Impact of Dermatophagoides pteronyssinus mite body raw material on house dust mite allergy diagnosis in a Serbian population

Mass spectrometry to complement standardization of house dust mite and other complex allergenic extracts

In the United States, the Center for Biologics Evaluation and Research of the US Food and Drug Administration regulates biologics used for diagnosis and treatment of allergic diseases. The Code of Federal Regulations 21CFR680.3(e) states that when measured, the potency of an allergenic extract is assessed according to its allergenic activity. As of 2016, 19 allergenic extracts are standardized for potency in the United States. While these standardized extracts constitute a minority of those available, they treat the most prevalent allergies (e.g. grass and ragweed pollens, dust mites, and cat) and those that induce life-threatening anaphylaxis (e.g. Hymenoptera venom). Standardization for potency enhances safety and efficacy of immunotherapy by minimizing the risks of variations in allergen dosing when switching from one lot of manufactured extract to another, and by providing an objective measure of stability of each lot of allergenic extract over time. Allergenic extracts that have multiple immunodominant allergenic proteins are standardized with little or no information about compositional differences among extracts. Here, we propose application of mass spectrometry towards measurement of compositional differences among extracts that may affect the efficacy and safety of allergen immunotherapy. In addition, we discuss of house dust mite allergen extracts as a prototypical complex extract that may be standardized by mass spectrometry.

Population growth and allergen accumulation of Dermatophagoides farinae cultured at 20 and 25 °C

House dust mites are cultured to obtain mite allergen material to produce allergen extracts (vaccines) for diagnostic tests, immunotherapy, and research purposes. Research laboratories and manufacturers have their own culturing protocols to grow these mites and these may vary between manufacturers and between research laboratories. The temperature at which mites are cultured may influence the allergen composition, allergen ratio of Der 1: Der 2 and endotoxin levels in the extracts produced from these cultured mites. In order to produce standardized and uniform extracts, across the industry and in various research laboratories, the influence of culture conditions must be understood. Here we determined how temperature affects mite population growth rates, dynamics of allergen production, Der f 1: Der f 2 ratio and endotoxin levels in extracts made from Dermatophagoides farinae mites cultured at 20 and 25 °C. We found that Der f 1 and Der f 2 accumulated exponentially in the cultures with Der f 1 accumulating faster than Der f 2. When the live mite populations peaked, the ratios for Der f 1: Der f 2 were 4.1 and 4.7 for cultures reared at 20 and 25 °C, respectively. Most of the Der f 1 and Der f 2 allergen in whole cultures is not in mite bodies and is lost when the mite material is washed. Thus, if the ratio of Der f 1 and Der f 2 is an important consideration for commercial and research extracts, then the temperature at which the mites are cultured and the collection procedure are important considerations.

Standardization of house dust mite extracts in Korea

PURPOSE

House dust mites are the most important cause of respiratory allergy in Korea. Standardization of allergen extracts is essential for improving diagnostics and immunotherapeutics. This study was undertaken to evaluate the allergenicity of standardized house dust mite allergen extracts from Korean house dust mite isolates.

METHODS

Allergen extracts were prepared from cultured Korean house dust mites (Dermatophagoides farinae and D. pteronyssinus). Allergenic activities of Korean house dust mite extracts were compared to standardized extracts from a company in the United States whose allergen concentrations were expressed as Allergy Units (AUs). Specifically, we compared group 1 and 2 major allergens using two-site enzyme-linked immunosorbent assay (ELISA) kits and an in vivo intradermal test.

RESULTS

Major allergen concentrations were 17.0 µg/mg (5.0 µg/mg of Der f 1 and 12.0 µg/mg of Der f 2) for a D. farinae extract and 24.0 µg/mg (11.6 µg/mg of Der p 1 and 12.4 µg/mg of Der p 2) for a D. pteronyssinus extract. Using chloramphenicol (CAP) inhibition assays, AUs were 12.5 AU/µg for a D. farinae extract and 12.8 AU/µg for a D. pteronyssinus extract. Allergenic activities were 3- to 4-fold stronger when assessed by intradermal skin tests for in vivo standardization.

CONCLUSIONS

Allergen extracts were prepared from Korean house dust mites and the allergenicities of the extracts were estimated using AU measurements. House dust mite extracts prepared in this study could be utilized as a reference material, which will be useful for the development of diagnostic and immunotherapeutic reagents in Korea.

Optimization of allergen standardization

Preparation of high quality allergen extracts is essential for the diagnosis and immunotherapy of allergic disorders. Standardization of allergen extracts concerns determination of the allergen unit, development of reference material and measurement of the overall IgE binding capacity of an allergen extract. Recently, quantification of individual allergens has been the main focus of allergen standardization because the allergenicity of most allergen extracts is known to be mainly dependent on the content of a small number of allergen molecules. Therefore, characterization of major allergens will facilitate the standardization of allergens. In this article, we review the current state of allergen standardization. In addition, we briefly summarize the components of allergen extracts that should be under control for the optimization of allergen standardization, since its adjuvant-like activities could play an important role in allergic reactions even though the molecule itself does not bind to the IgE antibodies from subjects.