Allergenic cross-reactivity among pollens of Urticaceae

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.

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.

Association of responsiveness to the major pollen allergen of Parietaria officinalis with HLA-DRB1* alleles: a multicenter study

Parietaria, a plant belonging to the family of Urticaceae, is a major source of allergenic pollen in Europe. In the context of a multinational study, we investigated whether in allergic subjects antibody response towards Par o 1, the major allergen from P. officinalis, was associated with defined HLA-DRB1* alleles. The study population consisted of 234 allergic patients: 65 from Bulgaria, 30 from Israel, 99 from Italy, and 40 from Spain. In the Italian study group, the prevalence of ST positivity to Parietaria was 77%. In Parietaria ST-positive subjects, the prevalences of IgG and IgE serum Ab towards Par o 1 were 91% and 75%, respectively. HLA-DRB1*1101 and/or 1104 were significantly positively associated with the presence of IgG Ab and with high levels of IgE Ab towards this allergen (p = 0.0007 and p = 0.012, respectively). In the Spanish study group, the positive association of DR1100 with responsiveness to Par o 1 was confirmed (p = 0.02, RR = 4, and p = 0.002, RR = 7, for IgG and IgE Ab, respectively). None of the Bulgarian patients had IgE Ab to Par o 1, whereas IgG Ab response was observed in 7 out of 65 subjects and was positively associated with DRB1*1101 and/or 1104 (p = 0.025). In the Israeli study group, responsiveness to Par o 1 was not associated with specific HLA-DRB1* alleles. In conclusion, this study shows that in allergic patients from three European populations antibody response to the major allergen from the pollen of Parietaria is associated with HLA-DRB1*1101 and/or 1104. Our data suggest that this association is stronger in subjects monosensitized to Parietaria.

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.

Allergens of Arizona cypress (Cupressus arizonica) pollen: characterization of the pollen extract and identification of the allergenic components

Species of the Cupressaceae family are an important cause of respiratory allergies in countries with a Mediterranean climate. An allergenic extract from Cupressus arizonica pollen was prepared with two extraction steps followed by ammonium sulfate precipitation, giving a protein yield of about 3%. Cupressus arizonica pollen extract was also characterized by means of sodium dodecylsulfate-polyacrylamide gel electrophoresis, followed by IgE and IgG immunoblotting and lectin blotting. IgE reactivity was restricted to six components, whereas IgG binding showed a more complex pattern. A 43 kd component, predominant both in its intensity and frequency of recognition by human IgE antibodies, was identified as the major allergen of C. arizonica. Four of the six IgE-binding components, including the major allergen, seem to be glycoproteins, as confirmed by the lectin blotting analysis. The extract produced inhouse was used to set up an immunoenzymatic test to evaluate the specific IgE binding in a panel of sera from 33 immunotherapy-free subjects who were monosensitized to cypress pollen. The percent of positivity obtained was much higher than that reported in the literature for commercial immunoassays.

Detection of Parietaria judaica airborne allergenic activity: comparison between immunochemical and morphological methods including clinical evaluation

Airborne pollen grains and small plant particles of respirable size are the main causes of rhinitis and asthma in pollinosis patients. Consequently, it could be useful to quantify atmospheric variations in these biological aerosols and their allergenic activity as a basis for establishing correlations with the clinical symptoms in these allergic subjects. Our study was conducted in Naples from May to August 1992 and from May to August 1993 and concentrated on Parietaria judaica (Par j) the most important hay fever-provoking plant in southern Italy. The aim of this study was to evaluate the day-to-day variation in counts of Par j. pollen, the day-to-day variation in allergenic activity specific for this plant, and to relate these two variables to symptom scores in patients with respiratory allergy to Par j. The airborne pollen grains were collected by a Hirst-like volumetric trap and examined through an optical microscope, while the allergenic activity of particles trapped on glass fibre filters in a high volume air-sampler was determined by immunochemical assay. The two devices were placed on the flat roof of the 'A. Cardarelli' Hospital. The results of this preliminary study suggest that both methods could have useful clinical relevance, since these two biological parameters were significantly correlated with the symptom scores of allergic patients. However, pollen count with morphological quantification of grains/m3 of air is a more simple technique.

Isolation by mAb based affinity chromatography of two Par j I isoallergens. Comparison of their physicochemical, immunochemical and allergenic properties

We report the identification and separation of two isoallergen components of Par j I, the major allergen from Parietaria judaica pollen. First, electrophoretic conditions for consistently separating both isoforms in an SDS-PAGE system were established, and mol. wt values of 13,000 (isoallergen IA) and 10,500 (isoallergen IB) were estimated. Immunoblot, after SDS-PAGE experiments, with individual P. judaica-sensitive human sera revealed a slightly different IgE-binding pattern for each isoallergen. Four anti-Par j I mAbs were obtained from BALB/c mice immunized with a purified Par j I preparation comprising IA and IB isoallergens. Three mAbs were directed to an epitope shared by both isoallergens, and the fourth one recognized specifically one epitope on Par j IB. Dot-blot experiments with the deglycosylated allergen showed that the mAbs did not recognize the carbohydrate prosthetic group of the molecules. Affinity chromatography using the mAbs allowed the separation of the isoallergens that retained their IgE-binding ability after the purification process. Amino acid composition analyses and partial N-terminal sequencing demonstrated an extensive homology and also the existence of some structural differences between Par j I isoallergens, which is in agreement with the high, but not complete, cross-reactivity observed in competition ELISA experiments. Finally, skin prick tests performed on 28 P. judaica-sensitive patients showed that all of them recognized both isoforms and that allergenic epitopes present in Par j IA and IB are responsible for most of the allergenic activity of the whole extract.

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.

Role of carbohydrate moieties in cross-reactivity between different components of Parietaria judaica pollen extract

Cross-reactivity between the different components in Parietaria judaica pollen extract has been investigated by polyclonal as well as monoclonal antibodies before and after chemical deglycosylation obtained by trifluoromethanesulphonic acid (TFMS) treatment of the extract. In western blotting a polyclonal rabbit antiserum, obtained by injecting purified Par j I, was able to recognise many components of the native extract. However, its reactivity was restricted, after chemical deglycosylation of the extract, to the major allergen alone, indicating that its cross-reactivity was due to sugar moieties. Moreover, out of several monoclonal antibodies raised by injecting the whole Parietaria judaica extract, one (1A4/2F8) was also able in western blotting to recognise an epitope shared by many components of the extract except the major allergen Par j I. However, in this case the broad reactivity of the antibody was not affected by the deglycosylating procedure. When the reactivity of Parietaria judaica extract was tested before and after sugar removal, against specific IgE from a pool of patient sera, no differences could be demonstrated, thus indicating that carbohydrates are not strongly involved in the binding of Parietaria judaica-specific IgE. The results indicate that both proteic and carbohydratic cross-reactive epitopes are shared by many components of Parietaria judaica pollen extract.