Composition and stability of allergenic extracts made from gamma-irradiated rye grass (Lolium perenne) pollen

BACKGROUND: Phenol is commonly added to allergenic extracts as a bacteriostatic agent, but it is poisonous and also detrimental to proteins, which accelerates extract degradation. Sterilization by gamma-irradiation of the source material could be an alternative to the use of phenol. OBJECTIVE: To analyse the potential effects of gamma-irradiation of pollen on the composition, potency, and stability of the resulting extract, and compare them with those of phenol. METHODS: Ryegrass (Lolium perenne) pollen was sterilized by gamma-irradiation at a dose of 25 kGy. Extracts prepared from the irradiated pollen were then compared by electrophoresis techniques and RAST inhibition to extracts, without or with 0.5% phenol, from nonirradiated pollen. In addition, proteolytic activity was compared in extracts from irradiated and nonirradiated pollen. To evaluate the stability of extracts on storage, they were analysed after forced degradation for up to 7 days at 37 degrees C. RESULTS: When fresh extracts were analysed, there were no noticeable differences between the three types, as judged by immunoblotting and RAST inhibition experiments. However, on storage, extracts from irradiated pollen appeared to be superior to extracts from nonirradiated pollen, as some proteins were more stable in the former. This could be related to the lower proteolytic activity we have also observed in extracts from irradiated pollen. In contrast, extracts containing phenol degraded much faster, as proven by all our methods of investigation. CONCLUSION: Gamma-irradiation of pollen did not influence the IgE-binding capacity of the resulting extracts, but did yield extracts with somewhat improved stability, probably by reducing the proteolytic activity. It may be concluded that gamma-irradiation of the source material represents a good alternative to the use of phenol for the preparation of allergenic extracts.     

Purification and molecular weight studies on the components of a parietaria pollen extract

The pollen extract of the allergenic plant Parietaria judaica, growing throughout the Mediterranean region, has been purified by high performance liquid chromatography (HPLC) operating in size-exclusion followed by ion exchange. Molecular weight determination of the components and isoelectrofocusing studies on the enriched material have been performed.     

Purified Timothy grass pollen major allergen Phl p 1 may contribute to the modulation of allergic responses through a pleiotropic induction of cytokines and chemokines from airway epithelial cells

By definition, allergens are proteins with the ability to elicit powerful T helper lymphocyte type 2 (Th2) responses, culminating in immunoglobulin (Ig)E antibody production. Why specific proteins cause aberrant immune responses has remained largely unanswered. Recent data suggest that there may be several molecular paths that may affect allergenicity of proteins. The focus of this study is the response of airway epithelium to a major allergen from Phleum pratense Phl p 1. Instead of focusing on a few genes and proteins that might be affected by the major allergen, our aim was to obtain a broader view on the immune stimulatory capacity of Phl p 1. We therefore performed detailed analysis on mRNA and protein level by using a microarray approach to define Phl p 1-induced gene expression. We found that this allergen induces modulation and release of a broad range of mediators, indicating it to be a powerful trigger of the immune system. We were able to show that genes belonging to the GO cluster 'cell communication' were among the most prominent functional groups, which is also reflected in cytokines and chemokines building centres in a computational model of direct gene interaction. Further detailed comparison of grass pollen extract (GPE)- and Phl p 1-induced gene expression might be beneficial with regard to the application of single components within diagnosis and immunotherapy.     

Stability of Protease-Rich <Emphasis Type="Italic">Periplaneta americana</Emphasis> Allergen Extract During Storage: Formulating Preservatives to Enhance Shelf Life

Allergenic proteins in extracts degrade rapidly and lose potency on storage. Hence, formulation of optimum conditions is required to enhance shelf life of extracts for proper allergy diagnosis and immunotherapy. In the present study, allergenic potency of P. americana proteins was evaluated after storage with ε-aminocaproic acid (EACA), sucrose, glycerol, pepstatin A, and aprotinin, individually for 1, 3, 6, and 12 months at 4, 25, and 37°C. P. americana extract stored with EACA and sucrose individually retained potency comparable to proteins in standard extract (freeze-dried extract, stored at−70°C) upto 6 months at 4°C. The extracts without preservatives or with glycerol, pepstatin A, aprotinin, or stored at 37/25°C were severely degraded and lost potency by 3 months. A formulation containing a combination of EACA and sucrose enhanced the shelf life of P. americana proteins upto 12 months at 4°C. Hence, EACA and sucrose together show better potential for stabilization of protease-rich extracts.     

Altered antigenicity of M-177, a 177-kDa allergen from the house dust mite Dermatophagoides farinae, in stored extract

BACKGROUND: A high molecular weight allergen, M-177 (177 kDa) was isolated from Dermatophagoides farinae using a specific antibody raised to an allergenic clone Mag 3, which was obtained by immunoscreening a mite cDNA library. The potent IgE reactivity of M-177 is comparable with that of Der f 2. OBJECTIVE: The aim of this study was to analyse the molecular characteristics and the allergenic activity of M-177 in stored mite extracts. METHODS: Antigens were analysed by immunoblotting and enzyme-linked immunosorbent assay (ELISA; inhibition). Allergenic activity was estimated from IgE reactivity and the results of a histamine release assay. RESULTS: The intact M-177 molecule was present in high concentrations in fresh extract obtained from purified mite bodies, but was only detected in small amounts in stored extracts. Instead of the intact molecule, anti-Mag 3 antibody detected various cross-reactive antigens in the stored preparations. Studies of a stored liquid extract showed that these cross-reactive antigens were produced by the degradation of M-177, and that this change was suppressed by the addition of protease inhibitors. Interestingly, the allergenic activity of the fragmented M-177 (sM-177) isolated from the stored extracts was greater than that of the intact antigen. Specific IgE reacted with sM-177 in 84.2% of 38 sera samples from patients allergic to mites, while 65.8% were positive for M-177-specific IgE. Similarly, the histamine release test showed that sM-177 had greater allergenic activity in vitro. ELISA inhibition indicated that the increased allergenic activity resulted from alteration of the antigenicity with the degradation of M-177. CONCLUSIONS: M-177 is a protease-sensitive allergen. The breakdown products of M-177 provoked higher allergenic activity than the intact allergen.     

Effect of grass pollen immunotherapy with Alutard SQ on quality of life in seasonal allergic rhinoconjunctivitis

BACKGROUND: Treatment of allergic rhinitis with subcutaneous allergen immunotherapy is effective in terms of reductions in symptoms and seasonal use of reliever medication. Its effect on quality of life (QoL), reflecting the impact of symptoms on work/school performance and leisure activities is, however, important and often overlooked. AIMS OF THE STUDY: To assess effect on QoL of specific immunotherapy with two doses of Alutard SQ Phleum pratense in patients with moderately to severe seasonal allergic rhinoconjunctivitis inadequately controlled by standard drug therapy. METHODS: Double-blind, randomized, placebo-controlled study of 410 patients with seasonal allergic rhinoconjunctivitis. Participants were randomized (2 : 1 : 1) to receive Alutard SQ P. pratense (ALK-Abelló) at maintenance doses of 100,000 SQ-U (203 subjects), 10,000 SQ-U (104 subjects) or placebo (103 subjects) given by subcutaneous injections. The groups were well matched for demographics and baseline symptoms. Quality of life was assessed using the Rhinoconjunctivitis Quality of Life Questionnaire which covers seven domains of health before and in the peak of the pollen season. RESULTS: While all domain scores were significantly improved when comparing 100,000 SQ-U with placebo, two domain scores were significantly improved when comparing 10,000 SQ-U with placebo. When comparing 100,000 SQ-U with 10,000 SQ-U, four domain scores were significantly improved. CONCLUSION: Treatment with Alutard SQ significantly improved the seasonal QoL of patients suffering from allergic rhinoconjunctivitis. The improvement was more pronounced and wider ranging in patients who received the higher 100,000 SQ-U maintenance dose.     

Spatial clustering of the IgE epitopes on the major timothy grass pollen allergen Phl p 1: importance for allergenic activity

BACKGROUND: The major timothy grass pollen allergen Phl p 1 is one of the most potent and frequently recognized environmental allergens. OBJECTIVE: We sought to study at a molecular and structural level the IgE recognition of Phl p 1 and its relation to allergenic activity. METHODS: Monoclonal human IgE antibody fragments specific for Phl p 1 and group 1 allergens from various grasses were isolated from a combinatorial library made of lymphocytes from patients with grass pollen allergy. Recombinant Phl p 1 fragments and the 3-dimensional structure of Phl p 1 were used to localize the major binding site for the IgE antibodies. A rPhl p 1 fragment containing this binding site was expressed in Escherichia coli, purified, and tested for IgE reactivity and allergenic activity with sera and basophils from patients with grass pollen allergy. RESULTS: Monoclonal antibodies, as well as polyclonal serum IgE, from patients with grass pollen allergy defined a C-terminal fragment of Phl p 1 that represents a sterically oriented portion on the Phl p 1 structure. This Phl p 1 portion bound most of the allergen-specific IgE antibodies and contained the majority of the allergenic activity of Phl p 1. CONCLUSION: IgE recognition of spatially clustered epitopes on allergens might be a general factor determining their allergenic activity. CLINICAL IMPLICATIONS: Geographic distribution of IgE epitopes on an allergen might influence its allergenic activity and hence explain discrepancies between diagnostic test results based on IgE serology and provocation testing. It might also form a basis for the development of low allergenic vaccines.     

Isolation and immunochemical characterization of the major allergen of birch pollen (Betula verrucosa)

The classification of some of the extractable birch pollen antigens as allergens was established by crossed radioimmunoelectrophoresis (CRIE). In CRIE the major allergen (antigen 23) exhibited the strongest “radiostaining” and only a few other components of birch pollen extract were visibly radiostained. The major allergen and a preparation containing mainly the minor allergens, antigens 25 and 19, were isolated from a crude aqueous birch pollen extract by a combination of anion-exchange, size-exclusion, and chelate chromatography. Antigen 23 was purified to near homogeneity. The molecular weights and the pIs of antigens 23, 25, and 19 were determined to be 17,000 daltons, pI 5.25 (5.5, 5.0); 25,000 daltons, pI 5.0 (4.9, 5.4); and 29,000 daltons, pI 6.2 (5.4), respectively. The classification of antigen 23 as the major allergen in birch pollen was supported by results of RAST inhibition experiments, RAST screening, and skin prick testing.     

Discontinuous IgE-binding epitopes contain multiple continuous epitope regions: results of an epitope mapping on recombinant Hol l 5, a major allergen from velvet grass pollen

The knowledge of IgE-binding epitopes on allergen molecules is important for better understanding allergen-antibody interactions and, thus, for developing new strategies for immunotherapy. Our purpose was to more precisely define the number and structure of IgE-binding epitopes of a paradigmatic major grass pollen allergen. We performed an IgE-binding epitope mapping of rHol l 5, a group V pollen allergen of velvet grass (Holcus lanatus), with overlapping fragments (length between 15 and 186 amino acids), which were expressed in E. coli as MBP fusion proteins. Using sera of 65 grass pollen allergic patients, the fragments were analysed by immunoblotting for IgE reactivity. Specificity of antibody binding was confirmed by competitive blot inhibition assays. At least four different continuous IgE-binding epitopes were identified on small fragments (about 30 amino acids), and at least five different discontinuous IgE-binding epitopes on larger fragments, which were destroyed by further fragmentation. The fragments were differentially recognized by individual patients' sera. By investigating IgE-binding to one of the small fragments in more detail, we found further epitope regions on this fragment. It was noteworthy that IgE reactivity to small fragments was weak compared to large fragments or to the complete molecule. Competitive blot inhibition experiments showed that binding of IgE antibodies to the small fragments was specific but with lower avidity than to the complete rHol l 5. rHol l 5 harbours multiple discontinuous as well as continuous IgE-binding epitopes spread over the whole molecule, which were individually recognized by IgE antibodies from different patients. Low avidity of IgE antibodies to small fragments suggests that the continuous epitope regions do not represent the complete epitope and are most probably parts of discontinuous epitopes.