Chronic cat allergen exposure induces a TH2 cell-dependent IgG4 response related to low sensitization

Allergic Rhinitis and Cancer Risk: A Two-Sample Mendelian Randomization Study

Background: There is increasing evidence that allergic rhinitis (AR) is associated with cancer. However, these results are inconsistent. Because of common risk factors, there may be reverse causality and confounding factors that affect our understanding of the relationship between AR and cancer. We aimed to explore the role of AR in cancer development using Mendelian randomization (MR) analysis. Materials and Methods: We performed a two-sample MR analysis using summary data from genome-wide association studies (GWAS). Single nucleotide polymorphisms (SNPs) strongly associated with AR (or hay fever) were used as instrumental variables, mainly using the inverse variance weighted analysis method, supplemented by MR Egger, maximum likelihood, weighted media, and penalized weighted media for MR analysis. Sensitivity analyses included heterogeneity and horizontal pleiotropy; and leave-one-out analyses were performed to test the robustness of our results. Results: MR analysis revealed no evidence of a causal relationship between AR and any of the examined cancers (all p > 0.05). The results using five different analytical approaches were similar. Sensitivity analyses showed no evidence of heterogeneity nor horizontal pleiotropy. According to the leave-one-out sensitivity analyses, no individual SNP was significantly influencing the causal effect of AR on cancers. Conclusions: These findings do not provide evidence to support that AR has a large impact on the risk of eight common cancers in the European population. However, we cannot rule out a very minor effect of AR on cancer. Further large-scale studies are necessary to validate our findings.

Divergent Trends in the Prevalence of Children's Asthma, Rhinitis and Atopic Dermatitis and Environmental Influences in the Urban Setting of Zagreb, Croatia

BACKGROUND

Previous studies have reported that the allergy epidemic in developed countries has reached its plateau, while a rise is expected in developing ones. Our aim was to compare the prevalence of allergic diseases among schoolchildren from the city of Zagreb, Croatia after sixteen years.

METHODS

Symptoms of asthma, allergic rhinitis (AR) and atopic dermatitis (AD) and risk factors were assessed using the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. An allergic profile was determined by a skin prick test.

RESULTS

The prevalence of current, ever-in-a-lifetime and diagnosed AR of 35.7%, 42.5% and 14.9% and AD of 18.1%, 37.1% and 31.1% demonstrated a significant increase. The asthma prevalence has remained unchanged. The allergen sensitivity rate has remained similar, but pollens have become dominant. Mould and dog exposure are risks for asthma (OR 14.505, OR 2.033). Exposure to cat allergens is protective in AR (OR 0.277). Parental history of allergies is a risk factor in all conditions.

CONCLUSION

Over sixteen years, the prevalence of AR and AD, but not of asthma, have increased. The proportion of atopy has remained high. The AR/AD symptom rise is probably a consequence of increased pollen sensitisation united with high particulate matter concentrations. The stable asthma trend could be a result of decreasing exposures to indoor allergens.

The clinical significance of allergen-specific IgG4 in allergic diseases

IgG4 is a subclass of IgG antibody with a unique molecular feature of (Fragment antigen- binding) Fab-arm exchange, allowing bispecific antigen binding in a mono-valent manner. With low binding affinity to C1q and Fcγreceptors, IgG4 is incapable of forming immune complexes and activating the complement pathway, exhibiting a non-inflammatory feature. IgG4 is produced similarly to IgE and is considered a modified reaction to IgE class-switching response under certain conditions. It could also counteract IgE-activated inflammation. However, the clinical significance of IgG4 in allergic diseases is complex and controversial. Three viewpoints have been suggested to describe the role of IgG4. IgG4 can act as a tolerance-inducer to play a protective role under repeated and rapid incremental dosing of allergen exposure in allergen immunotherapy (AIT), supported by allergies in cat raisers and venom desensitization in beekeepers. Another viewpoint accepted by mainstream specialists and guidelines of Food Allergy and Management in different countries points out that food-specific IgG4 is a bystander in food allergy and should not be used as a diagnostic tool in clinical work. However, eosinophilic esophagitis (EoE) investigation revealed a direct clinical relevance between physiopathology and serum IgG4 in cow milk and wheat. These factors indicate that allergen-specific IgG4 plays a multifaceted role in allergic diseases that is protective or pathogenic depending on different allergens or exposure conditions.

Clinical and immunological evaluation of cat-allergic asthmatics living with or without a cat

BACKGROUND

Characterising the clinical and immunological impact of daily cat exposure in cat-allergic subjects with asthma who live with cats (WC) and those who do not (WoC) may provide understanding of the drivers of the allergic response.

METHODS

Clinical and immunological characteristics (skin prick test, spirometry, symptom assessments, immunological markers) were compared between asthmatic subjects WC (n = 10) and WoC (n = 9).

RESULTS

WC subjects had greater use of long-acting beta agonists (p < .05) and high-potency corticosteroids. No differences were observed in lung function, nasal and ocular symptoms, or asthma control between the groups. Cat dander- and Fel d 1-specific IgG₄ concentrations were higher in WC than WoC subjects (both p < .05). Total IgE and cat dander-, Fel d 1- and Fel d 7-specific IgE concentrations were similar, but Fel d 4-sIgE was higher in WC subjects (p < .05) versus WoC. Basophil sensitivity to cat dander extract and Fel d 1 was lower in WC versus WoC subjects (p < .05) and correlated with higher IgG₄ concentrations (r = 0.63; p = .009). Fel d 1-specific CD4+ T-cell responses polarised toward Th2A responses in WC versus WoC subjects; Fel d 1-specific IgE correlated with surface expression of CRTH2 and CD200R (both p ≤ .05).

CONCLUSION

Immunological differences observed in WC versus WoC did not reflect clinical tolerance with natural cat exposure. The ability to live with a cat despite allergy could be driven by higher preventative medication use. This study may support design of novel therapeutics for allergy management.

An Overview of the Relevance of IgG4 Antibodies in Allergic Disease with a Focus on Food Allergens

Antibodies of the IgG4 isotype are strongly associated with allergic disease but have several properties such as not precipitating with allergens, not activating complement and poor binding to Fcγ receptors that argue against a pro-inflammatory role. In keeping with that, IgG4 antibodies are a striking feature of the response to immunotherapy. In two naturally occurring situations IgG4 antibodies are common with low or absent IgE antibodies. The first example is children raised in a house with a cat and the second is eosinophilic esophagitis (EoE). In many population-based cohorts, the ownership of a cat in early childhood is associated with a decreased prevalence of a cat allergy at age 10. The second example (i.e., EoE) is a novel form of food allergy that is not mediated by IgE and is related to consuming cow’s milk or wheat. In EoE, patients have IgG4 to milk proteins in high > 10 µg/mL or very high > 100 µg/mL titers. Enigmatically these patients are found to have deposits of IgG4 in the wall of their inflamed esophagus. The factors that have given rise to EoE remain unclear; however, changes in food processing over the past 50 years, particularly ultra-heat treatment and the high pressure homogenization of milk, represent a logical hypothesis.

Integrative molecular profiling of autoreactive CD4 T cells in autoimmune hepatitis

BACKGROUND & AIMS

In most autoimmune disorders, crosstalk of B cells and CD4 T cells results in the accumulation of autoantibodies. In autoimmune hepatitis (AIH), the presence of anti-soluble liver antigen (SLA) autoantibodies is associated with reduced overall survival, but the associated autoreactive CD4 T cells have not yet been characterised. Herein, we isolated and deeply characterised SLA-specific CD4 T cells in patients with AIH.

METHODS

We used brief ex vivo restimulation with overlapping SLA peptides to isolate and phenotype circulating SLA-specific CD4 T cells, and integrative single-cell RNA-seq (scRNA-seq) to characterise their transcriptome and T-cell receptor (TCR) repertoire. Autoreactive TCRs were cloned and used to identify dominant SLA-derived epitopes. SLA-specific CD4 T cells were tracked in peripheral blood through TCR sequencing to identify their phenotypic niche. We further characterised disease-associated peripheral blood T cells by high-content flow cytometry in 42 patients with AIH and 17 controls with non-alcoholic steatohepatitis.

RESULTS

Autoreactive SLA-specific CD4 T cells were only detected in patients with anti-SLA autoantibodies and had a memory PD-1⁺CXCR5^-CCR6^-CD27⁺ phenotype. ScRNA-seq revealed their pro-inflammatory/B-helper profile. SLA_81-100 and SLA_177-204 contain dominant T-cell epitopes. Autoreactive TCR clonotypes were predominantly found in the memory PD-1⁺CXCR5^-CD4 T cells, which were significantly increased in the blood of patients with AIH and supported B-cell differentiation through IL-21. Finally, we identified specific T-cell phenotypes linked to disease activity and IgG level during AIH.

CONCLUSIONS

We provide a deep characterisation of rare circulating autoreactive CD4 T cells and identify their peripheral reservoir in AIH. We also propose a specific phenotype of autoreactive T cells related to AIH disease activity, which will be essential to track, delineate, and potentially target these pathogenic cells.

LAY SUMMARY

One principal characteristic of autoimmune hepatitis (AIH), like for many other autoimmune diseases, is the accumulation of autoantibodies produced by B lymphocytes following their interaction with autoreactive CD4 T lymphocytes. In this study, we identified and characterised with high resolution these CD4 T cells. This will be essential to track, delineate, and potentially target them during AIH.

Allergen Immunotherapy in children with respiratory allergic diseases

Allergen immunotherapy (AIT) is a well-established treatment for allergic respiratory diseases. It represents a cornerstone in the clinical management of allergic children since it is the only curative option to date able to modify the natural history of Ig-E mediated allergic diseases. Through a well-defined immunologic mechanism, AIT promotes regulatory T cells and cuts down the immune response induced by allergens. According to current guidelines based on up-to-date evidence, AIT should be offered to children with moderate-severe allergic rhinitis and/or controlled asthma starting from 5 years of age, further to an adequate risk-benefit assessment which includes patient's adherence to the treatment and a proper selection of the right product. Younger age and mild disease could be considered based on an individual evaluation. Both subcutaneous (SCIT) and sublingual (SLIT) routes of administration have a good efficacy and safety profile with safer outcomes for SLIT compared to SCIT. Only standardized products with documented evidence of clinical efficacy should be used. Although AIT is used worldwide, there are still gaps and limitations, including the lack of reliable biomarkers predictive of the clinical outcome. Novel adjuvants are currently under investigations to boost the strength and efficiency of the immune response, as well as new formulations with better efficacy and better patient's adherence to the treatment. Herein, we aim to provide an overview of current key evidence with major regard to clinical practice as well as knowledge gaps and future research needs in the context of AIT in children with respiratory allergic diseases.

FB5P-seq: FACS-Based 5-Prime End Single-Cell RNA-seq for Integrative Analysis of Transcriptome and Antigen Receptor Repertoire in B and T Cells

Single-cell RNA sequencing (scRNA-seq) allows the identification, characterization, and quantification of cell types in a tissue. When focused on B and T cells of the adaptive immune system, scRNA-seq carries the potential to track the clonal lineage of each analyzed cell through the unique rearranged sequence of its antigen receptor (BCR or TCR, respectively) and link it to the functional state inferred from transcriptome analysis. Here we introduce FB5P-seq, a FACS-based 5'-end scRNA-seq method for cost-effective, integrative analysis of transcriptome and paired BCR or TCR repertoire in phenotypically defined B and T cell subsets. We describe in detail the experimental workflow and provide a robust bioinformatics pipeline for computing gene count matrices and reconstructing repertoire sequences from FB5P-seq data. We further present two applications of FB5P-seq for the analysis of human tonsil B cell subsets and peripheral blood antigen-specific CD4 T cells. We believe that our novel integrative scRNA-seq method will be a valuable option to study rare adaptive immune cell subsets in immunology research.

The effect of regulatory T cells on tolerance to airborne allergens and allergen immunotherapy

Forkhead box P3-positive regulatory T (Treg) cells are essential mediators of tolerance against self-antigens and harmless exogenous antigens. Treg cell deficiencies result in multiple autoimmune and allergic syndromes in neonates. How Treg cells affect conventional allergies against aeroantigens, which are restricted to a few specific proteins released from inhaled particles, remains controversial. The hallmarks of antigen-specific loss of tolerance are allergen-specific T_H2 cells and IgE. However, difficulties in identifying the rare allergen-specific Treg cells have obscured the cellular basis of tolerance to aeroallergens, which is also a major obstacle for the rational design of novel and more efficient allergen-specific immunotherapies. Recent technological progress allowing characterization of allergen-specific effectors and Treg cells with minimal in vitro manipulation revealed their detailed contribution to tolerance. The data identified inhaled particles as immunodominant Treg cell targets in healthy and allergic subjects. Conversely, the supposed immunodominant major allergens being rapidly released from inhaled particles apparently do not actively induce tolerance but are ignored by the immune system. Here, the partially contradictory data on various allergen-specific T-cell types in healthy subjects, allergic patients, and patients undergoing allergen-specific immunotherapy are discussed and integrated into one model, postulating Treg cell-dependent and Treg cell-independent checkpoints of tolerance and allergy development.

Measurement of Specific IgG4 Anti-mouse Urine Antibodies

IgG₄ and its role in immune tolerance has been investigated widely. Symptom reduction and improved clinical outcomes in immunotherapy trials are associated with significant increases in allergen-specific IgG₄ antibodies. Natural immune tolerance observed in beekeepers and cat owners has also been associated with elevated levels of bee venom and cat allergen-specific IgG₄, respectively. Functionally, allergen-specific IgG₄ has been shown to reduce the binding of IgE-allergen complexes to B cells, a key step in the initiation of the type 1 hypersensitivity allergic response. In laboratory animal allergy, IgG₄ has been described as a "protective/blocking" antibody. However, a consensus on the exact relationship between exposure, IgG₄, and tolerance has yet to be reached. In this chapter, we review the factors that require consideration when developing an ELISA for the quantification of allergen-specific IgG₄.

Der p 1-specific regulatory T-cell response during house dust mite allergen immunotherapy

BACKGROUND

Allergen-specific immunotherapy (AIT) is the only available treatment for allergic diseases that can induce specific immune tolerance to allergens. The key mechanisms involved in this process include changes in allergen-specific regulatory T (Treg) cells.

METHODS

We studied 25 allergic rhinitis patients undergoing subcutaneous house dust mite-specific immunotherapy. Peripheral blood mononuclear cells were studied before and after 10, 30 weeks, and 3 years of AIT. Der p 1-specific T regulatory cell responses were investigated by characterization of Der p 1-MHC class II tetramer-positive cells and correlated with nasal symptom score.

RESULTS

Twelve of 25 AIT patients matched with their MHC class II expression to the Der p 1 peptide-MHC class II tetramers. A significant increase in the numbers of Der p 1-specific FOXP3⁺ Helios⁺ CD25⁺ CD127^- Treg cells after 30 weeks was observed, which slightly decreased after 3 years of AIT. In contrast, Der p 1-specific immunoglobulin-like transcript 3 (ILT3)⁺ CD25⁺ Treg cells decreased substantially from baseline after 3 years of AIT. ILT3⁺ Treg cells displayed compromised suppressive function and low FOXP3 expression. In addition, Der p 1-specific IL-10 and IL-22 responses have increased after 30 weeks, but only IL-10⁺ Der p 1-specific Treg cells remained present at high frequency after 3 years of AIT. Increased number of FOXP3⁺ Helios⁺ and IL-10⁺ and decreased ILT3⁺ Treg cell responses correlated with improved allergic symptoms.

CONCLUSION

The results indicate that AIT involves upregulation of the activated allergen-specific Treg cells and downregulation of dysfunctional allergen-specific Treg cell subset. Correction of dysregulated Treg cells responses during AIT is associated with improved clinical response.

Significance of IgG4-positive cells in severe eosinophilic chronic rhinosinusitis

BACKGROUND

IgG4 production is regulated by type 2 (IL-4 and IL-13) and regulatory (IL-10) cytokines involved in the pathophysiology of chronic rhinosinusitis (CRS). We sought to determine the pathophysiological characteristics of IgG4-positive cells in sinonasal tissues in CRS, especially eosinophilic CRS (ECRS).

METHODS

IgG4-positive cells in uncinate tissues (UT) and nasal polyps (NP) were examined by immunohistochemistry. Associations between the number of IgG4-positive cells and clinicopathological factors were analyzed. Receiver operating characteristics (ROC) analysis was performed to determine the cut-off value of IgG4-positive cells in tissue that can predict the post-operative course.

RESULTS

IgG4 was mainly expressed in infiltrating plasma and plasmacytoid cells, and the number of IgG4-positive cells was significantly higher in NP, especially those from severe ECRS patients, than in UT. In CRS patients, the number of IgG4-positive cells significantly and positively correlated with blood and tissue eosinophilia, radiological severity, and serum level of total IgE. The number of infiltrating IgG4-positive cells was significantly higher in patients with a poor post-operative course (sustained sinus shadow 6 months after surgery) than in those with a good one. The number of IgG4-positive cells in NP could discriminate patients with a good or a poor post-operative course (area under the curve: 0.769). Also, 73.3% sensitivity and 82.5% specificity were achieved when the cut-off value was set at 17 cells/high-power field.

CONCLUSIONS

Our results suggest that the local expression of IgG4 on cells may be used as a biomarker that reflects the pathophysiology of CRS, including the post-operative course.

Antigen-specific regulatory T-cell responses against aeroantigens and their role in allergy

The mucosal immune system of the respiratory tract is specialized to continuously monitor the external environment and to protect against invading pathogens, while maintaining tolerance to innocuous inhaled particles. Allergies result from a loss of tolerance against harmless antigens characterized by formation of allergen-specific Th2 cells and IgE. Tolerance is often described as a balance between harmful Th2 cells and various types of protective "regulatory" T cells. However, the identity of the protective T cells in healthy vs. allergic individuals or following successful allergen-specific therapy is controversially discussed. Recent technological progress enabling the identification of antigen-specific effector and regulatory T cells has significantly contributed to our understanding of tolerance. Here we discuss the experimental evidence for the various tolerance mechanisms described. We try to integrate the partially contradictory data into a new model proposing different mechanism of tolerance depending on the quality and quantity of the antigens as well as the way of antigen exposure. Understanding the basis of tolerance is essential for the rational design of novel and more efficient immunotherapies.

The future outlook on allergen immunotherapy in children: 2018 and beyond

Allergen immunotherapy (AIT) is the only currently available immune-modifying and aetiological treatment for patients suffering from IgE-mediated diseases. In childhood, it represents a suitable therapeutic option to intervene during the early phases of respiratory allergic diseases such as rhino-conjunctivitis and asthma, which is when their progression may be more easily influenced. A growing body of evidence shows that oral immunotherapy represents a promising treatment option in children with persistent IgE- mediated food allergy. The efficacy of AIT is under investigation also in patients with extrinsic atopic dermatitis, currently with controversial results. Furthermore, AIT might be a strategy to prevent the development of a new sensitization or of a (new) allergic disease. However, there are still some methodological criticisms, such as: a) the regimen of administration and the amount of the maintenance dose are both largely variable; b) the protocols of administration are not standardized; c) the description and classification of side effects is variable among studies and needs to be standardized; d) quality of life and evaluation of health economics are overall missing. All these aspects make difficult to compare each study with another. In addition, the content of major allergen(s) remains largely variable among manufacturers and the availability of AIT products differences among countries. The interest and the attention to AIT treatment are currently fervent and increasing. Well-designed studies are awaited in the near future in order to overcome the current gaps in the evidence and furtherly promote implementation strategies.

Heterogeneity of Ara h Component-Specific CD4 T Cell Responses in Peanut-Allergic Subjects

Understanding the peanut-specific CD4 T cell responses in peanut-allergic (PA) subjects should provide new insights into the development of innovative immunotherapies for the treatment of peanut allergy. Although peanut-specific CD4 T cells have a TH2 profile in PA subjects, the immunogenicity of different Ara h components in eliciting specific CD4 T cell responses and the heterogeneity of these Ara h-reactive TH2 cells remains unclear. In this study, we investigated Ara h 1, 2, 3, 6, and 8-specific T cell responses in PA and sensitized non-peanut-allergic (sNPA) subjects, using the CD154 upregulation assay and the class II tetramer technology. In the PA group, T cells directed against Ara h 1, 2, 3, and 6 have a heterogeneous TH2 phenotype characterized by differential expression of CRTH2, CD27, and CCR6. Reactivity toward these different components was also distinct for each PA subject. Two dominant Ara h 2 epitopes associated with DR1501 and DR0901 were also identified. Frequencies of Ara h-specific T cell responses were also linked to the peanut specific-IgE level. Conversely, low peanut-IgE level in sNPA subjects was associated with a weak or an absence of the allergen-specific T cell reactivity. Ara h 8-specific T cell reactivity was weak in both PA and sNPA subjects. Thus, peanut-IgE level was associated with a heterogeneous Ara h (but not Ara h 8)-specific T cell reactivity only in PA patients. This suggests an important immunogenicity of each Ara h 1, 2, 3, and 6 in inducing peanut allergy. Targeting Ara h 1-, 2-, 3-, and 6-specific effector-TH2 cells can be the future way to treat peanut allergy.

Cross-sectional study on sensitization to mite and cockroach allergen components in allergy patients in the Central European region

Background

The major sources of allergens in the indoor air include house dust mites, dander derived from domestic animals and rodents, cockroach, and several fungi. Mites are the main cause of allergies in some countries with a warmer climate, but the epidemiological significance of mite and cockroach allergens in Central Europe has not been established yet.

Methods

We assessed sensitization profiles of allergy patients in a Central European region in regard to sensitization to mites and cockroach. We used molecular diagnosis by means of the microarray ISAC, and we investigated 1766 patients with clinical suspicion to an allergic disorder. 1255 of them were positive to at least one allergen component, and this group was subjected to statistical analysis.

Results

The sensitization to at least one mite-specific molecule (Der p 1, 2, Der f 1, 2) was observed relatively frequently in 32.7% of patients. Specific IgE to mite group 2 molecules is almost fully cross-reactive. Group 1 allergens are also cross-reactive, but in some patients, a species-specific response was observed. Relatively high rate of sensitization both to group 1 and 2 allergens in our patients indicates the greater role of co-sensitizations. Isolated sensitizations to molecules derived from glyciphagid mites Lep d 2 and/or Blo t 5 without sensitization to other mite-derived molecules were observed only exceptionally (in 0.6% of cases). True sensitization to at least one cockroach-specific molecule (Bla g 1, 2, 5) was very rare (in 0.6% of cases), and nearly all of them were co-sensitizations with other noncockroach-derived molecules. Sensitization to an inhaled tropomyosin was observed rarely in 2.2% of patients (Der p 10 in 1.9% and Bla g 7 in 1.5%). Co-sensitization of inhaled tropomyosins with the respective mite- or cockroach-specific molecules was observed only in the minority of patients suggesting the different route of sensitization being more frequent.

Conclusions

The majority of patients are co-sensitized to several molecules of the respective allergen source. The knowledge of this molecular spectrum of sensitization is important for optimal diagnosis and treatment in respect to allergen content in mite extracts used for diagnostic and therapeutic purposes. In regard to the sensitization patterns of Central European patients, it is necessary to point out the importance of quantifying at least three major mite components Der f 1, Der p 1 and Der f 2 (or Der p 2).

Synchronous immune alterations mirror clinical response during allergen immunotherapy

BACKGROUND

Three years of treatment with either sublingual or subcutaneous allergen immunotherapy has been shown to be effective and to induce long-term tolerance. The Gauging Response in Allergic Rhinitis to Sublingual and Subcutaneous Immunotherapy (GRASS) trial demonstrated that 2 years of treatment through either route was effective in suppressing the response to nasal allergen challenge, although it was insufficient for inhibition 1 year after discontinuation.

OBJECTIVE

We sought to examine in the GRASS trial the time course of immunologic changes during 2 years of sublingual and subcutaneous immunotherapy and for 1 year after treatment discontinuation.

METHODS

We performed multimodal immunomonitoring to assess allergen-specific CD4 T-cell properties in parallel with analysis of local mucosal cytokine responses induced by nasal allergen exposure and humoral immune responses that included IgE-dependent basophil activation and measurement of serum inhibitory activity for allergen-IgE binding to B cells (IgE-facilitated allergen binding).

RESULTS

All 3 of these distinct arms of the immune response displayed significant and coordinate alterations during 2 years of allergen desensitization, followed by reversal at 3 years, reflecting a lack of a durable immunologic effect. Although frequencies of antigen-specific T_H2 cells in peripheral blood determined by using HLA class II tetramer analysis most closely paralleled clinical outcomes, IgE antibody-dependent functional assays remained inhibited in part 1 year after discontinuation.

CONCLUSION

Two years of allergen immunotherapy were effective but insufficient for long-term tolerance. Allergen-specific T_H2 cells most closely paralleled the transient clinical outcome, and it is likely that recurrence of the T-cell drivers of allergic immunity abrogated the potential for durable tolerance. On the other hand, the persistence of IgE blocking antibody 1 year after discontinuation might be an early indicator of a protolerogenic mechanism.

Food allergy to previously tolerated foods: Course and patient characteristics

BACKGROUND

The acquisition of food allergy (FA) to previously safely consumed basic food proteins is an unusual presentation of immunoglobulin E (IgE)-mediated allergic disease.

OBJECTIVE

We sought to characterize patients who developed FA to previously tolerated foods (FA-PTF), including underlying reasons for and length of elimination diet of previously tolerated foods.

METHODS

Patients (n = 30) with complaints consistent with FA to foods previously consumed safely were evaluated. Clinical history was obtained, and skin prick testing and graded oral food challenges (OFC) were performed. One fatal case of FA-PTF was reported by a physician.

RESULTS

Twenty-two of 30 patients (ages 1.2-50 years) were diagnosed with FA-PTF by OFC to milk (n = 17), egg (n = 2), and peanuts (n = 3). One additional patient with FA-PTF had a fatal reaction to milk. Anaphylactic reactions were reported in 12 of these 23 FA-PT patients (52%); 8 experienced multiple episodes. Atopic dermatitis was diagnosed in 52% (12/23) of patients, 8 of 12 as severe; overall, 18 of 23 (78%) of patients had marked personal atopic background. Sixteen patients (70%) initiated an elimination diet, 12 of whom did so on advice from a health care provider, before the appearance of allergic symptoms. However, in 4 patients with FA-PTF, reactivity to the food protein emerged during uninterrupted consumption.

CONCLUSION

Food allergy to previously tolerated foods primarily appears after an elimination diet in atopic patients. Anaphylactic reactions are common. Health care providers should consider these risks before recommending elimination diet of tolerated foods.

Immunotherapy for pet allergies

Allergic diseases compose a serious challenge for modern societies. Their individual, medical and economical burden is large. As humans spend most of their time indoors, exposure to indoor allergens is a significant contributor to the development of allergic sensitization and respiratory allergies, such as allergic rhinoconjunctivitis and asthma. One important source of indoor allergens are pets, in particular cats and dogs. Allergens from these and other mammals spread effectively and they are encountered widely in public places. If patient education, allergen avoidance and pharmacotherapy do not suffice for controlling the symptoms of pet allergy, allergen immunotherapy can be a treatment option. Current information on allergen immunotherapy in pet allergy suggests that it can be effective in reducing allergic symptoms. However, the low number of high-quality randomized controlled trials of allergen immunotherapy in pet allergy warrants for further investigations.

Mechanisms of allergen immunotherapy for inhaled allergens and predictive biomarkers

Allergen immunotherapy is effective in patients with IgE-dependent allergic rhinitis and asthma. When immunotherapy is given continuously for 3 years, there is persistent clinical benefit for several years after its discontinuation. This disease-modifying effect is both antigen-specific and antigen-driven. Clinical improvement is accompanied by decreases in numbers of effector cells in target organs, including mast cells, basophils, eosinophils, and type 2 innate lymphoid cells. Immunotherapy results in the production of blocking IgG/IgG₄ antibodies that can inhibit IgE-dependent activation mediated through both high-affinity IgE receptors (FcεRI) on mast cells and basophils and low-affinity IgE receptors (FcεRII) on B cells. Suppression of T_H2 immunity can occur as a consequence of either deletion or anergy of antigen-specific T cells; induction of antigen-specific regulatory T cells; or immune deviation in favor of T_H1 responses. It is not clear whether the altered long-term memory resides within the T-cell or the B-cell compartment. Recent data highlight the role of IL-10-producing regulatory B cells and "protective" antibodies that likely contribute to long-term tolerance. Understanding mechanisms underlying induction and persistence of tolerance should identify predictive biomarkers of clinical response and discover novel and more effective strategies for immunotherapy.

Pregnancy modulates the allergen-induced cytokine production differently in allergic and non-allergic women

BACKGROUND

The immunological environment during pregnancy may differ between allergic and non-allergic women. This study investigates the effect of maternal allergy on the allergen-induced cytokine and chemokine levels and whether pregnancy modulates these immune responses differently in allergic and non-allergic women.

METHODS

The birch-, cat-, phytohemagglutinin- and tetanus toxoid-induced interferon-γ (IFN-γ), interleukin (IL)-4, IL-5, IL-10, IL-13, the T-helper 1 (Th1)-associated chemokine CXCL10 and the Th2-associated chemokine CCL17 levels were quantified in 20 women with allergic symptoms (sensitized, n = 13) and 36 women without allergic symptoms (non-sensitized, n = 30) at gestational weeks 10-12, 15-16, 25, 35 and 2 and 12 months post-partum.

RESULTS

Birch-, but not cat-induced, IL-5, IL-13 and CCL17 levels were increased during pregnancy as compared to post-partum in the sensitized women with allergic symptoms. In contrast, cat-, but not birch-induced, IL-5 and IL-13 levels were increased during pregnancy as compared to post-partum in the non-sensitized women without allergic symptoms. Furthermore, IFN-γ secretion was increased in the first and decreased in the second and third trimesters in response to birch and decreased in the third trimester in response to cat as compared to post-partum in the non-sensitized women without allergic symptoms. Increased allergen-induced IL-4, IL-5 and IL-13 levels were associated with allergic symptoms and sensitization.

CONCLUSIONS

Pregnancy had a clear effect on the allergen-induced IL-5, IL-13, CCL17, IFN-γ and CXCL10 production, with distinct enhanced Th2-responses to birch in the allergic group and to cat in the non-allergic group.

Pathogenic CD4+ T cells in patients with asthma

Asthma encompasses a variety of clinical phenotypes that involve distinct T cell-driven inflammatory processes. Improved understanding of human T-cell biology and the influence of innate cytokines on T-cell responses at the epithelial barrier has led to new asthma paradigms. This review captures recent knowledge on pathogenic CD4+ T cells in asthmatic patients by drawing on observations in mouse models and human disease. In patients with allergic asthma, TH2 cells promote IgE-mediated sensitization, airway hyperreactivity, and eosinophilia. Here we discuss recent discoveries in the myriad molecular pathways that govern the induction of TH2 differentiation and the critical role of GATA-3 in this process. We elaborate on how cross-talk between epithelial cells, dendritic cells, and innate lymphoid cells translates to T-cell outcomes, with an emphasis on the actions of thymic stromal lymphopoietin, IL-25, and IL-33 at the epithelial barrier. New concepts on how T-cell skewing and epitope specificity are shaped by multiple environmental cues integrated by dendritic cell "hubs" are discussed. We also describe advances in understanding the origins of atypical TH2 cells in asthmatic patients, the role of TH1 cells and other non-TH2 types in asthmatic patients, and the features of T-cell pathogenicity at the single-cell level. Progress in technologies that enable highly multiplexed profiling of markers within a single cell promise to overcome barriers to T-cell discovery in human asthmatic patients that could transform our understanding of disease. These developments, along with novel T cell-based therapies, position us to expand the assortment of molecular targets that could facilitate personalized treatments.

House Dust Mite Allergens: New Discoveries and Relevance to the Allergic Patient

PURPOSE OF REVIEW

Recent findings on house dust allergens and their contribution to knowledge that will significantly impact on current and future allergy treatments are appraised.

RECENT FINDINGS

Quantitation of IgE binding to a spectrum of allergen components in several independent studies in varying locations has largely affirmed the main components as the groups 1 and 2 and possibly 23 allergens with mid-tier contributions from the groups 4, 5, 7, and 21. Prevalent binding to Der p 23 has been recapitulated sometimes with low titers. The IgE of non-asthmatic atopic subjects binds at lower titer and to fewer components than that of asthmatics, and their IgG binding relative to IgE is higher especially for children hospitalized for exacerbation. The higher IgG ratios were associated with increased IL-10 a cytokine more readily induced from T cells of allergic subjects. Peptides representing the groups 1 and 2 allergens can be used to stimulate ex vivo T cells showing responses correlating with IgE binding and providing a valuable tool for ascertaining the contribution of IgE and T cells to disease. Also, the induction of Th2 and follicular helper T cells are shown to make different contributions in mice. Cross-reactivity of IgE binding assays with high-titer cross-reactive antibodies induced by scabies is a problem in the many areas of the world where scabies is highly prevalent and endemic and from recent increases in immigration. In the last few years, allergen research has produced results that warrant rapid translation into diagnostic tools and the formulation of allergen components for immunotherapy.

Long-term exposure to Myozyme results in a decrease of anti-drug antibodies in late-onset Pompe disease patients

Immunogenicity of recombinant human acid-alpha glucosidase (rhGAA) in enzyme replacement therapy (ERT) is a safety and efficacy concern in the management of late-onset Pompe disease (LOPD). However, long-term effects of ERT on humoral and cellular responses to rhGAA are still poorly understood. To better understand the impact of immunogenicity of rhGAA on the efficacy of ERT, clinical data and blood samples from LOPD patients undergoing ERT for >4 years (n = 28) or untreated (n = 10) were collected and analyzed. In treated LOPD patients, anti-rhGAA antibodies peaked within the first 1000 days of ERT, while long-term exposure to rhGAA resulted in clearance of antibodies with residual production of non-neutralizing IgG. Analysis of  T cell responses to rhGAA showed detectable T cell reactivity only after in vitro restimulation. Upregulation of several cytokines and chemokines was detectable in both treated and untreated LOPD subjects, while IL2 secretion was detectable only in subjects who received ERT. These results indicate that long-term ERT in LOPD patients results in a decrease in antibody titers and residual production of non-inhibitory IgGs. Immune responses to GAA following long-term ERT do not seem to affect efficacy of ERT and are consistent with an immunomodulatory effect possibly mediated by regulatory T cells.

Effect of allergen-specific immunotherapy on CD4+ T cells

PURPOSE OF REVIEW

The aims of this review are to discuss the impact of chronic high-dose allergen exposure on allergen-specific CD4(+) T-cell subset during allergen-specific immunotherapy (AIT) and discuss recent advances supporting novel mechanisms for desensitization and tolerance induction during AIT. (Figure is included in full-text article.)

RECENT FINDINGS

New technologies for direct molecular and cellular analysis have now provided an unprecedented opportunity to compare the functions and phenotypes of allergen-specific T cells at a single cell level, both in the context of disease and clinical intervention. Recent studies have demonstrated that AIT may restore tolerance by transiently inducing interleukin (IL)-10 producing T cells followed by selective deletion of allergen-specific TH2 cell subset.

SUMMARY

With antigen-specific TH2 cells at the core of the allergic process in atopic individuals, the duration and dose of antigen exposure can be the driving force behind current AIT protocol. Mechanisms modulating allergen-specific CD4(+) T-cell responses may include autocrine IL-10 production to limit excessive TH2 cell effector responses, T-cell exhaustion, and preferential proallergic TH2 cell deletion allowing concurrent downregulating T-cell responses to emerge. Administration of AIT in the context of immune modulating strategies able to induce counter-regulatory immune response may lead to improved AIT with durable clinical benefit.