Stability and mixing compatibility of dog epithelia and dog dander allergens

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.

Math-free guides for glycerin and allergens at variable subcutaneous injection volumes: How's my dosing? Update

BACKGROUND

Current summaries of effective maintenance dose ranges for subcutaneous immunotherapy (SCIT) are based on administration of 0.5-mL volumes. Extract formulations delivering equivalent dose ranges for practices using different injection volumes have not been reported, and calculation of the final glycerin concentrations in these solutions remains an inconvenient and repetitive process.

OBJECTIVE

To create math-free guides for allergen doses and glycerin concentrations that identify the extract concentrate volumes required to deliver doses within the ranges cited in the 2011 immunotherapy practice parameters for clinicians using 5.0-mL maintenance vials and injection volumes ranging from 0.2 to 1.0 mL.

METHODS

Algebraic calculations were performed to determine the specific combinations of extract concentrate strengths, volumes of these products in patient vaccines, and injection volumes needed for administration of target allergen doses spanning the current SCIT practice parameter recommendations.

RESULTS

For each product or group (nonstandardized extracts), tables were constructed to define the allergen doses provided by various combinations of extract concentrate volumes and injection volumes. The values within the effective dose ranges for each product were highlighted to facilitate comparisons of specific conditions relevant to allergy specialists. Glycerin tables were also created to permit convenient assessments of the final concentrations of this stabilizer in patient prescriptions.

CONCLUSION

SCIT dosing and glycerin tables are useful tools to assist allergists with practice decisions that involve variable patient formulas and injection volumes and can help identify suitable conditions for treatment of patients presenting with diverse allergen sensitivities and specificity profiles.

Allergen extracts for immunotherapy: to mix or not to mix?

Allergen immunotherapy (AIT) is established as a curative treatment for allergic rhinitis, asthma, as well as insect venom allergy. AIT is based on the administration of natural allergen extracts via the subcutaneous or sublingual routes to reorient the immune system towards tolerogenic mechanisms. In this regard, since many patients are poly-allergic, mixtures of allergen extracts are often used with a potential risk to cause allergen degradation, thereby affecting treatment efficacy. Herein, we discuss the advantages and drawbacks of mixing homologous (i.e., related) or heterogeneous (i.e., unrelated) allergen extracts. We provide evidence for incompatibilities between mixes of grass pollen and house dust mite extracts containing bodies and feces, and summarize critical points to consider when mixing allergen extracts for AIT.

Dog allergen immunotherapy: past, present, and future

OBJECTIVE

To review the published medical literature on dog allergy immunotherapy and discuss prior clinical trials, important allergens, extract specifics, and potential future treatment options for dog allergy relevant to the clinical allergist.

DATA SOURCES

MEDLINE search was performed using the terms dog, immunotherapy, and allergy limited to human studies from any period. Articles cited in selected studies also were reviewed for appropriateness of inclusion into this review.

STUDY SELECTIONS

Publications were included that were original research and fit the topic of dog allergen immunotherapy, specifically articles that investigated prior effectiveness and safety of dog allergen immunotherapy, dog extracts, identification of dog allergens, and current prescribing trends among allergists.

RESULTS

Two hundred fifteen articles were initially identified and 60 were reviewed in complete detail for inclusion in this review. The primary focus was placed on the 17 clinical trials that investigated the safety and efficacy of dog immunotherapy and the 19 studies that explored and defined the complex allergenic profile of dog extracts.

CONCLUSION

The medical literature on the use of dog extract immunotherapy in patients with hypersensitivity to dog shows poor and conflicting results of clinical efficacy, which has been attributed to poor-quality extracts and the inherent complex allergenic profile of dogs that remains without a clearly dominant allergen.

Clinical Evaluation and Management of Patients with Suspected Fungus Sensitivity

Fungus-sensitized patients usually present with symptoms that are similar to symptoms presented by those who are sensitized to other aeroallergens. Therefore, diagnosis and management should follow the same pathways used for patients with allergic conditions in general. The physician should consider that a relationship between fungal exposure and symptoms is not necessarily caused by an IgE-mediated mechanism, even when specific fungal IgE is detected. Until recently, IgE-mediated allergy has been documented only for a limited number of fungi. We propose a series of questions to be used to identify symptoms that occur in situations with high fungal exposure and a limited skin-prick-test panel (Alternaria, Cladosporium, Penicillium, Aspergillus, Candida) that can be amplified only in cases of high suspicion of other fungal exposure (eg, postfloods). We also review in vitro testing for fungi-specific IgE. Treatment includes environmental control, medical management, and, when appropriate, specific immunotherapy. Low-quality evidence exists supporting the use of subcutaneous immunotherapy for Alternaria to treat allergic rhinitis and asthma, and very low quality evidence supports the use of subcutaneous immunotherapy for Cladosporium and sublingual immunotherapy for Alternaria. As is the case for many allergens, evidence for immunotherapy with other fungal extracts is lacking. The so-called toxic mold syndrome is also briefly discussed.

Allergen stabilities and compatibilities in immunotherapy mixtures that contain cat, dog, dust mite, and cockroach extracts

BACKGROUND

Indoor allergen mixtures that contain cat, dog, dust mite, and cockroach extracts are commonly used in allergy clinics for subcutaneous immunotherapy, but product-specific stabilities and mixing compatibilities in these complex patient formulas have not been determined.

OBJECTIVES

To assess the recoveries of cat, dog epithelia, dog dander, dust mite Dermatophagoides farinae, and cockroach mix allergen activities in 5 component mixtures and 1:10 (vol/vol) dilutions stored for up to 12 months.

METHODS

Concentrated stock mixtures, 10-fold dilutions of these mixtures in human serum albumin-saline diluent, and analogous single-extract controls were analyzed for major allergen concentrations (cat Fel d 1, dog dander Can f 1) and multiallergen IgE-binding potencies (dog epithelia, D farinae, cockroach mix) after storage for 3, 6, 9, and 12 months at 2°C to 8°C.

RESULTS

The selected immunoassays were specific for individual target extracts in the 5-component mixtures and exhibited analytical sensitivities sufficient for evaluation of both the concentrated and diluted indoor allergen formulas. All control samples except diluted cockroach extract had near-complete stabilities during refrigerated storage. Mixtures that contained cat, dog epithelia, dog dander, and D farinae extracts exhibited favorable mixing compatibilities in 1:1 (vol/vol) concentrates (47.5% glycerin) and 1:10 (vol/vol) dilutions (4.75% glycerin), relative to corresponding control sample reactivities. Cockroach allergens in both 1:1 (vol/vol) and 1:10 (vol/vol) concentrations were stabilized significantly by mixing with the other 4 indoor allergen extracts.

CONCLUSION

Extracts in mixtures that contained 5 common sources of indoor allergens possess favorable stabilities and mixing compatibilities and support the practice of combining these products in the same patient treatment formulations for subcutaneous immunotherapy.

Practical recommendations for mixing allergy immunotherapy extracts

Critical aspects of formulating allergy immunotherapy vaccines include the selection, total number, and proportions of each allergen component in therapeutic mixtures. The immunotherapy prescription, determined by a medical provider, details the dosing and schedule for treatment as well as the specific composition of the treatment vials. Allergen extracts are composed of many components such as proteins, glycoproteins, and proteases. Some components in allergen extracts are cross-reactive, meaning that treatment with an extract from one species may confer partial protection against a triggering allergen from another species. Conversely, some allergen extracts are incompatible with other extracts when combined in a mixture for treatment, resulting in lowered therapeutic potential for the patient. Therefore, knowledge of allergen extract cross-reactivities and incompatibilities guides the preparation of subcutaneous immunotherapy prescriptions. In a clinical setting, an understanding of what can and can not be mixed is one critical element in improving treatment outcomes.

Mixing compatibilities of Aspergillus and American cockroach allergens with other high-protease fungal and insect extracts

BACKGROUND

Recent studies have shown that Alternaria and German cockroach allergens can be degraded by endogenous proteases from other insect and fungal extracts when combined for immunotherapy, but data supporting the compatibilities of other high-protease products in comparable mixtures have not been reported.

OBJECTIVE

To assess the stabilities and compatibilities of Aspergillus fumigatus and American cockroach allergens after mixing with protease-rich extracts from other insects or fungi at concentrations similar to those recommended for subcutaneous immunotherapy.

METHODS

Mixtures containing A fumigatus, American cockroach, and other fungal or insect extracts were evaluated by quantitative (enzyme-linked immunosorbent assays) and qualitative (immunoblotting) methods. Test mixtures and control samples at 10% to 50% glycerin concentrations were analyzed after storage for up to 12 months at 2°C to 8°C.

RESULTS

Moderate to high recoveries of Aspergillus extract activities were retained in control samples and extract mixtures under all conditions examined. American cockroach extract controls were partly degraded at 10% to 25% glycerin, and cockroach allergen compatibilities were decreased significantly in mixtures with several fungal extracts at 25% glycerin. Mixing with other insects did not compromise the stability of American cockroach allergens at 25% to 50% glycerin.

CONCLUSION

Aspergillus extracts exhibited favorable stabilities after mixing with other high-protease products. American cockroach extract potencies were unstable in less than 50% glycerin, even in the absence of other protease-containing allergens, and were destabilized in mixtures with several fungal extracts. Addition of fungal and insect extracts to separate treatment vials or preparation of fungal-insect mixtures at elevated glycerin concentrations might be necessary to produce compatible patient formulations for allergen immunotherapy injections.

Allergen stabilities and compatibilities in mixtures of high-protease fungal and insect extracts

BACKGROUND

Current practice guidelines state that protease-rich fungal and insect extracts can be combined when preparing immunotherapy vaccines, but data supporting the stability of allergens in these mixtures have not been reported.

OBJECTIVE

To determine the stabilities and compatibilities of Alternaria alternata and German cockroach allergens in mixtures with other high-protease fungal and insect (cockroach, imported fire ant) extracts at final extract concentrations consistent with injection dose targets for maintenance immunotherapy.

METHODS

Mixtures containing Alternaria, German cockroach, and other fungal and insect extracts frequently included in immunotherapy vaccines were analyzed by a combination of quantitative analyses (enzyme-linked immunosorbent assays for multiallergen immunoglobulin E [IgE]-binding potency, major Alternaria allergen Alt a 1, and major German cockroach allergens Bla g 1 and Bla g 2) and qualitative methods (immunoblotting). Mixtures and analogous single-extract controls containing 10 to 50% glycerin were evaluated after storage for up to 12 months at 2°C to 8°C.

RESULTS

Mixtures of extracts within the same phylogenetic groups (fungal-fungal, insect-insect) retained favorable Alternaria and German cockroach allergen levels and activities under most conditions examined. For several cross-taxonomic (fungal-insect) extract combinations at 10 to 25% glycerin concentrations, different immunochemical test methods measuring single (major) or multiple allergens yielded threefold to 10-fold variations in allergen recoveries.

CONCLUSION

Allergen compatibilities can be compromised in some fungal-insect extract mixtures, contrary to current immunotherapy practice parameter recommendations. Separation of these products into different treatment vials may be required to produce stable mixtures for subcutaneous immunotherapy. Data from assay methodologies with distinct binding specificities provide a critical assessment of allergen activities in high-protease extract mixtures.

How's my dosing? A one-step, math-free guide for comparing your clinic's maintenance immunotherapy doses to current practice parameter recommendations

BACKGROUND

Immunotherapy dose recommendations for allergens specified in practice parameter updates have varied from version to version, and no convenient methods are available to incorporate dose changes or targets into maintenance vial formulations for patients.

OBJECTIVES

To compare the allergen immunotherapy dose recommendations published between 2003-2011, and to provide math-free dosing tables that translate dose targets for single or multiple extracts into maintenance vial compositions.

METHODS

Dose recommendations obtained from immunotherapy practice parameters published in 2003, 2007 and 2011, plus a worksheet created in 2004, were tabulated and compared. Conversion tables were created based on the fixed mathematical relationships between extract concentrate strengths and maintenance immunotherapy dose targets. Considerations of stock mixes, glycerin levels, and allergen compatibilities were applied using two examples of common extract formulations.

RESULTS

Changes to immunotherapy dose ranges for standardized extracts included adjustment of upper limits (short ragweed), lower limits (pasture grasses), or both (cat, dust mites, Bermuda grass). Dose ranges for non-standardized products have also been modified over time. Conversion tables specified the extract concentrate volumes or percentages required to deliver minimum, midrange and maximum recommended doses with 0.5 mL injection volumes.

CONCLUSIONS

These dosing guides, used in conjunction with cross-reactivity, compatibility and glycerin tolerance information, provide clinicians with a convenient and systematic method for determining the numbers and strengths of extracts that can be combined into treatment vials at various dose levels, and can facilitate optimization of maintenance immunotherapy mixtures for patients exhibiting a wide range of allergen sensitivities and specificities.

Allergen compatibilities in extract mixtures

Stability studies with a few well-characterized allergen extracts have yielded useful information about the shelf-life of these products stored under various conditions. The development of validated stability-indicating tests and their clinical verification remains a fundamental challenge for extending this information to cover more products. This challenge becomes even greater for evaluations of more complex, multiextract mixtures that are used in clinical practice. Thus, the current approach for developing guidelines for extract expiration dating practices must rely on extrapolations of data obtained from a few well-controlled studies.

Allergen immunotherapy practice in the United States: guidelines, measures, and outcomes

To discuss recent issues pertinent to allergen immunotherapy practice in the United States. Allergen extract preparation guidelines, updated allergen immunotherapy practice parameter (AIPP) guidelines, and evolving trends in how immunotherapy outcomes will be measured and assessed. Allergen extract preparation guidelines have been established by 2 entities: the US Pharmacopeia and an American Academy of Allergy, Asthma, and Immunology/American College of Allergy, Asthma, and Immunology/Joint Council of Allergy, Asthma, and Immunology Joint Task Force. Minor differences exist between these guidelines, but both focus on aseptic techniques and require that compounding personnel pass a written examination and annual media fill test. The AIPP third update provides new dosing recommendations for Bermuda grass, imported fire ant, and nonstandardized extracts distinguishing between pollen (0.5 mL of a 1:100 or 1:200 vol/vol) and mold/fungi or cockroach (highest tolerated dose) extracts. Because of limited and sometimes conflicting data on high and low proteolytic-containing extract compatibility, the AIPP continues to recommend against mixing these together. Although the AIPP does not specifically recommend a specific diluent, recent evidence suggests normal saline may not be as effective a stabilizer for extract dilutions as glycerin or human serum albumin. Currently, immunotherapy efficacy is determined with subjective assessments that rely on patient reporting, but this may change as health care reform evolves. It will likely become more important for US allergy/immunology practices to demonstrate immunotherapy comparative-effectiveness and report quality measures. Recent comparative-effectiveness studies have demonstrated the cost-effectiveness of immunotherapy compared with symptomatic drug treatment.