Quality requirements for allergen extracts and allergoids for allergen immunotherapy

Novel monoclonal antibodies against house dust mite allergen Der p 21 and their application to analyze allergen extracts

Background

Allergen extracts and recombinant allergens are used in allergy diagnostics and immunotherapy. Since allergen extracts from different manufacturers lack proper standardization regarding their composition, monoclonal antibodies (MAbs) against specific allergen components can be used for their identification and quantification in allergen extracts. This study aimed to generate MAbs against allergen Der p 21 of Dermatophagoides pteronyssinus for the analysis of allergen extracts.

Methods

Recombinant Der p 21 was expressed in E. coli and purified using affinity chromatography. MAbs against Der p 21 were generated using hybridoma technology. House dust mite (HDM) allergen extracts were analyzed using the newly developed sandwich enzyme-linked immunosorbent assay, Western blotting and microarray immunoassay.

Results

MAbs raised against recombinant Der p 21 were characterized in detail and proven to be reactive with natural Der p 21. Highly specific sandwich enzyme-linked immunosorbent assay for the quantification of Der p 21 was developed and optimized. The allergen was detected and its concentration was determined in only three of six analyzed HDM allergen extracts from different manufacturers.

Conclusion

HDM analysis by MAb-based immunoassays shows their differences in allergen composition. The results demonstrate the importance of allergen-specific MAbs as a tool for the characterization of allergen extracts and the need for their appropriate standardization before their use for allergy diagnostics or immunotherapy.

Comparative study of the commonly used protein quantitation assays on different Hymenoptera venoms: A fundamental aspect of Hymenoptera venom proteome analysis

Determination of protein concentration in Hymenoptera venoms requires an accurate and reproducible assay as the results will be used to support subsequent proteomic techniques employed in their analyses. However, all protein assay techniques have inherent strengths and weaknesses, demanding their assessment before selecting the most suitable platform for sample analysis. In this study, protein profiles of ant, honeybee, and wasp venoms, and bovine serum albumin (BSA) and hyaluronidase standards were qualitatively assessed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Their amino acid and protein concentration were quantitatively determined via Amino Acid Analysis (AAA). Amino acid concentration was determined via hydrolysis, derivatization, and chromatographic quantification. Protein concentration was estimated using four different protein concentration assays. The ratios of protein concentration in venom samples to protein standards were calculated, and the accuracy of the protein concentration assays was analysed relative to the concentration determined from AAA. SDS-PAGE analysis showed that BSA contained several protein bands, while hyaluronidase contained a mixture of peptide and protein bands. Ant and honeybee venoms contained a higher proportion of peptide bands, while wasp venom contained more protein bands. As determined by AAA, the ratio of protein concentration in Hymenoptera venoms varied between 1.01 and 1.11 to BSA, and between 0.96 and 1.06 to hyaluronidase. Overall, the Bradford assay was found to be the least accurate and the BCA assay was the most accurate in estimating protein concentration in Hymenoptera venoms. There was no significant advantage in using hyaluronidase as a standard or increasing incubation temperature of BCA assay when analysing Hymenoptera venoms. Diluent solutions containing phenol and human serum albumin interfered with Lowry-based assays.

Quality control of allergen products with mass spectrometry part I: Positioning within the EU regulatory framework

Mass spectrometry (MS) has advanced greatly and many of its applications are ready for utilization within regulatory procedures and could significantly contribute to overcome challenges in standardization of allergen products. It seems sensible to discuss MS within the regulatory framework, before addressing technical questions. While the application to purified proteins is well established from product development to manufacturer's release analytics, its application to complex products such as allergen products is still under development. It needs to be determined where it can complement or replace established methods or where MS offers limited improvement. Despite its technical appeal and versatility, currently MS is mentioned in regulatory guidelines only as one possible measurement method. For example, no specific MS method is given in the European Pharmacopoeia. We discuss applications of MS within the EU regulatory framework. This includes their advantages and disadvantages and their positioning between research, characterization, manufacturer's release analytics and official batch testing. We discuss the qualitative detection of single and multiple allergens as proof of identity, qualitative to semi-quantitative protein profiles for batch to batch consistency testing, and quantification of allergens to state mass units of allergens. MS may also facilitate standardization of allergen products, reference products and reference standards.

360° approach to the patient with mite allergy: from scientific evidence to clinical practice

In the recent years, several important advances have been made in the diagnosis of allergy using molecular techniques. The aetiological diagnosis of allergy using molecular components of allergens allows a more precise definition of the patient's IgE repertoire. Precision medicine is a structural model aimed at personalising healthcare and places the patient at the centre of the specialist's decision-making process. To this end, an accurate characterisation of the external exposome at a molecular level and their putative role as clinically relevant allergens is essential to elucidate the phenotypic diversity of atopic disease, with a view to personalising diagnosis and therapy. It has been proposed a decision algorithm, the Top-Down approach, where the clinical history is set first and is followed by the use of skin tests or specific IgE techniques, which facilitates the clinicians to make decisions. The therapeutic intervention driven by the standard diagnostic approach, but supported by these innovative tools, can lead to a better phenotyping of highly complex patients, and a more appropriate prescription of AIT. To this end, the allergen extracts used for diagnosis require to be of proven quality and contain the most relevant allergens. Likewise, allergen vaccines must gather efficacy, safety, duration, and patient compliance, hence the demand for new vaccines to overcome these drawbacks.

Advocacy of Precision Allergy Molecular Diagnosis in Decision Making for the Eligibility of Customized Allergen Immunotherapy

Allergen immunotherapy (AIT) with aeroallergens is the only disease-modifying treatment for patients with different allergic conditions. Despite the effectiveness of AIT having been proven in both randomized controlled trials and real-world studies, it remains underused in less than 10% of subjects with allergic rhinitis (AR) and/or asthma (A). We aimed to determine the current eligibility for house dust mite (HDM) AIT by means of a precision allergy molecular diagnosis (PAMD@) model in a selected cohort of youngsters with different allergic phenotypes according to the available evidence. A complex response to both HDM and storage mite allergens was depicted regardless of the subjects' basal atopic condition. No solely specific IgE-binding responses to Der p 1, Der p 2, and/or Der p 23 were found in the studied cohort. Despite the patients with A and atopic dermatitis showing significantly higher serum titers to six mite allergens than subjects with AR, no specific molecular profile was regarded as disease specific. Given the increasing complexity of specific IgE responses to the local prevailing aeroallergens, the identification and presence of such molecules are needed in commercially available AIT in the era of precision medicine.

Current practices and future trends in cockroach allergen immunotherapy

PURPOSE OF REVIEW

This review evaluates the current modes of allergen-specific immunotherapy for cockroach allergens, in terms of clinical outcomes and explores future trends in the research and development needed for a more targeted cockroach immunotherapy approach with the best efficacy and minimum adverse effects.

SUMMARY

Cockroach allergy is an important risk factor for allergic rhinitis in the tropics, that disproportionately affects children and young adults and those living in poor socio-economic environments. Immunotherapy would provide long-lasting improvement in quality of life, with reduced medication intake. However, the present treatment regime is long and has a risk of adverse effects. In addition, cockroach does not seem to have an immuno-dominant allergen, that has been traditionally used to treat allergies from other sources. Future trends of cockroach immunotherapy involve precision diagnosis, to correctly identify the offending allergen. Next, precision immunotherapy with standardized allergens, which have been processed in a way that maintains an immunological response without allergic reactions. This approach can be coupled with modern adjuvants and delivery systems that promote a Th1/Treg environment, thereby modulating the immune response away from the allergenic response.

The History, Present and Future of Allergen Standardization in the United States and Europe

The topic of standardization in relation to allergen products has been discussed by allergists, regulators, and manufacturers for a long time. In contrast to synthetic medicinal products, the natural origin of allergen products makes the necessary comparability difficult to achieve. This holds true for both aspects of standardization: Batch-to-batch consistency (or product-specific standardization) and comparability among products from different manufacturers (or cross-product comparability). In this review, we focus on how the United States and the European Union have tackled the topic of allergen product standardization in the past, covering the early joint standardization efforts in the 1970s and 1980s as well as the different paths taken by the two players thereafter until today. So far, these two paths have been based on rather classical immunological methods, including the corresponding benefits like simple feasability. New technologies such as mass spectrometry present an opportunity to redefine the field of allergen standardization in the future.

Global View on Ant Venom Allergy: from Allergenic Components to Clinical Management

Hymenoptera venom allergy is characterised by systemic anaphylactic reactions that occur in response to stings from members of the Hymenoptera order. Stinging by social Hymenoptera such as ants, honeybees, and vespids is one of the 3 major causes of anaphylaxis; along with food and drug exposure, it accounts for up to 43% of anaphylaxis cases and 20% of anaphylaxis-related fatalities. Despite their recognition as being of considerable public health significance, stinging ant venoms are relatively unexplored in comparison to other animal venoms and may be overlooked as a cause of venom allergy. Indeed, the venoms of stinging ants may be the most common cause of anaphylaxis in ant endemic areas. A better understanding of the natural history of venom allergy caused by stinging ants, their venom components, and the management of ant venom allergy is therefore required. This article provides a global view on allergic reactions to the venoms of stinging ants and the contemporary approach to diagnose and manage ant venom allergy.

Understanding differences in allergen immunotherapy products and practices in North America and Europe

Allergen immunotherapy (AIT) is thought to be clinically effective and safe in treating allergic rhinitis, asthma, and stinging insect allergy in Europe and North America. However, there are intercontinental differences in AIT therapeutic products in terms of their application and regulation. In North America unmodified standardized and nonstandardized aqueous aeroallergen extracts are approved and used almost exclusively for subcutaneous immunotherapy, whereas more product options are available in Europe, including adsorbed allergens, chemically modified allergens, or both. Both liquid extracts and tablets are approved for sublingual immunotherapy in Europe. Nevertheless, within the European Union, there are major differences in AIT products approved and used in individual countries. There are major differences in the clinical approach to subcutaneous immunotherapy in polysensitized patients; in the United States mixed extracts containing multiple aeroallergens are used, whereas European allergists preferably administer separate injections of single allergen sources or homologous groups deemed to be clinically relevant. Moreover, the regulatory approach differs between the European Union and United States. In contrast to the United States, where common allergen standards exist based on biologic activity, no common standards exist in Europe. In terms of development of new investigational products, the United States has followed the European example for phase II and III studies; no formal US Food and Drug Administration guidance has been issued.

Molecular approaches to allergen-specific immunotherapy: Are we so far from clinical implementation?

Conventional allergen-specific immunotherapy (AIT), based on administrations of allergen extracts, represents up to now the unique protocol for the desensitization of allergic patients. Whereas the effectiveness of AIT was evidenced for the treatment of allergic rhinitis and allergic asthma, such strategy remains experimental for food allergies up to now. However, important issues are commonly associated with AIT as the quality of natural allergen extracts, the long duration and adverse side-effects which negatively affect successful desensitization together with the patient compliance. The rapid progression of molecular allergology made possible the quest of safer, shorter and more effective immunotherapeutic approaches. The aim of this review was to provide an update on these different innovative recombinant derivatives including their efficacy but also their limitations. Despite promising preclinical and early clinical studies, the absence of convincing data in large phase III trials precludes so far the translation of these immunotherapeutic candidates into the clinic.

The safety of carbamylated monomeric allergoids for sublingual immunotherapy. Data from a pharmacovigilance study

Aim: Sublingual immunotherapy (SLIT) is significantly less concerned by systemic reactions than subcutaneous immunotherapy. Allergoids were introduced to reduce systemic reaction to subcutaneous immunotherapy, but may also be used for SLIT. Methods: This pharmacovigilance study evaluated the post-marketing reports collected in a safety database, including the number and the type (serious or not serious) of adverse drug reactions (ADRs) in Italy by SLIT with the carbamylated monomeric allergoid (CMA). Results: More than 15,000,000 CMA tablets were administered, with 25 spontaneous reports of ADRs, only two being serious. Conclusion: The rate of ADRs to CMA we found in this pharmacovigilance survey, corresponding to 0.0004% of all administered doses, is far lower than the rates commonly reported for allergen SLIT products.

Prioritizing research challenges and funding for allergy and asthma and the need for translational research-The European Strategic Forum on Allergic Diseases

The European Academy of Allergy and Clinical Immunology (EAACI) organized the first European Strategic Forum on Allergic Diseases and Asthma. The main aim was to bring together all relevant stakeholders and decision-makers in the field of allergy, asthma and clinical Immunology around an open debate on contemporary challenges and potential solutions for the next decade. The Strategic Forum was an upscaling of the EAACI White Paper aiming to integrate the Academy's output with the perspective offered by EAACI's partners. This collaboration is fundamental for adapting and integrating allergy and asthma care into the context of real-world problems. The Strategic Forum on Allergic Diseases brought together all partners who have the drive and the influence to make positive change: national and international societies, patients' organizations, regulatory bodies and industry representatives. An open debate with a special focus on drug development and biomedical engineering, big data and information technology and allergic diseases and asthma in the context of environmental health concluded that connecting science with the transformation of care and a joint agreement between all partners on priorities and needs are essential to ensure a better management of allergic diseases and asthma in the advent of precision medicine together with global access to innovative and affordable diagnostics and therapeutics.

Allergen manufacturing and quality aspects for allergen immunotherapy in Europe and the United States: An analysis from the EAACI AIT Guidelines Project

Adequate quality is essential for any medicinal product to be eligible for marketing. Quality includes verification of the identity, content and purity of a medicinal product in combination with a specified production process and its control. Allergen products derived from natural sources require particular considerations to ensure adequate quality. Here, we describe key aspects of the documentation on manufacturing and quality aspects for allergen immunotherapy products in the European Union and the United States. In some key parts, requirements in these areas are harmonized while other fields are regulated separately between both regions. Essential differences are found in the use of Reference Preparations, or the requirement to apply standardized assays for potency determination. As the types of products available are different in specific regions, regulatory guidance for such products may also be available in one specific region only, such as for allergoids in the European Union. Region-specific issues and priorities are a result of this. As allergen products derived from natural sources are inherently variable in their qualitative and quantitative composition, these products present special challenges to balance the variability and ensuring batch-to-batch consistency. Advancements in scientific knowledge on specific allergens and their role in allergic disease will consequentially find representation in future regulatory guidelines.