Molecular, proteomic and immunological parameters of allergens provide inclusion criteria for new candidates within established grass and tree homologous groups

Assessing IgE sensitization profiles to birch and timothy grass pollen allergens in birch pollen allergic blood donors using an oligoplex specific IgE assay

IgE sensitization profiles to single birch allergens in birch-sensitized patients differ among European countries. The aim of this study was to determine the distribution of specific IgE antibodies to major and minor birch pollen allergens in a population of allergic Norwegian individuals by using a birch allergic blood donor population as a surrogate sample. Sixty blood donors were recruited and sampled based on birch allergy symptoms such as rhinitis, rhinoconjunctivitis and/or mild asthma in previous seasons. All sera were collected before start of the pollen season and tested using a line blot assay (Euroimmun AG, Lübeck, Germany) for IgE to birch and timothy pollen. Both extracts, single allergens, and cross-reacting carbohydrate determinants (CCD) were analysed. Only donors with specific IgE to birch and/or timothy grass were further evaluated. Specific IgE to birch pollen extract was found in 52 sera, and sensitization to timothy grass in 40 sera. Specific IgE to Bet v 1 was predominant in contrast to Bet v 4 which was absent. However, sensitization to the minor allergens Bet v 2 and 6 was always found together with high levels of IgE to Bet v 1. Subjects sensitized to the profilin Bet v 2 from birch were also sensitized to Phl p 12 from timothy grass. In conclusion, there was predominantly Bet v 1 sensitization in this cohort and low sensitization to minor allergens and cross-reactive allergens (Bet v 2, Bet v 4, Phl p 7 and Phl p 12).

Perspectives of Proteomics in Respiratory Allergic Diseases

Proteomics in respiratory allergic diseases has such a battery of techniques and programs that one would almost think there is nothing impossible to find, invent or mold. All the resources that we document here are involved in solving problems in allergic diseases, both diagnostic and prognostic treatment, and immunotherapy development. The main perspectives, according to this version, are in three strands and/or a lockout immunological system: (1) Blocking the diapedesis of the cells involved, (2) Modifications and blocking of paratopes and epitopes being understood by modifications to antibodies, antagonisms, or blocking them, and (3) Blocking FcεRI high-affinity receptors to prevent specific IgEs from sticking to mast cells and basophils. These tools and targets in the allergic landscape are, in our view, the prospects in the field. However, there are still many allergens to identify, including some homologies between allergens and cross-reactions, through the identification of structures and epitopes. The current vision of using proteomics for this purpose remains a constant; this is also true for the basis of diagnostic and controlled systems for immunotherapy. Ours is an open proposal to use this vision for treatment.

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 1_142-153 . 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.

IgE-cross-blocking antibodies to Fagales following sublingual immunotherapy with recombinant Bet v 1

BACKGROUND

Evidence has accumulated that birch pollen immunotherapy reduces rhinoconjunctivitis to pollen of birch homologous trees. Therapeutic efficacy has been associated with IgE-blocking IgG antibodies. We have recently shown that sera collected after 16 weeks of sublingual immunotherapy with recombinant Bet v 1 (rBet v 1-SLIT) display strong IgE-blocking bioactivity for Bet v 1. Here, we assessed whether rBet v 1-SLIT-induced IgG antibodies display cross-blocking activity to related allergens in Fagales pollen.

METHODS

IgE, IgG1 and IgG4 reactivity to recombinant Bet v 1, Aln g 1, Car b 1, Ost c 1, Cor a 1, Fag s 1, Cas s 1 and Que a 1 were assessed in pre- and post-SLIT samples of 17 individuals by ELISA. A basophil inhibition assay using stripped basophils re-sensitized with a serum pool containing high Bet v 1-specific IgE levels was established and used to assess CD63 expression in response to allergens after incubation with pre-SLIT or post-SLIT samples. IgG1 and IgG4 were depleted from post-SLIT samples to assess its contribution to IgE-cross-blocking.

RESULTS

Sublingual immunotherapy with recombinant Bet v 1 boosted cross-reactive IgE antibodies and induced IgG1 and IgG4 antibodies with inter- and intra-individually differing reactivity to the homologs. Highly variable cross-blocking activities of post-SLIT samples to the different allergens were found. IgG1 and IgG4 antibodies displayed cross-blocking activity with individual variance.

CONCLUSIONS

Our mechanistic approach suggested that immunotherapy with the reference allergen Bet v 1 induces individual repertoires of cross-reactive IgG1 and IgG4 antibodies. The cross-blocking bioactivity of these antibodies was also highly variable and neither predictable from protein homology nor IgE-cross-reactivity.

Allergy to oak pollen in North America

Background: Oak pollen is an important allergen in North America. The genus Quercus (oak) belongs to the family Fagaceae under the order Fagales. Objective: The objective of this article was to narratively review the oak pollen season, clinical and epidemiologic aspects of allergy to oak pollen, oak taxonomy, and oak allergen cross-reactivity, with a focus on the North American perspective. Methods: A PubMed literature review (no limits) was conducted. Publications related to oak pollen, oak-related allergic rhinitis with or without conjunctivitis, and oak-related allergic asthma were selected for review. Results: Oak species are common throughout the United States and contribute up to 50% to overall atmospheric pollen loads. Mean peak oak pollen counts can reach >2000 grains/m³. The start of the oak pollen season generally corresponds to the seasonal shift from winter to spring based on latitude and elevation, and may begin as early as mid February. The duration of the season can last > 100 days and, in general, is longer at lower latitudes. In the United States, ∼30% of individuals with allergy are sensitized to oak. The oak pollen season correlates with increased allergic rhinitis symptom-relieving medication use and asthma-related emergency department visits or hospitalizations. Oak falls within the birch homologous group. Extensive immunologic cross-reactivity has been demonstrated between oak pollen and birch pollen allergens, and, more specifically, their major allergens Que a 1 and Bet v 1. The cross-reactivity between oak and birch has implications for allergy immunotherapy (AIT) because guidelines suggest selecting one representative allergen within a homologous group for AIT, a principle that would apply to oak. Conclusion: Allergy to oak pollen is common in North America and has a substantial clinical impact. Oak pollen allergens are cross-reactive with birch pollen allergens, which may have implications for AIT.

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.

Initiating pollen sensitization - complex source, complex mechanisms

The mechanisms involved in the induction of allergic sensitization by pollen are not fully understood. Within the last few decades, findings from epidemiological and experimental studies support the notion that allergic sensitization is not only dependent on the genetics of the host and environmental factors, but also on intrinsic features of the allergenic source itself. In this review, we summarize the current concepts and newest advances in research focusing on the initial mechanisms inducing pollen sensitization. Pollen allergens are embedded in a complex and heterogeneous matrix composed of a myriad of bioactive molecules that are co-delivered during the allergic sensitization. Surprisingly, several purified allergens were shown to lack inherent sensitizing potential. Thus, growing evidence supports an essential role of pollen-derived components co-delivered with the allergens in the initiation of allergic sensitization. The pollen matrix, which is composed by intrinsic molecules (e.g. proteins, metabolites, lipids, carbohydrates) and extrinsic compounds (e.g. viruses, particles from air pollutants, pollen-linked microbiome), provide a specific context for the allergen and has been proposed as a determinant of Th2 polarization. In addition, the involvement of various pattern recognition receptors (PRRs), secreted alarmins, innate immune cells, and the dependency of DCs in driving pollen-induced Th2 inflammatory processes suggest that allergic sensitization to pollen most likely results from particular combinations of pollen-specific signals rather than from a common determinant of allergenicity. The exact identification and characterization of such pollen-derived Th2-polarizing molecules should provide mechanistic insights into Th2 polarization and pave the way for novel preventive and therapeutic strategies against pollen allergies.

Cross-reactivity between the Betulaceae family and fallout in the real atmospheric aeroallergen load

Betulaceae family is a dominant tree pollen type in the atmosphere at Northwest Spain, being a major cause of allergenic rhinitis or asthma symptoms. Alnus pollen cause symptoms in the 9-20% of the total hay fever sufferers mean while the 41.89% of patients present a positive skin-prick-test for Betula allergens. Aln g1 and Bet v1 aeroallergens belong to PR-10 protein family and are associated to cross-reactivity processes. Airborne pollen and aeroallergens from Alnus and Betula were sampled during their Main Pollen Season from 2016 to 2019. Pollen sampling was conducted by means of a Hirst volumetric trap and aeroallergens were sampled using a Multi Vial Cyclone Sampler. Alnus flowering took place from January to February, with an average duration of 44 days. Betula bloom occurred from April to May with an average pollen season of 33 days. The major innovation of our study was the first detection of Aln g1 allergens in the atmosphere by using Bet v1 antibodies. This fact verified the cross-reactivity between the main allergens of Betula and Alnus pollen. Along the study period, an average of 18 days/year and 14 days/year with high potential risk of allergy due to Alnus pollen and allergen respectively, was registered. For Betula an average of 16 days/year with high potential risk of allergy due to pollen and 22 days for allergen was registered. The main consequence of the successive bloom of both trees would be the so-called "priming effect". Urban population sensitized to Betula pollen could suffer allergic symptoms during winter (as a consequence of Alnus), and in spring with the manifestation of higher symptoms under low birch pollen grain levels in the atmosphere. The traditional information to prevent allergies, such as the airborne pollen concentrations, should be combined with the data of aeroallergen to identify the real allergenic load in the atmosphere.

Flowering Phenology and Characteristics of Pollen Aeroparticles of Quercus Species in Korea

In recent decades, airborne allergens for allergic respiratory diseases have been found to increase significantly by a process of converting coniferous forests into broad-leaved forests in Korea. This study was conducted to evaluate factors, including airborne pollen counts, micromorphology, and flowering phenology, that can affect oak pollen-related allergic symptoms. The catkin of Mongolian oak (Quercus mongolica Fisch. ex Ledeb.) showed the most rapidly blooming catkin on Julian day 104 in flower development. Among six species, the last flowering was observed on Julian day 119 in Korean oak (Quercus dentata Thunb.). The pollen dispersal was persisted for about 32 days from Julian day 104 to Julian day 136. Airborne pollen was observed about 2 weeks after flowering phase H, the senescence phase. Pollen size varied by species, with the largest from Q. mongolica (polar axis length, PL = 31.72 µm, equatorial axis length, EL = 39.05 µm) and the smallest from Jolcham oak (Quercus serrata Murray) (PL = 26.47 µm, EL = 32.32 µm). Regarding pollen wall structure, endexine of Q. dentata was coarsely laminated or fragmented. The endexine thicknesses of Sawtooth oak (Quercus acutissima Carruth.) and Q. serrata were thick and stable, whereas Galcham oak (Quercus aliena Blume), Q. mongolica, and Oriental cork oak (Quercus variabilis Blume) had thinner endexines. The area occupied by pollenkitt of Q. variabilis was significantly larger than that of Q. acutissima. Importantly, Q. variabilis had a distinctly thick 17 kDa protein band, a presumed major allergen. Oak species differ in pollen protein composition, and thus there is a possibility that the allergenic activity of pollen proteins vary depending on oak species. This study highlights the fact that native oak species in Korea differ in flowering pattern of male flowers, pollen morphology, and pollen chemical constituents. These discrepancies in flowering and pollen properties imply variable allergic responses to oak pollen from different species.

A quality-of-life mapping function developed from a grass pollen sublingual immunotherapy trial to a tree pollen sublingual immunotherapy trial

Aims: Allergic rhinitis is caused by sensitivity to environmental allergens that can significantly impact quality-of-life. The objective of this analysis was to estimate health state utilities and quality-adjusted life days (QALDs) for a tree allergy immunotherapy trial, TT-04 (EudraCT No.2015-004821-15). Health-state utilities are a measure of patient preference for health states and are necessary to derive QALDs for cost-utility analysis. Preference-based utilities were not collected in the TT-04 trial, so a mapping algorithm was developed based on a similar grass allergy immunotherapy trial, GT-08 (EudraCT No. 2004-000083-27), to estimate utilities.Methods: A two-part model was developed to predict utilities for the GT-08 trial and applied to the TT-04 trial to estimate the difference in mean utility and QALDs between SQ tree sublingual immunotherapy (SLIT)-tablet and placebo.Results: Mean utility difference between SQ tree SLIT-tablet and placebo was 0.030 [95% CI = 0.015-0.046] during the birch pollen season (BPS), 0.019 [95% CI = 0.007-0.030] during the tree pollen season (TPS) and 0.018 [95% CI = 0.007-0.030] during the full trial. The treatment showed a QALD benefit of 1.26 [95% CI = 0.619-1.917] during the BPS, 1.90 [95% CI = 0.692-3.047] during the TPS, and 2.47 [95% CI = 0.930-4.101] during the full trial.Limitations: The generalizability of this algorithm is limited to allergy trials containing the same covariates as those present in the model. The analysis also assumes that grass and tree pollen allergy have the same relationship with EQ5D utilities, which is supported by the fact that both grass and tree pollen induce similar symptoms.Conclusions: Application of the mapping function enabled the calculation of QALDs associated with the treatment, with the caveat that data were extrapolated from grass seasonal allergy to tree seasonal allergy. The results showed a significant QALD benefit of the treatment over placebo in treatment of tree pollen-induced rhinoconjunctivitis.

High-Yield Production of the Major Birch Pollen Allergen Bet v 1 With Allergen Immunogenicity in Nicotiana benthamiana

Type I allergy is an immunological disorder triggered by allergens and causes significant health problems. The major allergen of birch pollen is Bet v 1, which belongs to the pathogen-related protein 10 (PR-10) family. Here, we established a rapid and robust method for the production of Bet v 1 in Nicotiana benthamiana leaves, with binding activity to allergic patients' IgE. The Bet v 1 allergen was expressed in N. benthamiana using a strong agroinfiltration-based transient protein expression system, which consists of a deconstructed geminiviral vector system with a double terminator. Five days post-infiltration, the allergen concentration in N. benthamiana leaves was 1.2 mg/g of fresh mass, being this the maximum yield of Bet v 1 in plants reported up to now. A part of plant-derived Bet v 1 was glycosylated. Bet v 1 purified from N. benthamiana or Brevibacillus brevis was used to carry out enzyme-linked immunoassays; both recombinant allergens were found to have comparable binding properties to the IgE of allergic patients. These results suggest that our plant expression system allows rapid and robust production of the allergen, which keeps the immunogenicity.

Birch pollen allergy in Europe

Birch and other related trees of the families Betulaceae and Fagaceae (alder, hazel, oak, hornbeam, chestnut, and beech) constitute the birch homologous group. This grouping is primarily based on the extensive IgE cross-reactivity of allergen homologs to the major birch allergen Bet v 1. Birch pollen is the most dominant tree pollen in Northern and Central Europe and is a major cause of allergic rhinitis and, possibly, asthma symptoms. Over the last few decades, levels of birch pollen have risen and the period of exposure has increased due to climate changes. Subsequently, the prevalence of birch pollen sensitization has also increased. The cross-reactivity and sequential pollen seasons within the birch homologous group create a prolonged symptomatic allergy period beyond birch pollen alone. Furthermore, many plant food allergens contain homologs to Bet v 1, meaning that the majority of patients with birch pollen allergy suffer from secondary pollen food syndrome (PFS). As a result, the negative impact on health-related quality of life (HRQoL) in patients allergic to birch pollen is significant. The purpose of this manuscript was to narratively review topics of interest such as taxonomy, cross-reactivity, prevalence, clinical relevance, PFS, and HRQoL with regard to birch pollen allergy from a European perspective.

The SQ tree SLIT-tablet is highly effective and well tolerated: Results from a randomized, double-blind, placebo-controlled phase III trial

BACKGROUND

The SQ tree sublingual immunotherapy (SLIT)-tablet (ALK-Abelló, Hørsholm, Denmark) is developed for treatment of tree pollen-induced allergic rhinoconjunctivitis (ARC).

OBJECTIVE

The aim of this pivotal phase III trial was to demonstrate the efficacy and safety of the SQ tree SLIT-tablet.

METHODS

This was a randomized, double-blind, placebo-controlled trial with 634 subjects (12-65 years) with moderate-to-severe ARC despite use of symptom-relieving medication. Eligible subjects were randomized 1:1 to active or placebo treatment. The primary end point was the average daily ARC total combined score (TCS) during the birch pollen season (BPS) analyzed for subjects with diary data during the BPS. Secondary end points included average daily symptom scores (DSS) during the BPS, average TCS and DSS during the tree pollen season (TPS), and average daily medication scores (DMS) in the BPS and TPS.

RESULTS

The primary and key secondary end points demonstrated statistically significant and clinically relevant effects of the SQ tree SLIT-tablet compared with placebo. For the BPS, absolute (relative) differences from placebo were 3.02 (40%) for TCS, 1.32 (37%) for DSS, and 1.58 (49%) for DMS (all P < .0001). For the TPS, absolute (relative) differences from placebo were 2.27 (37%) for TCS, 0.99 (33%) for DSS, and 1.20 (47%) for DMS (all P < .0001). Treatment was well tolerated. The most frequently reported treatment-related adverse events were mild or moderate local reactions related to sublingual administration.

CONCLUSION

The trial demonstrated the efficacy and safety of the SQ tree SLIT-tablet compared with placebo during the BPS and TPS in adolescents and adults with birch pollen-induced ARC (EudraCT 2015-004821-15).

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.