Allergen Preparation and Standardization: An Update

Allergy is defined as an exaggerated response of the adaptive immune system typified by immunoglobulin E (IgE) responses against the offending substance called ‘allergen’ [1]. The immunologic basis of allergic diseases is observed in two phases: sensitization and development of memory T and B cell responses along with IgE production [2]. Allergy manifests in form of various conditions such as anaphylaxis, urticaria, angioedema, allergic rhinoconjunctivitis, allergic asthma, serum sickness, allergic vasculitis, hypersensitivity pneumonitis, atopic dermatitis (eczema), contact dermatitis and granulomatous reactions, as well as the colorful spectrum of food or drug induced hypersensitivity reactions [2]. Asthma, allergic rhinitis, atopic dermatitis and inhalant sensitization have been appropriately referred to as first wave of the epidemic of the 21st century [3,4]. During the last 60 years, there has been a rise in the epidemic prevalence of allergic disorders, which is expected to reach up to 4 billion in 2050s [5]. Allergic reactions are initiated by certain types of antigens, referred to as allergens, which have been broadly categorized into four classes as Inhalant (pollen,fungi,dust), Ingestants (food, drugs), Contactants (latex, plant trichomes) and Injectants (drugs). Allergen immunotherapy (AIT) has been used to treat allergic disease since the early 1900s [6]. Allergen-specific immunotherapy (also known as allergy shots) identified as disease-modifying intervention for allergic disease involves subcutaneous administration of gradually increasing quantities of the patient’s relevant allergens until a dose is reached that is effective in inducing immunologic tolerance to the allergens [7]. The term “allergen extracts” refers to solutions of proteins or glycoproteins extracted from source material not yet incorporated into a therapeutic allergen immunotherapy extract [8]. Vials of allergen immunotherapy extracts are prepared individually (specifically customized) using saline buffers for each patient to reduce the risk of allergen cross-contamination, anaphylactic side effects, sensitization to unknown allergens in extract. Major allergens responsible for allergy in extract can be modified chemically or enzymatically to reduce their allergenic potential while still retaining the immunogenicity for achieving same tolerance as natural counterpart. The collection of raw materials for allergen preparation should be performed by qualified personnel and appropriate, measures should be taken to ensure correct characterization and quality check of source materials. For allergen immunotherapy trained Compounding personnel including, but not limited to, registered nurses, medical assistants, or physicians’ assistants, be employed which strictly follow allergen extract preparation guidelines. Allergen immunotherapy efficacy and precision of diagnostic allergy skin testing are entirely dependent on the quality of the allergen extracts used [8]. Standardized allergen preparations have been recommended for use in immunotherapy and diagnostic kits as evident in position papers [8-10]. The advantage of standardized extracts is that the biologic activity is more consistent, and therefore the risk of an adverse reaction caused by extract potency variability should be diminished.