Cross-reactivity of plant and animal allergens

Assessing cross-reactivity in allergen immunotherapy

Knowledge of patterns of pollen cross-reactivity is crucial for formulation of immunotherapy vaccines. As phylogenetic relationships have become better clarified through the use of tools such as gene sequencing, it is apparent that cross-reactivity reflects taxonomy in the vast majority of cases. Contradictory observations of unexpected cross-reactivity between distantly related plants require explanation. There are many proteins, presumably performing vital functions, tightly preserved throughout the evolutionary tree from plants to animals. Examples are profilins, lipid transfer proteins, and pathogenesis-related proteins. These may function as panallergens. The small differences that exist between these ubiquitous proteins may explain why these are frequently minor allergens, not reacting in the majority of allergic sera. This article summarizes cross-reactivity from older studies using crude pollen extracts as well as newer research of purified or recombinant allergenic proteins. The patterns of cross-allergenicity that emerge should be helpful in guiding therapeutic decisions.

Correlation of skin prick testing to environmental allergens

BACKGROUND

To diagnose and adequately treat allergies, identification of sensitizing allergens is crucial. Skin prick or serum immunoglobulin E testing determines sensitization to potential allergens. Consensus varies regarding degree of cross-reactivity between aeroallergens.

OBJECTIVE

To quantify correlations between aeroallergen skin prick test results.

METHODS

A total of 11,832 patients' quantitative skin prick test results and basic characteristics were obtained from a tertiary academic center's electronic medical record and deidentified. Data were analyzed using Spearman's rank correlation coefficients to detect nonlinear associations between wheal sizes of skin prick test results.

RESULTS

The highest correlation among grasses was 0.903 (fescue and red top). Of note, 13 more grass pairs had correlation more than 0.8, and 19 had correlation between 0.7 and 0.8. The Northern grass comparative results are from a satellite clinic that tested more grasses than the main clinic, in which only Kentucky blue and Bermuda were tested (correlation 0.768; n = 9348). Highest correlation among weeds was 0.74 (lambs quarter and pigweed). In addition, 6 more weed pairs had correlation more than 0.7. Highest correlation among trees was 0.724 (palm and alder) and 6 more tree pairs had correlation more than 0.7. Highest correlation among molds was 0.711 (Helminthosporium and Epicoccum). Dust mite correlation between Dermatophagoides farinae and Dermatophagoides pteronyssinus was 0.848 (n = 10,022).

CONCLUSION

This study confirmed the expected high degrees of correlation not only between skin prick test results of related environmental allergens but also between less closely related Northern grasses and Bermuda grass. This has implications for simplification of testing and immunotherapy protocols in the future.

The association between glaucoma and immunoglobulin E antibody response to indoor allergens

PURPOSE

To evaluate the association between sensitization to indoor allergens and glaucoma in participants of the National Health and Nutrition Examination Survey (NHANES).

DESIGN

Retrospective cross-sectional study.

METHODS

This study examined the association between serum immunoglobulin E (IgE) levels for a panel of common indoor allergens and glaucoma for 2005-2006 NHANES participants. The exposures of interest were serum IgE levels to a panel of common indoor allergens. The outcome of interest was a clinical diagnosis of glaucoma based on the Rotterdam criteria. Logistic regression modeling was performed to assess the association between each type of IgE and glaucoma, while controlling for age, ethnicity, and steroid use. All estimates were weighted based on the multistage NHANES sampling design.

RESULTS

Among a weighted total of 83 308 318 participants, the overall prevalence of glaucoma was 3.2% (95% confidence interval [CI]: 2.8%, 3.6%). The majority of patients were non-Hispanic white (n = 10 547 654; 77.1%). The American dust mite antigen had the highest proportion of participants with positive IgE values (n = 12 093 038; 14.5%). In the full model including all allergen-specific IgE subtypes as predictors, there were statistically significant associations between IgE subtypes and glaucoma for the cockroach (odds ratio [OR] = 2.78; 95% CI = 1.34, 5.76), cat (OR = 3.42; 95% CI = 1.10, 10.67), and dog (OR = 0.24; 95% CI = 0.06, 0.96) antigens.

CONCLUSIONS

In NHANES, participants with glaucoma had significantly higher odds of sensitization to the cockroach and cat allergens compared to those without glaucoma. These findings indicate the need for further research to elucidate the role of chronic indoor allergen exposure in the development of glaucomatous optic neuropathy.

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.

Grass-specific CD4(+) T-cells exhibit varying degrees of cross-reactivity, implications for allergen-specific immunotherapy

BACKGROUND

Conceptually, allergic responses may involve cross-reactivity by antibodies or T-cells. While IgE cross-reactivity among grass-pollen allergens has been observed, cross-reactivity at the allergen-specific T-cell level has been less documented. Identification of the patterns of cross-reactivity may improve our understanding, allowing optimization of better immunotherapy strategies.

OBJECTIVES

We use Phleum pratense as model for the studying of cross-reactivity at the allergen-specific CD4(+) T cell level among DR04:01 restricted Pooideae grass-pollen T-cell epitopes.

METHODS

After in vitro culture of blood mono-nucleated cells from grass-pollen-allergic subjects with specific Pooideae antigenic epitopes, dual tetramer staining with APC-labelled DR04:01/Phleum pratense tetramers and PE-labelled DR04:01/Pooideae grass homolog tetramers was assessed to identify cross-reactivity among allergen-specific DR04:01-restricted T-cells in six subjects. Direct ex vivo staining enabled the comparison of frequency and phenotype of different Pooideae grass-pollen reactive T-cells. Intracellular cytokine staining (ICS) assays were also used to examine phenotypes of these T-cells.

RESULTS

T-cells with various degrees of cross-reactive profiles could be detected. Poa p 1 97-116 , Lol p 1 221-240 , Lol p 5a 199-218 , and Poa p 5a 199-218 were identified as minimally cross-reactive T-cell epitopes that do not show cross-reactivity to Phl p 1 and Phl p 5a epitopes. Ex vivo tetramer staining assays demonstrated T-cells that recognized these minimally cross-reactive T-cell epitopes are present in Grass-pollen-allergic subjects.

CONCLUSIONS

Our results suggest that not all Pooideae grass epitopes with sequence homology are cross-reactive. Non-cross-reactive T-cells with comparable frequency, phenotype and functionality to Phl p-specific T-cells suggest that a multiple allergen system should be considered for immunotherapy instead of a mono-allergen system.

Immunotherapy preparation guidelines, rules, and regulation

Allergen immunotherapy has been used to treat allergic diseases for more than 100 years. In the U.S., the preparation of diagnostic and therapeutic extracts requires the cooperation of the extract manufacturer, who provides the individual allergen concentrates, and the practicing physician who formulates, dilutes, and administers the final patient-specific treatment extract. The guidelines, rules, and regulations for these activities have been established and continue to be developed as progress is made. The molecular characterization and standardization of allergenic extracts has allowed for improvements in defining the potency of these products. In turn, these advances have led to improved dosing regimens and formulation practices. This review will describe in detail some of these interactions and will identify issues that require more attention.

Impact of thermal processing on legume allergens

Food induced allergic manifestations are reported from several parts of the world. Food proteins exert their allergenic potential by absorption through the gastrointestinal tract and can even induce life threatening anaphylaxis reactions. Among all food allergens, legume allergens play an important role in induction of allergy because legumes are a major source of protein for vegetarians. Most of the legumes are cooked either by boiling, roasting or frying before consumption, which can be considered a form of thermal treatment. Thermal processing may also include autoclaving, microwave heating, blanching, pasteurization, canning, or steaming. Thermal processing of legumes may reduce, eliminate or enhance the allergenic potential of a respective legume. In most of the cases, minimization of allergenic potential on thermal treatment has generally been reported. Thus, thermal processing can be considered an important tool by indirectly prevent allergenicity in susceptible individuals, thereby reducing treatment costs and reducing industry/office/school absence in case of working population/school going children. The present review attempts to explore various possibilities of reducing or eliminating allergenicity of leguminous food using different methods of thermal processing. Further, this review summarizes different methods of food processing, major legumes and their predominant allergenic proteins, thermal treatment and its relation with antigenicity, effect of thermal processing on legume allergens; also suggests a path that may be taken for future research to reduce the allergenicity using conventional/nonconventional methods.