Allergy in the Mediterranean area. II: Cross-allergenicity among Urticaceae pollens (Parietaria and Urtica)

Neural networks for increased accuracy of allergenic pollen monitoring

Monitoring of airborne pollen concentrations provides an important source of information for the globally increasing number of hay fever patients. Airborne pollen is traditionally counted under the microscope, but with the latest developments in image recognition methods, automating this process has become feasible. A challenge that persists, however, is that many pollen grains cannot be distinguished beyond the genus or family level using a microscope. Here, we assess the use of Convolutional Neural Networks (CNNs) to increase taxonomic accuracy for airborne pollen. As a case study we use the nettle family (Urticaceae), which contains two main genera (Urtica and Parietaria) common in European landscapes which pollen cannot be separated by trained specialists. While pollen from Urtica species has very low allergenic relevance, pollen from several species of Parietaria is severely allergenic. We collect pollen from both fresh as well as from herbarium specimens and use these without the often used acetolysis step to train the CNN model. The models show that unacetolyzed Urticaceae pollen grains can be distinguished with > 98% accuracy. We then apply our model on before unseen Urticaceae pollen collected from aerobiological samples and show that the genera can be confidently distinguished, despite the more challenging input images that are often overlain by debris. Our method can also be applied to other pollen families in the future and will thus help to make allergenic pollen monitoring more specific.

Parietaria major allergens vs pollen in the air we breathe

BACKGROUND

Parietaria and Urtica are the genera from the Urticaceae family more frequent in Mediterranean and Atlantic areas. Moreover, both genera share pollination periods, and their pollen (of the main species) is so similar that there is no aerobiological evidence of the proportion of each of them in the airborne pollen identification, except in the case of U. membranacea. However, Parietaria is one of the most important causes of pollinosis and Urtica is not. Our aim is determine if airborne Urticaceae pollen concentrations show the aerodynamics of the two major allergens of Parietaria (Par j 1 and Par j 2) as well as the allergen distribution in the different-sized particles.

METHODS

The air was sampled during the pollination period of Urticaceae using Hirst Volumetric Sampler and Andersen Cascade Impactor in two cities of Southern Spain (Córdoba and Granada). The samples were analysed by the methodology proposed by the Spanish Aerobiology Network (REA) and the minimum requirements of the European Aeroallergen Society (EAS) for pollen, and by ELISA immunoassay for allergens.

RESULTS

The patterns of airborne pollen and Par j 1-Par j 2 were present in the air during the studied period, although with irregular oscillations. Urticaceae pollen and Par j 1-Par j 2 allergens located in PM2.5 showed positive and significant correlation during the period with maximum concentrations (March to April).

CONCLUSION

Parietaria aeroallergens show similar pattern of Urticaceae airborne pollen. Urticaceae pollen calendar is as a good tool for allergy prevention. On the other hand, important concentrations of Par j 1 and Par j 2 were located in the breathable fraction (PM2.5), which could explain the asthmatic symptoms in the allergic population to Parietaria.

Assessment of neural networks and time series analysis to forecast airborne Parietaria pollen presence in the Atlantic coastal regions

Pollen forecasting models are a useful tool with which to predict episodes of type I allergenic risk and other environmental or biological processes. Parietaria is a wind-pollinated perennial herb that is responsible for many cases of severe pollinosis due to its high pollen production, the long persistence of the pollen grains in the atmosphere and the abundant presence of allergens in their cytoplasm and walls. The aim of this paper is to develop artificial neural networks (ANNs) to predict airborne Parietaria pollen concentrations in the northwestern part of Spain using a 19-year data set (1999-2017). The results show a significant increase in the length of time Parietaria pollen is in the air, as well as significant increases in the annual Parietaria pollen integral and mean daily maximum pollen value in the year. The Neural models show the ability to forecast airborne Parietaria pollen concentrations 1, 2, and 3 days ahead. A developed model with five input variables used to predict concentrations of airborne Parietaria pollen 1 day ahead shows determination coefficients between 0.618 and 0.652.

Urtica dioica pollen allergy: Clinical, biological, and allergomics analysis

BACKGROUND

The most emblematic members of Urticaceae at allergic risk level are wall pellitories (Parietaria), whereas nettle (Urtica) pollen is considered as poorly allergenic. No allergen from nettle pollen has yet been characterized, whereas 4 are listed for Parietaria pollen by the International Union of Immunological Societies. Clinical and biological profiles of 2 adult men who developed symptoms against nettle pollen and/or leaves were studied.

OBJECTIVE

To characterize the allergic reaction and identify the potential nettle pollen sensitizing allergens.

METHODS

IgE-mediated reaction to nettle pollen extract was evaluated by skin prick test, immunoassay, nasal provocation, and basophil activation test. To characterize specific nettle pollen allergens, an allergomic (IgE immunoproteomic) analysis was performed combining 1- and 2-dimensional electrophoresis, IgE immunoblots of nettle pollen extract, identification of allergens by mass spectrometry, and database queries.

RESULTS

The results of biological and immunochemical analyses revealed that the allergic rhinitis was due to Urtica dioica pollen in both patients. The allergomic analysis of nettle pollen extract allowed the characterization of 4 basic protein allergens: a thaumatin-like protein (osmotin) with a relative molecular mass of 27 to 29 kDa, a pectinesterase (relative molecular mass, 40 kDa), and 2 other basic proteins with relative molecular masses of 14 to 16 kDa and 43 kDa. There is no or only very weak allergen associations between pellitory and nettle pollen.

CONCLUSION

Exposure to nettle pollen can be responsible of allergic symptoms, and several allergens were characterized. Unravelling the allergens of this underestimated allergy might help to improve diagnosis and care for patients, to predict cross-reactivities and design adapted specific immunotherapy.

Airborne pollen in European and Asian parts of Istanbul

Pollen concentrations in the atmosphere of Istanbul, a city located between two continents, has been monitored for 1 year as part of a larger research program. The sampling sites were located in two different continents: the Asian part (AS) and the European part (EP). The sampling was performed in AS and EP of the city by using Hirst type volumetric method, and pollen grains of 58 and 62 taxa were identified in the two parts, respectively. The pollen spectrum reflected the floristic diversity of the region. The main pollen producers at the sites were characterized by some allergenic pollen and were identified as Cupressaceae/Taxaceae, Urticaceae, Pistacia sp., Quercus sp., Platanus sp., Fraxinus sp., and Xanthium sp. These pollen types contributed to the total pollen sum with a percentage of more than 80% at both monitoring sites. The highest amount of pollen grains was recorded in April. The greatest number of species was recorded in May, when 42 types (AS) and 44 types (EP) were present.

Skin prick test reactivity in allergic rhinitis patients to airborne pollens

The aim was to investigate the impact of atmospheric pollen in determining allergic rhinitis. It was conducted with 130 patients with allergic rhinitis in three different sites in Eskisehir, Turkey, in 2000-2001, using a gravimetric method with a Durham sampler. Skin prick test results, the symptoms of patients and their findings all confirmed the presence of allergic reactions to pollen allergens in the patients observed. During the period, a total of 47,082 pollen grains/cm(2) belonging to 45 taxa were recorded. Of the total pollen grains, 81.0% were arboreal and 18% non-arboreal. The majority of the investigated pollen grains were from Pinaceae, Salix spp., Chenopodiaceae/Amaranthaceae, Cupressaceae and Poaceae. Pollen concentrations reached the highest level in May (54.36%). The pollen allergens provoking severe sensitization were grasscereal mixtures (58.5%), followed by arboreals (33.8%). All patients (100.0%) were sensitive to grass. This study emphasizes the significance of determining the types and concentrations of pollen with a view to comparing changes in highly concentrated allergens.

Analysis of airborne pollen grains in Bilecik, Turkey

In this study, pollen grains in the atmosphere of Bilecik were studied for a continuous period of 2 years (2005 and 2006) by using Durham sampler. During this period, pollen grains belonging to 46 taxa were recorded, 26 of which belonged to arboreal plants and 20 to non-arboreal. Of total 14,269 pollen grains determined in Bilecik atmosphere, 6,675 were recorded in 2005 and 7,594 were in 2006. From these, 75.74% were arboreal, 21.80% were non-arboreal and 2.47% unidentifiable. Pinus sp., Poaceae, Cupressaceae, Platanus sp., Quercus sp., Salix sp., Ailanthus sp., Fagus sp., Urticaceae, Chenopodiaceae/Amaranthaceae were the main pollen producers in the atmosphere of Bilecik, respectively. Pollen concentrations reached their highest levels in May. Atmospheric pollen concentrations in February, March, September, October and November were less than those in other months.

Concentrations of airborne pollen grains in Sivrihisar (Eskisehir), Turkey

Pollen grains in the atmosphere of Sivrihisar were studied for a continuous period of 2 years (1 January 2005-31 December 2006) using a Durham sampler. During this period, pollen grains belonging to 41 taxa were recorded, 24 of which belonged to arboreal plants and 17 to non-arboreal. From these, 23,219 were identified in 2005 and 34,154 in 2006. Of the total pollen grains, 90.46% were arboreal, 9.43% non-arboreal, and 0.1% unidentifiable. The majority of the investigated allergic pollen grains were from Pinaceae, Cupressaceae, Fraxinus spp., Cedrus spp., Artemisia spp., Poaceae, Chenopodiaceae/Amaranthaceae, Populus spp., Quercus spp., Urticaceae and Asteraceae, respectively. Pollen concentrations reached their highest levels in May. This information was then established into a calendar form according to the pollens determined in 2005-2006, in terms of annual, monthly and weekly numbers of taxa fall per cm2. A comparison between the results and the meteorological factors revealed a close relationship between pollen concentrations in the air and meteorological conditions. An increase in pollination was also linked to increasing temperatures and the wind. It was therefore concluded that high temperatures and relative humidity were also effective in increasing the number of pollens in the air.

Geographical variation in the prevalence of positive skin tests to environmental aeroallergens in the European Community Respiratory Health Survey I

BACKGROUND

Many studies have reported the prevalence of sensitization using skin prick tests. However, comparisons between studies and between regions are difficult because the number and the type of allergens tested vary widely. Using the European Community Health Respiratory Survey I data, the geographical variation of sensitization to environmental allergen as measured by skin tests was established.

METHODS

Adults aged 20-44 years, living in 35 centres in 15 developed countries, underwent skin tests for allergy to nine common aeroallergens: Dermatophagoides pteronyssinus, timothy grass, cat, Cladosporium herbarium, Alternaria alternata, birch, Olea europea, common ragweed and Parietaria judaica. The age-sex standardized prevalence of sensitization was determined and centres with high (95% confidence interval above and excluding study median) and low prevalence (95% confidence interval below and excluding study median) of sensitization to each allergen and to any of the nine allergens were identified.

RESULTS

There was substantial geographical variation in the prevalence of sensitization to each of the nine allergens tested and in the prevalence of sensitization to any allergen (lowest 17.1%, median 36.8% and highest 54.8%). Sensitization to D. pteronyssinus, grass pollen and cat were usually the most prevalent (median between centre 21.7%, 16.9% and 8.8%, respectively). Timothy grass sensitization was higher than that for any other pollen species.

CONCLUSIONS

As expected, geographical variations of sensitization to environmental allergen were observed across centres. These findings were compatible for those observed with serum-specific IgE. Skin tests can be used to assess the geographical distribution of allergens in a multicentric epidemiological survey.

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.

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.

Cross-reactivity of pollen allergens

Pollen cross-allergenicity has practical implications on the management of inhalant allergy, in both evaluation and therapy, especially with allergen vaccine immunotherapy. The study of cross-reactivity among pollen allergens has expanded beyond investigation of crude extracts to the characterization and cloning of numerous pollen proteins. In this review, the interrelationships between these pollen allergens in the context of botanical systematics are examined, to provide a framework for cross-reactivity understanding. Recommendations for choices in evaluation and therapy are given.

Complement inactivation by allergenic plant pollen extracts

Dialyzed aqueous extracts of plant pollen are widely used in the clinical practice of allergy for diagnostic and therapeutic purposes. The present investigation shows that such allergenic extracts are capable of consuming complement in every human serum, independent of the clinical condition. Complement is engaged by way of the first component C1, but without the participation of allergen-specific antibodies. The capacity of distinct pollen extracts to inactivate haemolytic complement was found to depend on the plant species, the most potent extracts being from the pollen of the weeds and trees. Analysis by UV-spectroscopy of the flavonoids remaining firmly bound to the proteins gives rise to the proposal that complement inactivation by allergenic and non-allergenic pollen extracts is due to polyphenolic (flavonoid) structures complexed with, or chemically conjugated to, the pollen proteins.

Comparison between outdoor and indoor airborne allergenic activity

BACKGROUND

Allergenic pollens are usually detected in outdoor air by using volumetric spore traps, which allow measurement of atmospheric concentration as pollen grains per m3 of air. The results of the pollen count are useful primarily for outdoor environments while most people spend most of the day indoors.

OBJECTIVE

The purpose of our study was to compare outdoor pollen levels with allergenic activity measured both outdoors and indoors.

METHODS

We used a Lanzoni spore trap to measure airborne Urticaceae pollen and filters collecting particles simultaneously indoors and outdoors and assayed each filter for Parietaria judaica allergenic activity. Samples were collected at the Allergological Service of the "A. Cardarelli" Hospital in Naples with the balcony open on some days and closed on others. Allergenic activity (ng/m3) was measured using the immunocapture RAST.

RESULTS

With the balcony open there was no great difference between outdoor and indoor allergenic activity, but with the balcony closed there was a reduction of indoor allergenic activity of about one-third in comparison with outdoor allergenic activity. Statistical analysis (Pearson correlation test) indicated a significant correlation between outdoor allergen levels and indoor allergen levels with the balcony open (r = .4415, P < .05), but not with the balcony closed (r = .3160, P > .05); a significant correlation between outdoor pollen count and indoor allergen levels with the balcony open (r = .4809, P < .05), but not with the balcony closed (r = .3858, P > .05); and a highly significant correlation (r = .5225, P < .001) between outdoor pollen count and outdoor allergen levels.

CONCLUSIONS

These data provide scientific evidence for the recommendation to hay fever patients to remain indoors during seasons with high levels of outdoor pollens.

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

BACKGROUND

Plants of the genus Parietaria, Urticaceae family, represent a major cause of pollinosis in the Mediterranean area. Different Parietaria species crossreact to a great extent, but studies on the crossreactivity among the major allergens of these pollens have not been carried out so far.

OBJECTIVE

To develop an immunochemical method to quantify the major Parietaria judaica allergen, Par j 1, as well as to verify the presence of Par j 1-like proteins in different Urticaceae pollens. These proteins would be purified in order to study the cross-reactivity among them.

METHODS

Immunoaffinity chromatography with a monoclonal antibody, solid-phase enzyme-linked immunoassays and SDS-PAGE.

RESULTS

A monoclonal antibody-based ELISA for the quantification of Par j 1 has been developed. The assay has a sensitivity of 0.2 ng/mL and shows a high correlation with the allergenic activity of P. judaica extracts determined by radioallergosorbent assay (RAST) inhibition. By means of this assay, proteins homologous to Par j 1 were detected in P. officinalis and P. mauritanica. These proteins (Par o 1 and Par m 1, respectively) were purified by affinity chromatography using the same monoclonal antibody employed in the ELISA. Crossed-inhibition experiments demonstrated that Par j 1, Par o 1, and Par m 1, competed for the binding of specific IgE from a P. judaica-sensitive patients serum pool.

CONCLUSION

The results here described suggest that shared allergenic epitopes are present in the three main allergens investigated, which may simplify the diagnosis and therapy for Parietaria allergy.

Clustering of allergenic pollen on the basis of skin responses of atopic patients by matrix analysis

The responses of 148 atopic patients to some 43 different extracts of allergenic pollen were tested by prick tests. The measure of dissimilarity was introduced and calculated for all pairs of allergens. The investigated allergens were clustered into groups, according to their unbiased greatest similarity, by a matrix-structuring method. Results indicate that subgroups of allergens can be distinguished even within groups of closely related pollen allergens that were believed to be fully cross-reactive. A few cases are demonstrated for various varieties of olives, pecans, date palms, and turf grasses and for some wild chenopods and amaranths. The usefulness of the suggested solution for allergy research and for clinical practice is discussed.

Parietaria pollinosis: a review

Species of the genus Parietaria (pellitory) are a prevalent cause of allergy in the Mediterranean area and the most important in some European regions such as southern Italy and coastal Spain (14, 26, 27, 29, 30, 31, 36, 59, 69). Up to now, however, Parietaria has received little attention in northern Europe and the US because of its limited regional distribution. Therefore, less is known about Parietaria allergy than about other inhalant allergens such as those of grasses, ragweed, and mites. During the last 5 years, only 31 reports on Parietaria allergy have appeared in the literature, as compared with 37 papers on birch pollen. This ratio may appear unbalanced, considering that millions of people suffer from pollinosis caused by Parietaria, while a much smaller number have rhinitis and/or asthma caused by birch pollen. The increasing movement of people throughout Europe and to and from the US is reason to broaden our knowledge of patterns of inhalant allergy in each geographic area, especially where tourism and immigration are high. This paper briefly reviews available data and personal studies on the botanical, aerobiological, immunochemical, and clinical features of Parietaria allergy.

Allergenic pollens and pollinosis in Italy: recent advances

The authors have mapped the occurrence of allergenic pollens throughout Italy and defined their most common clinical symptoms. To obtain an accurate aerobiological and clinical picture of such a geographically complex country as Italy, a detailed investigation was carried out involving 80 data-gathering stations and 40 clinical centers nationwide. Three main pollination periods can be distinguished: winter-pre-spring (January to March) for Betulaceae, Corylaceae, Cupressaceae, Salicaceae and Ulmaceae: spring-summer (April to June) for Gramineae, Urticaceae, Oleaceae, Plantago, Fagaceae, Pinaceae and Polygonaceae, and summer-autumn (August to September) for Urticaceae, Compositae and Chenopodiaceae. Examination of 49,660 patients affected by pollinosis (conjunctivitis, rhinitis, asthma, with positive skin tests or IgE-specific serum determination: RAST, ELISA) throughout Italy revealed sensitivity to Gramineae in 64.6%, to Parietaria in 36.7% to Olea in 15.8%, to Compositae in 13.2%, to Betulaceae-Corylaceae in 7% and to Fagaceae-Cupressaceae-Plantago in 4%-10%; marked regional variations were observed. The patients suffered from rhino-conjunctivitis (55.7%), rhino-conjunctivitis plus asthma (31.6%) and asthma (12.7%). In monosensitised individuals, Parietaria was seen to be the main cause of the asthmatic syndrome (though our preliminary data also implicate Olea) followed by Gramineae.

Sensitivity to Parietaria pollen in the Southampton area as determined by skin-prick and RAST tests

The pollen of Parietaria species is a well-recognized and important inhalant allergen in the Mediterranean area. Parietaria judaica (Pellitory-of-the-Wall) is native to the U.K., flowering from June to September, but is not usually considered to be of any clinical importance by U.K. allergists. We skin tested 62 patients with a clinical history of summer seasonal respiratory symptoms and a control group of 11 patients with perennial respiratory symptoms only. Each was skin tested in duplicate with extracts of grass pollen, birch pollen, Parietaria pollen, Dermatophagoides pteronyssinus, Cladosporium, Alternaria, nettle pollen and negative and positive controls, and serum samples were collected for RAST assays for Parietaria and nettle. Eight of the 62 patients in the main group showed skin reactivity to Parietaria. Five of these eight had never visited the Mediterranean area and therefore it is possible that sensitization occurred in the U.K. Thirteen of the 62 patients were skin reactive to nettle but there was no correlation between skin reactivity to Parietaria and nettle. This supports a recent report that, despite their close botanical relationship, no antigenic cross-reactivity exists between the two species. No correlation was seen between skin reactivity and serum RAST activity to Parietaria or nettle. It is not known whether exposure to Parietaria pollen contributes to the seasonal symptoms of the patients found to be skin reactive. None of the 11 patients in the control group was skin reactive to Parietaria.