Cross-reactivity of pollen allergens

Grassland allergenicity increases with urbanisation and plant invasions

Pollen allergies have been on the rise in cities, where anthropogenic disturbances, warmer climate and introduced species are shaping novel urban ecosystems. Yet, the allergenic potential of these urban ecosystems, in particular spontaneous vegetation outside parks and gardens, remains poorly known. We quantified the allergenic properties of 56 dry grasslands along a double gradient of urbanisation and plant invasion in Berlin (Germany). 30% of grassland species were classified as allergenic, most of them being natives. Urbanisation was associated with an increase in abundance and diversity of pollen allergens, mainly driven by an increase in allergenic non-native plants. While not inherently more allergenic than native plants, the pool of non-natives contributed a larger biochemical diversity of allergens and flowered later than natives, creating a broader potential spectrum of allergy. Managing novel risks to urban public health will involve not only targeted action on allergenic non-natives, but also policies at the habitat scale favouring plant community assembly of a diverse, low-allergenicity vegetation. Similar approaches could be easily replicated in other cities to provide a broad quantification and mapping of urban allergy risks and drivers.

High-Yield Production of the Major Birch Pollen Allergen Bet v 1 With Allergen Immunogenicity in Nicotiana benthamiana

Type I allergy is an immunological disorder triggered by allergens and causes significant health problems. The major allergen of birch pollen is Bet v 1, which belongs to the pathogen-related protein 10 (PR-10) family. Here, we established a rapid and robust method for the production of Bet v 1 in Nicotiana benthamiana leaves, with binding activity to allergic patients' IgE. The Bet v 1 allergen was expressed in N. benthamiana using a strong agroinfiltration-based transient protein expression system, which consists of a deconstructed geminiviral vector system with a double terminator. Five days post-infiltration, the allergen concentration in N. benthamiana leaves was 1.2 mg/g of fresh mass, being this the maximum yield of Bet v 1 in plants reported up to now. A part of plant-derived Bet v 1 was glycosylated. Bet v 1 purified from N. benthamiana or Brevibacillus brevis was used to carry out enzyme-linked immunoassays; both recombinant allergens were found to have comparable binding properties to the IgE of allergic patients. These results suggest that our plant expression system allows rapid and robust production of the allergen, which keeps the immunogenicity.

The effect of geographical and climatic properties on grass pollen and Phl p 5 allergen release

The Poaceae family, including grasses, comprises several cosmopolitan and allergenic species. The aim of this study was to determine the correlations between Poaceae pollen and Phl p 5 allergen concentrations in two cities with different geographical and climatic properties in Turkey. Pollen were collected from Burkard traps in Ankara and Zonguldak. Phl p 5 sampling was carried out between March and October in both 2015 and 2016 using a BGI900 Cascade High Volume Air Sampler (900 L/min.). The concentrations of Phl p 5 were measured by the enzyme-linked immunosorbent assay (ELISA) technique. The annual sum of Poaceae pollen (pollen index) during 2015-2016 was 5454 in Ankara and 4142 in Zonguldak. The total Phl p 5 concentration was 1309 pg/m³ in Zonguldak, whereas it was 8181 pg/m³ in Ankara over 2 years. About 90% of the allergen was found in the fraction with particulate matter (PM) > 10 μm in both cities. It was found that the main meteorological parameter which affected pollen and Phl p 5 was temperature in both stations. Rainfall was also found to be important for Zonguldak, due to its climatic and geographic properties. Lastly, we suggest that the primary wind direction, which is from the south of Zonguldak, could have a 'drift effect' for allergens because of the airborne pollen concentrations and the dates on which the allergen is released into the atmosphere. The wind direction may be an important factor in the distribution of allergen and pollen grains in stations, especially those with a hilly topography.

New biomolecular tools for aerobiological monitoring: Identification of major allergenic Poaceae species through fast real-time PCR

Grasses (Poaceae) are very common plants, which are widespread in all environments and urban areas. Despite their economical importance, they can represent a problem to humans due to their abundant production of allergenic pollen. Detailed information about the pollen season for these species is needed in order to plan adequate therapies and to warn allergic people about the risks they take in certain areas at certain moments. Moreover, precise identification of the causative species and their allergens is necessary when the patient is treated with allergen‐specific immunotherapy. The intrafamily morphological similarity of grass pollen grains makes it impossible to distinguish which particular species is present in the atmosphere at a given moment. This study aimed at developing new biomolecular tools to analyze aerobiological samples and identifying major allergenic Poaceae taxa at subfamily or species level, exploiting fast real‐time PCR. Protocols were tested for DNA extraction from pollen sampled with volumetric and gravimetric methods. A fragment of the matK plastidial gene was amplified and sequenced in Poaceae species known to have high allergological impact. Species‐ and subfamily‐specific primer–probe systems were designed and tested in fast real‐time PCRs to evaluate the presence of these taxa in aerobiological pollen samples. Species‐specific systems were obtained for four of five studied species. A primer–probe set was also proposed for the detection of Pooideae (a grass subfamily that includes also major cereal grains) in aerobiological samples, as this subfamily includes species carrying both grass allergens from groups 1 and 5. These, among the 11 groups in which grass pollen allergens are classified, are considered responsible for the most frequent and severe symptoms.

Comparative and Evolutionary Analysis of Grass Pollen Allergens Using Brachypodium distachyon as a Model System

Comparative genomics have facilitated the mining of biological information from a genome sequence, through the detection of similarities and differences with genomes of closely or more distantly related species. By using such comparative approaches, knowledge can be transferred from the model to non-model organisms and insights can be gained in the structural and evolutionary patterns of specific genes. In the absence of sequenced genomes for allergenic grasses, this study was aimed at understanding the structure, organisation and expression profiles of grass pollen allergens using the genomic data from Brachypodium distachyon as it is phylogenetically related to the allergenic grasses. Combining genomic data with the anther RNA-Seq dataset revealed 24 pollen allergen genes belonging to eight allergen groups mapping on the five chromosomes in B. distachyon. High levels of anther-specific expression profiles were observed for the 24 identified putative allergen-encoding genes in Brachypodium. The genomic evidence suggests that gene encoding the group 5 allergen, the most potent trigger of hay fever and allergic asthma originated as a pollen specific orphan gene in a common grass ancestor of Brachypodium and Triticiae clades. Gene structure analysis showed that the putative allergen-encoding genes in Brachypodium either lack or contain reduced number of introns. Promoter analysis of the identified Brachypodium genes revealed the presence of specific cis-regulatory sequences likely responsible for high anther/pollen-specific expression. With the identification of putative allergen-encoding genes in Brachypodium, this study has also described some important plant gene families (e.g. expansin superfamily, EF-Hand family, profilins etc) for the first time in the model plant Brachypodium. Altogether, the present study provides new insights into structural characterization and evolution of pollen allergens and will further serve as a base for their functional characterization in related grass species.

T-cell epitope conservation across allergen species is a major determinant of immunogenicity

BACKGROUND

Patients with pollen allergies are frequently polysensitized. Pollens contain epitopes that are conserved across multiple species.

OBJECTIVE

We sought to demonstrate that cross-reactive T cells that recognize conserved epitopes show higher levels of expansion than T cells recognizing monospecific epitopes because of more frequent stimulation.

METHOD

RNA was sequenced from 9 pollens, and the reads were assembled de novo into more than 50,000 transcripts. T-cell epitopes from timothy grass (Phleum pratense) were examined for conservation in these transcripts, and this was correlated to their ability to induce T-cell responses. T cells were expanded in vitro with P pratense-derived peptides and tested for cross-reactivity to pollen extracts in ELISpot assays.

RESULTS

We found that antigenic proteins are more conserved than nonimmunogenic proteins in P pratense pollen. Additionally, P pratense epitopes that were highly conserved across pollens elicited more T-cell responses in donors with grass allergy than less conserved epitopes. Moreover, conservation of a P pratense peptide at the transcriptomic level correlated with the ability of that peptide to trigger T cells that were cross-reactive with other non-P pratense pollen extracts.

CONCLUSION

We found a correlation between conservation of peptides in plant pollens and their T-cell immunogenicity within P pratense, as well as their ability to induce cross-reactive T-cell responses. T cells recognizing conserved epitopes might be more prominent because they can be stimulated by a broader range of pollens and thereby drive polysensitization in allergic donors. We propose that conserved peptides could potentially be used in diagnostic or immunomodulatory approaches that address the issue of polysensitization and target multiple pollen allergies.

Major allergen from Amaranthus palmeri pollen is a profilin: Isolation, partial characterisation and IgE recognition

BACKGROUND

Pollens represent a rich source of proteins that are also potential elicitors of IgE-mediated pollen allergy. Sensitisation to panallergens could play an important role in diagnosis and specific immunotherapy, because these molecules are present in different plant pollens and plant foods and have marked structural similarity in different species. Profilins are one of the most common panallergens to be studied because they are responsible for a large number of sensitisations and are clearly related to cross-reactivity and co-sensitisation. This study aimed to isolate and characterise a new allergen of Amaranthus palmeri pollen and to determine its allergenicity.

METHODS

A. palmeri pollen profilin was purified using poly-l-proline-Sepharose affinity chromatography followed by anion exchanger chromatography. Identification of purified protein was carried out by mass spectrometry. Specific IgE was estimated in sera of patients with positive skin prick test to A. palmeri pollen extract, by enzyme-linked immunosorbent assay (ELISA).

PRINCIPAL FINDINGS

Purified protein appeared as a single band at 14 kDa in SDS-PAGE gel. Mass spectrometric analysis of the gel band identified two highly conserved peptides corresponding to allergenic profilins from pollen of other plants. Sera from about 60% of allergic patients have IgE that recognises the purified A. palmeri protein.

CONCLUSION

A 14 kDa protein of A. palmeri pollen was purified and identified as allergenic profilin, which was recognised by sera from pollen allergic patients.

Relevance of a 5-grass sublingual tablet for immunotherapy of patients with grass pollen allergy in North America

Grass pollen allergy is common and clinically consequential in North America. While it is frequently treated with subcutaneous or sublingual immunotherapy, debate remains regarding whether allergen immunotherapy is best carried out using a single representative or multiple cross-reactive allergen(s). Patients are commonly exposed to pollens from multiple allergenic grass species belonging to the Pooideæ subfamily. Beyond the known IgE cross-reactivity, considerable molecular heterogeneity exists with respect to allergen content among grass species, with further evidence that these molecular variants can be detected by the patients' immune system. These observations provide a compelling scientific rationale for the use of mixed pollen allergen extracts to broaden the allergen repertoire, with the aim of reorienting inappropriate immune responses in allergic patients.

Quantitative DNA Analyses for Airborne Birch Pollen

Birch trees produce large amounts of highly allergenic pollen grains that are distributed by wind and impact human health by causing seasonal hay fever, pollen-related asthma, and other allergic diseases. Traditionally, pollen forecasts are based on conventional microscopic counting techniques that are labor-intensive and limited in the reliable identification of species. Molecular biological techniques provide an alternative approach that is less labor-intensive and enables identification of any species by its genetic fingerprint. A particularly promising method is quantitative Real-Time polymerase chain reaction (qPCR), which can be used to determine the number of DNA copies and thus pollen grains in air filter samples. During the birch pollination season in 2010 in Mainz, Germany, we collected air filter samples of fine (<3 μm) and coarse air particulate matter. These were analyzed by qPCR using two different primer pairs: one for a single-copy gene (BP8) and the other for a multi-copy gene (ITS). The BP8 gene was better suitable for reliable qPCR results, and the qPCR results obtained for coarse particulate matter were well correlated with the birch pollen forecasting results of the regional air quality model COSMO-ART. As expected due to the size of birch pollen grains (~23 μm), the concentration of DNA in fine particulate matter was lower than in the coarse particle fraction. For the ITS region the factor was 64, while for the single-copy gene BP8 only 51. The possible presence of so-called sub-pollen particles in the fine particle fraction is, however, interesting even in low concentrations. These particles are known to be highly allergenic, reach deep into airways and cause often severe health problems. In conclusion, the results of this exploratory study open up the possibility of predicting and quantifying the pollen concentration in the atmosphere more precisely in the future.

Grass-specific CD4(+) T-cells exhibit varying degrees of cross-reactivity, implications for allergen-specific immunotherapy

BACKGROUND

Conceptually, allergic responses may involve cross-reactivity by antibodies or T-cells. While IgE cross-reactivity among grass-pollen allergens has been observed, cross-reactivity at the allergen-specific T-cell level has been less documented. Identification of the patterns of cross-reactivity may improve our understanding, allowing optimization of better immunotherapy strategies.

OBJECTIVES

We use Phleum pratense as model for the studying of cross-reactivity at the allergen-specific CD4(+) T cell level among DR04:01 restricted Pooideae grass-pollen T-cell epitopes.

METHODS

After in vitro culture of blood mono-nucleated cells from grass-pollen-allergic subjects with specific Pooideae antigenic epitopes, dual tetramer staining with APC-labelled DR04:01/Phleum pratense tetramers and PE-labelled DR04:01/Pooideae grass homolog tetramers was assessed to identify cross-reactivity among allergen-specific DR04:01-restricted T-cells in six subjects. Direct ex vivo staining enabled the comparison of frequency and phenotype of different Pooideae grass-pollen reactive T-cells. Intracellular cytokine staining (ICS) assays were also used to examine phenotypes of these T-cells.

RESULTS

T-cells with various degrees of cross-reactive profiles could be detected. Poa p 1 97-116 , Lol p 1 221-240 , Lol p 5a 199-218 , and Poa p 5a 199-218 were identified as minimally cross-reactive T-cell epitopes that do not show cross-reactivity to Phl p 1 and Phl p 5a epitopes. Ex vivo tetramer staining assays demonstrated T-cells that recognized these minimally cross-reactive T-cell epitopes are present in Grass-pollen-allergic subjects.

CONCLUSIONS

Our results suggest that not all Pooideae grass epitopes with sequence homology are cross-reactive. Non-cross-reactive T-cells with comparable frequency, phenotype and functionality to Phl p-specific T-cells suggest that a multiple allergen system should be considered for immunotherapy instead of a mono-allergen system.

High IgE sensitization to maize and rice pollen in the highlands of Madagascar

Introduction

Maize and rice are two crops constituting the main food supply in many under-developed and developing countries. Despite the large area devoted to the culture, the sensitization to the pollen from these plants is reported to be low and often considered as an occupational allergy.

Methods

Sixty five Malagasy pollen allergic patients were clinically and immunochemically investigated with regard to maize and rice pollen allergens. Pollen extracts were electrophoretically separated in 1 and 2 dimensions and IgE and IgG reactivities detected upon immunoblotting.

Results

When exploring the sensitization profile of Malagasy allergic patients to maize and rice pollen, it appears that a high proportion of these patients consulting during grass pollinating season were sensitized to both pollen as revealed by skin prick testing (62 vs. 59%) and IgE immunoblotting (85 vs. 40%). Several clinically relevant allergens were recognized by patients’ serum IgE in maize and rice pollen extracts.

Conclusion

The high levels of maize and rice pollen sensitization should be related, in this tropical region, to a specific environmental exposure including i) a proximity of the population to the allergenic sources and ii) a putative exacerbating effect of a highly polluted urban atmosphere on pollen allergenicity. Cross-reactivities between wild and cultivated grasses and also between rice and maize pollen are involved as well as some specific maize sensitizations. The presence of dense urban and peri-urban agriculture, in various African regions and worldwide, could be a high environmental risk factor for people sensitive to maize pollen.

Immunochemical characterization of acacia pollen allergens and evaluation of cross-reactivity pattern with the common allergenic pollens

Pollen from the Acacia has been reported as an important source of pollinosis in tropical and subtropical regions of the world. The aim of this study was to characterize the IgE binding protein of Acacia farnesiana pollen extract and evaluate cross-reactivity with the most allergenic pollens. In this study, pollen extract was fractionated by SDS-PAGE and the allergenic profile was determined by IgE-immunoblotting and specific ELISA using forty-two Acacia allergic patients. Potential cross-reactivity among Acacia and selected allergenic plants was evaluated with ELISA and immunoblotting inhibition experiments. There were several resolved protein fractions on SDS-PAGE which ranged from 12 to 85 kDa. Several allergenic protein bands with molecular weights approximately between 12 and 85 kDa were recognized by IgE-specific antibodies from Acacia allergic patients in the immunoblot assay. The inhibition by the Prosopis juliflora pollen extract was more than those by other pollen extracts. Moreover, the wheal diameters generated by the Acacia pollen extract were highly correlated with those of P. juliflora pollen extracts. The findings suggest that several proteins such as 15, 23, 45, and 50 kDa proteins could be used as diagnostic and therapeutic reagents for patients allergic to A. farnesiana and P. juliflora.

Exploring the spatio-temporal relationship between two key aeroallergens and meteorological variables in the United Kingdom

Constructing accurate predictive models for grass and birch pollen in the air, the two most important aeroallergens, for areas with variable climate conditions such as the United Kingdom, require better understanding of the relationships between pollen count in the air and meteorological variables. Variations in daily birch and grass pollen counts and their relationship with daily meteorological variables were investigated for nine pollen monitoring sites for the period 2000-2010 in the United Kingdom. An active pollen count sampling method was employed at each of the monitoring stations to sample pollen from the atmosphere. The mechanism of this method is based on the volumetric spore traps of Hirst design (Hirst in Ann Appl Biol 39(2):257-265, 1952). The pollen season (start date, finish date) for grass and birch were determined using a first derivative method. Meteorological variables such as daily rainfall; maximum, minimum and average temperatures; cumulative sum of Sunshine duration; wind speed; and relative humidity were related to the grass and birch pollen counts for the pre-peak, post peak and the entire pollen season. The meteorological variables were correlated with the pollen count data for the following temporal supports: same-day, 1-day prior, 1-day mean prior, 3-day mean prior, 7-day mean prior. The direction of influence (positive/negative) of meteorological variables on pollen count varied for birch and grass, and also varied when the pollen season was treated as a whole season, or was segmented into the pre-peak and post-peak seasons. Maximum temperature, sunshine duration and rainfall were the most important variables influencing the count of grass pollen in the atmosphere. Both maximum temperature (pre-peak) and sunshine produced a strong positive correlation, and rain produced a strong negative correlation with grass pollen count in the air. Similarly, average temperature, wind speed and rainfall were the most important variables influencing the count of birch pollen in the air. Both wind speed and rain produced a negative correlation with birch pollen count in the air and average temperature produced a positive correlation.

Glycoproteins are species-specific markers and major IgE reactants in grass pollens

Grass pollen allergic patients are concomitantly exposed and sensitized to pollens from multiple Pooideae (i.e. common grass) species. As such, they are currently desensitized by allergen-specific immunotherapy using extracts made from mixes of pollens from Anthoxanthum odoratum, Dactylis glomerata, Lolium perenne, Phleum pratense and Poa pratensis. Herein, we demonstrate that species-specific glycoprotein patterns are documented by 1D and 2D electrophoresis and Western blotting analysis, which can be used as an identity test for such pollens. Most allergens are glycoproteins bearing complex N-glycans encompassing β1,2 xylose and α1,3 fucose glycoepitopes. Glycoepitope destruction using periodate oxidation has no impact on seric IgE reactivity in 75% atopic patients (n = 24). The latter have thus no significant IgE responses to carbohydrate-containing epitopes. In contrast, periodate treatment strongly impairs IgE recognition of glycoallergens in 25% of patients tested, demonstrating the presence of carbohydrate-specific IgE in those patients. While the clinical impact of carbohydrate-specific IgE is still a matter of controversy, the presence of these IgE in the serum of many allergic patients illustrates the need for cross-reacting carbohydrate epitope-free recombinant allergens to develop relevant diagnostic tests. These data also support the pertinence of mixing multiple grass pollens to desensitize atopic patients, with the aim to broaden the repertoire of glycoepitopes in the vaccine, thus mimicking natural exposure conditions.

Sensitization to cereals and peanut evidenced by skin prick test and specific IgE in food-tolerant, grass pollen allergic patients

BACKGROUND

The botanical relation between grass and cereal grains may be relevant when diagnosing food allergy to cereals. The aim was to investigate the diagnostic specificity of skin prick test (SPT) and specific immunoglobulin E (sIgE) tests to cereals and peanut in grass pollen allergic subjects without history of, and clinically reactions to foods botanically related to grass.

METHODS

70 subjects (41 females; mean age 32 years) and 20 healthy controls (13 females; mean age 24 years) were tested by open food challenge (OFC) with cereals and peanut. SPT and sIgE both with Immulite® (Siemens) and ImmunoCAP® (Phadia) to grass and birch pollen, cereals, peanut and bromelain were performed.

RESULTS

Of the 65 OFC-negative subjects 29-46% (SPT, depending on cut-off), 20% (Immulite) and 38% (ImmunoCAP) had positive results to one or more of the foods tested. Controls were negative in all tests. Cross-reactive carbohydrate determinants (CCD) as evidenced by reaction to bromelain could explain only a minority of the measured IgE-sensitizations.

CONCLUSION

Grass pollen allergic patients with documented food tolerance to cereals and peanut may express significant sensitization. False-positive cereal or peanut allergy diagnoses may be a quantitatively important problem both in routine clinical work and epidemiological studies.

In vivo and in vitro allergy diagnostics: it's time to reappraise the costs

BACKGROUND

The in vivo skin prick test (SPT) is widely considered less expensive than in vitro gamma-immunoglobulin E (IgE) determination in the diagnosis of allergy. The aim of the present paper is to evaluate the relevance of component-resolved in vitro diagnosis in comparison to extract-based diagnosis and the relative global costs in relation to clinical outcomes.

METHODS

For 50 individuals with suspected seasonal allergic rhinitis, we compared the costs of skin testing with those of specific IgE antibody measurement.

RESULTS

The costs were higher for in vitro than in vivo testing. However, the clinical information obtained using recombinant reagents allowed correct identification of the sensitizing molecule.

CONCLUSIONS

Recombinant allergens for specific IgE in vitro measurement provide more reliable information for immunotherapy prescription. This should be translated into a significant reduction in the overall costs sustained by the healthcare system.

Comparative genomics of fungal allergens and epitopes shows widespread distribution of closely related allergen and epitope orthologues

BACKGROUND

Allergy is a common debilitating and occasionally life threatening condition. The fungal kingdom contains a number of species that produce a wide range of well defined protein allergens although the vast majority of fungal species have unknown allergenic potential. The recent genome sequencing of a variety of fungi provides the opportunity to assess the occurrence of allergen orthologues across the fungal kingdom. Here we use comparative genomics to survey the occurrence of allergen orthologues in fungi.

RESULTS

A database of 82 allergen sequences was compiled and used to search 22 fungal genomes. Additionally we were able to model allergen structure for representative members of several highly homologous allergen orthologue classes. We found that some allergen orthologue classes that had predicted structural congruence to allergens and allergen epitopes were ubiquitous in all fungi. Other allergen orthologues classes were less well conserved and may not possess conserved allergen epitope orthologues in all fungi. A final group of allergen orthologues, including the major allergens Asp f 1 and Alt a 1, appear to be present in only a limited number of species.

CONCLUSION

These results imply that most fungi may possess proteins that have potential to be allergens or to cross react with allergens. This, together with the observation that important allergens such as Asp f 1 are limited to genera or species, has significant implications for understating fungal sensitization, and interpreting diagnosis and management of fungal allergy.

Cross-reactivity of pollen allergens: recommendations for immunotherapy vaccines

PURPOSE OF REVIEW

This review will summarize recent research on pollen allergen and epitope cross-reactivity. Knowledge of these relationships aids in the rational formulation of allergen immunotherapy vaccines.

RECENT FINDINGS

There has been further clarification of panallergens and their roles as both major and minor allergens. Recent studies have targeted non-specific lipid transfer proteins and calcium-binding proteins (polcalcins), as well as pathogenesis-related protein families and profilins. Polcalcins and non-specific lipid transfer proteins are responsible for pollen-fruit interactions as well as pollen cross-reactivity, in some cases, but not all, accounting for major allergenicity. Delineation of the enzymatic activity of certain allergens explains the ubiquitous nature of these pollen proteins.

SUMMARY

Characterization of specific pollen allergens and their protein families has provided insight into the grounds for cross-reactivity. Continuing clarification of these relationships will allow the substitution and consolidation of inhalant extracts as described in the conclusion.