Group V allergens in grass pollens: IV. Similarities in amino acid compositions and NH2-terminal sequences of the group V allergens from Lolium perenne, Poa pratensis and Dactylis glomerata

Impact of elevated air temperature and drought on pollen characteristics of major agricultural grass species

Grass pollen allergens are known to be one of the major triggers of hay fever with an increasing number of humans affected by pollen associated health impacts. Climate change characterized by increasing air temperature and more frequent drought periods might affect plant development and pollen characteristics. In this study a one-year (2017) field experiment was conducted in Bavaria, Germany, simulating drought by excluding rain and elevated air temperature by installing a heating system to investigate their effects primarily on the allergenic potential of eight selected cultivars of the two grass species timothy and perennial ryegrass. It could be shown for timothy that especially under drought and heat conditions the allergen content is significantly lower accompanied by a decrease in pollen weight and protein content. In perennial ryegrass the response to drought and heat conditions in terms of allergen content, pollen weight, and protein content was more dependent on the respective cultivar probably due to varying requirements for their growth conditions and tolerance to drought and heat. Results support recommendations which cultivars should be grown preferentially. The optimal choice of grass species and respective cultivars under changing climate conditions should be a major key aspect for the public health sector in the future.

Grass pollen production and group V allergen content of agriculturally relevant species and cultivars

Grass pollen is the main cause of hay fever and allergic asthma in warm temperate climates during summer. The aim of this study was to determine the content of group 5 major allergens in pollen grains of agriculturally important grass species/cultivars. For each cultivar flowering dates and pollen production of cut anthers were observed in the field and in a climate chamber, respectively. An ELISA was used to quantify the group 5 allergens (Phl p5) in pollen extracts which were gained from the grass species Kentucky bluegrass, perennial rye grass, timothy, cocksfoot, annual / Italian rye grass, hybrid rye grass and festulolium. The group 5 allergen content of species varied between 0.01 ng (Kentucky bluegrass) and 0.06 ng (timothy) per pollen grain. On cultivar level the pollen allergenic content differed up to 74-times within the selected grass species. Results from this study might be helpful for the reduction of allergen exposure coming from agriculture grass production e.g. by an adapted grass selection or by the cultivation of grasses with low allergenic content in plant breeding.

The Major Grass Pollen Group 5 Allergen from Dactylis glomerata and Its C-Terminal Split Product Both Behave as Dimers: Implications for Allergen Standardization

BACKGROUND

On SDS-PAGE grass pollen group-5 allergens migrate as a doublet with an apparent molecular mass (M(r)) of 25 kDa. Immunoblot analysis revealed additional group 5 reactivity at double and half this M(r). The aim of this study was to investigate these group 5 molecular entities and to compare their allergenicity and behavior in quantitative immunoassays.

METHODS

Group-5-specific monoclonal antibodies were produced and used for the development of a group-5-specific sandwich ELISA. Affinity-purified Dac g 5 was separated by SDS-PAGE/Western blotting; individual bands were analyzed by N-terminal sequencing. Size exclusion chromatography (SEC) in conjunction with group-5-specific ELISA, competitive RIA and RAST inhibition were used to analyze the size distribution of Dac g 5. Basophil histamine release assays were used to assess biological activity.

RESULTS

The lower band of the typical group 5 doublet was identified as a truncated form lacking the typical group 5 N-terminus AD(L)/(A)GY, observed in the upper band. The 12-kDa peptide was shown to be the C-terminal half of Dac g 5 (amino acid 127 onwards). SEC in conjunction with competitive RIA revealed that around 45% of Dac g 5 is represented by the 12-kDa peptide. Both the C-terminal half and the whole allergen dimerize under nondenaturing conditions. In competitive RIA and RAST inhibition both forms are equally well detected. In contrast, the half molecule is poorly recognized in sandwich ELISA and displays negligible biological activity in basophil histamine release tests with purified IgE.

CONCLUSIONS

These observations stress the need to evaluate the performance of allergen standardization protocols in detail, with special attention to allergen size distribution.

Phleum pratense-specific T cells of allergic rhinitis patients display a broader recognition pattern than phleum pratense-specific serum immunoglobulin E

BACKGROUND

The role of allergen-specific CD4+ T lymphocytes in the pathophysiology of atopic disease is well established. Previous studies on allergen-specific T-cell responses have focused on the recognition of single major allergens to identify T-cell epitopes.

OBJECTIVE

However, it is not clear whether immune responses to allergen extracts are exclusively targeted at major allergens or whether additional proteins are recognized.

METHODS

Here we describe the Phleum pratense-specific immunoglobulin E (IgE) and T-cell responses of six allergic rhinitis patients. Reactivity was measured to size-separated fractions of a P. pratense extract as well as to the purified major allergens Phl p 1, Phl p 2/3 and Phl p 5.

RESULTS

The specificity of the patients' serum IgE, measured in a fluid phase assay, was restricted to one or two of the major allergens. Even though the majority of the patients had IgE antibodies reactive with a single major allergen, one patient reacted with both Phl p 5 and with Phl p 2/3. Analysis of the T-cell repertoire with P. pratense-specific T-cell lines (TCLs) and CD4+ T-cell clones (TCCs) revealed that at least six different proteins were recognized, including the three major allergens, most notably Phl p 5. Simultaneous production of IL-5 and interferon (IFN) -gamma was detected in supernatants of the TCLs stimulated with P. pratense extract and the major allergens.

CONCLUSION

These results indicate that allergic rhinitis patients have a large pool of circulating allergen-specific CD4+ T cells that recognize many different proteins in an allergenic extract, whereas only a small number of these proteins are recognized by serum IgE.

Cutting Edge: Identification of Novel T Cell Epitopes in Lol p5a by Computational Prediction

Although atopic allergy affects ≤20% of the total population, the relationship between the protein structure and immunogenic activity of the allergens is still largely unknown. We observed that group 5 grass allergens are characterized by repeated structural motifs. Using a new algorithm, TEPITOPE, we predicted promiscuous HLA-DR ligands within the repeated motifs of the Lol p5a allergen from rye grass. In vitro binding studies confirmed the promiscuous binding characteristics of these peptides. Moreover, most of the predicted ligands were novel T cell epitopes that were able to stimulate T cells from atopic patients. We generated a panel of Lol p5a-specific T cell clones, the majority of which recognized the peptides in a cross-reactive fashion. The computational prediction of DR ligands might thus allow the design of T cell epitopes with potential useful application in novel immunotherapy strategies.

Genetic and environmental risk factors for asthma: a cotwin-control study

In complex diseases of genetic etiology such as asthma and atopy, it is difficult to differentiate causes of disease from consequences, and quantitate the importance of such causative factors. We examined possible risk factors for the development of wheezing and bronchial hyperresponsiveness in a cotwin-control study nested within a larger community-based twin-family study. In 62 monozygotic (MZ) twin pairs discordant for a history of wheezing, skin prick test to house dust extract was the most important discriminator, followed by sensitization to cat and cockroach allergens. In contrast, 62 dizygotic (DZ) discordant twin pairs differed additionally in sensitization to grass pollens and fungi. Markers such as serum haptoglobin, serum magnesium, and alpha-1-antitrypsin levels did not differ significantly between discordant twins. This MZ/DZ difference suggests that pollen allergy in asthmatics is more an epiphenomenon due to a genetic correlation between asthma and the allergic diathesis, whereas indoor allergens are likely to be direct environmental causes of asthma.

Group 5 determination in Pooideae grass pollen extracts by monoclonal antibody-based ELISA. Correlation with biologic activity

A solid-phase, monoclonal antibody-based ELISA was set up to quantitate group 5 allergens in pollen extracts of wild and cultivated Pooideae grasses. The method was able to evaluate group 5 concentration in mass units with a sensitivity in the ng/ml range and a practical working range of 1-100 ng/ml. The group 5 ELISA was compared with rocket immunoelectrophoresis for determination of allergen levels in several Phleum pratense extracts, and a very good quantitative correlation was found (r = 0.98; P < 0.0001). A highly significant correlation (r > 0.8) was also obtained in comparing allergenic potency determined by RAST inhibition to group 5 content in several wild and cultivated grass species. The results proved the usefulness of the method in the standardization of Pooideae pollen extracts employed in diagnosis and treatment.

Identification of a novel hydroxyproline-rich glycoprotein as the major allergen in Parthenium pollen

BACKGROUND

The airborne pollen of the Compositae weed, Parthenium hysterophorus, is a major cause of allergic rhinitis in the Indian subcontinent and in certain parts of the southern United States and western Australia. Earlier studies have identified a 31 kd protein as the major allergen in Parthenium pollen.

OBJECTIVE

This study was undertaken to carry out the purification, immunochemical characterization, sequencing, and epitope analysis of this major allergen, designated as Par h I.

METHODS

The IgE-binding activity of the allergen was evaluated by immunoblot and inhibition ELISAs. Pronase digestion, periodate oxidation, and chemical deglycosylation were performed to determine the role of peptide and carbohydrate components of the allergen in IgE binding.

RESULTS

The data provide evidence for the involvement of carbohydrate moieties on Par h 1 in its IgE-binding ability. The N-terminal 91 amino acid sequence of Par h 1 shows 81% identity with a protein from sunflower anther, and the hydroxyproline-rich region of Par h 1 is 30% to 40% identical to similar stretches in extensins, a class of hydroxyproline-rich cell wall glycoproteins from different plant species. IgE antibodies in the sera of individuals allergic to Parthenium cross-reacted with a 50 kd hydroxyproline-arabinose-rich extensin precursor from potato tuber, and this binding was periodate-sensitive.

CONCLUSIONS

It appears that a group of soluble plant glycoproteins, which are related to the ubiquitous extensins, have certain carbohydrate-containing IgE-binding epitopes that may contribute to allergenic cross-reactivity among specific pollens and foods.

Application of reversed-phase high-performance liquid chromatography in the purification of major allergens from grass pollen

Group 1 and 5 allergens of different grasses possess similar physicochemical parameters (molecular weight, pI) and therefore separation with conventional chromatographic methods (gel filtration, ion exchange chromatography) is difficult or impossible to achieve. In this paper we describe the isolation of biologically active group 1 and 5 allergens from extracts of Lolium perenne and Phleum pratense by means of reverse phase chromatography on HPLC. The chromatograms showed very different retention times for group 1 (Rt 19.1-20.5 min) and group 5 (Rt 24.3-26.3 min) containing fractions. In addition, this technique is suitable for the separation of group 5 allergens into 5a and 5b subgroups and for the estimation of the amounts of allergen (groups 1 and 5) in the different extracts.

Cloning, sequencing and immunological characterization of Dac g 3, a major allergen from Dactylis glomerata pollen

Preliminary work showed that a 14-kDa allergen with a pI of 9 was recognized by more than 60% of sera from Dactylis glomerata (Dac g) pollen-allergic individuals. The N-terminal amino acid sequence of this Dac g allergen was determined by Edman degradation and compared with that of Lol p 3, a major allergen of Lolium perenne. A sequence identity of 65% was found, suggesting that the Dac g allergen could be the homologue of Lol p 3 and therefore named Dac g 3. We report the cloning and sequence analysis of a cDNA encoding the Dac g 3 pollen allergen. The recombinant allergen (rDac g 3) expressed in plasmid vector pGEX-2T contained IgE-reactive epitopes found in its natural counterpart, and induced histamine release from basophils of Dac g-allergic individuals, confirming that the recombinant protein has biological properties similar to the pollen extracted allergen. Computer analyses showed that, in spite of a high degree of sequence homology, even closely related allergens such as Dac g 3 and Lol p 3 have dissimilar predictive secondary structures and potential different antigenicity. Because it possesses the properties of the native counterpart, rDac g 3 could be a relevant tool for molecular studies in allergy.

Cloning of a cDNA encoding a group-V (group-IX) allergen isoform from rye-grass pollen that demonstrates specific antigenic immunoreactivity

We have isolated and characterized the cDNA clone, 19R, that encodes an isoform of a major rye-grass pollen allergen, Lol p V [previously referred to as Lol p 1b; Singh et al., Proc. Natl. Acad. Sci. USA 88 (1991) 1384-1388; and Lol p IX; Suphioglu et al., Lancet 339 (1992) 569-572]. Clone 19R was isolated from a rye-grass pollen cDNA expression library using grass pollen-specific immunoglobulin E (IgE) antibodies (Ab) from an allergic serum pool. The nucleotide (nt) sequence of clone 19R potentially encodes a 33.8-kDa protein of 339 amino acids (aa). It possesses a leader peptide essentially identical to the previously characterized isoform of Lol p V (Lol p VA). This indicates a mature processed 31.3-kDa protein of 314 aa, correlating well with the size of the polypeptides revealed by Western analysis of pollen proteins using IgE Ab affinity purified from recombinant fusion protein (reFP) encoded by clone 19R as solid matrix. There is no N-glycosylation motif. The protein encoded by clone 19R, designated Lol p VB, has 66.4% identity and 80.4% similarity with Lol p VA. However, a Lol p VA-specific monoclonal Ab, FMC A7, does not recognize reFP encoded by clone 19R, indicating that Lol p VB does not share this epitope. Cross-reactivity studies using affinity purified IgE Ab showed that both isoforms share similar allergenic epitopes. Immunoblot analysis using sera from a population of 30 patients showed that 80% possess IgE Ab that recognize both Lol p V isoforms. Variation occurred in the signal intensities of IgE binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Monoclonal antibody immunoassay for quantitative analysis of group V allergens in grass pollen extracts

A two-site monoclonal antibody (MoAb) ELISA has been developed for the quantification of the Phleum pratense major allergen, Phl p V. The assay is based on two MoAbs which recognize different non-overlapping epitopes on the Phl p V molecule; one antibody (1D11) was immobilized on the solid phase and the other (3B2) was biotinylated. An affinity-purified Phl p V preparation (purity of 95%) was used as standard. The assay has a sensitivity of 10 ng/ml of allergen and is suitable for the detection of group V allergen in aqueous grass extracts. The specificity of the assay was investigated with 14 grass pollen and five non-grass pollen extracts. Different levels of group V allergen were detected in extracts of grasses, but not in non-grasses. The assay gives a good correspondence with allergenic activity of extracts as determined by ELISA inhibition using serum pool of allergic patients. The results indicate that the two-site MoAb ELISA could be very useful in the standardization of allergenic extracts from grass pollen.

Comparison of four grass pollen species concerning their allergens of grass group V by 2D immunoblotting and microsequencing

The identification and characterization of allergenic components is a vital step towards improving diagnosis and therapy. Members of the grass family (Poaceae) reveal a high cross-reactivity among each other caused by the close phylogenetical relationship. In order to investigate the variability between allergenic components, we studied the allergen grass group V, one of the major allergens. Pollen extracts of 4 different tribes (timothy grass (Phleum pratense)--Agrostidae, perennial rye grass (Lolium perenne)--Festuceae, meadow velvet (Holcus lanatus)--Aveneae, and rye (Secale cereale)--Triticeae) of the Festucoideae subfamily were separated by 2D PAGE and investigated by immunoblotting using patients' poolserum and monoclonal antibodies (raised against group V allergens of timothy grass pollen). The antibodies identify different allergens in the four grass species. The components vary from 30-50 kDa and pI 4.8-7.0. The eight NH2-terminal amino acids were determined and indicated high similarities between the different components. These results cast doubt on the suitability of classifying allergens into groups based only on their molecular mass, isoelectric point and N-terminal sequence analysis. It suggests to classify allergens according to their IgE-reactive epitopes.

IgE specific immune responses to an African grass (Kikuyu, Pennisetum clandestinum)

Kikuyu grass (Pennisetum clandestinum) is widely used as a grazing pasture in Africa and, although it is extensively cultivated as a lawn for sports fields and domestic gardens, its allergenicity has never been studied in vitro. Using an extract of Kikuyu grass pollen, polyacrylamide gel electrophoresis, Western blotting and a monoclonal anti-human IgE antibody, the specific IgE binding, in the serum of 160 allergic and non-allergic patients in the Cape Town area, to a Kikuyu grass extract was studied. IgE in the sera of 43/104 known grass-allergic individuals bound to Kikuyu grass on the Western blots. In addition, 4/28 'non-allergic' control subjects were found to have Kikuyu grass-specific IgE. Five different profiles of specific IgE reactivity to Kikuyu grass antigens were observed. In 29/43 patients, IgE bound to two dominant 48 and 70 kD allergens in the Kikuyu extract. Although a degree of cross-reactivity with Bermuda grass (Cynodon dactylis) was found in immunoabsorption studies, the 48 and 70 kD allergens appear to be unique to Kikuyu grass. Exposure of heparinized blood from Kikuyu grass-positive patients to the Kikuyu extract stimulated the release of histamine from their basophils in vitro. Kikuyu grass pollen is thus identified as an important aero-allergen in South Africa.