Purification of Parj I, a major allergen from Parietaria, judaica pollen

cDNA cloning, sequence analysis and allergological characterization of Par j 2.0101, a new major allergen of the Parietaria judaica pollen

A clone (P2) coding for an allergen of Parietaria judaica (Pj) pollen has been isolated and sequenced from a cDNA library in lambda ZAP using a pool of 23 sera from Pj-allergic patients. The clone contained an insert of 622 nucleotides with an open reading frame of 133 amino acids (aa) and a putative signal peptide of 31 aa giving a deduced mature processed protein of 102 aa with a molecular mass of 11344 Da. The expressed recombinant protein, named rPar j 2.0101, was a major allergen since it reacted with IgE of 82% (23/28) of the sera of Pj-allergic subjects analyzed. It was shown to be a new allergen since (i) the amino acid sequence homology with the already reported recombinant allergen Par j 1.0101 was 45% and (ii) there was no cross-inhibition between rPar j 2.0101 and rPar j 1.0101. In addition, rPar j 2.0101 inhibited 35% of the specific IgE for 10-14 kDa native allergens and preincubation of sera from Pj-allergic patients with both rPar j 2.0101 and rPar j 1.0101 fully abolished the IgE recognition of the 10-14 kDa native allergen region, suggesting that these two allergens contributed to the region.

Extraordinary stability of IgE-binding Parietaria pollen allergens in relation to chemically bound flavonoids

It is known that the skin-active and IgE-binding components in Parietaria pollen extracts are not restricted to the predominant protein allergens of M(r) 12000-15000, but are present as well among the naturally occurring constituents of M(r) < 10000. Indeed, the IgE-binding Parietaria pollen components are quite heterogeneous, ranging from high- to low-molecular mass, whereby the IgE-binding epitopes display an unusual chemical stability. Furthermore, the pollen of Parietaria species demonstrably contain a high proportion of flavonoid pigments. Since these pollen grains cannot be collected entirely free from non-pollen plant parts, the usual allergenic extracts of Parietaria encompass both the polyphenolic substrate molecules and the enzyme polyphenoloxidase as ingredients for the oxidative generation of flavonol-protein conjugates during the extraction process. In the present work this is illustrated by spectroscopic analyses of the free and bound flavonoids in Parietaria pollen extracts, as well as of the peptide fragments produced from the allergenic proteins by enzymatic or chemical hydrolysis. None of these relatively harsh treatments had a significant effect on the IgE-binding properties of the allergenic (sub-)components, even though detectable proteins in isoelectric focusing and immunoblotting were lost. It is proposed that the extraordinary stability of IgE-binding Parietaria components over a wide molecular range may be attributed to chromophoric flavonoid side-chains as (parts of) the corresponding B-cell epitopes.

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.

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.

Modified par j I allergen from P judaica pollen and its rate of absorption in rats

Polymerized allergens (allergoids) have been introduced in the immunotherapy of allergic disease in order to reduce the risk of side effects. However, their high molecular weight can be a limit, particularly when they are administered by a route involving passage through the mucosal barrier. We describe a simple procedure aimed at developing an original modified allergen with significantly less allergenic potential (intended as human IgE-binding capacity) but preserving the monomeric nature of the molecule. Par j I, the major allergen of Parietaria judaica pollen, was purified by a combination of monoclonal antibodies and affinity chromatography. Par j I allergen was then modified by reaction with potassium cyanate (KCNO), and compared with the native allergen to evaluate its allergenic potency (RAST-inhibition) and molecular weight (SDS-PAGE). Modified allergen showed significantly lower allergenic potency but kept its original molecular weight, making it particularly suitable for buccal (sublingual) administration. To study the adsorption profile, modified Par j I was radiolabeled and administered intravenously and sublingually to normal rats. The prospects for clinical application of the modified allergen are discussed.

cDNA cloning, expression and primary structure of Par jI, a major allergen of Parietaria judaica pollen

A 659 bp cDNA clone** coding for an allergen of Pj pollen has been isolated from a lambda gt11 library, and its DNA sequence determined. The cDNA insert showed an open reading frame of 429 bp coding for an allergenic protein of 14,866 Da and a deduced amino acid sequence containing 143 residues. The expressed recombinant protein represented the major allergen Par jI since it reacted with 95% of the sera from Pj-allergic patients (n = 22) and with two Par jI-specific monoclonal antibodies. No similarity with other known DNA and protein sequences has been detected.

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 fragments in Parietaria judaica pollen extract

High-performance ion-exchange chromatography and immunoaffinity chromatography suggest that Par jI, the principal allergenic component of Parietaria judaica pollen, is a very unstable molecule, which tends to fragment in solution. Several fragments were obtained from Par jI and some of them show positivity toward the anti-Par jI monoclonal antibody, suggesting that they retain the entire structure of the allergenic determinant. These fragments could be the target for sequence and conformation studies.