Immunoproteomics of tree of heaven (Ailanthus atltissima) pollen allergens

An emerging aeroallergen in Europe: Tree-of-Heaven (Ailanthus altissima [Mill.] Swingle) inventory and pollen concentrations - Taking a metropolitan region in Germany as an example

Urban areas are often hotspots for the dissemination of non-native (invasive) plant species, some of which release (potentially) allergenic pollen. Given the high population density in cities, a considerable number of people can be regularly and potentially intensively exposed to the pollen from these plants. This study delves into the Tree-of-Heaven (Ailanthus altissima, [Mill.] Swingle), native to East Asia, which is known for its high invasiveness in temperate regions worldwide, particularly favoring urban colonization. This study explores the botanical and aerobiological dimensions of this species using the central European metropolitan region of Berlin, Germany, as a case study, and provides a comprehensive global overview of allergological insights. The number of Ailanthus trees decreased markedly from the center to the periphery of Berlin City, following a temperature gradient. The same spatial trend was mirrored by airborne Ailanthus pollen concentrations measured with volumetric spore traps (Hirst-type) at five sites using seven traps. Ailanthus pollen was most abundant around midday and in the afternoon, with concentrations tenfold higher at street level than at roof level. The Ailanthus flowering period in June and July coincided well with the pollen season. To the best of our knowledge this is the first study to investigate Ailanthus altissima pollen production. On average, 5539 pollen grains were found per anther. A literature review on the allergy relevance of Ailanthus altissima pollen indicates the high allergenic potential of pollen from this species. Considering the anticipated expansion of suitable habitats for Ailanthus owing to global warming and the allergological significance of its pollen, it is recommended to include Ailanthus pollen in routine pollen monitoring, particularly in areas colonized by this species. This comprehensive study provides new insights into a pollen taxon whose significance as an emerging aeroallergen should be factored into plant selection and greenspace management in all temperate regions.

Immunoproteomic identification of allergenic proteins in pecan (Carya illinoinensis) pollen

Pecan (C. illinoinensis) pollen is an important cause of allergic respiratory disease. Pecan is distributed worldwide as shade, ornamental or cultivation tree. To date three well known pecan food allergens have been reported, however, pollen allergens have not been identified. Here, we describe the first identification of IgE recognized pecan pollen proteins, for which proteins were analyzed by 2-DE and immunoblotting using a pool of 8 sera from pecan sensitive patients as primary antibody. IgE recognized protein spots were analyzed by LC-MS/MS and identified using a database of translated protein sequences obtained by the assembly of C. illinoinensis public transcriptomic information. This study has identified 17 IgE binding proteins from pecan pollen including proteins widely recognized as allergens and panallergens. These findings will contribute to develop specific diagnosis and treatment of pecan pollen allergy. SIGNIFICANCE: Pecan is a tree highly valued for its fruits that have a great commercial value. To date three pecan seed storage proteins have been officially recognized by the WHO/IUIS allergen nomenclature subcommittee as food allergens (Car i 1, Car i 2 and Car i 4). Pecan tree pollen is highly allergenic and a clinically relevant cause of allergies in North America (USA and Mexico) and regions where the tree is extensively cultivated (Israel, South Africa, Australia, Egypt, Peru, Argentina, and Brazil). Here, we describe the first identification of IgE recognized pollen proteins using an immunoproteomics approach and a protein database created by the assembly of pecan public transcriptomic information. The findings described here will allow the development of new diagnostic and therapeutic modalities for pecan pollen allergy.

The Role of Enolases in Allergic Disease

Enolase is one of the most abundant cytosolic enzymes as well as an important glycolytic metalloenzyme highly conserved among organisms from different taxonomical groups. Participation of enolase in processes in which its enzymatic activity is not required has been widely reported. Some of these processes provide special qualities to microorganisms, which favor, in some cases, their pathogenicity. Remarkably, enolase has been reported as an allergen by itself, it is well recognized as allergenic in molds and yeasts, whereas it has also been recognized by the immune system of susceptible individuals acting as a food and inhaled allergen from other diverse sources such as insects, birds, fishes, and plants. To date, 14 enolases have been officially recognized by the World Health Organization/International Union of Immunological Societies Allergen Nomenclature Subcommittee. The use of discovery proteomics has also uncovered novel allergenic enolases, particularly from pollen sources. Here, we review the relevance of enolases as sensitizers and as nonsensitizing cross-reactive allergens in allergic disease.

Transcriptome sequencing and microsatellite marker discovery in Ailanthus altissima (Mill.) Swingle (Simaroubaceae)

Ailanthus altissima Swingle, is a tree species native to East Asia and has a great potential in decorative, bioenergy and industrial applications in many countries. To date, despite its commercial importance, the genomic and genetic resources available for this species are still insufficient. In this study, we characterized the transcriptome of A. altissima and developed thirteen EST-SSRs (expressed sequence tag-simple sequence repeats) based on Illumina paired-end RNA sequencing (RNA-seq). Besides, we developed ten polymorphic chloroplast microsatellite (cpSSR) markers using the available chloroplast genome of A. altissima. The transcriptome data produced 87,797 unigenes, of which 64,891 (73.91%) unigenes were successfully annotated in at least one protein database. For cpSSR markers the number of detected alleles (N) per marker varied from three at cpSSR12 to twelve at cpSSR8, the unbiased haploid diversity indices (uh) varied from 0.111 to 0.485, and haploid diversity indices (h) ranged from 0.101 to 0.444 with an average unbiased haploid diversity index (uh) of 0.274. Overall, a total of 65 different cpSSR alleles were identified at the ten loci among 165 individuals of A. altissima. The allele number per locus for EST-SSRs varied from 2.143 to 9.357, and the values of observed and expected heterozygosity ranged from 0.312 to 1.000 and 0.505 to 0.826, respectively. The molecular markers developed in this study will facilitate future genetic diversity, population structure, long distance-gene transfer and pollen-based gene flow analyses of A. altissima populations from its known distribution ranges in China focusing on planted and natural forest stands.

Allergenicity assessment of Delonix regia pollen grain and identification of allergens by immunoproteomic approach

Background

Plantation of road-side avenue trees has become a major part of urbanization programme for megacity beautification and environmental management. Due to evergreen habit and vibrant flower colour, Delonix regia (Gulmohor/Flamboyant) is frequently selected as ornamental tree for plantation programme. However, D. regia pollen is related to IgE mediated allergic reactions and no allergen has been reported so far.

Objective

Measuring the prevalence of D. regia pollen sensitivity among the local atopic individuals and identifying the allergens using immunoproteomic tools.

Methods

Aerobiological study was conducted for a period of two years to record the D. regia pollen concentration in the outdoor ambient air. Clinico-immunological tests were performed on atopic individuals to check the prevalence of sensitivity against D. regia pollen. Allergens were detected in the pollen proteome, fractionated in 1D and 2D gel by IgE serology and finally identified by mass spectrometry.

Result

In the study area D. regia pollen grains were present in ample amount in the air during May to July. About 38% of atopic individuals displayed positive Skin Prick Test (SPT) against D. regia pollen along with elevated level of specific IgE and histamine in the sera. Immunoproteomic analyses revealed the presence of 14 IgE reactive proteins in the 2D pollen proteome, of which 8 IgE reactive proteins were identified by MALDI TOF/TOF using homology driven proteomic approach.

Conclusion

This study demonstrated pollen related allergy symptoms by D. regia and gave significant message regarding the plantation programme to avoid the unnecessary load of allergic pollen. Also, a panel of 8 allergens were identified for the first time from D. regia pollen. Detailed study of these allergens would help to design immunotherapeutic strategies for pollinosis management.

Proteomic identification of allergenic proteins in red oak (Quercus rubra) pollen

BACKGROUND

Red oak pollen is an important cause of allergic respiratory disease and it is widely distributed in North America and central Europe. To date, however, red oak pollen allergens have not been identified. Here, we describe the allergenic protein profile from red oak pollen.

METHODS

Total proteins were extracted from red oak pollen using a modified phenolic extraction method, and, subsequently, proteins were separated by two-dimensional gel electrophoresis (2DE) for both total protein stain (Coomassie Blue) and immunoblotting. A pool of 8 sera from red oak sensitive patients was used to analyze blotted proteins. Protein spots were analyzed by Mass Spectrometry.

RESULTS

Electrophoretic pattern of total soluble proteins showed higher intensity bands in the regions of 26-40 and 47-52 kDa. Two dimensional immunoblots using pool sera from patients revealed four allergenic proteins spots with molecular masses in the range from 50 to 55 kDa. Mass spectrometry analysis identified 8 proteins including Enolase 1 and Enolase 1 chloroplastic, Xylose isomerase (X1 isoform), mitochondrial Aldehyde dehydrogenase, UTP-Glusose-1-phosphate uridylyltransferase, Betaxylosidase/alpha-l-arabinofuranosidase and alpha- and beta subunits of ATP synthase.

CONCLUSIONS

This study has identified for first time 8 IgE binding proteins from red oak pollen. These findings will pave the way towards the development of new diagnostic and therapeutic modalities for red oak allergy.

Year-to-year variation of the elemental and allergenic contents of Ailanthus altissima pollen grains: an allergomic study

The Ailanthus altissima pollen (AAP) has been reported as an emerging aeroallergen worldwide. This paper aims at examining the allergen pattern and the elemental composition of A. altissima pollen collected during two consecutive seasons (2014 and 2015). A gel-based allergomic study and SEM coupled to energy-dispersive X-ray (EDX) analysis have been carried out in order to evaluate the allergenic and elemental composition of AAP in two consecutive years. The IgE reactive patterns of 2014 and 2015 AAP PBS extracts were compared using the serum of a 31-year-old woman suffering from severe pollinosis symptoms to AAP. The EDX analysis revealed an important year-to-year variation in the ratios of some polluting elements such as nickel, sulfur, aluminum, lead, and copper. Gel alignments and comparative immunoproteomic analyses showed differential protein expression and IgE reactive patterns between AAPs collected in 2014 and 2015 pollinating seasons. From 20 distinct IgE-reactive spots detected in AAP extracts, 13 proteins showed higher expression in 2014 sample, while 7 allergen candidates exhibited an increased expression in AAP collected in 2015. Matrix-assisted laser desorption ionization-MS/MS analyses led to the identification of 13 IgE-binding proteins with confidence, all belonging to well-known allergenic protein families, i.e., enolase, calreticulin, and pectate lyase. Overall, the 2014 AAP showed higher concentrations of urban polluting elements as well as an increased expression of allergenic pectate lyase isoforms of about 52 kDa. This study demonstrates that the implementation of allergomic tools for the safety assessment of newly introduced and invasive plant species would help to the comprehensive monitoring of proteomic and transcriptomic alterations involving environmental allergens.

IgE-mediated allergic responses associated to Ailanthus altissima pollen using an animal model

BACKGROUND

Murine models have been widely used in the study of allergy as sensitized mice can produce IgE and/or IgG1in response after the injection of an antigen/adjuvant combination. Ailanthus altissima pollen (AAP) has been recently reported as an emerging aeroallergen in Iran. So far, several AAP candidate allergens by the screening of allergen-specific IgE in the sera from AAP sensitized patients in Iran.

OBJECTIVE

The aim of the present study was to detect and compare the allergens eliciting an IgE response in a mouse model, and in human, using pollen extract of A. altissima and an immunoproteomics based approach.

METHODS

The pollen proteins were extracted in phosphate-buffered saline (PBS). Thirty male BALB/c mice were randomly divided into two groups of AP extract sensitized and sham that respectively received AAP PBS extract and a PBS control by intraperitoneal injections at regular intervals. The optimized AAP protein extracts were analyzed using 2D-gel electrophoresis and were subsequently confronted to pooled sera of sensitized mice.

RESULTS

Two-D gel electrophoresis of AAP extract allowed the separation of 125 protein spots distributed in a wide range of pI and molecular masses. Two-DE immunoblotting using pooled sera of sensitized mice led to the detection of 14 IgE reactive spots with molecular masses ranging from 12 to 40-42kDa.

CONCLUSION

The results do not correlate with our previous analyses using human AAP-sensitized sera. These findings reflect some differences in the sIgE reactivity to allergenic proteins in animal models.

Proteomics, Holm Oak (Quercus ilex L.) and Other Recalcitrant and Orphan Forest Tree Species: How do They See Each Other?

Proteomics has had a big impact on plant biology, considered as a valuable tool for several forest species, such as Quercus, Pines, Poplars, and Eucalyptus. This review assesses the potential and limitations of the proteomics approaches and is focused on Quercus ilex as a model species and other forest tree species. Proteomics has been used with Q. ilex since 2003 with the main aim of examining natural variability, developmental processes, and responses to biotic and abiotic stresses as in other species of the genus Quercus or Pinus. As with the progress in techniques in proteomics in other plant species, the research in Q. ilex moved from 2-DE based strategy to the latest gel-free shotgun workflows. Experimental design, protein extraction, mass spectrometric analysis, confidence levels of qualitative and quantitative proteomics data, and their interpretation are a true challenge with relation to forest tree species due to their extreme orphan and recalcitrant (non-orthodox) nature. Implementing a systems biology approach, it is time to validate proteomics data using complementary techniques and integrate it with the -omics and classical approaches. The full potential of the protein field in plant research is quite far from being entirely exploited. However, despite the methodological limitations present in proteomics, there is no doubt that this discipline has contributed to deeper knowledge of plant biology and, currently, is increasingly employed for translational purposes.

Double One-Dimensional Electrophoresis (D1-DE) Adapted for Immunoproteomics

The classical proteomics approach for the identification of allergen candidates consists on the separation of proteins by high-resolution two-dimensional electrophoresis (2-DE) with subsequent IgE immunoblotting and further analysis of IgE-reactive protein spots with mass spectrometry. In this approach at least two gels most be run. One gel is used for staining and the other is for immunoblotting by antibodies labeled with specific immunostains. Additional functional characterizations require either protein purification or 2-DE replicates and appear to be time- and reagent-consuming. Here we described a modified double one-dimensional electrophoresis (D1-DE) allowing the conversion of a protein spot previously visualized by 2-DE into an extended protein band. In D1-DE, the purity of the protein of interest is similar to 2-DE spots, but its abundance is many times higher than what can be found in a 2-DE single spot allowing many other functional analyses from a single D1-DE separation.

Identification of a polygalacturonase (Cup s 2) as the major CCD-bearing allergen in Cupressus sempervirens pollen

As IgE glyco-epitopes, also referred to as cross-reactive carbohydrate determinants (CCDs), can share significant structural homologies between different plants, they are prone to extensive cross-reactivity among allergen pollen extracts. Here, cypress pollen allergens, especially a polygalacturonase (PG), were further characterized using double one-dimensional electrophoresis (D1-DE). The presence of specific IgE directed against CCDs was investigated by bromelain IgE inhibition and concanavalin A binding assays using sera of cypress pollen-sensitized patients. Our results showed that IgE reactivity to CCDs in Cupressus sempervirens pollen extracts is mainly related to bromelain-type epitopes of a newly identified cypress PG. This glycoprotein has been further characterized through an immunoproteomic approach and officially indexed as Cup s 2 by the WHO/IUIS allergen nomenclature. Cup s 2 could thus be associated with the increased prevalence of IgE reactivity to cypress pollen extracts because of CCD interference.

Projecting potential distribution of Eucryptorrhynchus scrobiculatus Motschulsky and E. brandti (Harold) under historical climate and RCP 8.5 scenario

Ailanthus altissima (Mill.) Swingle and its variant A. altissima var. Qiantouchun are notorious invasive weeds. Two weevils, Eucryptorrhynchus scrobiculatus (ESC) and E. brandti (EBR) are considered as candidates for biological control of A. altissima. The aim of this study was to model the potential distributions of ESC and EBR using CLIMEX 4.0. The projected potential distributions of ESC and EBR included almost all current distribution areas of A. altissima, except Southeast Asia. Under historical climate, potential distribution area of EBR is larger than that of ESC, 46.67 × 10⁶ km² and 35.65 × 10⁶ km², respectively. For both ESC and EBR, climate change expanded the northern boundary of potential distributions northward approximately 600 km by the middle of 21st century, and 1000 km by the end of 21st century under RCP 8.5. However, the suitable range decreased to the south in the Southern Hemisphere because of heat stress. The modelled potential distributions of ESC and EBR in the United States demonstrated that the climate was suitable for both weevils. Therefore, considering only climate suitability, both ESC and EBR can be considered as potential biological control agents against A. altissima with some confidence that climatic conditions are likely suitable.