Quantitation of the major allergen of several Parietaria pollens by an anti-Par 1 monoclonal antibody-based ELISA. Analysis of crossreactivity among purified Par j 1, Par o 1 and Par m 1 allergens

Lipid nanoparticles as delivery vehicles for the Parietaria judaica major allergen Par j 2

Parietaria pollen is one of the major causes of allergic reaction in southern Europe, affecting about 30% of all allergic patients in this area. Specific immunotherapy is the only treatment able to modify the natural outcome of the disease by restoring a normal immunity against allergens. The preparation of allergen-solid lipid nanoparticles as delivery vehicles for therapeutic proteins, P. judaica major allergen Par j 2, was investigated. The Par j 2 allergen was expressed in a large amount in Escherichia coli and purified to homogeneity. Its immunological properties were studied by western blotting and enzyme-linked immunosorbent assay inhibition. Solid lipid nanoparticles were obtained by water-in-oil-in-water multiple emulsion method and characterized in terms of mean size and surface charge. These systems (approximately 250 nm diameter and negative surface charge) incorporated recombinant Par j 2 with 40% or greater efficiency. Moreover, the endotoxin level and anaphylactic activity of the empty solid lipid nanoparticles and recombinant Par j 2-loaded solid lipid nanoparticles were evaluated by looking at the overexpression of CD203c marker on human basophils. These results demonstrate that recombinant Par j 2-nanoparticles could be proposed as safe compositions for the development of new therapeutic dosage forms to cure allergic reactions.

Isolation, expression and immunological characterization of a calcium-binding protein from Parietaria pollen

The diagnosis and therapy of allergic disorders are usually performed with crude extracts which are a heterogeneous mixture of proteins with different allergenic potency. The knowledge of the allergenic composition is a key step for diagnostic and therapeutic options. Parietaria judaica pollen represents one of the main sources of allergens in the Mediterranean area and its major allergens have already been identified (Par j 1 and Par j 2). In addition, inhibition studies performed using a calcium-binding protein (CBP) from grass pollen (Phl p 7) showed the presence of a homologue of this cross-reactive allergen in the Parietaria extract. Screening of a cDNA library allowed us to isolate a 480bp cDNA containing the information for an 87 AA long protein with high level of homology to calcium-binding proteins from other allergenic sources. It was expressed as a recombinant allergen in Escherichia coli and purified by affinity chromatography. Its expression allowed us to study the prevalence of this allergen in a population of allergic patients in southern Europe. Immunoblotting and inhibition studies showed that this allergen shares a pattern of IgE epitopes in common with other 2-EF-hand calcium-binding proteins from botanically non-related species. The immunological properties of the Pj CBP were investigated by CD63 activation assay and CFDA-SE staining. In conclusion, DNA recombinant technology allowed the isolation, expression and immunological characterization of a cross-reactive calcium-binding protein allergen from Parietaria judaica pollen.

Immunology

The concept of forbidden foods that should not be eaten goes back to the Garden of Eden and apart from its religious meanings it may also have foreshadowed the concept of foods that can provoke adverse reactions. Thus we could say that allergic diseases have plagued mankind since the beginning of life on earth. The prophet Job was affected by a condition that following the rare symptoms described by the Holy Bible might be identified as a severe form of atopic dermatitis (AD). The earliest record of an apparently allergic reaction is 2621 B.C., when death from stinging insects was first described by hieroglyphics carved into the walls of the tomb of Pharaoh Menes depicting his death following the sting of a wasp. In 79 A.D., the death of the Roman admiral Pliny the Elder was ascribed to the SO₂-rich gases emanating from the eruption of Mount Vesuvius. Hippocrates (460–377 B.C.) was probably the first to describe how cow’s milk (CM) could cause gastric upset and hives, proposing dietetic measures including both treatment and prevention for CM allergy.

Allergenic proteins in Urtica dioica, a member of the Urticaceae allergenic family

BACKGROUND

Allergy to the pollen of flowering plant species significantly affects the health of people in many parts of the world. Pollens of related genera usually share common antigens and are often, but not always, cross-reactive. Several studies have shown that Parietaria pollen is one of the most common causes of pollinosis in the Mediterranean area, whereas Urtica has no allergenic significance.

OBJECTIVES

To report on the localization of Parietaria judaica major allergen in Urtica dioica pollen grains and on the detection of allergenic proteins in U. dioica pollen grains during the hydration-activation process.

METHODS

A combination of transmission electron microscopy and immunocytochemical methods was used to locate allergenic proteins in U. dioica pollen grains after different periods of hydration-activation using the anti-Par j 1 (4.1.3.) monoclonal antibody and serum samples from allergic patients.

RESULTS

No significant labeling was noted for Parj 1 allergen after 10, 15, and 20 minutes in the walls and cytoplasm. Slight labeling was observed for allergic proteins in the walls of U. dioica after 10 minutes of hydration, and no significant labeling was found after 15 and 20 minutes of hydration.

CONCLUSIONS

Immunocytochemical methods confirmed the absence of cross-reactivity between 2 related genera, Parietaria and Urtica, and the lowest allergenic potential of U. dioica.

Correlation between Olea europaea and Parietaria judaica pollen counts and quantification of their major allergens Ole e 1 and Par j 1-Par j 2

BACKGROUND

In patients with pollinosis, allergic symptoms are often correlated with the number of airborne pollen grains, although this correlation is not always close. The direct measurement of the concentration of aeroallergens has only recently been introduced and is an important advance in public health information systems.

OBJECTIVE

To compare specific quantification of aeroallergens Ole e 1 and Par j 1-Par j 2 Olea and Urticaceae pollen counts.

METHODS

The Hirst method sampler and the Burkard Cyclone sampler were used for pollen count and allergen quantification, respectively. The aerosol was extracted and quantified for Ole e 1 and Par j 1-Par j 2 content using enzyme-linked immunosorbent assay procedures.

RESULTS

Day-to-day variations were observed in both the pollen count and the amount of allergens. Pollen counts and aeroallergen quantification were closely correlated with 99% significance (Olea/Ole e 1: R = 0.892, P < .001; Urticaceae/Par j 1-Par j 2: R = 0.734, P < .001).

CONCLUSION

The technique for the sampling and quantification of aeroallergens presented in this article, based on enzyme-linked immunosorbent assay and applied to the protein extracts directly obtained from the bioaerosol, represents an important advance in the epidemiologic study of allergic respiratory diseases.

A sensitive monoclonal antibody-based enzyme-linked immunosorbent assay to quantify Parietaria judaica major allergens, Par j 1 and Par j 2

BACKGROUND

Parietaria pollen is one of the most important causes of pollinosis in Mediterranean countries. Parietaria judaica pollen extract presents two major allergens, Par j 1 and Par j 2, that belong to the lipid transfer protein family.

OBJECTIVE

To develop an ELISA for quantification of both major allergens of P. judaica pollen extracts, and to assert correlation of these allergens content with the allergenic activity of extracts.

METHODS

Natural Par j 1-Par j 2 allergens were purified by gel filtration, ion exchange, and affinity chromatography and identified by mass spectrometry. Rabbit antisera were obtained using this protein preparation as antigen and used for immunoaffinity purification of nPar j 1-Par j 2. BALB/c mice were immunized with the immunopurified nPar j 1-Par j 2 and after fusion and screening by direct ELISA, 5D4 monoclonal antibody was selected as capture antibody to develop a quantitative two-site ELISA. Bound proteins were detected by a biotinylated Par j 1-Par j 2-specific polyclonal antibody.

RESULTS

The optimized ELISA was developed from 25 to 8000 pg/mL of purified Par j 1-Par j 2, and a linear portion of 200-1000 pg/mL. The intraassay and interassay coefficients of variation were lower than 7% and 14% respectively. The assay was very sensitive and specific as it had a detection limit of 25 pg/mL and did not detect reactivity with the same family plants, as Urtica. Par j 1-Par j 2 allergens content was measured in 14 P. judaica and two P. officinalis pollen extracts showing a significant correlation with their allergenic activity measured by enzyme allergosorbent test inhibition.

CONCLUSIONS

The results proved the usefulness of the two-sandwich ELISA for the standardization of Parietaria pollen extracts intended for clinical use, because of its good correlation with allergenic potency.

Lipid transfer proteins in Parietaria judaica L. pollen grains: immunocytochemical localization and function

Parietariajudaica L. (Urticaceae) pollen is considered one of the most common causes of allergic respiratory symptoms in the Mediterranean area. The localization of lipid transfer proteins (LTPs) in P. judaica mature and hydrated-activated pollen grains was investigated applying a combination of transmission electron microscopy (TEM) with immunocytochemical methods. Our results show that the content of LTPs in P. judaica pollen grains changes during the process of hydration. The localization of judaica LTPs in the cytoplasm and in the lipid bodies associated with vacuoles demonstrated that LTPs represent primarily intracellular proteins. On the other hand, exposure of the pollen grains to germination medium induced the release of LTPs from the pollen grain. Thus, LTPs are cytoplasmic proteins that are secreted to become available for pollen-stigma interactions and probably induce the IgE antibody responses in allergic patients.

Evaluation of Cross-Reactivity between Holoptelea integrifolia and Parietaria judaica

BACKGROUND

Holoptelea integrifolia and Parietaria judaica belong to the family Urticaceae, but are geographically distantly located. H. integrifolia is an important pollen allergen of India and sensitizes almost 10% of the atopic population in Delhi. P. judaica, on the other hand, is a very dominant pollen allergen of the Mediterranean region, sensitizing almost 80% of the allergic population. Since both these important pollen allergens belong to the family Urticaceae, the objective of the present study was to assess cross-reactivity between these two pollen allergens from different geographical regions.

METHODS

Cross-reactivity between these two pollen allergens was assessed on the basis of skin prick tests and ELISA, ELISA inhibition and immunoblot inhibition studies.

RESULTS

Out of 44 atopic Indian patients skin prick tested with H. integrifolia extract, 34% were found to be sensitized. All the patients sensitized to H. integrifolia also showed varying degrees of skin positivity to P. judaica pollen extract. ELISA and ELISA inhibition studies suggested strong cross-reactivity between H. integrifolia and P. judaica pollen. Immunoblot inhibition studies revealed that 14-, 16-, 28-, 38-, 42- and 46-kDa proteins are the cross-reactive proteins in H. integrifolia and P. judaica. However, Par j 1, the major allergen of P. judaica, is absent in H. integrifolia pollen.

CONCLUSION

H. integrifolia and P. judaica pollens share cross-reactive as well as unique epitopes. The major allergen of P. judaica, Par j 1, seems to be absent in H. integrifolia pollen allergen.

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

BACKGROUND

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

OBJECTIVE

To assess the pattern of sensitization to an array of mugwort allergens in a Mediterranean population, and to study the cross-reactivity of Art v 3 with Pru p 3 and Par j 1, relevant LTP allergens in the area.

METHODS

Skin prick test was performed with whole extracts (A. vulgaris, Parietaria judaica and peach) and pure natural allergens Art v 1, Art v 3, Art v 60 kDa and Par j 1 in 24 mugwort-allergic patients from a Mediterranean area. In vitro assays included measurement of specific IgE and ELISA inhibition among LTP allergens.

RESULTS

The three Artemisia allergens elicited a positive skin response in 70-80% of the patients. Seven patients were clearly sensitized to Par j 1 and 11 to Pru p 3. There was no correlation between Par j 1 and Pru p 3 sensitization, but a highly significant correlation was found between peach extract and Art v 3 as regards the skin response. No IgE cross-reactivity was observed between Art v 3/Par j 1 or Pru p 3/Par j 1. In contrast, Art v 3 significantly inhibited the binding to Pru p 3 of IgE from three patients' sera out of six studied, but Pru p 3 was not able to inhibit the IgE binding to Art v 3.

CONCLUSION

Art v 3 is a major mugwort allergen and in some patients with IgE to both Art v 3 and Pru p 3, Art v 3 behaves as the primary sensitizing agent.

Proteomics of allergens

The present state of proteomics research is generally outlined and the character of allergenic compounds briefly elucidated. The principles of experimental approaches to isolation, purification, identification and characterization of allergens and to monitoring of their biological activity are described, with emphasis on the most modern methods. Selected examples are given for illustration and important results are summarized in tables.

Quantification in mass units of group 1 grass allergens by a monoclonal antibody-based sandwich ELISA

BACKGROUND

Grass pollen extracts currently used for allergy diagnosis and immunotherapy are a complex mixture of proteins of which only a few have allergenic activity. Lol p 1 is one of the most important allergens in grass pollen extracts.

OBJECTIVES

To develop a two-site enzyme-linked immunosorbent assay for the quantification of Lol p 1 and other group 1 allergens from grass species, and to assess its suitability for quantifying this group of allergens.

METHODS

Balb/c mice immunized with recombinant Lol p 1 were used for the production of monoclonal antibodies. Screening of hybridomas was performed by direct ELISA, and selected monoclonal antibodies were immobilized on ELISA plates and incubated with samples containing group 1 allergens. Bound allergens were detected by a combination of biotinylated Lol p 1-specific monoclonal antibody and peroxidase-streptavidin conjugate.

RESULTS

The assay is based on three Lol p 1-specific monoclonal antibodies with different epitope specificities. The optimized ELISA measured Lol p 1 concentrations ranging from 125 to 1000 ng/mL and could quantify group 1 allergen from grass species belonging to the Pooidea subfamily. The assay does not depend on anti-sera production or availability of human sera and thus reactives can be produced in unlimited amounts.

CONCLUSION

This sensitive and specific Lol p 1 assay will be helpful both for quantifying the group 1 allergen content of Pooideae pollen extracts intended for clinical use and for studying cross-reactivities among pollen extracts.

Monoclonal antibodies against the major allergen of Plantago lanceolata pollen, Pla l 1: affinity chromatography purification of the allergen and development of an ELISA method for Pla l 1 measurement

BACKGROUND

Plantago lanceolata (English plantain) pollen is a relevant cause of pollinosis in temperate regions. The major allergen of this pollen, Pla l 1, is recognized by the specific IgE from more than 80% of plantain-sensitive patients. It displays significant sequence homology with the major olive-pollen allergen Ole e 1. The objective was to develop a monoclonal antibody-based ELISA to quantify Pla l 1, and to assess the correlation of Pla l 1 content with the biologic activity of plantain pollen extracts. We also aimed to establish the specificity of the monoclonal antibodies against the potentially cross-reactive allergen Ole e 1, and to investigate the presence of Pla l 1-like proteins in psyllium and melon that have been reported to cross-react with P. lanceolata pollen.

METHODS

After fusion of myeloma cells with spleen cells from a BALB/c mouse, two Pla l 1-specific monoclonal antibodies secreting hybridomas were selected, and the antibodies characterized. One of them (2A10) was used as the capture antibody in an ELISA for Pla l 1 quantitation. An anti-P. lanceolata rabbit serum was used as the second antibody. Pla l 1 was purified by immunoaffinity chromatography and used as the standard in the assay.

RESULTS

The ELISA developed was highly reproducible and sensitive, with a detection limit of 0.1 ng/ml, and a practical working range of 0.4-12 ng/ml. The specificity was demonstrated against a large battery of allergens, including Ole e 1. The concentration of Pla l 1 was measured in 19 extracts of P. lanceolata pollen, and a good correlation was observed between the Pla l 1 content and the allergenic activity of the extracts. Pla l 1 was not detected in psyllium or melon extracts.

CONCLUSION

The results prove the usefulness of the Pla l 1-ELISA for the standardization of extracts of P. lanceolata pollen intended for clinical use.

A monoclonal antibody specific for a carbohydrate epitope recognizes an IgE-binding determinant shared by taxonomically unrelated allergenic pollens

Carbohydrate epitopes are capable of binding human IgE from allergic subjects and these epitopes play a role in the cross-reactivity between allergens from unrelated sources. A monoclonal antibody (5E6), specific for a carbohydrate epitope detectable on components of Cupressus arizonica pollen extract, has been produced and characterized. To study the relationship between the epitopes recognized by the monoclonal antibody and by IgE from allergic subjects. To investigate the presence of such carbohydrate IgE determinant in extracts from 21 pollen species belonging to 16 taxonomically related and unrelated families, by means of the monoclonal antibody. IgG-depleted fraction from protein G-purified human allergic serum was obtained. The monoclonal antibody and the IgE from the purified fraction were tested on two glycoproteins, polyamine oxidase and ascorbate oxidase, adsorbed on the ELISA plates. The relationship between the monoclonal- and the IgE-recognized epitopes was investigated by ELISA-competition experiments. Analysis of the distribution of this carbohydrate epitope was performed by direct binding of the monoclonal antibody onto the various extracts. The monoclonal antibody and the IgE were able to bind carbohydrate epitopes on the two plant glycoproteins, ascorbate oxidase and polyamine oxidase. Polyamine oxidase shows only one N-glycosilation site whose carbohydrate moiety seems to be composed of a branched chain of seven ordered sugars, i.e. two N-acetyl-D-glucosamine-, three mannose-, one fucose- and one xylose-residues. This structure bears the epitope recognized by mAb 5E6. Human IgE from the IgG-depleted fraction were found capable of inhibiting the monoclonal antibody binding. The allergenic epitope identified was shared by a large number of extracts with different levels of reactivity (OD490 ranging from 0.110 to 2.060). Our data support the finding that a monoclonal antibody specific for a carbohydrate epitope of Cupressus arizonica pollen extract detects an epitope which is also recognized by IgE from allergic subjects. This characterized reagent could be a useful tool for studying distribution of cross-reactive carbohydrate determinants in allergenic pollen extracts and their components.

Quantification of profilins by a monoclonal antibody-based sandwich ELISA

Profilins are plant allergens responsible for cross-reactivities in pollen and fruit-allergic patients. A two-site enzyme-linked immunosorbent assay has been developed for the quantification of profilins and its suitability for quantifying profilin in different plant extracts has been evaluated. The assay is based on two profilin-specific monoclonal antibodies (mAbs) with different epitope specificities. These antibodies were immobilized on ELISA plates and incubated with samples containing profilin. Bound profilin was detected by a combination of biotinylated profilin-specific antiserum and peroxidase-streptavidin conjugate. The optimized ELISA measured profilin concentrations ranging from 4 to 250 ng/ml and could quantify profilins from plant species of a variety of different botanical families. No reactivity to mites, molds, or crustaceans was detected, suggesting that the immunoassay is plant-specific. The results indicate that this sensitive profilin-assay will be helpful both for quantifying the profilin content of allergenic extracts intended for clinical use and for studying cross-reactivities between pollen extracts.

Arizona cypress (Cupressus arizonica) pollen allergens. Identification of cross-reactive periodate-resistant and -sensitive epitopes with monoclonal antibodies

Species of the Cupressaceae family are a worldwide cause of respiratory allergies. We used monoclonal antibodies (mAbs) to investigate the presence and the nature of cross-reacting epitopes shared by various components within Cupressus arizonica pollen extract (CaE) or by CaE and pollen extract from C. sempervirens (CsE). mAbs were produced in mice immunized with whole CaE (4A6 and 5E6) or with the major allergen components (2D5). Their reactivity was investigated by ELISA and immunoblotting before and after CaE periodate treatment. Cross-reactivity was evaluated by ELISA inhibition and immunoblotting. mAbs 2D5 and 4A6 recognized periodate-resistant epitopes, whereas the mAb 5E6 reacted with a periodate-sensitive determinant. The former mAbs recognized epitopes present on CaE major allergen and also shared by other components. mAb 5E6 showed a spread reactivity on CaE, with exclusion of the major allergen. When the three mAbs were tested with CsE, a restricted pattern of reactivity to mAbs 2D5 and 4A6 was obtained, whereas mAb 5E6 maintained a spread reactivity. The CaE major allergen is represented by two components recognized by human IgE and sharing common epitopes, as proven by mAbs reactivity. The use of these mAbs demonstrates that cross-reactivity within CaE components and between CaE and CsE is due to the presence of periodate-sensitive as well as -resistant epitopes.

Highly sensitive and specific ELISA with monoclonal antibody capture to measure Dermatophagoides farinae 1-specific IgE

BACKGROUND

Dermatophagoides farinae (Der f) is a major allergen in Der f extract. Measurement of Der f I-specific IgE has not been commonly used, because of the difficulty in obtaining large amounts of purified Der f 1.

OBJECTIVES

To improve the diagnosis of dust mite allergy, we wanted to develop an ELISA to measure Der f 1-specific IgE in which purified Der f 1 is not required.

METHODS

Using a monoclonal antibody (mAb) against Der f 1, a mAb-capture ELISA was developed. Microplates coated with the mAb were sequentially incubated with crude Der f extract, serum samples, goat anti-human IgE, and conjugated rabbit anti-goat IgG. A conventional ELISA using purified Der f 1 as capture (Der f 1-ELISA) was developed to compare it with the mAb-capture ELISA.

RESULTS

There was a significant correlation between the two ELISAs (r = 0.89, P < .001) with a sensitivity of 0.8 U/mL. Both the assays were inhibited by the crude Der f extract in a dose-dependent manner. Using the two ELISAs, serum Der f 1-specific IgE was evaluated in 12 allergic patients with positive skin tests to Der f extract, 14 allergic patients with negative skin tests to Der f extract, and 15 healthy subjects. The mean Der f 1-IgE and the positivity rate of Der f I-IgE were higher in the mite-allergic group and lower in the healthy group when the mAb-ELISA was used (P < .01) than when the Der f 1-ELISA was used (P < .05).

CONCLUSIONS

Der f 1-specific IgE can be measured by mAb-capture ELISA using crude Der f extract. The mAb-ELISA is more sensitive and specific than the conventional Der f 1-capture ELISA in diagnosing dust mite allergy.

Development of a two-site enzyme-linked immunosorbent assay for alpha-amylase from Aspergillus oryzae based on monoclonal antibodies

A two-site monoclonal antibody ELISA was developed to quantify the allergen Asp o 2 (alpha-amylase from Aspergillus oryzae). Two mAbs recognizing distinct epitopes were selected, enriched by in vitro production in a modular minifermenter and affinity-purified. The first antibody was bound to microtiter plates which were then incubated with samples containing the allergen. Bound allergen was detected using a biotinylated second antibody and peroxidase-polymer-labelled streptavidin. The assay had a sensitivity of 0.6 ng/ml and did not react to high concentrations of wheat and rye flour or yeast proteins. The mAb ELISA will be useful in individual or epidemiological studies of baker's asthma to assess workplace allergen concentrations and the efficacy of allergen exposure prevention. It can be used as a standard assay for the quantification of alpha-amylase and the establishment and control of threshold limits in European bakeries.