Monoclonal Antibody-Based ELISA to Quantify the Major Allergen of Cynodon dactylon (Bermuda Grass) Pollen, Cyn d 1

Isolating the species element in grass pollen allergy: A review

Grass pollen is a leading cause of allergy in many countries, particularly Europe. Although many elements of grass pollen production and dispersal are quite well researched, gaps still remain around the grass species that are predominant in the air and which of those are most likely to trigger allergy. In this comprehensive review we isolate the species aspect in grass pollen allergy by exploring the interdisciplinary interdependencies between plant ecology, public health, aerobiology, reproductive phenology and molecular ecology. We further identify current research gaps and provide open ended questions and recommendations for future research in an effort to focus the research community to develop novel strategies to combat grass pollen allergy. We emphasise the role of separating temperate and subtropical grasses, identified through divergence in evolutionary history, climate adaptations and flowering times. However, allergen cross-reactivity and the degree of IgE connectivity in sufferers between the two groups remains an area of active research. The importance of future research to identify allergen homology through biomolecular similarity and the connection to species taxonomy and practical implications of this to allergenicity is further emphasised. We also discuss the relevance of eDNA and molecular ecological techniques (DNA metabarcoding, qPCR and ELISA) as important tools in quantifying the connection between the biosphere with the atmosphere. By gaining more understanding of the connection between species-specific atmospheric eDNA and flowering phenology we will further elucidate the importance of species in releasing grass pollen and allergens to the atmosphere and their individual role in grass pollen allergy.

Update: stability of allergen extracts to establish expiration dating

PURPOSE OF REVIEW

The article reviews studies pertaining to US manufactured allergen extract stability that contribute to guidance for expiration dating for bulk concentrates, diluted patient testing and treatment vials, and adjustments following elevated temperature excursions.

RECENT FINDINGS

Studies on allergen stability were completed to satisfy the Food and Drug Administration requirements supporting labeled expiration dating for standardized short ragweed, dust mites, cat, grass, and venom extracts and are not published. These studies demonstrated the stability enhancing parameters of 50% glycerin and support the Food and Drug Administration mandated expiration of nonstandardized extracts allowing glycerin extracts twice the dating of nonglycerin aqueous extracts. Patient vials are commonly given 6-12 months dating. There is adequate evidence that human serum albumin stabilizes low protein diluted vials. High protease allergens such as molds and insects compromised potency of pollens when mixed. Subsequent work continued to define the effects of diluents on extract dilutions, temperature excursions that occasionally occur with shipping or refrigerator malfunctions, and allergen compatibility.

SUMMARY

Potency has been determined for allergen dilutions with diluents typically used for allergen immunotherapy. These studies along with changes of potency under various storage conditions and mixing designed to improve our guidance on expiration dating of allergen extracts will be discussed.

Grass pollen allergens globally: the contribution of subtropical grasses to burden of allergic respiratory diseases

Grass pollens of the temperate (Pooideae) subfamily and subtropical subfamilies of grasses are major aeroallergen sources worldwide. The subtropical Chloridoideae (e.g. Cynodon dactylon; Bermuda grass) and Panicoideae (e.g. Paspalum notatum; Bahia grass) species are abundant in parts of Africa, India, Asia, Australia and the Americas, where a large and increasing proportion of the world's population abide. These grasses are phylogenetically and ecologically distinct from temperate grasses. With the advent of global warming, it is conceivable that the geographic distribution of subtropical grasses and the contribution of their pollen to the burden of allergic rhinitis and asthma will increase. This review aims to provide a comprehensive synthesis of the current global knowledge of (i) regional variation in allergic sensitivity to subtropical grass pollens, (ii) molecular allergenic components of subtropical grass pollens and (iii) allergic responses to subtropical grass pollen allergens in relevant populations. Patients from subtropical regions of the world show higher allergic sensitivity to grass pollens of Chloridoideae and Panicoideae grasses, than to temperate grass pollens. The group 1 allergens are amongst the allergen components of subtropical grass pollens, but the group 5 allergens, by which temperate grass pollen extracts are standardized for allergen content, appear to be absent from both subfamilies of subtropical grasses. Whilst there are shared allergenic components and antigenic determinants, there are additional clinically relevant subfamily-specific differences, at T- and B-cell levels, between pollen allergens of subtropical and temperate grasses. Differential immune recognition of subtropical grass pollens is likely to impact upon the efficacy of allergen immunotherapy of patients who are primarily sensitized to subtropical grass pollens. The literature reviewed herein highlights the clinical need to standardize allergen preparations for both types of subtropical grass pollens to achieve optimal diagnosis and treatment of patients with allergic respiratory disease in subtropical regions of the world.

Generation and characterization of anti-chitinase monoclonal antibodies

Class IV chitinase, an allergenic protein of Vitis vinifera (grape), was purified by anion exchange chromatography and used for immunization of Balb/c mice. Monoclonal antibodies (MAbs) were raised by hybridoma technology using Sp2/0 myeloma cells. Finally after three limiting dilutions, six stable clones were generated. Antibody isotyping showed that IgG(2a), IgG(2b), and IgM were produced by one, two, and three of the clones, respectively. All of the MAbs had kappa light chain. The affinities were in the range of 3 × 10(8) to 1.2 × 10(9) M(-1). The MAbs were specific for grape chitinase as confirmed by Western blotting. In conclusion, we successfully produced several MAbs against grape class IV chitinase, which could be used for assessment of this allergen in different grape cultivars.

Stability of allergen extracts used in skin testing and immunotherapy

PURPOSE OF REVIEW

The present article reviews allergen extract stability applied to US manufactured products. Methods used to measure potency of extract concentrates, patient prescription dilute extracts, and mixes containing degrading enzymes will be discussed.

RECENT FINDINGS

Information about the allergen extract active ingredient components contributing to potency is increasing. Pertinent stability issues include the type of diluent used for extraction and mixing. Fifty percent glycerin greatly extends the time over which extracts remain potent, including in mixes with fungal and insect extracts known to contain protein-degrading enzymes. Diluents that contain additional protein content such as human serum albumin increase stability of dilute solutions. Many of the most rigorous studies on allergen stability have been performed by allergenic extract manufacturers in support of Food and Drug Administration approved dating for standardized products and are not published.

SUMMARY

Studies addressing how antigens in extracts change under various storage conditions have provided general guidance for expiration dating, but the diversity of extracts and testing methods have been less than complete. Additional findings that are increasing our knowledge of extract shelf life will be discussed.

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.

Standardization of allergen extracts for immunotherapy: where do we stand?

PURPOSE OF REVIEW

The current state of the art in allergen standardization and recent progress in the field is summarized, and future developments are discussed.

RECENT FINDINGS

The main focus of recent research in allergen standardization was on sandwich enzyme-linked immunosorbent assays or competitive tests for the quantification of individual allergens in extracts. New assays for quantifying major or minor allergens have been developed for tree and weed pollens from the Mediterranean area, grass pollens, and foods such as peanut and apple. In several cases, a good correlation with allergenic activity, measured by inhibition tests, was obtained. In addition, the potential of cellular mediator release assays in allergen standardization was evaluated in one study.

SUMMARY

Several new tests have been developed to make more major and minor allergens from various allergen sources accessible to allergen standardization programmes such as the CREATE project. It is expected that assays to determine the majority of all clinically relevant major allergens from aeroallergen sources will be available in the near future. Standardized and validated mediator release assays may be a complementary tool for evaluating the biological potency of reference allergens and for correlating allergen concentrations to biological potency.