Sublingual immunotherapy: from proven prevention to putative rapid relief of allergic symptoms

Digitally-enabled, person-centred care (PCC) in allergen immunotherapy: An ARIA-EAACI Position Paper

In rhinitis and asthma, several mHealth apps have been developed but only a few have been validated. However, these apps have a high potential for improving person-centred care (PCC), especially in allergen immunotherapy (AIT). They can provide support in AIT initiation by selecting the appropriate patient and allergen shared decision-making. They can also help in (i) the evaluation of (early) efficacy, (ii) early and late stopping rules and (iii) the evaluation of (carried-over) efficacy after cessation of the treatment course. Future perspectives have been formulated in the first report of a joint task force (TF)-Allergic Rhinitis and Its Impact on Asthma (ARIA) and the European Academy of Allergy and Clinical Immunology (EAACI)-on digital biomarkers. The TF on AIT now aims to (i) outline the potential of the clinical applications of mHealth solutions, (ii) express their current limitations, (iii) make proposals regarding further developments for both clinical practice and scientific purpose and (iv) suggest which of the tools might best comply with the purpose of digitally-enabled PCC in AIT.

Allergy immunotherapy across the life cycle to promote active and healthy ageing: from research to policies: An AIRWAYS Integrated Care Pathways (ICPs) programme item (Action Plan B3 of the European Innovation Partnership on active and healthy ageing) and the Global Alliance against Chronic Respiratory Diseases (GARD), a World Health Organization GARD research demonstration project

Allergic diseases often occur early in life and persist throughout life. This life-course perspective should be considered in allergen immunotherapy. In particular it is essential to understand whether this al treatment may be used in old age adults. The current paper was developed by a working group of AIRWAYS integrated care pathways for airways diseases, the model of chronic respiratory diseases of the European Innovation Partnership on active and healthy ageing (DG CONNECT and DG Santé). It considered (1) the political background, (2) the rationale for allergen immunotherapy across the life cycle, (3) the unmet needs for the treatment, in particular in preschool children and old age adults, (4) the strategic framework and the practical approach to synergize current initiatives in allergen immunotherapy, its mechanisms and the concept of active and healthy ageing.

Safety profile of sublingual immunotherapy

Sublingual immunotherapy (SLIT) was proposed for clinical practice about 20 years ago with the main aim of improving the safety and avoiding the adverse effects of traditional treatment for allergic airways disease. To date, 32 randomized controlled trials and 6 postmarketing surveys have been published that provide a robust documentation of the safety profile of the treatment.Looking at the randomized trials it emerges that the more frequent adverse event of SLIT is oral itching or swelling, followed by gastrointestinal complaints. These adverse events are invariably described as mild and easily managed by adjusting the dose. Relevant systemic adverse events (asthma, urticaria, angioedema) occur sporadically and, with the exception of oral/gastrointestinal adverse events, the incidence of adverse events seems not to differ between the placebo and active groups. The safety profile of SLIT does not differ between adults and children.The postmarketing surveys consistently show that the incidence of adverse events associated with SLIT is less than 10%, corresponding to less than 1 adverse event per 1000 doses, and is thus quite superior to the safety profile of subcutaneous immunotherapy. Of note, the most recent data show that the rate of adverse events with SLIT is not increased in children below the age of 5 years.

Undertreatment of allergy: exploring the utility of sublingual immunotherapy

Allergic syndromes are highly prevalent and are comprised of a wide variety of clinical problems, including rhinitis, conjunctivitis, atopic dermatitis and urticaria, asthma, and food allergies. Numerous studies have shown that allergic syndromes are both underdiagnosed and undertreated. This is related to many factors, including trivialization of allergic conditions by physicians and patients, failure to adhere to diagnostic and treatment guidelines, and dissatisfaction with conventional pharmacologic treatments. Immunotherapy involves the administration of allergen extracts in an attempt to induce immunologic tolerance and has been used for the treatment of allergic syndromes and the prevention of long-term complications. Conventional subcutaneous immunotherapy is effective but is also associated with a risk of serious adverse events, requires administration by a trained health care professional, and is contraindicated in certain populations. By contrast, sublingual immunotherapy has been used extensively in Europe and possesses most of the benefits of subcutaneous immunotherapy along with increased safety, tolerability, and convenience. This narrative review explores data from selected clinical studies and concludes that sublingual immunotherapy may be well suited to fill the gap posed by the undertreatment of allergic syndromes in the United States.

Safety of sublingual immunotherapy started during the pollen season

BACKGROUND

Sublingual immunotherapy (SLIT) is safer than subcutaneous immunotherapy (SCIT) and this has lead to the reconsideration of the use of ultra-rush schedules for SLIT. The aim of this study was to assess the safety of ultra-rush SLIT in pollen-allergic children according to different timing of administration in relation to the pollen season.

METHODS

In total, 34 children with pollen-induced rhinitis and 36 with pollen-induced asthma and rhinitis, were enrolled and assigned to three study groups: group 1 (n = 17 patients): conventional pre-seasonal-SLIT treatment; group 2 (n = 23 patients), seasonal SLIT ended before the pollen seasonal peak; group 3 (n = 30 patients), SLIT began after the pollen seasonal peak and ended after the pollen season. SLIT was performed using extracts from Stallergenes (Antony, France) and following an ultra-rush schedule, consisting in four doses at a 30-min intervals, and maintenance treatment by administering the top dose three times a week.

RESULTS

In all, 54 adverse events (AEs) were reported: 12 in nine patients in group 1 (9/17, 52.9%), 22 in 14 patients in group 2 (14/23, 60.9%), and 20 in 13 patients in group 3 (13/30, 43.3%). No statistically significant differences were found between the three groups. Local AEs (oral itching and burning) were short lasting and self-resolving. Systemic AEs were also mild, except for a case of asthma, which lasted 5 days, in a patient from group 1. There were no severe reactions, and none of the patients dropped out.

CONCLUSIONS

This study suggests that SLIT with pollen extracts may be safely started at the beginning and also during the pollen season, with a tolerability profile comparable to the conventional pre-seasonal SLIT.

Immunotherapy: clinical trials--optimal trial and clinical outcomes

PURPOSE OF REVIEW

The methodology of randomized clinical trials is essential to assess and register treatment interventions. Although specific immunotherapy was introduced a century ago, very few trials meet the criteria for pivotal studies. The paper reviews the methods which should be used to investigate specific immunotherapy.

RECENT FINDINGS

Large pivotal trials on specific immunotherapy were published within the last year and made sublingual immunotherapy an accepted treatment in Europe. Moreover, a study proposed the guidelines for conducting trials on immunotherapy. Phase I studies were also published on sublingual immunotherapy. A large trial on subcutaneous immunotherapy confirmed its efficacy, but showed that this form of treatment is associated with side effects.

SUMMARY

The clinical efficacy of subcutaneous and sublingual immunotherapy with pollen and mites is well established for both rhinitis and asthma, but the methodology of many specific immunotherapy trials was found to be insufficient until recent large pivotal studies. The present paper reviews the requirements for conducting trials in allergen-specific immunotherapy including allergen standardization, patient inclusion and exclusion criteria, phase I trials to assess safety, dose-ranging studies, and pivotal trials. These need to be randomized, parallel group, placebo-controlled designs. The number of patients should be sufficient. Primary and secondary outcome measures are listed. Trials for asthma need specific requirements. In all trials, safety should be carefully monitored. Studies in children are required.

Sublingual immunotherapy: a novel, albeit not so new, immunotherapy treatment modality

BACKGROUND

Specific allergy immunotherapy traditionally has been thought of as subcutaneous injection immunotherapy (SCIT). There also are noninjection routes for the administration of immunotherapy. The best-known and studied of these noninjection routes is the sublingual route, usually known as sublingual immunotherapy (SLIT). SLIT has been in use for many decades; however, to this date, it is not well known to the majority of allergy practitioners in this country. The purpose of this study is to help change this perception so that SLIT eventually can be considered one more tool in the allergist's armamentarium.

METHODS

A literature review was performed. It included articles from the early American clinicians and present publications that are mostly of European origin.

RESULTS

It will become clear to the reader that the key features of SLIT are its efficacy, great safety, and simplicity of administration.

CONCLUSION

SLIT is a safe treatment modality that should be considered as a useful additional tool in the therapeutic armamentarium.

Sublingual immunotherapy induces IL-10-producing T regulatory cells, allergen-specific T-cell tolerance, and immune deviation

BACKGROUND

The immunologic mechanisms underlying sublingual immunotherapy (SLIT) are still unclear, particularly the role of regulatory T cells.

OBJECTIVE

We sought to characterize allergen-specific T-cell responses during successful birch pollen SLIT.

METHODS

Proliferation of PBMCs and PBMCs depleted of CD25(+) cells obtained from 9 patients before, after 4 weeks, and after 52 weeks of SLIT was assessed in response to the major birch pollen allergen Bet v 1, the homologous apple allergen Mal d 1, or tetanus toxoid. Allergen-induced cytokine responses and FoxP3 expression of T cells were analyzed by using real-time PCR. The role of IL-10 for regulatory activity of T cells was investigated.

RESULTS

After 4 weeks, higher frequencies of circulating CD4(+)CD25(+) T cells were detected together with increased FoxP3 and IL-10 and reduced IL-4 and IFN-gamma mRNA expression levels compared with those before SLIT. Proliferation to all 3 antigens was markedly reduced but increased significantly after depletion of CD25(+) cells or addition of anti-IL-10 antibodies. After 52 weeks, proliferation in response to Mal d 1 or tetanus toxoid returned to pre-SLIT levels, whereas Bet v 1-induced proliferation remained significantly suppressed and was enhanced by neither depletion of CD25(+) cells nor addition of anti-IL-10 antibodies. In parallel, increased IFN-gamma and reduced IL-4, IL-10, and FoxP3 mRNA expression was detected. Neither TGF-beta levels nor cell-cell contact-mediated suppression of CD4(+)CD25(+) cells changed during the course of SLIT.

CONCLUSION

SLIT induces regulatory T-cell suppression through IL-10 during the early phase and specific nonreactivity and immune deviation of allergen-specific T cells during the later phase of therapy.

CLINICAL IMPLICATIONS

SLIT induces immune mechanisms comparable with subcutaneous specific immunotherapy.

Allergic rhinitis and its impact on asthma update: allergen immunotherapy

The Allergic Rhinitis and its Impact on Asthma document was first published in 2001. Since then, new data on specific immunotherapy have appeared. This review is intended as an update to the original document. MedLine (2001 to June 2006) was searched with appropriate key words, and panelists were asked to identify further relevant articles. Randomized controlled trials were considered for the evaluation of efficacy. For the evaluation of safety and additional effects, studies with lower grades of evidence were included. The clinical efficacy of injection immunotherapy in rhinitis and asthma was confirmed, as well as the safety, provided that recommendations are followed. Studies have demonstrated the long-term efficacy and the preventive effect of immunotherapy in reducing the onset of new sensitizations. One randomized open trial demonstrated that in children with allergic rhinitis, injection immunotherapy may reduce the risk of developing asthma. There is strong evidence that sublingual immunotherapy is effective in allergic rhinitis in adults. Recent meta-analyses demonstrated its efficacy in allergic rhinitis in children and in asthma, although more definitive trials are required. Current data indicate that sublingual immunotherapy is safe and the rate of adverse reactions is not greater below 5 years of age. One randomized open trial showed that in children with allergic rhinitis, sublingual immunotherapy reduced the onset of asthma. Further studies are needed to identify the optimal maintenance dose and to elucidate the mechanism of action. Novel approaches for immunotherapy are currently under evaluation, including the use of adjuvants, peptides, and DNA-conjugated and recombinant allergens.

Successful sublingual immunotherapy with birch pollen has limited effects on concomitant food allergy to apple and the immune response to the Bet v 1 homolog Mal d 1

BACKGROUND

Cross-reactivity between the major birch pollen allergen, Bet v 1, and the apple protein, Mal d 1, frequently causes food allergy.

OBJECTIVE

To investigate the effects of successful sublingual immunotherapy (SLIT) with birch pollen extract on apple allergy and the immune response to Bet v 1 and Mal d 1.

METHODS

Before and after 1 year of SLIT, Bet v 1-sensitized patients with oral allergy syndrome to apple underwent nasal challenges with birch pollen and double-blind placebo-controlled food challenges with apple. Bet v 1-specific and Mal d 1-specific serum antibody levels and proliferation in PBMCs and allergen-specific T-cell lines (TCLs) were determined. Bet v 1-specific TCLs were mapped for T-cell epitopes.

RESULTS

In 9 patients with improved nasal provocation scores to birch pollen, apple-induced oral allergy syndrome was not significantly reduced. Bet v 1-specific IgE and IgG(4) levels significantly increased. Bet v 1-specific T-cell responses to all epitopes and those cross-reactive with Mal d 1 significantly decreased. However, neither Mal d 1-specific IgE and IgG(4) levels nor Mal d 1-induced T-cell proliferation changed significantly. In contrast, Mal d 1-specific TCLs showed increased responses to Mal d 1 after 1 year of SLIT.

CONCLUSION

This longitudinal study indicates that pollen SLIT does not efficiently alter the immune response to pollen-related food allergens, which may explain why pollen-associated food allergy is frequently not ameliorated by pollen immunotherapy even if respiratory symptoms significantly improve.

CLINICAL IMPLICATIONS

SLIT with birch pollen may have no clinical effect on associated apple allergy.

The impact of pollen-related food allergens on pollen allergy

Patients with birch pollen allergy frequently develop hypersensitivity reactions to certain foods, e.g. apples, celery, carrots and hazelnuts. These reactions are mainly caused by IgE-antibodies specific for the major birch pollen allergen, Bet v 1, which cross-react with homologous proteins in these foods. Analyzing the T-cell response to Bet v 1-related food allergens revealed that these dietary proteins contain several distinct T-cell epitopes and activate Bet v 1-specific T cells to proliferate and produce cytokines. Several of these cross-reactive T-cell epitopes were not destroyed by simulated gastrointestinal digestion of food allergens and stimulated Bet v 1-specific T cells despite nonreactivity with IgE antibodies. Similarly, cooked food allergens did not elicit IgE-mediated symptoms (oral allergy syndromes) but caused T-cell-mediated late-phase reactions (deterioration of atopic eczema) in birch pollen-allergic patients with atopic dermatitis because thermal processing affected their conformational structure and not the primary amino acid sequence. Thus, T-cell cross-reactivity between Bet v 1 and related food allergens occurs independently of IgE-cross-reactivity in vitro and in vivo. We speculate that symptom-free consumption of pollen-related food allergens may have implications for the pollen-specific immune response of allergic individuals.

Pollen immunotherapy: selection,prevention, and future directions

Pollens are an important cause of allergic rhinitis and asthma. Pollen immunotherapy is effective and potentially curative. It has been shown to prevent new sensitizations, to prevent the development of asthma in children, and to induce long-term benefit. Standardization of allergen extracts is necessary to improve immunotherapy safety and efficacy. Knowledge of the local plant taxonomy and allergen cross-reactivity is important in selecting clinically relevant vaccines. In general, allergenic cross-reactivities correspond to taxonomic relations. Tree and weed species demonstrate variable degrees of cross-reactivity. Most grasses have extensive allergenic cross-reactivity. Mechanism of action continues to be an area of investigation, including the induction of immunoglobulin G blocking antibodies. Sublingual immunotherapy, concurrent anti-immunoglobulin E use, hypoallergic peptides, and DNA vaccines are other promising technologies.

Efficacy of sublingual immunotherapy in the treatment of allergic rhinitis in pediatric patients 3 to 18 years of age: a meta-analysis of randomized, placebo-controlled, double-blind trials

OBJECTIVE

To evaluate the efficacy of sublingual immunotherapy (SLIT) in the treatment of allergic rhinitis in children.

DATA SOURCES

A comprehensive search of the EMBASE, MEDLINE, LILACS, and CINAHL databases from January 1966 to February 10, 2006, was performed.

STUDY SELECTION

Randomized, double-blind, placebo-controlled trials of SLIT in the treatment of allergic rhinitis in patients 18 years or younger were selected. Outcomes measured were symptom scores and rescue medication use. Analysis was performed with standardized mean differences (SMDs) and a random-effects model.

RESULTS

Seventy articles were identified and reviewed. Ten studies, published between 1990 and 2004, fulfilled the selection criteria. Five hundred seventy-seven patients were initially included in the studies. Of these patients, 484 (245 SLIT and 239 placebo) had a final clinical evaluation and could be evaluated. A relevant heterogeneity due to widely differing scoring systems was found. Overall, there was a significant reduction in both symptoms (SMD, 0.56, 95% confidence interval, 1.01-0.10; P = .02) and medication use (SMD, 0.76; 95% confidence interval, 1.46-0.06; P = .03) after immunotherapy. The subanalyses performed for treatment duration and type of allergen showed that SLIT for more than 18 months and with pollen extracts was effective compared with SLIT courses shorter than 18 months and with mites.

CONCLUSION

The results of this meta-analysis showed that,compared with placebo, SLIT with standardized extracts is effective in pediatric patients with allergic rhinitis.

Mechanisms of allergen specific immunotherapy--T-cell tolerance and more

Specific immune suppression and induction of tolerance are essential processes in the regulation and circumvention of immune defence. The balance between allergen-specific T-regulatory (Treg) cells and T helper 2 cells appears to be decisive in the development of allergic and healthy immune response against allergens. Treg cells consistently represent the dominant subset specific for common environmental allergens in healthy individuals. In contrast, there is a high frequency of allergen-specific T helper 2 cells in allergic individuals. A decrease in interleukin (IL)-4, IL-5 and IL-13 production by allergen-specific CD4+ T cells due to the induction of peripheral T cell tolerance is the most essential step in allergen-specific immunotherapy (SIT). Suppressed proliferative and cytokine responses against the major allergens are induced by multiple suppressor factors, such as cytokines like IL-10 and transforming growth factor (TGF)-beta and cell surface molecules like cytotoxic T lymphocyte antigen-4, programmed death-1 and histamine receptor 2. There is considerable rationale for targeting T cells to increase efficacy of SIT. Such novel approaches include the use of modified allergens produced using recombinant DNA technology and adjuvants or additional drugs, which may increase the generation of allergen-specific peripheral tolerance. By the application of the recent knowledge in Treg cells and related mechanisms of peripheral tolerance, more rational and safer approaches are awaiting for the future of prevention and cure of allergic diseases.

Comparison of the biological activity of the most common sublingual allergen solutions made by two European manufacturers

BACKGROUND

The clinical efficacy of sublingual immunotherapy has been documented in numerous studies and meta-analyses and is argued to be a favored alternative to the subcutaneous route if allergic symptoms are treated with a high-dose therapy. What is still lacking is a 'conversion rate' between the biological activities of different allergen solutions to determine the one with the higher concentration.

METHODS

A randomized, double-blind, parallel-group study was done with three groups sensitized to the allergens birch, grass or house dust mite via skin prick test. Staloral in the concentrations 10, 100 and 300 IR and SLITone in the concentration of 1,000 STU per milliliter were used for a computer-based comparison of the geometric mean wheal sizes of the different solutions. For each patient, individual regression curves led to the calculation of a mean corresponding IR value for the SLITone solution.

RESULTS

A total of 47 patients took part in this clinical trial, most of whom were sensitized to more than one allergen. Values for birch (30 patients) showed that 1,000 STU corresponded to 77 IR, for grass (29 patients) 1,000 STU matched 78 IR and for house dust mite (30 patients) 1,000 STU matched 27 IR based on dose-response relationships. The Wilcoxon test showed that for all allergens the allergenic activity of the SLITone solution was significantly higher than the 10 IR solution and significantly lower than the 100- and 300-IR solutions.

CONCLUSION

We established a conversion rate between the two leading sublingual allergen solutions on the European market to compare different units of measurement.

New insights into the mechanisms of allergen-specific immunotherapy

PURPOSE OF REVIEW

Specific immunotherapy represents the only curative treatment of a specific allergy, and is therefore of great interest in terms of immunological mechanisms and therapeutic developments.

RECENT FINDINGS

Allergen-specific regulatory T cells are induced after the initiation of specific immunotherapy, and are assumed to suppress effector T cells directly mediating allergic inflammation. Therefore regulatory T cells may play a key role in the re-induction of allergen tolerance. Multiple pathways in many systems are described to promote or enhance regulatory T cells. This review summarizes the current view on immunological mechanisms leading to and coming from regulatory T cells.

SUMMARY

The highlighted mechanisms may not only contribute to improved specific immunotherapy, but also give insight into a clinically relevant therapy targeting regulatory T cells. The approach of addressing endogenous regulatory mechanisms specifically controlling inflammation instead of targeting inflammation itself is relevant for future pharmacological developments.

Immune mechanisms of allergen-specific sublingual immunotherapy

Sublingual immunotherapy has been shown in some clinical studies to modulate allergen-specific antibody responses [with a decrease in the immunoglobulin E/immunoglobulin G4 (IgE/IgG4) ratio] and to reduce the recruitment and activation of proinflammatory cells in target mucosa. Whereas a central paradigm for successful immunotherapy has been to reorient the pattern of allergen-specific T-cell responses in atopic patients from a T helper (Th)2 to Th1 profile, there is currently a growing interest in eliciting regulatory T cells, capable of downregulating both Th1 and Th2 responses through the production of interleukin (IL)-10 and/or transforming growth factor (TGF)-beta. We discuss herein immune mechanisms involved during allergen-specific sublingual immunotherapy (SLIT), in comparison with subcutaneous immunotherapy. During SLIT, the allergen is captured within the oral mucosa by Langerhans-like dendritic cells expressing high-affinity IgE receptors, producing IL-10 and TGF-beta, and upregulating indoleamine dioxygenase (IDO), suggesting that such cells are prone to induce tolerance. The oral mucosa contains limited number of proinflammatory cells, such as mast cells, thereby explaining the well-established safety profile of SLIT. In this context, second-generation vaccines based on recombinant allergens in a native conformation formulated with adjuvants are designed to target Langerhans-like cells in the sublingual mucosa, with the aim to induce allergen-specific regulatory T cells. Importantly, such recombinant vaccines should facilitate the identification of biological markers of SLIT efficacy in humans.

Safety and tolerability of ultra-rush induction, less than one hour, of sublingual immunotherapy in children

BACKGROUND

The safety and tolerability of sublingual immunotherapy (SLIT) has been documented in allergic patients both in the build-up phase as well as during maintenance, but only two studies have evaluated the occurrence of adverse reactions with an ultra-rush regimen of SLIT induction in a mixed paediatric/adult population. Moreover one of these two studies used a chemically modified extract (allergoid). The aim of the present study was to evaluate the occurrence of immediate or late adverse reactions in allergic children after a very fast (40 min) ultra-rush SLIT induction with two different allergen extract solutions.

METHODS

We studied 100 children (64 boys, mean age of 9.6 years, range 3.5-16.8), with a history of intermittent/persistent rhinitis and/or intermittent/mild persistent asthma due to inhalant allergens. The ultra-rush build-up phase involved the administration, every 10 min, of increasing doses of the highest-concentration vial of SLIT of two different manufacturers (Anallergo and Stallergènes).

RESULTS

All patients completed the treatment, side-effects have been recorded in 19% of the cases: 10% within 1 h after the build-up phase, 7% within 48 h and 2% mixed. A major difference (p = 0.0001) was recorded between Anallergo (6 patients, 8.7%) and Staloral (13 patients, 41.9%), but all the reactions were mild: principally oral symptoms, in 1 case rhinorrhoea and cough, and delayed abdominal pain and diarrhoea in another patient.

CONCLUSIONS

No severe adverse reactions were observed with this ultra-rush SLIT induction also in the paediatric age; statistical differences have been documented between the two different extracts.

Three-year follow-up of clinical and inflammation parameters in children monosensitized to mites undergoing sub-lingual immunotherapy

Parallel follow-up of clinical and inflammatory markers during sub-lingual immunotherapy (SLIT) is highly beneficial. Twenty-four children (age 4-16) monosensitized to house dust mite were randomized to receive either active or placebo SLIT for 1 yr in a double-blind placebo controlled design (Marcucci et al., Allergy 2003: 58: 657-62). Thereafter, for 2 yr they all received active treatment. Symptom scores for rhinitis, asthma, and drug usage were daily recorded. Eosinophil cationic protein (ECP) and tryptase in sputum and nasal secretions, serum and nasal mite-specific immunoglobulin E (IgE) were recorded before treatment and at 10-12 months intervals. Nasal ECP and nasal tryptase after specific nasal provocation tests were significantly reduced as compared to baseline values (p = 0.0043 and 0.0195, respectively) in the third year of active treatment. None of the other inflammatory parameters was increased. In placebo treated patients all these parameters tended to decrease only after switching to active treatment. Clinical scores did not improve in treated vs. placebo patients in the double-blind placebo-controlled phase of the study. In both cohorts a clinical benefit was observed as intra-group score reduction as compared to baseline. A significant difference was reached in patients treated for 2 yr for rhinitis and asthma (p = 0.0009 and 0.0019, respectively) but not for drug usage and in patients treated for 3 yr for rhinitis, asthma, and drug usage (p = 0.0105, 0.0048, and 0.02, respectively). SLIT in children monosensitized to mites reverted the spontaneous increase in nasal IgE and in local parameters of allergic inflammation. These outcomes were followed by a consolidated clinical improvement in the second and third year of treatment.

Targeting memory Th2 cells for the treatment of allergic asthma

Th2 memory cells play an important role in the pathogenesis of allergic asthma. Evidence from patients and experimental models indicates that memory Th2 cells reside in the lungs during disease remission and, upon allergen exposure, become activated effectors involved in disease exacerbation. The inhibition of memory Th2 cells or their effector functions in allergic asthma influence disease progression, suggesting their importance as therapeutic targets. They are allergen specific and can potentially be suppressed or eliminated using this specificity. They have distinct activation, differentiation, cell surface phenotype, migration capacity, and effector functions that can be targeted singularly or in combination. Furthermore, memory Th2 cells residing in the lungs can be treated locally. Capitalizing on these unique attributes is important for drug development for allergic asthma. The aim of this review is to present an overview of therapeutic strategies targeting Th2 memory cells in allergic asthma, emphasizing Th2 generation, differentiation, activation, migration, effector function, and survival.