitro. PbrPOE21 was selected for further functional analysis on the basis of its high and differential expression pattern in pollen. Antisense oligodeoxynucleotide assays demonstrated that PTG was augmented in vitro when PbrPOE21 expression was significantly inhibited. Moreover, pollen tube length in vitro was reduced when PbrPOE21 was transitorily over-expressed using particle bombardment technology. Exogenous PbrPOE21 recombinant protein inhibited PTG in vitro at an optimum concentration of 1.8 µM. PbrPOE21 also affected reactive oxygen species content in the pear pollen tube apex. We suggest that PbrPOE21 inhibits PTG in vitro by altering apical reactive oxygen species content.

Ligustrum pollen: New insights into allergic disease

Respiratory allergies are important medical conditions because they affect nearly 20% of the population worldwide, with higher prevalence in industrialized cities. Aeroallergens such as pollen are responsible for up to 40% of respiratory allergies. The pollen from Ligustrum (privet hedge) is a great source of inhalant allergens associated with allergic respiratory diseases around the world. However, it has been underestimated as a sensitization factor. Interestingly, over the last few years a number of novel allergens have been identified from Ligustrum using immunoproteomics technologies. Cross-linking of IgE and Ligustrum allergens could lead to the rapid release of inflammatory mediators by mast cells and basophils. These will promote a late response characterized by activation of T cells and overproduction of Th2 cytokines such as IL-4, IL-5, IL-9, and IL-13. These inflammatory changes cause respiratory diseases like asthma and allergic rhinitis in sensitized subjects. Here, we review Ligustrum pollen allergens and focus on their clinical and immunological significance in allergic disease as well as the use of hypoallergenic derivatives in personalized therapy.

Cloning and Expression of Ama r 1, as a Novel Allergen of Amaranthus retroflexus Pollen

Sensitisation to Amaranthus retroflexus pollen is very common in tropical and subtropical countries. In this study we aimed to produce a recombinant allergenic Ole e 1-like protein from the pollen of this weed. To predict cross-reactivity of this allergen (Ama r 1) with other members of the Ole e 1-like protein family, the nucleotide sequence homology of the Ama r 1 was investigated. The expression of Ama r 1 in Escherichia coli was performed by using a pET-21b(+) vector. The IgE-binding potential of recombinant Ama r 1 (rAma r 1) was evaluated by immunodetection and inhibition assays using 26 patients' sera sensitised to A. retroflexus pollen. The coding sequence of the Ama r 1 cDNA indicated an open reading frame of 507 bp encoding for 168 amino acid residues which belonged to the Ole e 1-like protein family. Of the 26 serum samples, 10 (38.46%) had significant specific IgE levels for rAma r 1. Immunodetection and inhibition assays revealed that the purified rAma r 1 might be the same as that in the crude extract. Ama r 1, the second allergen from the A. retroflexus pollen, was identified as a member of the family of Ole e 1-like protein.

Identification of Ligustrum lucidum pollen allergens using a proteomics approach

BACKGROUND

Ligustrum spp. are members of the Oleaceae family, one of the most prominent allergic families worldwide. The genus Ligustrum contains approximately fifty species, including Ligustrum lucidum, which have been widely cultivated as ornamental plants, and its pollen is a source of inhalant allergens associated with respiratory allergic diseases. Little is known about the presence of allergenic proteins in L. lucidum.

METHODS

The L. lucidum pollen proteins were extracted by a modified phenolic extraction method. A pool of four sera from mono sensitive patients was analyzed by 2DE immunoblotting and mass spectrometric analysis was performed on 6 immunoreactive protein spots.

RESULTS

SDS-PAGE of L. lucidum pollen extract revealed proteins in ranges of 15-150 kDa. The 2DE gel profile of the L. lucidum pollen protein extract showed approximately 180 spots, and the 2DE immunoblots obtained using sera from Ligustrum monosensitive patients as the source of IgE antibodies revealed six allergen protein spots, corresponding to Profilin, Enolase, Fra e 9.01 (β-1,3-glucanase), Pollen-specific Polygalacturonases, Alanine aminotransferase, and two ATP synthase beta subunits.

CONCLUSION

We report for the first time the identification of IgE-reactive proteins from L. lucidum.

Tree pollen allergens-an update from a molecular perspective

It is estimated that pollen allergies affect approximately 40% of allergic individuals. In general, tree pollen allergies are mainly elicited by allergenic trees belonging to the orders Fagales, Lamiales, Proteales, and Pinales. Over 25 years ago, the gene encoding the major birch pollen allergen Bet v 1 was the first such gene to be cloned and its product characterized. Since that time, 53 tree pollen allergens have been identified and acknowledged by the WHO/IUIS allergen nomenclature subcommittee. Molecule‐based profiling of allergic sensitization has helped to elucidate the immunological connections of allergen cross‐reactivity, whereas advances in biochemistry have revealed structural and functional aspects of allergenic proteins. In this review, we provide a comprehensive overview of the present knowledge of the molecular aspects of tree pollen allergens. We analyze the geographic distribution of allergenic trees, discuss factors pivotal for allergic sensitization, and describe the role of tree pollen panallergens. Novel allergenic tree species as well as tree pollen allergens are continually being identified, making research in this field highly competitive and instrumental for clinical applications.

Reduction of the number of major representative allergens: from clinical testing to 3-dimensional structures

Vast amounts of allergen sequence data have been accumulated, thus complicating the identification of specific allergenic proteins when performing diagnostic allergy tests and immunotherapy. This study aims to rank the importance/potency of the allergens so as to logically reduce the number of allergens and/or allergenic sources. Meta-analysis of 62 allergenic sources used for intradermal testing on 3,335 allergic patients demonstrated that in southern China, mite, sesame, spiny amaranth, Pseudomonas aeruginosa, and house dust account for 88.0% to 100% of the observed positive reactions to the 62 types of allergenic sources tested. The Kolmogorov-Smironov Test results of the website-obtained allergen data and allergen family featured peptides suggested that allergen research in laboratories worldwide has been conducted in parallel on many of the same species. The major allergens were reduced to 21 representative allergens, which were further divided into seven structural classes, each of which contains similar structural components. This study therefore has condensed numerous allergenic sources and major allergens into fewer major representative ones, thus allowing for the use of a smaller number of allergens when conducting comprehensive allergen testing and immunotherapy treatments.

The spectrum of olive pollen allergens. From structures to diagnosis and treatment

Olive tree is one of the main allergy sources in Mediterranean countries. The identification of the allergenic repertoire from olive pollen has been essential for the development of rational strategies of standardization, diagnosis, and immunotherapy, all of them focused to increase the life quality of the patients. From its complex allergogram, twelve allergens - Ole e 1 to Ole e 12 - have been identified and characterized to date. Most of them have been cloned and produced as recombinant forms, whose availability have allowed analyzing their three-dimensional structures, mapping their T-cell and B-cell epitopes, and determining the precise allergenic profile of patients for a subsequent patient-tailored immunotherapy. Protein mutant, hypoallergenic derivatives, or recombinant fragments have been also useful experimental tools to analyze the immune recognition of allergens. To test these molecules before using them for clinic purposes, a mouse model of allergic sensitizations has been used. This model has been helpful for assaying different prophylactic approaches based on tolerance induction by intranasal administration of allergens or hypoallergens, used as free or integrated in different delivery systems, and their findings suggest a promising utilization as nasal vaccines. Exosomes - nanovesicles isolated from bronchoalveolar lavage fluid of tolerogenic mice - have shown immunomodulatory properties, being able to protect mice against sensitization to Ole e 1.

A non-allergenic Ole e 1-like protein from birch pollen as a tool to design hypoallergenic vaccine candidates

Recombinant DNA technology offers several approaches to convert allergens into hypoallergenic derivatives that can represent the basis of novel, safer and more effective forms of allergy vaccines. In this context, we used a new strategy for the design of a hypoallergenic derivative of Ole e 1, the main allergen of olive pollen. By screening a cDNA library from birch pollen, the clone BB18, encoding the birch counterpart of Ole e 1, was identified. In this study, BB18 has been produce in Pichia pastoris as a recombinant protein and immunologically characterized. The well-established non-allergenic properties of BB18 were used to generate a genetic variant of Ole e 1, named OB(55-58), by site-direct mutagenesis of four residues (E(55)V(56)G(57)Y(58)) in an IgE/IgG epitope of Ole e 1 by the corresponding ones in BB18 (SDSE). OB(55-58) was expressed in P. pastoris, purified to homogeneity and analyzed for IgE-reactivity by means of ELISA using sera from olive pollen allergic patients and rat basophil activation assay. T cell reactivity was assayed in a mouse model of Ole e 1 sensitization. The mutant OB(55-58) exhibited an impaired IgE reactivity, but not affected T cell reactivity, compared to wild type rOle e 1. This study emphasizes the usefulness of BB18 as a tool for epitope mapping and for engineering hypoallergenic derivatives of Ole e 1 as vaccine candidates for allergy prevention and treatment.

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.

Hypoallergenic mutants of Ole e 1, the major olive pollen allergen, as candidates for allergy vaccines

BACKGROUND

The C-terminal region of Ole e 1, a major allergen from olive pollen, is a dominant IgE-reactive site and offers a target for site-directed mutagenesis to produce variants with reduced IgE-binding capability.

OBJECTIVE

To evaluate in vitro and in vivo the immunogenic properties of three engineered derivatives of Ole e 1.

METHODS

One point (Y141A) and two deletion (135Delta10 and 140Delta5) mutants were generated by site-directed mutagenesis of Ole e 1-specific cDNA and produced in Pichia pastoris. Ole e 1 mutants were analysed for IgE reactivity by ELISA using sera from olive pollen-allergic patients. Their allergenicity was also investigated in both a mouse model of allergic sensitization and in basophil activation assays. IgG1 response was assayed by immunoblotting and competitive ELISA. T cell reactivity was evaluated by proliferation assays and cytokine production in splenocyte cultures.

RESULTS

The 135Delta10 mutant showed the strongest reduction in the IgE-binding capability of sera from olive pollen-allergic patients. Rat basophil leukaemia assays identified the deletion mutant 135Delta10 as the variant with the lowest beta-hexosaminidase-releasing capacity. Furthermore, the same 135Delta10 mutant induced the lowest IgE levels in a BALB/c mouse model of sensitization. All Ole e 1 mutants retained their allergen-specific T cell reactivity. Immunization of mice with the mutants induced IgG1 antibodies, which cross-reacted with Ole e 1 and Ole e 1-like allergens from ash, lilac and privet pollens. The ability of the human IgE to block the binding of anti-Ole e 1 mutant-specific mouse IgG1 antibodies to natural Ole e 1 demonstrated that Ole e 1 mutants are able to induce in vivo antibodies reactive to the natural allergen.

CONCLUSION

The 135Delta10 mutant with reduced allergenicity, intact T cell reactivity and capacity to induce blocking antibodies could provide a suitable candidate vaccine for efficient and safer therapy of olive pollen allergy.

Emerging pollen allergens

Numerous pollen allergens have been reported over the last few years. Most of them belong to well-known families of proteins but some others constitute the first member of new allergenic families. Some of the factors that can contribute to the detection and identification of new pollen allergens are: a) advances in the technology tools for molecular analysis; and b) the deep knowledge of many allergenic sources. The combination of these factors has provided vast information on the olive pollen allergogram and the identification of minor allergens that become major ones for a significant population. The close taxonomical relationship between olive tree and ash -both Oleaceae- has permitted to identify Fra e 1 (the Ole e 1-like allergen) in ash pollen and to detect the presence of protein homologues of Ole e 3 and Ole e 6. In the other hand, extensive areas of south Europe are suffering an increasing desertification. As a consequence of this, new botanical species are spontaneously growing in these areas or being used in greening ground programs: Chenopodium album and Salsola kali are some examples recently recognized as allergenic woods. The identification of the complete panel of allergens from the hypersensitizing sources might help to develop more accurate diagnosis, and efficient and safer therapy tools for Type-I allergic diseases.

Detection of airborne allergen (Ole e 1) in relation to Olea europaea pollen in S Spain

BACKGROUND

In recent years, it has been demonstrated that the air carries not only airborne pollen but also plant particles of smaller size that have allergenic activity, and, being within the respirable range, these particles can trigger rapid attacks in the lower respiratory tract. The study of particles according to size (0.7-40 micro m) could provide valuable information on the real allergenic activity in the atmosphere.

OBJECTIVE

The purpose of this study was to analyse the dynamics of airborne Olea europaea pollen in contrast to the allergenic activity of Ole e 1 in the atmosphere.

METHODS

The analyses were carried out with a Hirst-type volumetric collector and a cascade impactor simultaneously during the MPS of the olive. The indirect ELISA was used to detect the allergenic activity. The sampling was performed in Granada city centre (S Spain), in the Science Faculty building on the University of Granada from 30 April to 26 June 2005.

RESULTS AND CONCLUSIONS

This research demonstrates that both the allergenic activity as well as the pollen particles follow in a similar curve, except in periods before or succeeding the main Olea pollen season. The study of the distribution of the allergenic particles according to their sizes reveals that the highest concentrations are between 3.3 and <0.7 micro m, thus indicating that allergenic activity primarily involves paucimicronic particles.

Isolation of the main allergen Fra e 1 from ash (Fraxinus excelsior) pollen: comparison of the natural and recombinant forms

BACKGROUND

Fra e 1 is a major allergen for ash pollen-sensitized individuals in northern and central Europe. It belongs to the Ole e 1-like family and displays high cross-reactivity with taxonomically related members.

OBJECTIVES

To isolate and characterize natural Fra e 1 (nFra e 1) from ash pollen and to compare its structural, antigenic, and allergenic properties with those of its recombinant form (rFra e 1).

METHODS

The allergen was isolated by means of gel permeation chromatography and reverse-phase high-performance liquid chromatography columns. Molecular characterization was performed by means of Edman degradation, mass spectrometry, circular dichroism, concanavalin A lectin reaction, and anti-horseradish peroxidase polyclonal antibody. Immunologic characterization was performed using immunoblotting and enzyme-linked immunosorbent assay, inhibition experiments, and histamine release assays with serum samples from allergic patients with well-known reactivity to Fra e 1 or Ole e 1 and with polyclonal antiserum and monoclonal antibodies against Ole e 1. The protein used as a reference was rFra e 1, which was produced in the yeast Pichia pastoris.

RESULTS

Purified nFra e 1 appeared as 5 variants with different glycosylation degrees. Both nFra e 1 and rFra e 1 were equivalently folded as deduced from the spectroscopic analysis using circular dichroism. Both molecules share the antigenic and allergenic epitopes after the purification process, and the glycan group of nFra e 1 is a potential epitope. Natural Fra e 1 displayed strong cross-reactivity with Ole e 1.

CONCLUSIONS

Natural Fra e 1 is a heterogeneously glycosylated protein with high allergenic relevance. It displays structural, antigenic, and allergenic similarity with rFra e 1. Both proteins could be used for clinical purposes.

Analysis of IgE and IgG B-cell immunodominant regions of Ole e 1, the main allergen from olive pollen

Ole e 1 is a major allergen from olive pollen with an IgE-binding frequency around 80% among allergic population. Its diagnostic value has been demonstrated, and cross-reactive allergens have been found in ash, lilac and privet. We sought to determine IgE- and IgG-binding regions of Ole e 1. Ole e 1-specific polyclonal antiserum and sera from patients allergic to olive pollen were used to analyze IgG and IgE epitopes, respectively. Short overlapping synthetic peptides covering the complete sequence of Ole e 1 and point mutants of these peptides bound to membranes, as well as long recombinant peptides fused to GST were used in dot blot immunostaining and ELISA. Skin prick tests were performed on 14 allergic patients to assay the response in vivo to the recombinant fusion peptides. Residues at positions 8-11, 29, 32, 33, 55-59, 70, 107-110, 112, 120, 123, 141 of Ole e 1 sequence were found to be antigenically relevant in the IgG-binding. Although amino acids K137, L138, G139, Y141 and P142 were involved in the IgE-recognition of a pool of sera from allergic individuals, the response to the IgEs seemed to be preferentially conformational. IgE-binding capability of recombinant GST-fused peptide T114-M145 was demonstrated by in vivo (prick test) and in vitro (ELISA) experiments. Major IgG and IgE-binding regions of Ole e 1 have been identified being the C-terminal an immunodominant region. These data could help to design hypoallergenic forms of the allergen.

Cloning, expression, and clinical significance of the major allergen from ash pollen, Fra e 1

BACKGROUND

Ash tree, an Oleaceae member, is considered an important source of pollen allergy in Central Europe. Fra e 1 is a protein of the Ole e 1-like family, which regulates pollen tube growth. It has been suggested to be a relevant allergen from ash pollen.

OBJECTIVE

Cloning Fra e 1-cDNA and overproducing a properly folded recombinant allergen to analyze its clinical significance.

METHODS

Fra e 1-encoding cDNA was amplified by PCR, cloned in Escherichia coli , and sequenced. The recombinant allergen was produced in Pichia pastoris and used in immunoblotting, ELISA, histamine release, and skin prick tests. Sera and blood cells from patients sensitized to ash pollen as well as anti-Ole e 1 monoclonal and polyclonal antisera were used.

RESULTS

Recombinant Fra e 1 (rFra e 1) is a glycoprotein of 145 amino acids exhibiting 82%, 88%, and 91% identity with Syr v 1, Ole e 1, and Lig v 1, allergens of the Oleaceae family. It was secreted to the extracellular medium of the yeast cultures and purified by means of 3 chromatographic steps. IgG from Ole e 1-specific antibodies recognized rFra e 1. IgE antibodies from ash-sensitized patients bound to rFra e 1 with a prevalence of 75%. The recombinant allergen induced histamine release. Twenty-nine of 30 ash-sensitized patients were positive to rFra e 1 by skin prick tests.

CONCLUSION

Fra e 1 is a relevant allergen in ash pollen sensitization. It has been efficiently produced in P pastoris and could be used in diagnosis.

Ole e 1, the major allergen from olive (Olea europaea L.) pollen, increases its expression and is released to the culture medium during in vitro germination

Ole e 1 is a well-characterized allergenic protein from olive pollen. This paper examines its presence and that of its transcripts during in vitro pollen germination and pollen tube growth. A significant increase of the protein was detected after the emergence of the pollen tube, whereas part of the protein was released into the culture medium throughout pollen germination. A slight increase in the number of Ole e 1 transcripts was also detected prior to the described rise in the protein level. Within the pollen tube, the allergen was localized in the subapical region, mainly in the lumen of endoplasmic reticulum cisternae. Ole e 1 was also localized extracellularly in the vicinity of the pollen tube cell wall. These findings are discussed regarding the biological role attributed to the protein during pollen hydration and pollen tube growth and in terms of their importance for the understanding of the allergenic response in humans. On the basis of recent findings for the LAT52 protein in tomato, we propose that the homologous Ole e 1 protein might participate in a similar signal transduction pathway in olive, to control pregermination and pollen tube emergence and guidance.

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.

Influence of the 3D-conformation, glycan component and microheterogeneity on the epitope structure of Ole e 1, the major olive allergen. Use of recombinant isoforms and specific monoclonal antibodies as immunological tools

Ole e 1 is the main allergen of olive pollen, which is a major cause of pollinosis in countries of the Mediterranean area. Nine Ole e 1-specific murine monoclonal antibodies (mAbs), as well as two Ole e 1-isoforms and two Ole e 1-like allergens from lilac and privet, all of them obtained in Pichia pastoris by recombinant methods, have been used as tools to determine the role of the three-dimensional (3D)-folding, the glycan component and several point changes of the amino acid sequence in the binding of murine IgG mAbs and human IgE to the olive allergen. Seven mAb families (F1-F7) were established, two of which (F1 and F2) recognize continuous epitopes. The carbohydrate moiety of Ole e 1 was involved in the binding to F2 and F4, whereas F3 and F7 were able to bind to all Ole e 1 variants. The remaining families of IgG murine antibodies exhibited different affinities for the antigens assayed in a native or denatured conformation. Although the binding of human IgE to Ole e 1 was not affected by heat treatment, it was shown to be strongly dependent on the integrity of the disulfide bridges and was partially inhibited by F3-F7 IgG antibodies, their individual values ranging from 12 to 31% and reaching 53% with their mixture. The IgE from sera of olive-allergic patients showed a significant diversity of binding capacity to the members of the Ole e 1-like family due to the microheterogeneity of their polypeptide sequences, in spite of their highly conserved primary structures. Whereas one of the isoforms of Ole e 1 exhibits a highly similar behavior to the natural form, being a putative molecule for diagnostic purposes, other ones can be considered as hypoallergenic variants of this allergen and, thus, potential candidates to be used in immunotherapy.

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.

The allergen profile of ash (Fraxinus excelsior) pollen: cross-reactivity with allergens from various plant species

BACKGROUND

Ash, a wind-pollinated tree belonging to the family Oleaceae, is distributed world-wide and has been suggested as a potent allergen source in spring time.

OBJECTIVE

The aim of this study was to determine the profile of allergen components in ash pollen in order to refine diagnosis and therapy for patients with sensitivity to ash pollen

METHODS

The IgE reactivity profile of 40 ash pollen-allergic patients was determined by immunoblotting. Antibodies raised to purified pollen allergens from tree and grass pollens were used to identify cross-reactive structures in ash pollen extract. IgE immunoblot inhibition studies were performed with recombinant and natural pollen allergens to characterize ash pollen allergens and to determine the degree of cross-reactivity between pollen allergens from ash, olive, birch, grasses and weeds.

RESULTS

The allergen profile of ash pollen comprises Fra e 1, a major allergen related to the major olive allergen, Ole e 1, and to group 11 grass pollen allergens, the panallergen profilin, a two EF-hand calcium-binding protein, a pectinesterase-like molecule and an allergen sharing epitopes with group 4 grass pollen allergens. Thus, the relevant allergens of ash are primarily allergens that share epitopes with pollen allergens from other tree, grass and weed species.

CONCLUSIONS

Allergic symptoms to ash pollen can be the consequence of sensitization to cross-reactive allergens from other sources. The fact that ash pollen-allergic patients can be discriminated on the basis of their specific IgE reactivity profile to highly or moderately cross-reactive allergens has implications for the selection of appropriate forms of treatment.

Immunological and molecular characterization of the major allergens from lilac and privet pollens overproduced in Pichia pastoris

The main allergens from privet and lilac pollens, Lig v 1 and Syr v 1, are proteins homologous to Ole e 1 and have been shown to be involved in cross-reactivity. To overproduce the correctly folded Lig v 1 and Syr v 1 allergens and to study their immunological properties in comparison with those of their natural counterparts. The yeast Pichia pastoris was used as an expression system to produce these recombinant allergens. The proteins were isolated by ion-exchange and size-exclusion chromatographies. Amino acid quantifying, Edman degradation, mass spectrometry and circular dichroism were carried out to obtain molecular properties of the recombinant proteins. Anti-Ole e 1 monoclonal and polyclonal antibodies, as well as sera from patients allergic to olive pollen, were used in immunoblotting and ELISA for immunological characterization. Recombinant Lig v 1 and Syr v 1 were secreted at high yield to the extracellular medium of the yeast. The purified proteins displayed the native conformation, as deduced from their spectroscopic properties and binding ability to an IgG monoclonal antibody. The recombinant allergens behaved similarly to their natural counterparts when they were analysed against Ole e 1-specific antibodies. IgE and IgG binding properties of lilac and privet allergens to olive allergic sera and Ole e 1-specific antibodies indicated that these molecules share common B-cell epitopes with Ole e 1. P. pastoris yeast is an appropriate system for the efficient production of Ole e 1-like allergens, which could be used as analogous allergens and predictors of clinical sensitization.

Allergenic cross-reactivity of olive pollen

BACKGROUND

Sera of patients allergic to olive (Olea europaea) pollen were used to analyze the IgE cross-reactivity between olive-pollen extract and other pollens obtained from phylogenetically unrelated species.

METHODS

We used IgE immunostaining of pollen extracts blotted to nitrocellulose membranes after SDS-PAGE and inhibition analysis of this binding.

RESULTS

A high inhibition of the IgE binding on olive-pollen extract was exhibited by birch, mugwort, pine, and cypress pollens, suggesting that these extracts contain proteins which share common epitopes and thus can be recognized by olive-allergic sera. IgE binding to Gramineae pollen extracts was not inhibited by olive-pollen extract, indicating a primary sensitization of the patients to these species. From the inhibition assays, the presence of an allergen of 45 kDa in the olive pollen, which has no homologous counterparts in other allergenic species, has been inferred.

CONCLUSIONS

Olive pollen contains allergens which cross-react with pollens from unrelated species, a fact that could simplify the diagnosis and treatment of pollinosis.

Assignment of the disulfide bonds of Ole e 1, a major allergen of olive tree pollen involved in fertilization

The most prevalent allergen from olive tree pollen, Ole e 1, consists of a single polymorphic polypeptide chain of 145 amino acids which includes six cysteine residues at positions 19, 22, 43, 78, 90 and 131. By using an homogeneous form of the allergen expressed in Pichia pastoris, the array of the disulfide bridges has been elucidated. Specific proteolysis with thermolysin and reverse-phase HPLC separation of the peptides allowed the determination of the disulfide bond between Cys43 and Cys78. Another thermolytic product, which contained three peptides linked by the remaining four cysteines, was digested with Glu-specific staphylococcal V8 protease and the products isolated by reverse-phase HPLC. Amino acid compositions and Edman degradation of the peptide products indicated the presence of the disulfide bonds at Cys19-Cys90 and Cys22-Cys131. These data can help in the analysis of the three-dimensional structure of the protein as well as in studies of its allergenic determinants.