T cell clones specific for Bet v I, the major birch pollen allergen, crossreact with the major allergens of hazel, Cor a I, and alder, Aln g I

T cells specific to multiple Bet v 1 peptides are highly cross-reactive toward the corresponding peptides from the homologous group of tree pollens

Background

Allergens from Fagales trees frequently cause spring allergy in Europe, North America, and some parts of Asia. The definition of the birch homologous group, which includes birch (Bet v), oak (Que a), alder (Aln g), hazel (Cor a), hornbeam (Car b), beech (Fag s), and chestnut (Cas s), is based on high allergen sequence identity and extensive IgE cross-reactivity. Clinical effect was seen during the alder/hazel, birch, and oak pollen seasons after treatment with tree SLIT-tablets containing only birch allergen extract. Here, we characterize T-cell reactivity with respect to epitope specificities and cross-reactivity toward various Bet v 1 family members, (PR-10/group 1 major allergens). This cross-reactivity may be part of the immunological basis of clinical effect or cross-protection when exposed to birch homologous tree species.

Method

T-cell lines were generated from 29 birch-allergic individuals through stimulation of peripheral blood mononuclear cells (PBMCs) with birch/Bet v or oak/Que a allergen extracts. T-cell responses to allergen extracts, purified group 1 allergens, and overlapping 20-mer peptides (Bet v 1, Aln g 1, Cor a 1, and Que a 1) were investigated by T-cell proliferation and cytokine production. Cross-reactivity was evaluated based on Pearson's correlations of response strength and further investigated by flow cytometry using tetramer staining for homologous peptide pairs.

Results

T-cell reactivity toward extracts and group 1 allergens from across the birch homologous group was observed for birch/Bet v as well as oak/Que a T-cell lines. T-cell lines responded to multiple Bet v 1 homologous peptides from Aln g 1 and Cor a 1 and a subset of Que a 1 peptides. Significant Pearson's correlations between frequently recognized peptides derived from Bet v 1 and the corresponding peptides derived from alder, hazel, and oak strongly supported the T-cell cross-reactivity toward these allergens. Cross-reactivity between birch and birch homologous peptides was confirmed by pMHCII tetramer staining.

Conclusion

T cells from birch tree pollen allergic individuals respond to multiple trees within the birch homologous group in accordance with the level of sequence homology between Bet v 1 family members, (PR-10 allergens) from these allergen sources, confirming the basis for clinical cross-protection.

Bet v 1-independent sensitization to major allergens in Fagales pollen: Evidence at the T-cell level

BACKGROUND

In birch-dominated areas, allergies to pollen from trees of the order Fagales are considered to be initiated by the major birch pollen allergen Bet v 1. However, the sensitizing activity of Bet v 1-homologs in Fagales pollen might be underestimated. Allergen-specific T-cells are crucial in the sensitization process. The T-cell response to major allergens from alder, hazel, oak, hornbeam, chestnut, beech, and chestnut pollen has not yet been analyzed. Here, we characterized the cellular cross-reactivity of major allergens in Fagales pollen with Bet v 1.

METHODS

T-cell-lines (TCL) were established from allergic individuals with Aln g 1, Car b 1, Ost c 1, Cor a 1, Fag s 1, Cas s 1, and Que a 1, and tested for reactivity with Bet v 1 and synthetic overlapping 12-mer peptides representing its primary sequence. Aln g 1-specific TCL was additionally tested with Aln g 1-derived peptides and all allergens. IgE-competition experiments with Aln g 1 and Bet v 1 were performed.

RESULTS

T-cell-lines initiated with Fagales pollen allergens varied strongly in their reactivity with Bet v 1 and by the majority responded stronger to the original stimulus. Cross-reactivity was mostly restricted to the epitope Bet v 1142-153 . No distinct cross-reactivity of Aln g 1-specific T-cells with Bet v 1 was detected. Among 22 T-cell epitopes, Aln g 1 contained two immunodominant epitopes. Bet v 1 inhibited IgE-binding to Aln g 1 less potently than Aln g 1 itself.

CONCLUSION

The cellular cross-reactivity of major Fagales pollen allergens with Bet v 1 was unincisive, particularly for Aln g 1, most akin to Bet v 1. Our results indicate that humoral and cellular responses to these allergens are not predominantly based on cross-reactivity with the major birch pollen allergen but suggest a Bet v 1-independent sensitization in individuals from birch tree-dominated areas.

How Do Pollen Allergens Sensitize?

Plant pollen is one of the main sources of allergens causing allergic diseases such as allergic rhinitis and asthma. Several allergens in plant pollen are panallergens which are also present in other allergen sources. As a result, sensitized individuals may also experience food allergies. The mechanism of sensitization and development of allergic inflammation is a consequence of the interaction of allergens with a large number of molecular factors that often are acting in a complex with other compounds, for example low-molecular-mass ligands, which contribute to the induction a type 2-driven response of immune system. In this review, special attention is paid not only to properties of allergens but also to an important role of their interaction with lipids and other hydrophobic molecules in pollen sensitization. The reactions of epithelial cells lining the nasal and bronchial mucosa and of other immunocompetent cells will also be considered, in particular the mechanisms of the activation of B and T lymphocytes and the formation of allergen-specific antibody responses.

Increased sensitization rates to tree pollens in allergic children and adolescents and a change in the pollen season in the metropolitan area of Seoul, Korea

INTRODUCTION

Children with allergies are at greater risk of becoming sensitized to allergenic pollens in response to environmental changes. This study investigated the relationship between changes in pollination associated with meteorologic changes and the sensitization rates of children to tree pollen allergens in the metropolitan area of Seoul, Korea.

METHODS

The study population consisted of 8,295 children who visited the pediatric allergy clinics at Hanyang University Seoul and Guri Hospital for allergy symptoms between January 1, 1998, and December 31, 2019. Pollen was collected at the two hospitals during the study using a Burkard 7-day sampler. Meteorologic data were obtained from the National Weather Service.

RESULTS

Among the major tree pollens, the largest increase in allergic sensitization was to oak, hazel, and alder pollens (0.28% annually). The pollen-sensitization rates increased annually within younger age groups. The duration of the pollen season was 98 days in 1998 and 140 days in 2019. Positive correlations were determined between the duration of the pollen season and the rates of sensitization to tree pollens, as well as between the pollen-sensitization rates and increasing temperature.

CONCLUSIONS

This study demonstrated the correlation between weather changes and the resulting changes in the pollen season with sensitization rates to allergenic pollens in children living in the Seoul metropolitan area. An annual increase in sensitization rates in younger children was determined. This pattern is expected to continue due to continuing climate change.

Simplified AIT for allergy to several tree pollens-Arguments from the immune outcome analyses following treatment with SQ tree SLIT-tablet

BACKGROUND

The SQ tree SLIT-tablet (containing birch extract) proved clinically significant effects during the pollen season for birch as well as alder/hazel. Immune outcomes of this treatment for allergens from multiple birch homologous trees need further investigation. We hypothesize that birch pollen extract AIT modulates a highly cross-reactive immune response and that this may be the basis for the observed clinical cross-protection.

METHODS

Blood samples were collected from 397 birch allergic patients during SQ tree SLIT-tablet or placebo treatment (1:1) for up to 40 weeks. Serum IgE and IgG₄ specific to birch, and birch homologous tree pollens from alder, hazel, hornbeam, beech and chestnut were measured by ImmunoCAP. IgE-Blocking Factor (IgE-BF) for alder, birch and hazel during treatment was measured by Advia Centaur and blocking effects for birch and all these birch homologous tree pollens were further investigated by basophil activation (BAT). Antibody readouts were investigated in patient subsets. T-cell responses (proliferation) to allergen extracts and peptide pools (group 1 allergens) were investigated in T-cell lines from 29 untreated birch pollen-allergic individuals.

RESULTS

Significant Pearson correlations between serum IgE towards birch, alder, hazel, hornbeam and beech were observed (r-values > .86). T-cell reactivity was observed throughout the birch homologous group. Almost identical kinetics for changes in IgE towards birch, alder and hazel were observed during treatment and similar species-specific changes were seen for serum-IgG₄ . IgG₄ reactivity towards birch and alder, hazel, hornbeam and beech correlated significantly at end-of-treatment (r-values > .72). Treatment resulted in similar IgE-BF kinetics for alder, birch, and hazel and blocking of BAT for multiple trees in most actively treated patients investigated.

CONCLUSIONS

Systematic analyses of T-cell and antibody cross-reactivities before and during birch pollen extract AIT provide the immunological basis for the observed clinical effect of SQ tree SLIT-tablet treatment of tree pollen allergy induced by multiple trees in the birch homologous group.

Alder pollen concentrations in the air during snowfall

The focus of our study was airborne alder pollen because it is one of the main causes of inhalant allergies in many countries in the Northern Hemisphere. The main research setback was pollen concentrations during snowfall. Analyses from a 21-year database showed that the hourly patterns of occurrence of airborne Alnus pollen during snowfall differ. Snowfall can cause a decrease in pollen concentrations in the air that may persist for several hours. However, during the snowfall period of 2018, an increase in pollen concentrations was observed. High temperatures during the days preceding snowfall stimulate thermal currents, and pollen could become airborne. During snowfall, airborne pollen grains are supposedly washed out of the atmosphere and numerous pollen grains are deposited on the snow surface. Hypotheses about the long-distance transport of pollen have also been verified. Back-trajectory analysis has revealed that air masses from Belarus and Ukraine were transported to Rzeszow. We found that the influence of snowfall on pollen concentrations is ambiguous and individuals prone to allergies also notice symptoms on days with snowfall and temperatures below zero.

First comparison of symptom data with allergen content (Bet v 1 and Phl p 5 measurements) and pollen data from four European regions during 2009-2011

BACKGROUND

The level of symptoms in pollen allergy sufferers and users of the Patient's Hayfever Diary (PHD), does not directly reflect the total amount of pollen in the air. It is necessary to explain the symptom load and thus the development of allergic symptoms and to determine which environmental factors, besides the pollen load, influence variables. It seems reasonable to suspect allergen content because the amount of allergen varies throughout seasons and regions and is not always correlated with the total pollen amount.

METHODS

Data on the allergen content of ambient air (Bet v 1 and Phl p 5) from 2009 until 2011 was used to compare the respective pollen and symptom loads for study regions in Austria, Germany, France and Finland.

RESULTS

Our findings suggest that allergen amount (Bet v 1/Phl p 5) has a strong but regionally dependent impact on the symptom load of pollen allergy sufferers. Peak symptom loads can be traced with peak allergen loads. The influence of other important aeroallergens should also be assessed during the pollen season.

CONCLUSION

Allergen concentrations have an impact on pollen allergy sufferers although not as clear as assumed previously. The pattern of pollen load and major allergen content distribution does not directly explain the symptom load pattern, although significant positive correlations were found. Thus, monitoring of symptoms via voluntary crowdsourcing should be considered for future pollen and symptom forecasts in order to support pollen allergy sufferers.

Allergen hybrids - next generation vaccines for Fagales pollen immunotherapy

Background

Trees belonging to the order of Fagales show a distinct geographical distribution. While alder and birch are endemic in the temperate zones of the Northern Hemisphere, hazel, hornbeam and oak prefer a warmer climate. However, specific immunotherapy of Fagales pollen-allergic patients is mainly performed using birch pollen extracts, thus limiting the success of this intervention in birch-free areas.

Objectives

T cells are considered key players in the modification of an allergic immune response during specific immunotherapy (SIT), therefore we thought to combine linear T cell epitope-containing stretches of the five most important Fagales allergens from birch, hazel, alder, oak and hornbeam resulting in a Fagales pollen hybrid (FPH) molecule applicable for SIT.

Methods

A Fagales pollen hybrid was generated by PCR-based recombination of low IgE-binding allergen epitopes. Moreover, a structural-variant FPH4 was calculated by in silico mutagenesis, rendering the protein unable to adopt the Bet v 1-like fold. Both molecules were produced in Escherichia coli, characterized physico-chemically as well as immunologically, and tested in mouse models of allergic sensitization as well as allergy prophylaxis.

Results

Using spectroscopic analyses, both proteins were monomeric, and the secondary structure elements of FPH resemble the ones typical for Bet v 1-like proteins, whereas FPH4 showed increased amounts of unordered structure. Both molecules displayed reduced binding capacities of Bet v 1-specific IgE antibodies. However, in a mouse model, the proteins were able to induce high IgG titres cross-reactive with all parental allergens. Moreover, prophylactic treatment with the hybrid proteins prevented pollen extract-induced allergic lung inflammation in vivo.

Conclusion

The hybrid molecules showed a more efficient uptake and processing by dendritic cells resulting in a modified T cell response. The proteins had a lower IgE-binding capacity compared with the parental allergens, thus the high safety profile and increased efficacy emphasize clinical application for the treatment of Fagales multi-sensitization.

Variability of Corylus avellana, L. CorA and profilin pollen allergens expression

Corylus avellana is the source of inhalant allergies induced by hazel pollen as well as food allergies induced after ingestion of hazelnuts. In this study, real-time PCR approach was used to analyse expression of hazel pollen allergens on the molecular level. Relative quantity of hazelnut allergens Corylus avellana, L. CorA and Corylus avellana, L. pollen profiling in samples from different Ukraine areas were determining and comparing. Differences among the levels of both analysed allergen transcripts were found for hazel CorA and profillin. In both cases, the expression within the urbanized growth conditions was higher when compared to the sample from village area. The average expression for CorA was 0.84 times higher than for profilin and the results are very variable depending on the place of growth. Expression levels here were within the range of 2.957 up to the 52.936. Profilin expression was the highest in the sample from the polluted place of growth-cement plant area with the value of 52 times higher when compared to the sample from the village area. In this study, comparison of expression levels of hazel CorA and profiling pollen allergens was performed for the first time. Real-time PCR assay developed in this study proved the sensitivity for detection of the changes of the hazel pollen allergens expression levels and could benefit labs by fast and reproducible detection method of these allergens.

Cor a 1-reactive T cells and IgE are predominantly cross-reactive to Bet v 1 in patients with birch pollen-associated food allergy to hazelnut

BACKGROUND

IgE- and T-cell cross-reactivity contribute to the birch pollen-food syndrome.

OBJECTIVES

We performed a comprehensive analysis of T-cell cross-reactivity in primary cell cultures, facilitating the identification of allergen-specific T-cell subpopulations from individual patients.

METHODS

Patients with birch pollen allergy and associated food allergy to hazelnuts, carrots, or both were analyzed for IgE cross-reactivity, T-cell responses, and T-cell cross-reactivity to recombinant Bet v 1.0101 (Bet v 1; birch), Cor a 1.0401 (Cor a 1; hazelnut), and Dau c 1.0104 (Dau c 1; carrot). A novel flow cytometry-based method using a 2-step staining process with fluorescent dyes was established to identify subpopulations of cross-reactive T cells.

RESULTS

IgE-binding inhibition tests of individual sera revealed that the vast majority of Cor a 1-reactive IgE was cross-reactive to Bet v 1, whereas Bet v 1-reactive IgE was only partially inhibited by preincubation with Cor a 1. Primary stimulation of T cells with Bet v 1 or Cor a 1 resulted in a significant increase in specific responses to Cor a 1 or Bet v 1 after secondary stimulation, respectively, indicating T-cell cross-reactivity between birch and hazelnut allergens in all patients of the study cohort. Preactivation with Dau c 1 induced less pronounced effects. A novel flow cytometry-based proliferation assay identified a predominant Cor a 1/Bet v 1-cross-reactive T-cell subpopulation within highly Bet v 1/Cor a 1-responsive T cells.

CONCLUSION

Analysis of primary allergen-specific T cells combined with flow cytometry-based proliferation assays facilitates investigation of allergen-specific T-cell subpopulations in subjects and might be helpful to evaluate the effect of birch-specific immunotherapy on pollen-associated food allergies.

Differentiation stage determines pathologic and protective allergen-specific CD4+ T-cell outcomes during specific immunotherapy

BACKGROUND

The main obstacle to elucidating the role of CD4(+) T cells in allergen-specific immunotherapy (SIT) has been the absence of an adequately sensitive approach to directly characterize rare allergen-specific T cells without introducing substantial phenotypic modifications by means of in vitro amplification.

OBJECTIVE

We sought to monitor, in physiological conditions, the allergen-specific CD4(+) T cells generated during natural pollen exposure and during allergy vaccination.

METHODS

Alder pollen allergy was used as a model for studying seasonal allergies. Allergen-specific CD4(+) T cells were tracked and characterized in 12 subjects with alder pollen allergy, 6 nonallergic subjects, and 9 allergy vaccine-treated subjects by using peptide-MHC class II tetramers.

RESULTS

Allergen-specific CD4(+) T cells were detected in all of the subjects with alder pollen allergy and nonallergic subjects tested. Pathogenic responses--chemoattractant receptor homologous molecule expressed on T(H)2 lymphocytes (CRTH2) expression and T(H)2 cytokine production--are specifically associated with terminally differentiated (CD27(-)) allergen-specific CD4(+) T cells, which dominate in allergic subjects but are absent in nonallergic subjects. In contrast, CD27(+) allergen-specific CD4(+) T cells are present at low frequencies in both allergic and nonallergic subjects and reflect classical features of the protective immune response with high expression of IL-10 and IFN-γ. Restoration of a protective response during SIT appears to be due to the preferential deletion of pathogenic (CD27(-)) allergen-specific CD4(+) T cells accompanied by IL-10 induction in surviving CD27(+) allergen-specific CD4(+) T cells.

CONCLUSIONS

Differentiation stage divides allergen-specific CD4(+) T cells into 2 distinct subpopulations with unique functional properties and different fates during SIT.

Interaction of allergens, major histocompatibility complex molecules, and T cell receptors: a 'ménage à trois' that opens new avenues for therapeutic intervention in type I allergy

T cells are major players in the initiation and perpetuation of the allergic immune response. In this review, we summarize the current knowledge on allergen recognition by T lymphocytes and address the components of the trimeric recognition complex: T cell receptors, major histocompatibility complex molecules, and allergen-derived peptides. Furthermore, possible implications of this scientific background for future therapeutic developments are discussed.

T-cell epitopes of aeroallergens

OBJECTIVE

To describe the current knowledge of the T-cell epitopes of common aeroallergens, how they were discovered, and implications for future therapy.

DATA SOURCES

PubMed search of English-language articles without date limits pertaining to T-cell epitopes of aeroallergens included on a standard skin test panel.

STUDY SELECTION

A total of 127 articles were screened based on the results of the PubMed search and cross-indexed as needed. The highest quality and most clinically relevant articles were included for discussion.

RESULTS

Of the 47 allergen extracts included on the standard skin test panel at our instittition, T-cell epitopes have been described for 13. Immunodominant epitopes have been used for peptide immunotherapy trials.

CONCLUSIONS

T-cell epitopes have been characterized for a minority of common aeroallergens. However, knowledge is rapidly expanding and can lay the groundwork for therapies that specifically target T cells.

Correlations between alder specific IgE and alder-related tree pollen specific IgE by RAST method

BACKGROUND

Wild birch trees grow in limited areas in Japan and are not a common aero-allergen. However, many patients who do not live in the area show positive birch pollen Radioallergosorbent Test (RAST). Therefore, being sensitized by another tree pollen which is closely related to birch may result in showing a specific IgE antibody to birch. Alder is a one of these trees and in the past it grew widely in Japan. However, there is no available RAST data as to the correlations between alder and alder-related trees.

METHODS

We measured the alder specific IgE (CAP-RAST, Phadea) in stored sera which was positive in birch RAST (228 samples), beech RAST (36 samples), oak RAST (152 samples) and cedar RAST (411 samples) and examined correlations between the RAST of alder and other trees.

RESULTS

The correlation coefficient value of birch was very high (0.971). The other coefficient values of beech and oak were high (0.884 in beech and 0.895 in oak) but were slightly lower than that of the birch. This means that in terms of allergenicities, birch pollen is almost the same as alder and beech and oak are partly different from the alder.

CONCLUSIONS

The Japanese respond to alder pollen just same as they do to birch pollen in forming specific IgE antibody. In clinical practice, positive alder RAST has the same meaning as positive birch RAST.

Characterization of the T cell response to the major hazelnut allergen, Cor a 1.04: evidence for a relevant T cell epitope not cross-reactive with homologous pollen allergens

BACKGROUND

IgE antibodies specific for the major birch-pollen allergen, Bet v 1, cross-react with homologous allergens in particular foods, e.g. apples, carrots and hazelnuts. In a high number of tree pollen-allergic individuals, this cross-reactivity causes clinical symptoms, commonly known as the 'birch-fruit-syndrome'.

OBJECTIVE

To characterize the T cell response to the Bet v 1-related major allergen in hazelnuts, Cor a 1.04, and its cellular cross-reactivity with Bet v 1 and the homologous hazel pollen allergen, Cor a 1.

METHODS

Using recombinant Cor a 1.04, T cell lines (TCL) and T cell clones (TCC) were established from peripheral blood mononuclear cells of tree pollen-allergic patients with associated food allergy. T cell epitopes were determined using overlapping synthetic peptides in Cor a 1.04-reactive TCL and TCC. In parallel, reactivity to Bet v 1 and Cor a 1 was tested.

RESULTS

In total, 20 distinct T cell epitopes on the hazelnut allergen were identified. Several Cor a 1.04-specific TCL and TCC reacted with pollen allergens albeit less pronounced than with the hazelnut allergen. Several Cor a 1.04-specific TCC did not react with pollen allergens. Interestingly, these clones were found to react with the Bet v 1-related major allergen in carrots, Dau c 1. The cellular cross-reactivity between both food allergens could be associated with the most frequently recognized T cell epitope of Cor a 1.04, Cor a 1.04(142-153).

CONCLUSIONS

The major hazelnut allergen cross-reacts with the major allergens of birch and hazel pollen but apparently contains a relevant T cell epitope not shared with pollen allergens. Our finding may have important implications for the specific immunotherapy of tree pollen-allergic patients suffering from concomitant hazelnut allergy.

T-cell receptor-mediated cross-allergenicity

BACKGROUND

Profilins are conserved and ubiquitous plant and animal proteins. We wanted to discover whether the T-cell response to conserved epitopes on birch and grass profilins could account for cross-allergenicity in subjects allergic to these two pollens.

METHODS

Thirty-one patients allergic to grass and birch were recruited for the study. Grass and birch reactive T lymphocytes were studied by measuring proliferation to birch and grass allergen, respectively, followed by Vbeta T-cell receptor family-specific polymerase chain reaction and heteroduplex analysis. T-cell clones were derived from patients with cross-proliferating T cells.

RESULTS

In 25 of 31 subjects the T-cell response to grass was quite distinct from that to birch. In contrast, in 6 of 31 individuals grass T cells cross-proliferated to birch and this was reproduced in 4 patients by birch profilin. CD4 Th2 cell clones were derived which promiscuously recognized homologously conserved regions on birch and grass profilins.

CONCLUSION

We conclude that a functionally relevant T-cell response to conserved regions of panallergens underlie cross-allergenicity in a subset of allergic patients. These results suggest that a reciprocal modulation of the response to one sensitizing allergen can occur following natural exposure to or immunotherapy with another allergen. These results have relevance in the management of patients with multiple allergies.

Cytokine production in peripheral blood cells during and outside the pollen season in birch-allergic patients and non-allergic controls

BACKGROUND

The naturally occurring pollen season permits observation of the kinetic changes in the process of allergic inflammation. We examined cytokine production in peripheral blood (PB) T cells and monocytes obtained from birch-allergic patients both during and outside the pollen season.

METHODS

PB from 16 patients and six healthy controls was obtained during the alder pollen season, at the beginning and the peak of the birch pollen season and outside the pollen season. Mononuclear cells (MNC) were stimulated with allergen and polyclonal activators. For flow cytometric analysis, MNC were stained with monoclonal antibodies (MoAbs) against the cell surface markers CD3, CD8, CD14 and the intracellular cytokines IL-4, IL-5, IL-10, IL-12, IL-13, granulocyte macrophage-colony stimulating factor (GM-CSF) and IFN-gamma.

RESULTS

In allergic patients, significant increases in clinical symptoms, use of medication, eosinophil numbers and birch-specific IgE were found during the pollen season. In vitro allergen stimulation increased the number of GM-CSF+ monocytes (P<0.01) and this increase was dependent on allergen exposure. The IL-4/IFN-gamma ratio rose (P<0.001) at the peak of birch pollen season and the ratio correlated with symptom scores during the birch season. In the CD4+ cell population, the numbers of GM-CSF+ cells were higher throughout the alder and birch seasons compared with outside the pollen season (P<0.05). No such changes were seen in the healthy controls.

CONCLUSIONS

The main finding of our study was the increased percentage of GM-CSF+ monocytes in atopic subjects compared with healthy controls. In allergic patients, natural seasonal pollen exposure resulted in increased numbers of GM-CSF+ cells among both monocytes and CD4+ T cells. We have also shown that a seasonal change in Th2/Th1 cytokine ratio requires an adequate and prolonged allergen stimulation that is seen late in the pollen season.

Strategies for converting allergens into hypoallergenic vaccine candidates

Specific immunotherapy is based on the administration of increasing doses of allergens to allergic patients with the aim of inducing a state of antigen-specific unresponsiveness. Specific immunotherapy is one of the few causative treatment approaches for Type I allergy but may cause numerous side effects, including local inflammatory reactions, systemic manifestations (e.g., asthma attacks) and in the worst case, anaphylactic shock which may lead to death. Several attempts have been made in the past to reduce the rate of side effects. They included the chemical modification of allergen extracts to reduce their allergenic activity and the adsorption of allergen extracts to adjuvants to prevent the systemic release of allergens after administration. During the last decade, cDNAs coding for the most relevant allergens have been isolated and the corresponding allergens have been produced as recombinant molecules. Using allergen-encoding cDNAs, the amino acid sequence of allergens or purified recombinant allergens several strategies can now be applied to produce allergen derivatives with reduced allergenic activity for allergy vaccination in a controlled and reproducible manner. Currently, allergen-encoding cDNAs are used to engineer recombinant hypoallergenic allergen derivatives. According to the amino acid sequences and experimental epitope mapping data, synthetic peptides representing T- or B-cell epitopes are produced and purified recombinant allergens are coupled to novel adjuvants for vaccine formulation. In this article, strategies for the production and evaluation of allergen derivatives with reduced allergenic activity for allergy vaccination are described. These new vaccines hold great promise to improve the current practice of allergen-specific immunotherapy and maybe also used for prophylactic vaccination in the future.

Fagales pollen sensitization in a birch-free area: a respiratory cohort survey using Fagales pollen extracts and birch recombinant allergens (rBet v 1, rBet v 2, rBet v 4)

BACKGROUND

Birch allergy is one of the most common pollinosis in areas where exposure to high levels of birch pollen is common. Little is known about birch sensitivity in areas without birch pollen exposure and reactivity to birch-related species within the Fagales order.

OBJECTIVE

the aim was to evaluate Fagales reactivity within a population not exposed to birch pollen using epidemiological, diagnostic, and laboratory approaches by means of extracts and allergenic molecules.

METHODS

A cohort of 5335 respiratory allergic patients was screened by means of skin testing birch, hazel, and oak pollen extracts. Patients were from a birch-free area, but exposed to other Fagales pollen species. A subset of patients was from an intensively cultivated hazel area. A sample of the Fagales allergic population was tested with other Fagales pollen extract (alder, hornbeam, beech, chestnut) and with apple and hazelnut. IgE detection was performed with birch, hazel, oak, apple, and hazelnut extracts, and with Bet v 1, Bet v 2, Bet v 4, and bromelain. IgE immunoblots were performed using birch and hazel extracts. Epidemiological, clinical, and laboratory data were analysed by stratifying the allergic population.

RESULTS

Twenty-five percent of the pollen allergic cohort was skin test positive to at least one of the three Fagales species. Combined reactivity to the three species was recorded in 80% of this cohort. Isolated hazel pollen reactivity was recorded in 13.5% of the Fagales allergic patients. Sixty-six percent of these subjects were from the intensively cultivated hazel area. Reactivity to apple and hazelnut was detected by skin test (40%) and IgE reactivity (60%), but only 19% of the positive patients reported symptoms related to at least one of the two foods. Reactivity to Bet v 1 was recorded in 84% of the birch/hazel/oak co-reactivity group, and in 28% of the subjects with the same co-reactivity, but associating a multiple pollen sensitization. IgE to Bet v 2 (50%) and Bet v 4 (23%) panallergens were recorded positive in the latter subset. Bet v 1 prevalence ranged between 48% and 21% among subgroups of patients coming from different areas. Furthermore, an IgE reactivity to hazel-restricted allergenic components was detected among subjects coming from the same area and having a hazel isolated reactivity.

CONCLUSION

Fagales allergy can be found in birch-free areas caused by the exposure to other Fagales species. Birch allergens can be useful for mimicking the allergenic extract, but are also the exclusive tools for a fine diagnostic and epidemiological approach to Fagales pollen allergy. Allergenic molecules from the hazel family will increase the panel of available reagents for the molecule-based approach to allergy diagnosis and therapy.

Comparison of four variants of a major allergen in hazelnut (Corylus avellana) Cor a 1.04 with the major hazel pollen allergen Cor a 1.01

The aim of this study was to produce the Bet v 1-related major hazelnut allergen Cor a 1.0401 and variants thereof as recombinant allergens, and to compare their immuno-reactivity with the major hazel pollen allergen using sera of patients whose hazelnut allergy recently was confirmed by double-blind placebo-controlled food challenges (DBPCFC) in a multicenter study. Total RNA was isolated from immature hazelnuts and transcribed into cDNA. Full length coding DNA obtained by PCR-strategy was subcloned into pTYB11 vector and expressed in E. coli ER2566 cells. Native non-fusion target proteins were purified by DTT-induced self-cleavage of the intein-tagged N-terminal fusion proteins. IgE reactivity of the recombinant allergens was tested by enzyme allergosorbent test (EAST), EAST-inhibition, immunoblot-inhibition and histamine release assays. Four recombinant allergens were produced showing deduced amino acid sequence identities among each other of 97-99%, and were considered as variants Cor a 1.0401 (GenBank Accession no.: AF136945), Cor a 1.0402 (AF323973), Cor a 1.0403 (AF323974) and Cor a 1.0404 (AF323975). Cor a 1.0402 and 03 only differed in a C4S exchange. Cor a 1.0404 had a unique proline residue in position 99. Surprisingly, only 63% identity was revealed with hazel pollen Cor a 1. EAST with 43 sera of patients with positive DBPCFC to hazelnut indicated IgE reactivity to Cor a 1.0401 in 95% of the sera, to Cor a 1.0402 in 93%, to Cor a 1.0403 in 91%, and in only 74% of the sera to the proline variant Cor a 1.0404. The allergenic activity of the four variants was confirmed by histamine release assays in 15 hazelnut-allergic patients stimulated with the four variants and controls. Eleven sera were positive with extract from native hazelnut, 13 with rCor a 1.0401, 12 with rCor a 1.0402, 11 with rCor a 1.0403, and only two with rCor a 1.0404 containing the proline exchange. The high IgE binding variant Cor a 1.0401 showed only partial IgE cross-reactivity with pollen Cor a 1. IgE-binding and histamine release capacity led to a concordant ranking of the allergenic activity of the recombinant variants: Cor a 1.0401>Cor a 1.0402 and 03>Cor a 1.0404 (the proline variant). Similar results for Cor a 1.0402 and 03 suggest a minor influence in IgE binding of cysteine in position 4, whereas proline in position 99 appears to be responsible for the decrease in IgE reactivity in Cor a 1.0404. It appears that the epitopes of hazelnut Cor a 1.04 are less related to pollen Cor a 1 than to Bet v 1 from birch pollen. Low IgE binding variants or mutants of Cor a 1.04 are candidate compounds for developing a novel and safe approach of specific immunotherapy of hazelnut allergy.

Genetic engineering of a hypoallergenic trimer of the major birch pollen allergen Bet v 1

An estimated 100 million individuals suffer from birch pollen allergy. Specific immunotherapy, the only curative allergy treatment, can cause life-threatening anaphylactic side effects. Here, we report the genetic engineering of a recombinant trimer consisting of three covalently linked copies of the major birch pollen allergen, Bet v 1. The trimer exhibited profoundly reduced allergenic activity but contained similar secondary structures such as Bet v 1 wild type, Bet v 1-specific B cell and T-cell epitopes, and induced Th1 cytokine release. As immunogen, rBet v 1 trimer induced IgG antibodies, which blocked patients' IgE binding to Bet v 1 and related allergens. Thus, rBet v 1 trimer represents a novel hypoallergenic vaccine prototype for treatment of one of the most frequent allergy forms.

How far can we simplify in vitro diagnostics for Fagales tree pollen allergy? A study with three whole pollen extracts and purified natural and recombinant allergens

BACKGROUND

Current diagnostic tests for Fagales tree pollen allergy are often composed of mixtures of pollen of birch, alder and hazel. Their complex composition hampers accurate standardization.

OBJECTIVE

The aim of this study was to investigate whether mixtures of tree pollen extracts can be replaced by a single pollen species, and whether a single pollen species can be replaced by a limited number of purified natural or recombinant major allergens.

METHODS

Sera (n = 1725) were selected on ground of a general suspicion for inhalant allergy, and tested in a RAST for birch, alder and hazel pollen. Sera with > 0.5 RU/mL for any of the three species were tested in a RAST for natural Bet v 1 and Bet v 2 as well as for recombinant versions of both allergens.

RESULTS

Specific IgE antibodies (> 0.3 RU/mL) against birch, alder and hazel were found in 242, 298 and 292 sera, respectively. All sera with a positive RAST for alder and/or hazel and a negative RAST for birch were low-responder sera on alder and hazel, only five sera having a RAST value > 1.0 (all < 2.0). For all sera with a RAST > 0.5 RU/mL (n = 250), the mean of individual ratio's alder/birch and hazel/birch was 1.02 and 0.54, respectively. Of 223 of these sera, 63.2% had specific IgE against natural Bet v 1 and 63.7% against natural Bet v 2. When responses to both allergens were combined 93.7% were positive. The mean ratios Bet v 1 + 2/extract were 1.00, 1.04 and 2. 11 in case of birch, alder and hazel, respectively. For 211 sera the same analysis was performed with recombinant Bet v 1 and Bet v 2. Only six sera with Bet v 1-specific IgE (all < 0.5 RU/mL) were negative (< 0.3 RU/mL) on recombinant Bet v 1. For Bet v 2, 77/132 sera with specific IgE to the natural allergen did not react to the recombinant version. Twelve false-negatives had RAST values > 1.0 RU/mL. The mean of the individual recombinant/natural ratios was 0. 98 for Bet v 1 and 0.38 for Bet v 2 (P < 0.001). The mean ratio rBet v 1 + 2/birch was 0.75 with 17.5% false-negatives on the combination of recombinant allergens.

CONCLUSION

Reliable in vitro diagnosis is possible with a single tree pollen extract (birch or alder). The same is true for purified natural Bet v 1 and Bet v 2. A combination of recombinant molecules is slightly less efficient.

The role of allergen-specific T cells in the allergic immune response: relevance to allergy vaccination

Recent research has elucidated many of the immunologic mechanisms that underlie atopic allergies. In particular, it has become clear that the role of CD4+ allergen-specific T cells is crucial for the induction of IgE and eosinophilia, factors that mediate the immediate hypersensitivity reaction and late-phase responses, respectively. Therefore, the reactivity patterns and activation requirements of allergen-specific T cells are important parameters for understanding and manipulating the allergic immune response. This review addresses these issues and discusses their relevance to the further development of allergy vaccines.

Preserved epitope-specific T cell activation by recombinant Bet v 1-MBP fusion proteins

BACKGROUND

Allergen-specific T cells play an important role in the allergic immune response, and are thought to be the principal target in specific immunotherapy.

OBJECTIVE

The aim of the present study was to evaluate if fusion proteins of allergens with bacterial proteins can be used to activate and bias allergen-specific T cells, and to characterize T cell epitopes.

METHODS

The complete gene of Bet v 1, the major birch pollen allergen, was amplified by PCR from birch pollen mRNA, and cloned in pKK223-3. The complete gene or truncated sequences were transferred to pMAL-c and expressed in E. coli as fusion proteins with maltose binding protein (MBP). The complete fusion protein, and the truncated fusion proteins were used for studies with Bet v 1-specific T cells.

RESULTS

Bet v 1-specific T cells reacted similarly with purified and crude Bet v 1-MBP proteins. Therefore, crude preparations were used to study the epitope-specificity of 11 Bet v 1-specific T cell clones. Six distinct T cell epitopes were determined in this way. Interestingly, the T cell epitope of three T cell clones, that did not react with synthetic peptides in a previous study, was identified. In addition, the presence of MBP as a fusion partner to Bet v 1 was shown to influence TH2/TH1 cytokine production in T cell lines, but not in established T cell clones.

CONCLUSION

Using crude preparations of recombinant fusion proteins of Bet v 1 with MBP, multiple T cell epitopes were identified in Bet v 1. As T cell activation is preserved in this system, the generation of recombinant allergens with TH1-inducing proteins as fusion partners might be considered as a T-cell targeted approach for specific immunotherapy.

Sequence comparisons of the CDR3 hyper-variable loops of human T cell receptors specific for three major T cell epitopes of the birch pollen allergen Bet v 1

We have analysed the T cell receptor (TCR) alpha and beta chain sequences of 16 human CD4+ T cell clones (TCCs) specific for three important epitopes of the major birch pollen allergen Bet v 1. The TCCs were raised from the peripheral blood of eight patients with birch pollen allergy, showing allergic rhino-conjunctivitis and allergic asthma. The TCCs from these individuals were specific for Bet v 1-derived peptides: amino acids (aa)77-92 (epitope 1), aa93-108 (epitope 2) and aa113-126 (epitope 3). The DNA sequence analysis of the TCRAV and BV regions revealed heterogeneous repertoires for recognition of the peptides. Multiple combinations of AV/AJ and BV/BJ were used. However, some inter-individual restriction was evident. A limited selection of AVS and the normally infrequently used BV1S4 was obvious in TCCs specific for epitope 1. The TCRBV13 was more frequent in TCCs recognizing epitope 3. A very narrow distribution in length could be seen in the CDR3 sequences of the beta chain of TCRs with specificity for epitopes 1 and 2. Inter-individual positional micro-restriction was observed for the aa motif LR in the tCDR3 (epitope 1), for the aa residue M in the alphaCDR3 and for the aa residue G in the betaCDR3 (epitope 3). Our results illustrate clearly that each antigenic peptide derived from a single allergen, is capable of selecting different characteristics in the responding repertoire of TCRs, thus increasing the complexity of allergen-recognition by T lymphocytes. Therefore, our findings limit the potential use of TCR targeted therapeutical strategies in Type I allergy.

Diversity of human T cell receptor sequences of T cell clones with specificity for Bet v 1 peptide/MHC II complexes

T cell clones (TCC) were raised from the peripheral blood of patients suffering from tree pollen allergy. All TCC were restricted by HLA-DR molecules. In order to investigate possible intervention targets in Type I allergic diseases, we have examined T cell receptor (TCR) alpha- and beta-chain nucleotide sequences of several allergen-reactive human CD4+ TCC specific for four frequently found epitopes of Bet v 1, the major birch pollen allergen. In general, TCC specific for the 4 epitopes investigated, used diverse TCRAV and TCRBV gene segments. Moreover, the junctional regions encoding the third complementarity determining regions (CDR3) of the TCR showed striking heterogeneities in length and amino acid composition. A more restricted use of two J gene segments (TCRBJ1S4 and 2S7) was only observed in the beta-chain of TCR used by TCC specific for epitope 1. In addition, all TCC specific for epitope 4 showed an arginine residue in the N-terminal region of their TCRBV CDR3 loops despite their sequence diversities. In view of the striking heterogeneities found, therapeutical strategies aimed at the clonal deletion of allergen-specific T cell clones, providing help for IgE synthesis, may not be feasible. Moreover, our results cast a doubt on the theory, that the CDR3 exclusively provides the primary contact with the peptide bound in the major histocompatibility (MHC) groove, and suggest additional interaction with MHC class II.

T-cell epitopes of Phl p 1, major pollen allergen of timothy grass (Phleum pratense): evidence for crossreacting and non-crossreacting T-cell epitopes within grass group I allergens

BACKGROUND

The use of peptides representing T-cell epitopes of allergens is a modern concept for improvement of specific immunotherapy. A prerequisite for this approach is the identification of T-cell epitopes of atopic allergens.

METHODS

T-cell lines and 40 T-cell clones (TCC) specific for Phl p 1, the group I allergen of timothy grass (Phleum pratense), were established from the peripheral blood of nine patients allergic to grass pollen and mapped for epitope specificity by using overlapping dodecapeptides. Phenotype and cytokine production profile of TCC were investigated. Representative TCC were analyzed for HLA-restriction, T-cell receptor V beta gene usage, and crossreactivity with grass pollen extracts from Dactylis glomerata, Poa pratensis, Lolium perenne, Secale cereale, and selected amino acid sequence-derived peptides.

RESULTS

Patients displayed IgE binding to all grass species investigated. Forty TCC were established. Fifteen T-cell epitopes could be identified on Phl p 1. Of 40 TCC, 39 displayed the helper cell (Th) phenotype; one clone was CD8+. Specific stimulation induced a Th2-like type of cytokine production in 20 of 39 TCC. Crossreactivity studies revealed crossreacting and non-crossreacting T-cell epitopes.

CONCLUSION

Phl p 1, a major grass pollen allergen, harbors multiple T-cell epitopes. Species-specific and crossreacting T-cell epitopes exist among group I allergens of grasses. Epitope recognition patterns could not be correlated with particular HLA haplotypes. A restricted T-cell receptor V beta gene usage was not observed.

Diversity of TCRAV and TCRBV sequences used by human T-cell clones specific for a minimal epitope of Bet v 1, the major birch pollen allergen

T-cell clones (TCC) were raised from the peripheral blood of patients suffering from tree pollen allergy. All TCC were restricted by HLA-DR molecules. In order to investigate possible intervention targets in Type I allergic diseases, we examined T-cell receptor (TCR) alpha and beta chain nucleotide sequences of five allergen-reactive human CD4+ TCC specific for a C-terminal epitope (BV 144) of Bet v 1, the major birch pollen allergen. Proliferation assays using synthetic peptides revealed the 10-mer LRAVESYLLA as minimal epitope for three TCC; two TCC also displayed reactivity with the nonapeptide LRAVESYLL. Two TCC expressed TCRBV2S3, all other BV144-specific TCC used diverse TCRAV and TCRBV gene segments. Moreover, the junctional regions encoding the third complementary determining regions (CDR3) of the TCR showed a striking heterogeneity in length and amino acid composition. Nevertheless, all TCC showed an arginine residue in the N-terminal region of their TCRBV CDR3 loops. Therefore, therapeutical strategies aimed at the clonal deletion of allergen-specific T-cell clones, providing help for IgE synthesis, will not be feasible. Our results cast a doubt on the theory that the CDR3 exclusively provides the primary contact with the peptide bound in the major histocompatibility (MHC) groove, and suggest additional interaction with MHC class II.

Four recombinant isoforms of Cor a 1, the major allergen of hazel pollen, show different reactivities with allergen-specific T-lymphocyte clones

Purified preparations of allergenic proteins from plants, and in particular from pollens, consist of multiple closely related isoforms. These isoforms are highly similar in their amino acid sequences, yet they display different properties with respect to antibody binding. In this study we report of differential potencies of cross-reacting tree pollen allergens and cloned isoforms of these allergens to activate allergen-specific T-lymphocyte clones (T-cell clones; TCC). Six TCC with specificity for Bet v 1, a representative tree pollen major allergen, were established from peripheral blood of five birch-pollen-allergic donors. All TCC displayed the helper-cell phenotype. Five TCC reacted with distinct epitopes present on natural (n) and on recombinant (r) Bet v 1. One TCC could not be stimulated with r Bet v 1, in spite of strong reactivity with purified natural Bet v 1. The TCC were tested in proliferation assays using purified n Bet v 1, n Cor a 1 (the homologous major allergen of hazel pollen), r Bet v 1, four recombinant isoforms of Cor a 1 and peptides representing corresponding T-cell stimulating regions (isoepitopes) on these proteins. The clones showed different patterns of reactivity in response to stimulation with the five recombinant molecules and the corresponding peptides. Certain exchanges of amino acids within stimulating peptides correlated with a lack of proliferation of the TCC tested. These findings are important with respect to the use of broadly cross-reactive recombinant allergens or allergen-derived peptides for immunotherapy of type I allergy.