Molecular approaches for new vaccines against allergy

Construction by artificial intelligence and immunovalidation of hypoallergenic mite allergen Der f 36 vaccine

Background

The house dust mite (HDM) is widely recognized as the most prevalent allergen in allergic diseases. Allergen-specific immunotherapy (AIT) has been successfully implemented in clinical treatment for HDM. Hypoallergenic B-cell epitope-based vaccine designed by artificial intelligence (AI) represents a significant progression of recombinant hypoallergenic allergen derivatives.

Method

The three-dimensional protein structure of Der f 36 was constructed using Alphafold2. AI-based tools were employed to predict B-cell epitopes, which were subsequently verified through IgE-reaction testing. Hypoallergenic Der f 36 was then synthesized, expressed, and purified. The reduced allergenicity was assessed by enzyme-linked immunosorbent assay (ELISA), immunoblotting, and basophil activation test. T-cell response to hypoallergenic Der f 36 and Der f 36 was evaluated based on cytokine expression in the peripheral blood mononuclear cells (PBMCs) of patients. The immunogenicity was evaluated and compared through rabbit immunization with hypoallergenic Der f 36 and Der f 36, respectively. The inhibitory effect of the blocking IgG antibody on the specific IgE-binding activity and basophil activation of Der f 36 allergen was also examined.

Results

The final selected non-allergic B-cell epitopes were 25-48, 57-67, 107-112, 142-151, and 176-184. Hypoallergenic Der f 36 showed significant reduction in IgE-binding activity. The competitive inhibition of IgE-binding to Der f 36 was investigated using the hypoallergenic Der f 36, and only 20% inhibition could be achieved, which is greatly reduced when compared with inhibition by Der f 36 (98%). The hypoallergenic Der f 36 exhibited a low basophil-stimulating ratio similar to that of the negative control, and it could induce an increasing level of IFN-γ but not Th2 cytokines IL-5 and IL-13 in PBMCs. The vaccine-specific rabbit blocking IgG antibodies could inhibit the patients' IgE binding and basophil stimulation activity of Derf 36.

Conclusion

This study represents the first application of an AI strategy to facilitate the development of a B-cell epitope-based hypoallergenic Der f 36 vaccine, which may become a promising immunotherapy for HDM-allergic patients due to its reduced allergenicity and its high immunogenicity in inducing blocking of IgG.

Expression, epitope prediction and IgE-binding of the Tyrophagus putrescentiae group 13 allergen

Storage mites, such as Tyrophagus putrescentiae, are an important source of allergens that cause allergic diseases in humans. It has previously been indicated that T. putrescentiae has a high sensitization rate as an allergen in some Asian and European countries. Identifying and cloning the allergens in this species may enable improved diagnostic and therapeutic approaches. The aim of the present study was to clone and sequence the T. putrescentiae group 13 allergen (Tyr p 13) isolated from storage mites in China, to use bioinformatics tools to model its biophysical characteristics and to induce protein expression to test its IgE-binding activity. The full-length cDNA comprised 486 bp and was predicted to include a signal peptide of 22 amino acids. Its secondary structure was shown to comprise an α-helix (10.79%), extended strand (33.81%) and random coils (55.40%). Using homology modeling, the present study constructed a reasonable tertiary structure of Tyr p 13. Linear Bcell epitopes at amino acids 47-53, 70-76, 81-86, 101-105 and 112120 were predicted. Three discontinuous B-cell epitopes were also predicted: i) 47, 48, 49, 50, 51, 52, 53, 70, 71, 72 and 73; ii) 91, 92, 93, 94, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121 and 138; and iii) 74, 76, 79, 81, 82, 83, 84, 86, 101, 102, 103, 104 and 105. SDS-PAGE identified a specific band at the predicted molecular weight of the recombinant Tyr p 13 (rTyr p 13), demonstrating its successful expression. The rTyr p 13 bound to IgE in the serum of 13.2% (5/38) of patients allergic to T. putrescentiae, according to ELISA. The successful cloning of Tyr p 13 and basic bioinformatics analysis of the protein provided a foundation for the further study of this allergen with regards to the diagnosis and treatment of patients allergic to storage mites. These results provided a theoretical basis for the design of rTyr p 13 with modified B-cell epitopes.

[Molecular component-resolved allergy diagnostics in ENT]

Molecular component-resolved diagnostics (CRD) are, in addition to its research applications, being increasingly used in daily allergological routine. CRD offers improved diagnostic accuracy via a better understanding of the underlying allergen causing symptoms and helps to distinguish between true sensitization and cross reactions in polysensitized patients, thereby providing an approach for individual personalized therapy. Particularly in food allergies and anaphylaxis, CRD can stratify risks for the recurrence of reactions and their severity. The education and extended vocational training of clinical allergologists has to keep pace with the tremendous increase of knowledge in the field of molecular allergology.

Recombinant allergen-based provocation testing

Over the last 25 years, recombinant allergens from all important allergen sources have been cloned and are now available as recombinant proteins. These molecules can be produced in practically unlimited amounts without biological or batch-to-batch variability. It has been shown in provocation tests that recombinant allergens have similar clinical effects as their natural counterparts. With the help of these tools it is possible to reveal the precise reactivity profiles of patients and to uncover and differentiate cross-reactivity from genuine sensitization to an allergen source. Although it has been shown some time ago that it would be possible to replace crude allergen extracts with recombinant allergens for skin prick testing, and even though the use of allergen components can improve routine diagnosis, these tools are still not available for clinical routine applications. The use of provocation tests is a crucial step in the development of new, hypoallergenic vaccines for therapy of allergic disease. Here we describe important provocation methods (skin prick test, intradermal test, atopy patch test, nasal provocation, colonoscopic provocation test) and give an overview of the clinical provocation studies which have been performed with recombinant allergens so far.

Allergen Peptides, Recombinant Allergens and Hypoallergens for Allergen-Specific Immunotherapy

Allergic diseases are among the most common health issues worldwide. Specific immunotherapy has remained the only disease-modifying treatment, but it is not effective in all patients and may cause side effects. Over the last 25 years, allergen molecules from most prevalent allergen sources have been isolated and produced as recombinant proteins. Not only are these molecules useful in improved allergy diagnosis, but they also have the potential to revolutionize the treatment of allergic disease by means of immunotherapy. Panels of unmodified recombinant allergens have already been shown to effectively replace natural allergen extracts in therapy. Through genetic engineering, several molecules have been designed with modified immunological properties. Hypoallergens have been produced that have reduced IgE binding capacity but retained T cell reactivity and T cell peptides which stimulate allergen-specific T cells, and these have already been investigated in clinical trials. New vaccines have been recently created with both reduced IgE and T cell reactivity but retained ability to induce protective allergen-specific IgG antibodies. The latter approach works by fusing per se non-IgE reactive peptides derived from IgE binding sites of the allergens to a virus protein, which acts as a carrier and provides the T-cell help necessary for immune stimulation and protective antibody production. In this review, we will highlight the different novel approaches for immunotherapy and will report on prior and ongoing clinical studies.

Novel birch pollen specific immunotherapy formulation based on contiguous overlapping peptides

Background

Synthetic contiguous overlapping peptides (COPs) may represent an alternative to allergen extracts or recombinant allergens for allergen specific immunotherapy. In combination, COPs encompass the entire allergen sequence, providing all potential T cell epitopes, while preventing IgE conformational epitopes of the native allergen.

Methods

Individual COPs were derived from the sequence of Bet v 1, the major allergen of birch pollen, and its known crystal structure, and designed to avoid IgE binding. Three sets of COPs were tested in vitro in competition ELISA and basophil degranulation assays. Their in vivo reactivity was determined by intraperitoneal challenge in rBet v 1 sensitized mice as well as by skin prick tests in volunteers with allergic rhinoconjunctivitis to birch pollen.

Results

The combination, named AllerT, of three COPs selected for undetectable IgE binding in competition assays and for the absence of basophil activation in vitro was unable to induce anaphylaxis in sensitized mice in contrast to rBet v 1. In addition no positive reactivity to AllerT was observed in skin prick tests in human volunteers allergic to birch pollen. In contrast, a second set of COPs, AllerT4-T5 displayed some residual IgE binding in competition ELISA and a weak subliminal reactivity to skin prick testing.

Conclusions

The hypoallergenicity of contiguous overlapping peptides was confirmed by low, if any, IgE binding activity in vitro, by the absence of basophil activation and the absence of in vivo induction of allergic reactions in mouse and human.

Trial registration

ClinicalTrials.gov NCT01719133

Oral immunotherapy with transgenic rice seed containing destructed Japanese cedar pollen allergens, Cry j 1 and Cry j 2, against Japanese cedar pollinosis

Transgenic rice accumulating the modified major Japanese cedar pollen allergens, Cryptomeria japonica 1 (Cry j 1) and Cryptomeria japonica 2 (Cry j 2), which were deconstructed by fragmentation and shuffling, respectively, in the edible part of the seed was generated by transformation of a good-tasting rice variety, 'Koshihikari'. These modified cedar pollen antigens were deposited in ER-derived protein bodies (PB-I), which are suitable for delivery to the mucosal immune system in gut-associated lymphoid tissue when orally administered because antigens bioencapsulated in PB-I are resistant against hydrolysis by intestinal enzymes and harsh environments. Mice fed transgenic seeds daily for three weeks and then challenged with crude cedar pollen allergen showed marked suppression of allergen-specific CD4(+) T-cell proliferation, IgE and IgG levels compared with mice fed nontransgenic rice seeds. As clinical symptoms of pollinosis, sneezing frequency and infiltration of inflammatory cells such as eosinophils and neutrophils were also significantly reduced in the nasal tissue. These results imply that oral administration of transgenic rice seeds containing the structurally disrupted Cry j 1 and Cry j 2 antigens, serving as universal antigens, is a promising approach for specific immunoprophylaxis against Japanese cedar pollinosis.

Nanoparticulate adjuvants and delivery systems for allergen immunotherapy

In the last decades, significant progress in research and clinics has been made to offer possible innovative therapeutics for the management of allergic diseases. However, current allergen immunotherapy shows limitations concerning the long-term efficacy and safety due to local side effects and risk of anaphylaxis. Thus, effective and safe vaccines with reduced dose of allergen have been developed using adjuvants. Nevertheless, the use of adjuvants still has several disadvantages, which limits its use in human vaccines. In this context, several novel adjuvants for allergen immunotherapy are currently being investigated and developed. Currently, nanoparticles-based allergen-delivery systems have received much interest as potential adjuvants for allergen immunotherapy. It has been demonstrated that the incorporation of allergens into a delivery system plays an important role in the efficacy of allergy vaccines. Several nanoparticles-based delivery systems have been described, including biodegradable and nondegradable polymeric carriers. Therefore, this paper provides an overview of the current adjuvants used for allergen immunotherapy. Furthermore, nanoparticles-based allergen-delivery systems are focused as a novel and promising strategy for allergy vaccines.

In search of a vaccine for mouse allergy: significant reduction of Mus m 1 allergenicity by structure-guided single-point mutations

BACKGROUND

Mouse urinary proteins are relevant allergens from mice urine. We used the recombinant protein Mus m 1 as an allergen model to identify if, by altering Mus m 1 architecture via single-point mutations, we could effectively modify its allergenicity.

METHODS

Based on structural considerations, we synthesized two single-point mutants, Mus m 1-Y120A and Mus m 1-Y120F, which were expected to harbor large structural alterations. Circular dichroism and fluorescence analysis showed significant conformational rearrangements of the aromatic side chains in the internal cavity of Mus m 1-Y120A when compared to Mus m 1-Y120F and Mus m 1. Evaluation of the allergenic potential of the recombinant molecules was performed in vitro with both immunochemical approaches and assays based on the measurement of basophil degranulation. Moreover, to assess the integrity of the T cell epitopes and as an in vitro measure of immunogenicity, we tested the reactivity of T lymphocytes from subjects allergic to mouse urine against proteins and synthetic peptides encompassing the immunodominant linear epitope containing the mutation.

RESULTS

We found that the selected point mutation was able to modulate the protein allergenicity, and to severely impair the recognition of Mus m 1 by IgE, while T cell reactivity was fully maintained.

CONCLUSIONS

In silico predicted, minimum selected structural modifications allowed to design one protein with reduced allergenicity and preserved immunogenicity. Structurally guided mutations can direct the design of proteins with reduced allergenicity which can be used as vaccines for a safer and more effective immunotherapy of allergic disorders.

The diagnostic performance of allergen-molecules in comparison to allergen-extracts

BACKGROUND

This study evaluated the diagnostic performance of naturally purified allergen-molecules compared to that of allergen-extracts for house dust mite, cat dander epithelium and dog dander.

METHODS

In vitro tests for allergen-specific IgE were performed on the IMMULITE(®) 2000 in serum samples from 66 allergic patients.

RESULTS

House dust mite: specificity for the allergen-extract (D1) and the allergen-molecules (nDer p 1, nDer f 1, nDer p 2 and nDer f 2) is comparable. The allergen-extract has a significantly higher sensitivity (100%) and total agreement (TA) (93%) relative to sensitivity (57%-70%) and TA (76%-81%) of the individual allergen-molecules. Cat dander epithelium: sensitivity (90%), specificity (96%) and TA (94%) of the allergen-molecule (nFel d 1) are comparable to those of the allergen-extract (E1). Dog dander: The allergen-molecule (nCan d 1) and allergen-extract (E5) have comparable specificity and TA. The allergen-extract has a lower sensitivity (52%) than the allergen-molecule (71%), although not significant (p=0.125).

CONCLUSIONS

There is no diagnostic benefit of using allergen-molecules instead of allergen-extracts for initial allergy screening on cat dander epithelium and dog dander. However, use of these allergen-molecules might contribute to better standardization of the specific IgE tests. The studied allergen-molecules for house dust mite are of minor diagnostic value, because of loss of sensitivity.

Mapping of a conformational epitope on the cashew allergen Ana o 2: a discontinuous large subunit epitope dependent upon homologous or heterologous small subunit association

The 11S globulins are members of the cupin protein superfamily and represent an important class of tree nut allergens for which a number of linear epitopes have been mapped. However, specific conformational epitopes for these allergens have yet to be described. We have recently reported a cashew Ana o 2 conformational epitope defined by murine mAb 2B5 and competitively inhibited by a subset of patient IgE antibodies. The 2B5 epitope appears to reside on the large (acidic) subunit, is dependent upon small (basic) subunit association for expression, and is highly susceptible to denaturation. Here we fine map the epitope using a combination of recombinant chimeric cashew Ana o 2-soybean Gly m 6 chimeras, deletion and point mutations, molecular modeling, and electron microscopy of 2B5-Ana o 2 immune complexes. Key residues appear confined to a 24 amino acid segment near the N-terminus of the large subunit peptide, a portion of which makes direct contact with the small subunit. These data provide an explanation for both the small subunit dependence and the structurally labile nature of the epitope.

WITHDRAWN: An investigation on the protective efficiency of recombinant ovalbumin and its mutants against anaphylaxis in mice

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A hypoallergenic variant of Der p 1 as a candidate for mite allergy vaccines

BACKGROUND

Recombinant hypoallergens that display reduced allergenicity but retain T-cell reactivity represent promising candidates to improve the safety and efficacy of allergen-specific vaccines or immunotherapy.

OBJECTIVE

The current study reports the immunologic characterization of a hypoallergenic variant of the major mite allergen Der p 1.

METHODS

The recombinant proform of Der p 1 (ProDer p 1) was expressed in Escherichia coli (ProDer p 1 coli), purified and characterized at the level of its secondary structure, and IgE and T-cell reactivities. Moreover, the prophylactic potential of ProDer p 1 coli vaccinations was evaluated in a murine Der p 1 sensitization model.

RESULTS

After purification and refolding, ProDer p 1 coli remained aggregated with a higher beta-sheet content and altered Der p 1 conformational epitopes compared with the correctly folded monomeric ProDer p 1 produced in Chinese hamster ovary cells. Both ProDer p 1 forms were able to retain the Der p 1-specific T-cell reactivity but direct ELISA, competitive inhibition, and rat basophil leukemia assays clearly showed that ProDer p 1 coli displays a very weak IgE reactivity. Mice vaccinations with aggregated ProDer p 1 adjuvanted with alum induced a T(H)1-biased immune response that prevented the subsequent allergic response after Der p 1 sensitization and airway challenge with aerosolized mite extracts. Furthermore, ProDer p 1 coli treatment inhibited the development of airway eosinophilia and airway hyperresponsiveness to inhaled methacholine.

CONCLUSION

Aggregated forms of Der p 1 could represent hypoallergens suitable for the prevention of mite allergy.

Regulatory T cell therapy as individualized medicine for asthma and allergy

PURPOSE OF REVIEW

Regulatory T cells have been identified as key players in the maintenance of peripheral tolerance, which prevents inappropriate immune responses to both self-antigens and innocuous allergens. This review aims to provide an update on our current understanding of the therapeutic potential of naturally occurring and adaptive regulatory T cell subsets in allergic and asthmatic disease.

RECENT FINDINGS

Evidence is emerging that regulatory T cells control aberrant immune responses to allergens in health and exhibit impaired function in active disease. These data provide a rationale for developing therapeutic strategies that promote regulatory T cell numbers or function in patients.

SUMMARY

Preclinical studies of adoptive transfer of antigen-specific regulatory T cells into mouse models of allergic airway disease ameliorate the inflammatory response and in some studies airway hyperresponsiveness. Although these studies are encouraging this remains an invasive and expensive therapeutic protocol for the treatment of allergic disease in humans and a number of concerns relating to safety and efficacy exist. Existing therapies, both allergen specific immunotherapy and nonspecific treatments such as glucocorticoids, induce IL-10 secreting T regulatory populations in patients. Strategies to combine allergen immunotherapy with add-on treatments or adjuvants with the potential to boost regulatory T cells, safety and efficacy remain a major research focus.

Assessment of the immunoglobulin E-mediated immune response to milk-specific proteins in allergic patients using microarrays

BACKGROUND

Cow's milk allergy (CMA) is one of the most widespread human allergies, especially in young children. Although CMA is intensively studied, little is known about the recognition patterns of milk allergens in allergic patients, and the determination these patterns is a prerequisite for the development of efficient diagnostic and prognostic tools. Several factors present difficulties for such a determination, because (i) milk contains a large number of potential allergens; (ii) the majority of these allergens consist of complex suspensions rather than solutions; (iii) the major allergens, such as caseins, cannot be highly purified in large amounts; and (iv) most of the time, very small amount of young patients' sera are readily available.

METHODS

To overcome these difficulties, we developed a sensitive microarray assay that, in combination with near-infrared fluorescence detection, was used to study the immune response to milk and purified native milk proteins.

RESULTS

This new assay allowed us to assess the binding ability of IgE to milk allergens from a large number of young patients using reduced amounts of clinical material. The data show that bovine lactoferrin can be classed as a strong milk allergen. We confirmed that bovine caseins are the main allergens in milk and that alpha(S1)-casein is more allergenic than alpha(S2)-, beta- and kappa-caseins, which were recognized with almost a similar frequency by the sera of patients.

CONCLUSION

Microarray methods, in combination with near-infrared fluorescence detection, can be useful for the in vitro diagnosis of food allergies.

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.

Control of allergic reactions in mice by an active anti-murine IL-4 immunization

Pathogenesis of allergic inflammatory disorders is characterized by allergen-induced IgE stimulated by Th2 cytokines including mainly IL-4 overproduction. To counteract IL-4 effects in sensitized-BALB/c mice, we prepared an IL-4 derivative immunogen, made of KLH and murine IL-4 heterocomplex, termed mIL-4 kinoid. Murine IL-4 kinoid immunized mice produced high titer of anti-IL-4 neutralizing Abs. In contrast to KLH control immunization kinoid immunization reversed the allergic IgE:IgG ratio hallmark in rBet v 1a sensitized mice and reduced pulmonary eosinophil recruitment and bronchial hyperreactivity in Ova-sensitized mice. These data pave the way to alternative therapies to combat allergic conditions.

Safety of immunotherapy with therapeutic vaccines containing depigmented and polymerized allergen extracts

BACKGROUND

The major complication of allergen immunotherapy is a severe reaction.

OBJECTIVE

To evaluate the safety of depigmented and glutaraldehyde-modified allergen extracts in a large group of patients undergoing immunotherapy treatment.

MATERIAL AND METHODS

Seven hundred sixty-six patients, having rhinoconjunctivitis and/or asthma, were entered in a prospective, multi-centre, observational cohort study, to evaluate the safety of immunotherapy with modified allergen vaccines. Patients were sensitized to mites and/or pollen and received a therapeutic vaccine containing depigmented and polymerized allergen extracts of mites and/or pollens adsorbed onto aluminium hydroxide. The schedule of administration consisted of a build-up phase of 4- to 6-weekly injections, followed by 12-monthly injections of the maintenance dose. Tolerance was assessed by recording all side reactions related to immunotherapy.

RESULTS

All patients completed the study. Fifty-four clinically relevant local reactions (43 immediate and 11 delayed) were observed (0.4% of injections). The systemic reactions were 34 in 12 patients. Six reactions were immediate (all of grade 2) and 28 delayed (18 of grade 1 in two patients, nine of grade 2 and one of grade 3). The systemic reactions of grade 2 or 3 occurred in 0.12% of the injections. All systemic reactions were mild and resolved spontaneously without the need for medication.

CONCLUSION

Specific immunotherapy using modified allergen vaccines is safe to treat allergic patients. The percentage of adverse reactions detected is lower than those reported in the literature with native-unmodified allergen extracts.

Allergenicity and antigenicity of wild-type and mutant, monomeric, and dimeric carrot major allergen Dau c 1: destruction of conformation, not oligomerization, is the roadmap to save allergen vaccines

BACKGROUND

Carrot allergy is caused by primary sensitization to birch pollen. Continuous carrot exposure results in additional Dau c 1-specific allergic responses. Thus, immunotherapy with birch pollen may not improve the food allergy.

OBJECTIVE

Evaluation of mutation and oligomerization of the major carrot allergen, Dau c 1, in regard to alteration of antibody binding capacities, structure, and the ability to induce blocking IgG antibodies.

METHODS

Measurement of IgE reactivities to monomers, dimers of wild-type and mutant Dau c 1.0104 and Dau c 1.0201, and Dau c 1.0104 trimer, their ability to induce blocking antibodies in mice, and their allergenic potency by histamine release.

RESULTS

The reactivity of human IgE to the mutant dimer was reduced on average by 81%. Sera of immunized Balb/c mice showed specific IgG similar to the human IgE antibody response; Dau c 1.01 was more antigenic than Dau c 1.02. Both wild-type and mutant Dau c 1 variants induced cross-reacting IgG, which blocked binding of human IgE. The mutants were more antigenic than the wild-type forms, and the dimers induced higher IgG responses in mice than the monomers. The results of the histamine release experiments corroborated the findings of the antibody binding studies.

CONCLUSION

Destruction of native conformation rather than oligomerization is the appropriate strategy to reduce the allergenicity of Bet v 1-homologous food allergens.

CLINICAL IMPLICATIONS

The dimer composed of mutants of Dau c 1.0104 and Dau c 1.0201 is a promising candidate vaccine for treatment of carrot allergy because of its high immunogenicity and drastically reduced allergenicity.

Evaluation of allergen vaccine potency

The development of reliable and clinically relevant potency assays is essential to the practice of safe and effective allergen-specific immunotherapy. Allergen standardization in the United States is based on the establishment of a national reference assigned with a biological potency unit to which manufacturers' products are compared using validated relative potency assays. This ensures, at least with standardized allergen vaccines, comparability between lots used in clinical practice. Recent progress in the ability to measure the specific allergen content of allergen vaccines has led to its application in monitoring consistency and characterizing allergen preparations. More recently, the "major allergen" content of allergen vaccines has become a means to compare extracts from different manufacturers and to recommend immunotherapy dosing regimens. At the same time, qualitative differences exist between manufacturers' products, and most allergen vaccines used in clinical practice are nonstandardized. Therefore, this approach can be confusing and is misleading. The establishment of additional allergen reference standards and the development of reliable, accurate, and clinically relevant potency assays are urgently needed.