Physicochemical and immunologic characterization of low-molecular-weight allergoids of Dactylis glomerata pollen proteins

Characterisation of Alternaria alternata Allergoids: Evaluation of the Stability of Grass Pollen Allergen Extracts Mixed with Alternaria alternata Allergoids

Allergens from pollen, mites, and moulds often sensitise patients simultaneously, posing challenges for developing stable and effective combination vaccines. Alternaria alternata, a major source of indoor and outdoor allergens, is strongly linked to asthma development and contains proteolytic enzymes that can degrade other allergens, potentially reducing vaccine efficacy. This study aimed to evaluate the safety, efficacy, and stability of polymerised A. alternata extracts (allergoids) compared to native extracts and their compatibility with pollen extracts (Phleum pratense). Allergoids were prepared using glutaraldehyde and characterised through SDS-PAGE, LC-MS/MS, NMR, and gas chromatography. Their immunogenicity and IgE-binding properties were assessed via Western blot and ELISA competition assays, while enzymatic activity was analysed using ApiZym kits. Mice immunisation experiments were conducted to evaluate antibody responses. Polymerised extracts exhibited reduced IgE-binding capacity while maintaining IgG-binding and immunogenicity. Mice immunised with allergoids generated antibodies that efficiently blocked IgE binding in allergic patients. Proteolytic activity was significantly reduced in allergoids, and pollen extracts remained stable when combined with them. These findings demonstrate that A. alternata allergoids are a safer, more stable alternative for immunotherapy, offering enhanced efficacy and reduced injections for polysensitised patients. This study provides critical insights for designing optimised combination vaccines.

A novel and well tolerated mite allergoid subcutaneous immunotherapy: evidence of clinical and immunologic efficacy

Allergy to house dust mite is one of the most common causes of allergic rhinitis. A novel tyrosine-adsorbed, modified allergen product, Acarovac Plus, developed for the treatment of perennial mite allergy seeks to address the underlying cause of allergic rhinitis in this instance. One of two dosing regimens may be used, either the Conventional Regimen or the Cluster Regimen. We sought to compare the efficacy and safety of a specific immunotherapy, developed for the treatment of perennial mite allergy, administered under a Conventional and Clustered dosing schedule in patients with persistent allergic rhinitis. Thirty adult patients, between 18 and 65 years old, with allergic rhinitis and/or asthma secondary to hypersensitivity to Dermatophagoides pteronyssinus were administered with either conventional or cluster initial regime, with a final visit one week after the last dose administration. The efficacy to the Conventional and Cluster regimens was measured using a Nasal Challenge Test monitoring clinical symptoms and peak nasal inspiratory flow. Total IgE, serum-specific inmunoglobulins (IgE and IgG4) to Dermatophagoides pteronyssinus and relevant cytokines (IFN-γ, IL-4, IL-5, IL-10 and IL-13) were assessed. A Satisfaction Questionnaire (TSQM) was completed after each patient's final visit. The tolerability of the vaccine was assessed monitoring adverse reactions. No adverse events were recorded in either conventional or cluster regime. The specific Nasal Challenge Test led to a decrease in symptom scores and a significant decrease in mean nasal peak inspiratory flow drop was recorded in both dosing regimen groups. A significant increase in IgG4-specific antibody titres was assessed. No significant changes were observed in concentrations of total IgE, specific IgE or cytokines (IFN-γ, IL-4, IL-5, IL-10 and IL-13). Patients declared themselves most satisfied in relation to "Secondary effects", with high overall satisfaction in both groups. Cluster and conventional specific immunotherapy resulted in no adverse reaction(s) and led to similar improvements in immunological parameters, clinical efficacy (Nasal Challenge Test) and high overall satisfaction.

Detection of allergen composition and in vivo immunogenicity of depigmented allergoids of Betula alba

BACKGROUND

Chemical modification of allergen vaccines to reduce IgE binding improves safety while maintaining clinical efficacy. However, this also complicates the characterization of allergoids using techniques as for native allergen extracts.

OBJECTIVES

The objective of this study was to analyse the molecular size of Betula alba depigmented allergoids, conservation of major allergens in the allergoids and in vivo antibody response to immunization.

METHODS

The molecular size of depigmented allergoids was evaluated by high performance-size exclusion chromatography and light scattering techniques. Protein composition was compared with native extracts by capillary liquid chromatography-tandem mass spectrometry based peptide mapping. Rabbits were immunized with depigmented allergoid of Betula pollen adsorbed onto aluminium hydroxide (Depigoid). IgG antibodies against individual allergens were determined by ELISA and immunoblot.

RESULTS

Depigmented allergoids contained a range of high molecular weight particles, approximately 60% of which had a molecular weight of 1-3 MDa. Peptide sequencing confirmed the preservation of five isoforms of Bet v 1, as well as Bet v 2, Bet v 6 and Bet v 7. Sera from immunized rabbits showed high levels of specific IgG to rBet v 1.0101 and rBet v 2.

CONCLUSIONS

The mean protein content was 544+/-106 microg per mg of freeze-dried material for depigmented allergoids and 434+/-71 for native extracts. They retain the capacity to induce specific IgG antibodies against individual allergens present in the native extract. These findings confirm the immunogenicity of depigmented allergoids and may explain why patients treated with these vaccines are protected against the native allergens. Analysis of molecular size and allergen content may be useful techniques for characterization and standardization of allergoid products.

Allergenicity, immunogenicity and dose-relationship of three intact allergen vaccines and four allergoid vaccines for subcutaneous grass pollen immunotherapy

Different vaccines containing intact allergens or chemically modified allergoids as active ingredients are commercially available for specific immunotherapy. Allergoids are claimed to have decreased allergenicity without loss of immunogenicity and this is stated to allow administration of high allergoid doses. We compared the allergenicity and immunogenicity of four commercially available chemically modified grass pollen allergoid products with three commercially available intact grass pollen allergen vaccines. The allergenicity was investigated with immunoglobulin (Ig)E-inhibition and basophil activation assays. Human T cell proliferation and specific IgG-titres following mouse immunizations were used to address immunogenicity. Furthermore, intact allergen vaccines with different contents of active ingredients were selected to study the influence of the allergen dose. In general, a lower allergenicity for allergen vaccines was clearly linked to a reduced immunogenicity. Compared with the vaccine with the highest amount of intact allergen, the allergoids caused reduced basophil activation as well as diminished immunogenicity demonstrated by reduced T cell activation and/or reduced induction of murine grass-specific IgG antibodies. Interestingly, intact allergen vaccines with lower content of active ingredient exhibited similarly reduced allergenicity, while immunogenicity was still higher or equal to that of allergoids. The low allergenicity observed for some allergoids was inherently linked to a significantly lower immunogenic response questioning the rationale behind the chemical modification into allergoids. In addition, the linkage between allergenicity, immunogenicity and dose found for intact allergen vaccines and the immunogen as well as allergenic immune responses observed for allergoids suggest that the modified allergen vaccines do not contain high doses of immunologically active ingredients.

Quantification of Art v 1 and Act c 1 being major allergens of mugwort pollen and kiwi fruit extracts in mass-units by ion-exchange HPLC-UV method

A simple ion-exchange HPLC-UV method was developed for determination of major allergens from mugwort pollen and kiwi fruit extracts in mass-units. The separation of Art v 1 and Act c 1 from other components in the extracts was achieved in one step. The extinction coefficients used in the study were theoretically determined and compared to the extinction coefficients determined by gravimetry. We also reported a close correlation of the major allergen contents with the overall allergenic potency of the extracts determined by inhibition ELISA. This method could be a useful tool for standardization of allergenic extracts for clinical use.

Comparison of allergenicity and immunogenicity of an intact allergen vaccine and commercially available allergoid products for birch pollen immunotherapy

BACKGROUND

Specific immunotherapy with intact allergen vaccine is a well-documented treatment for allergic diseases. Different vaccine formulations are currently commercially available, the active ingredient either being intact allergens or chemically modified allergoids. The rationale behind allergoids is to decrease allergenicity while maintaining immunogenicity. However, data from the German health authorities based on reporting of adverse events over a 10-year period did not indicate increased safety of allergoids over intact allergens.

OBJECTIVE

The objective of this study was to investigate the effect of chemical modification on allergenicity and immunogenicity comparing four commercial allergoid products for birch pollen immunotherapy with an intact allergen vaccine.

METHODS

Solid-phase IgE inhibition and histamine release assays were selected as model systems for allergenicity, and a combination of human T cell proliferation and IgG titres following mouse immunizations were used to address the immunogenicity of the intact allergen vaccine and the four allergoids. In all assays, the products were normalized with respect to the manufacturer's recommended maintenance dose.

RESULTS

IgE inhibition experiments showed a change in epitope composition comparing intact allergen vaccine with allergoid. One allergoid product induced enhanced histamine release compared to the intact allergens, while the other three allergoids showed reduced release. Standard T cell stimulation assays using lines from allergic patients showed a reduced response for all allergoids compared with the intact allergen vaccine regardless of the cell type used for antigen presentation. All allergoids showed reduced capacity to induce allergen-specific IgG responses in mice.

CONCLUSION

While some allergoids were associated with reduced allergenicity, a clear reduction in immunogenicity was observed for all allergoid products compared with the intact allergen vaccine, and the commercial allergoids tested therefore do not fulfil the allergoid concept.

Artemisia vulgaris pollen allergoids digestibility in the simulated conditions of the gastrointestinal tract

Chemically modified allergens (allergoids) have found use in both traditional and novel forms of immunotherapy of allergic disorders. Novel forms of immunotherapy include local allergen delivery, via the gastrointestinal tract. This study conveys the gastrointestinal stability of three types of mugwort pollen allergoids under simulated conditions of the gut. Allergoids of the pollen extract of Artemisia vulgaris were obtained by means of potassium cyanate, succinic and maleic anhydride. Gastrointestinal tract conditions (saliva, and gastric fluid) were simulated in accordance with the EU Pharmacopoeia. The biochemical and immunochemical properties of the derivatives following exposure to different conditions were monitored by determining the number of residual amino groups with 2,4,6-trinitrobenzenesulfonic acid, SDS PAGE, immunoblotting and inhibition of mugwort-specific IgE. Exposure to saliva fluid for 2 min did not influence the biochemical and immunochemical properties of the derivatives. In the very acidic conditions of the simulated gastric fluid, the degree of demaleylation and desuccinylation, even after 4 h exposure, was low, ranging from 10 to 30 %. The digestion patterns with pepsin proceeded rapidly in both the unmodified and modified samples. In all four cases, a highly resistant IgE-binding protein the Mwof which was about 28-35 kD, was present. Within the physiological conditions, no new IgE binding epitopes were revealed, as demonstrated by immunoblot and CAP inhibition of the mugwort specific IgE binding. An important conclusion of this study is the stability of the modified derivatives in the gastrointestinal tract of patients, within physiological conditions. The means that they are suitable for use in much higher concentrations in local forms of immunotherapy than unmodified ones.

Overview of the most commonly used methods in allergen characterization

The characterization of an allergen is a troublesome and difficult process, as it requires both the precise biochemical characterization of a (glyco)protein molecule and the establishment of its susceptibility to IgE antibodies, as they are the main link to histamine release in some hypersensitivity states (type I allergies). As the characterization of an allergen includes molecular weight determination of the allergenic molecule, its structure determination, physicochemical properties, IgE binding properties of the allergen molecule, and its allergenicity, an overall review of which biochemical and immunochemical methods are used in achieving this goal are presented in this paper. The information on the molecular level on the structures of allergens indicates that allergens are considerably heterogeneous protein structures, and that there is no particular aminoacid sequence which is responsible for the allergenicity. Therefore, information gained from detailed structural, functional and immunochemical studies of these intriguing molecules, which nowadays modulate a variety of pathophysiological conditions, would greatly improve our understanding of the underlying disease mechanisms, and the way to handle them.

IgG binding of mugwort pollen allergens and allergoids exposed to simulated gastrointestinal conditions measured by a self-developed ELISAtest

This study considers the influence of exposure to simulated gastrointestinal conditions (saliva, gut, intestine and acidic conditions of the gut) on IgG binding of unmodified allergens and three types of LMW allergoids of Artemisia vulgaris pollen extract obtained by means of potassium cyanate succinic and maleic anhydride. It also concerns the optimization of a self-developed ELISA assay for comparison of the specific IgG binding of mugwort pollen extract and modified mugwort pollen derivatives. The ELISA was conducted with a mugwort pollen extract coupled to the plate, using the sera from 12 mugwort- pollen allergic patients. The exposure to saliva fluid for 2 min did not influence the IgG binding properties of allergens and allergoids. Exposure of mugwort pollen allergens and LMW allergoids to the acidic conditions of the gut did not dramatically change their IgG binding properties. By exposing mugwort pollen extract and LMW derivatives to the SGF conditions for 1 h, the percent of IgG binding epitopes was reduced to a half of its starting value in the extract and to about 30%in all the allergoid samples. After prolonged exposure only the carbamyl derivative showed reduced IgG binding. Changes of the IgG binding potential of all four samples after exposure in SIF followed a similar pattern.

The influence of a residual group in low-molecular-weight allergoids of Artemisia vulgaris pollen on their allergenicity, IgE- and IgG-binding properties

BACKGROUND

Reaction of epsilon-amino groups of lysine with potassium cyanate, maleic, or succinic anhydride leads to allergoids of low molecular weight. No study has been performed to compare their properties and investigate the influence of a residual group on allergenicity and human IgE- and IgG-binding of these derivatives.

METHODS

Allergoids of a pollen extract of Artemisia vulgaris were obtained by means of potassium cyanate, and succinic and maleic anhydride. Biochemical properties were investigated by determination of amino groups, enzyme activity, isoelectric focusing IEF and SDS-PAGE. IgE- and IgG-binding was determined using immunoblots and ELISA inhibition. Allergenicity was investigated by skin prick tests (SPT) on a group of 52 patients, of which 6 were control subjects, 30 were patients with no previous immunotherapy (IT), and 16 were patients undergoing immunotherapy.

RESULTS

The same degree of amino-group modification (more than 85%), residual enzyme activity (less then 15%), IEF, and SDS-PAGE pattern were noted. In the immunoblots of IgE-binding, there was more pronounced reduction in the succinyl and maleyl derivatives than in the carbamyl one. IgG-binding was less affected by carbamylation than by acid anhydride modification. The SPT showed that the succinylated derivative had the most reduced allergenicity (98% showed a reduced wheal diameter when tested with the succinyl derivative, 87% with the maleyl allergoid, and 83% with the carbamyl allergoid). The most significant difference among allergoids could be seen in the group of patients with high skin reactivity (83% of patients showed no reaction to the succinyl derivative when compared to the value of 28% for the carbamyl derivative or 22% for the maleyl derivative).

CONCLUSIONS

According to our results, all three modification procedures yielded allergoids with a similar extent of modification. No single biochemical parameter investigated in the study could predict the degree of reduced allergenicity in vivo. The most reduced allergenicity was seen in the succinyl derivative while the preservation of IgG binding epitopes was of the highest degree for the carbamyl derivative.

Isolation and partial characterization of an acid phosphatase from Artemisia vulgaris pollen extract

An acid phosphatase from an extract of mugwort (Artemisia vulgaris) pollen was purified by a factor of 48 by a combination of ion exchange and gel-chromatography. The molecular weights of the enzyme were 76 kDa and 73 kDa, determined by gel filtration on a Sephadex G-100 sf column and by SDS PAGE(under reducing and non-reducing conditions), respectively. In analytical isoelectrofocusing, the enzyme appears as two very close bands pI at about 4.2. The optimum pH for the enzyme is 5.4. The apparent Km for p-nitrophenyl phosphate was estimated to be 0.16mM. The purified enzyme has broad specificity, and hydrolyses p-nitrophenyl phosphate and ?-naphthyl phosphate. Pyrophosphate and O-phospho-L-tyrosine were estimated to be the best substrates for this enzyme as potential in vivo substrates. The enzyme is inhibited competitively by phosphate (Ki = 1.25 mM), molybdate (Ki = 0.055 mM) and pyrophosphate (Ki = 6.7 mM) and non-competitively by fluoride (Ki = 9.8 mM). Metal ions such as Hg2+, Cu2+ and Zn2+ express an inhibitory effect on the enzyme, while the enzyme is slightly activated by non-ionic detergents, Tween 20 and Triton X-100. There is no change in the enzyme activity in the presence of tartrate, citrate, EDTA, 1,10-phenanthroline and sulfhydryl-group modifiers such as p-chloromercuribenzoate and N-ethylmaleimide.

Regulation of specific immune responses by chemical and structural modifications of allergens

Specific immunotherapy (SIT) is an efficient treatment of allergic diseases to defined allergens. Despite being used in clinical practice since early in this century, more rational and safer regimens are required, because SIT is faced with the risk of anaphylaxis and standardization problems of allergen-extract-based treatments. A better understanding of the pathogenesis of allergy and of the mechanisms of SIT has led to various approaches to overcome these problems. Knowledge of the influence of IgE-facilitated antigen presentation on allergen-specific Th2 responses increased the efforts to generate non-IgE-binding allergens. The current principal approach to allergen modification is to modify B cell epitopes in order to prevent IgE binding and effector cell cross-linking while preserving T cell epitopes to retain the capacity of inducing tolerance. In this way, the modified allergen will be directed to T cells by a phagocytosis/pinocytosis-mediated antigen uptake mechanism, bypassing IgE cross-linking and IgE-dependent antigen presentation. Accordingly, a differential regulation of allergen-specific T cell cytokine patterns and IgE:IgG production was demonstrated by modifications of the three-dimensional structure of allergens because of linearity in T cell epitopes and conformation dependence in B cell epitopes. In this context, chemically modified allergen extracts with low IgE-binding capacity have been developed to reduce anaphylactic side effects since the early 1980s. The progress of recombinant techniques for producing allergens and allergen derivatives has led to a dramatic improvement in the ability of developing novel vaccines for the treatment of allergy. This has enabled mutation or deletion of decisive amino acids in B cell epitopes and fractionation or oligomerization of allergens by genetic engineering as fruitful approaches to generate hypoallergenic vaccines. Moreover, non-IgE-binding short T cell epitope peptides and single-amino-acid-altered peptide ligands represent potential candidates for future SIT.