Grass pollen sublingual immunotherapy for seasonal rhinoconjunctivitis: a randomized controlled trial

Sublingual immunotherapy for treating allergic conjunctivitis

BACKGROUND

Allergic ocular symptoms, although frequently trivialised, are common and represent an important comorbidity of allergic rhinitis. Sublingual Immunotherapy (SLIT) is an effective and well-tolerated treatment for allergic rhinitis, but its effects on symptoms of ocular allergy have not been well established.

OBJECTIVES

To evaluate the efficacy of SLIT compared with placebo for reductions in ocular symptoms, topical ocular medication requirements and conjunctival immediate allergen sensitivity.

SEARCH STRATEGY

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2011, Issue 1), MEDLINE (January 1950 to January 2011), EMBASE (January 1980 to January 2011), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to January 2011), Web of Science (January 1970 to January 2011), Biosis Previews, (January 1979 to January 2011), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com) (January 2011), ClinicalTrials.gov (www.clinicaltrials.gov) (January 2011), the Australian New Zealand Clinical Trials Registry (ANZCTR) (www.actr.org.au) (July 2010), SCOPUS (November 2008) and the UK Clinical Trials Gateway (January 2010). There were no language or date restrictions in the search for trials. All electronic databases except for SCOPUS, the UK Clinical Trials Gateway and ANZCTR were last searched on 19 January 2011.

SELECTION CRITERIA

Randomised controlled trials (RCTs), double-masked and placebo controlled, which evaluated the efficacy of SLIT in patients with symptoms of allergic rhinoconjunctivitis (ARC) or allergic conjunctivitis (AC).

DATA COLLECTION AND ANALYSIS

The primary outcome was the total ocular symptom scores. Secondary endpoints included individual ocular symptom scores (such as itchy eyes, red eyes, watery eyes, swollen eyes), ocular medication scores (eye drops) and conjunctival immediate allergen sensitivity (CIAS). Data were analysed and reported as standardised mean differences (SMDs) using Review Manager software.

MAIN RESULTS

Forty-two trials (n = 3958 total participants; n= 2011 SLIT and n = 1947 placebo) had available data to evaluate the efficacy of SLIT on AC and were included in the meta-analyses. Heterogeneity among studies (I(2) statistic) was around 50% or below for all endpoints. Sublingual immunotherapy induced a significant reduction in both total ocular symptom scores (SMD -0.41; 95% confidence interval (CI) -0.53 to -0.28; P < 0.00001; I(2) = 59%) and individual ocular symptom scores for red eyes (SMD -0.33; 95% CI -0.45 to -0.22; P < 0.00001; I(2) = 27%), itchy eyes (SMD -0.31; 95% CI -0.42 to -0.20; P < 0.00001; I(2) = 46%) and watery eyes (SMD -0.23; 95% CI -0.34 to -0.11; P < 0.0001; I(2) = 42%) compared to placebo. Those participants having active treatment showed an increase in the threshold dose for the conjunctival allergen provocation test (SMD 0.35; 95% CI 0.00 to 0.69; P = 0.05; I(2) = 43%). No significant reduction was observed in ocular eye drops use (SMD -0.10; 95% CI -0.22 to 0.03; P = 0.13; I(2) = 34%).

AUTHORS' CONCLUSIONS

Overall, SLIT is moderately effective in reducing total and individual ocular symptom scores in participants with ARC and AC. There were however some concerns about the overall quality of the evidence-base, this relating to inadequate descriptions of allocation concealment in some studies, statistical heterogeneity and the possibility of publication bias. There is a need for further large rigorously designed studies that study long-term effectiveness after discontinuation of treatment and establish the cost-effectiveness of SLIT.

Mechanisms of immunotherapy and surrogate markers

Understanding mechanisms of inducible antigen-specific tolerance will improve immunotherapy and reveal the most relevant biomarkers for objectively measuring response to immunotherapy in clinical trials and routine practice. Various physiological and laboratory parameters are proposed as biomarkers of an immunological response to vaccines, although their surrogacy for clinical end points is unproven. Examples of physiological biomarkers include suppression of allergen-induced early- and late-phase responses. Laboratory biomarkers include increases in bioactive allergen-specific IgG and IgA levels and T-cell interleukin (IL)-10 production. There is a continuing unmet need for biomarkers that will allow prediction of treatment efficacy and assist in monitoring the response after starting therapy or postwithdrawal.

Systematic reviews of sublingual immunotherapy (SLIT)

Allergic rhinitis is common worldwide, with significant morbidity and impact on quality of life. In patients who don't respond adequately to anti-allergic drugs. Subcutaneous allergen immunotherapy is effective although requires specialist administration. Sublingual immunotherapy may represent an effective and safer alternative. This Cochrane systematic review is an update of one published in 2003. We searched Cochrane ENT Group Trials Register, Central, PubMed, EMBASE, CINAHL, Web of Science, Biosis Previews, Cambridge Scientific Abstarcts, mRCT and additional sources. We included randomised, double-blind, placebo- controlled trials of sublingual immunotherapy in adults and children. Two authors selected studies and assessed them for quality. Data were put into RevMan 5.0 for a statistical analysis. We used standardised mean difference (SMD), with a random effect model to combine data. Sixty studies were included, with 49 suitable for meta-analysis. We found significant reductions in symptoms (SMD -0.49; 95%CI (-0.64 to -0.34, P < 0.00001)) and medication requirements (SMD -0.32; 95%CI (-0.43 to -0.21, P < 0.00001)) compared with placebo. None of the trials reported severe systemic reactions, anaphylaxis or use of Adrenaline. This updated review reinforces the conclusion of the original 2003 Cochrane Review that sublingual immunotherapy is effective for allergic rhinitis and appears a safe route of administration.

Stress and allergic diseases

Allergy describes a constellation of clinical diseases that affect up to 30% of the world's population. It is characterized by production of allergen-specific IgE, which binds to mast cells and initiates a cascade of molecular and cellular events that affect the respiratory tract (rhinitis and asthma), skin (dermatitis, urticaria), and multiple systems (anaphylaxis) in response to a variety of allergens including pollens, mold spores, animal danders, insect stings, foods, and drugs. The underlying pathophysiology involves immunoregulatory dysfunctions similar to those noted in highly stressed populations. The relationships in terms of potential for intervention are discussed.

Development and preliminary clinical evaluation of a peptide immunotherapy vaccine for cat allergy

BACKGROUND

Allergic sensitization to cat allergens is common and represents a major risk factor for asthma. Specific immunotherapy (SIT) is effective but cumbersome and associated with IgE-dependent adverse events. Immunotherapy targeting allergen-specific T cells, with synthetic peptides representing T-cell epitopes, might improve safety and reduce the duration of treatment.

OBJECTIVE

We sought to define major T-cell epitopes of Fel d 1 for peptide immunotherapy, generate a peptide vaccine, and evaluate its safety and tolerability in subjects with cat allergy.

METHODS

We determined the binding affinities of Fel d 1 peptides for 10 commonly expressed HLA-DR molecules. Functionally immunodominant peptides were identified by means of proliferation and cytokine secretion. Histamine-releasing activity was assessed, and a peptide vaccine was formulated. Safety and tolerability were evaluated in a dose-ranging phase IIa clinical trial.

RESULTS

MHC-binding sequences were identified throughout Fel d 1. Some regions contained multiple overlapping T-cell epitopes that bound multiple MHC molecules. Immunodominant sequences were identified on the basis of proliferative and cytokine (IFN-γ, IL-10, and IL-13) responses. Cat allergen extract, but not peptides, induced histamine release in blood basophils. A single administration of peptide vaccine was safe and well tolerated. The dose of vaccine resulting in the greatest inhibition of the late-phase skin response to intradermal whole allergen challenge was 3 nmol.

CONCLUSIONS

Fel d 1 contains multiple overlapping MHC-binding motifs. A peptide vaccine comprising the immunodominant regions of the allergen was safe and well tolerated when given to subjects with cat allergy as a single dose. The dose of vaccine resulting in the greatest reduction in late-phase skin response was defined for future clinical development.

Sublingual immunotherapy for allergic rhinitis

BACKGROUND

This is an update of a Cochrane Review first published in The Cochrane Library in Issue 2, 2003.Allergic rhinitis is a common condition which can significantly impair quality of life. Immunotherapy by injection can significantly reduce symptoms and medication use but its use is limited by the possibility of severe systemic adverse reactions. Immunotherapy by the sublingual route is therefore of considerable interest.

OBJECTIVES

To evaluate the efficacy and safety of sublingual immunotherapy for allergic rhinitis in adults and children.

SEARCH STRATEGY

We searched the Cochrane ENT Group Trials Register; CENTRAL (2010, Issue 3); PubMed; EMBASE; CINAHL; Web of Science; BIOSIS Previews; Cambridge Scientific Abstracts; mRCT and additional sources for published and unpublished trials. The date of the most recent search was 14 August 2009.

SELECTION CRITERIA

Randomised, double-blind, placebo-controlled trials of sublingual immunotherapy in adults or children. Primary outcome measures were symptom and medication scores. We also collected adverse event data.

DATA COLLECTION AND ANALYSIS

Two independent authors selected studies and assessed risk of bias. One author extracted data which was rechecked by two other authors. We used the standardised mean difference (SMD) with a random-effects model to combine data.

MAIN RESULTS

We included a total of 60 randomised controlled trials in the review. Forty-nine were suitable for pooling in meta-analyses (2333 SLIT, 2256 placebo participants). Overall, we found a significant reduction in symptoms (SMD -0.49; 95% confidence interval (CI) -0.64 to -0.34, P < 0.00001) and medication requirements (SMD -0.32; 95% CI -0.43 to -0.21, P < 0.00001) in participants receiving sublingual immunotherapy compared to placebo. None of the trials included in this review reported severe systemic reactions or anaphylaxis, and none of the systemic reactions reported required the use of adrenaline.

AUTHORS' CONCLUSIONS

This updated review reinforces the conclusion of the original 2003 Cochrane Review that sublingual immunotherapy is effective for allergic rhinitis and has been proven to be a safe route of administration.

Immunological effects of sublingual immunotherapy: clinical efficacy is associated with modulation of programmed cell death ligand 1, IL-10, and IgG4

Sublingual immunotherapy (SLIT) is an alternate route of administration of allergen-specific immunotherapy with an improved safety profile; to clarify the immune mechanisms elicited by this therapy, we analyzed the clinical and immunologic effects of SLIT in patients with a clinical history of ragweed sensitization. To analyze possible difference among immunotherapeutic protocols, we also compared patients receiving preseasonal, seasonal, or prolonged sublingual therapy (≥ 3 y); patients receiving symptomatic therapy alone were enrolled as well in the study. Clinical and immunological parameters were measured twice in and out of the pollination period. Clinical benefits, as measured by the visual analog scale for symptoms and for use of drugs, were evident in all three groups of individuals receiving immunotherapy, but were significantly better in patients undergoing prolonged SLIT. Immunologically, SLIT resulted in increased IL-10 production, programmed cell death ligand 1 expression, and concentration of allergen-specific IgG4, as well as in the reduction of CD80 and CD86 expression and IL-4 production. SLIT, thus, is associated with modulation of programmed cell death ligand 1 expression and IL-10 synthesis and favors the production of allergen-specific IgG4. These effects are evident from the first pollen season, independently from therapeutic regimen (preseasonal or seasonal) even if a prolonged treatment is necessary to obtain full clinical efficacy. A more detailed understanding of the interaction of allergen and APCs within the oral mucosa will allow improved targeting of allergy vaccine.

Emerging sublingual immunotherapy drugs

IMPORTANCE OF THE FIELD

There is epidemiological evidence that respiratory allergy has reached epidemic proportions; owing to the related socio-economic impact, this topic deserves particular attention. An integrated approach involving pharmacotherapy and the immunomodulatory effect of immunotherapy is expected to optimize the management of respiratory allergy, reducing its clinical and economic burdens. Sublingual immunotherapy (SLIT) has gained increasing interest for its efficacy comparable to traditional subcutaneous immunotherapy and its good safety profile.

AREAS COVERED IN THIS REVIEW

A review of the up-to-date state of the art concerning the key aspects of SLIT is provided; the critical issues are discussed in the light of the comprehensive revision of the recent World Allergy Organization position paper and the subsequent literature, paying particular attention to efficacy, safety, additional effects, adherence and clinical developments.

WHAT THE READER WILL GAIN

The overview of current certainties and concerns, related to the use of SLIT, allows the reader's insight into the future directions of research and clinical applications of SLIT, aimed at covering current unmet needs.

TAKE HOME MESSAGE

A large amount of experimental evidence sustains the use of SLIT, though some aspects still need to be clarified to provide clear, evidence-based recommendations. Unmet needs represent the basis for future research, while clinical hypotheses would open the search for new indications and modalities.

Towards evidence-based medicine in specific grass pollen immunotherapy

When initiating grass pollen immunotherapy for seasonal allergic rhinoconjunctivitis, specialist physicians in many European countries must choose between modalities of differing pharmaceutical and regulatory status. We applied an evidence-based medicine (EBM) approach to commercially available subcutaneous and sublingual Gramineae grass pollen immunotherapies (SCIT and SLIT) by evaluating study design, populations, pollen seasons, treatment doses and durations, efficacy, quality of life, safety and compliance. After searching MEDLINE, Embase and the Cochrane Library up until January 2009, we identified 33 randomized, double-blind, placebo-controlled trials (including seven paediatric trials) with a total of 440 specific immunotherapy (SIT)-treated subjects in seven trials (0 paediatric) for SCIT with natural pollen extracts, 168 in three trials (0 paediatric) for SCIT with allergoids, 906 in 16 trials (five paediatric) for natural extract SLIT drops, 41 in two trials (one paediatric) for allergoid SLIT tablets and 1605 in five trials (two paediatric) for natural extract SLIT tablets. Trial design and quality varied significantly within and between SIT modalities. The multinational, rigorous trials of natural extract SLIT tablets correspond to a high level of evidence in adult and paediatric populations. The limited amount of published data on allergoids prevented us from judging the level of evidence for this modality.

Antigen-specific immunotherapy against allergic rhinitis: the state of the art

Allergic rhinitis is the most prevalent type I allergy in industrialized countries. Pollen scattering from trees or grasses often induces seasonal allergic rhinitis, which is known as pollinosis or hay fever. The causative pollen differs across different areas and times of the year. Impaired performance due to pollinosis and/or medication used for treating pollinosis is considered to be an important reason for the loss of concentration and productivity in the workplace. Antigen-specific immunotherapy is an only available curative treatment against allergic rhinitis. Subcutaneous injection of allergens with or without adjuvant has been commonly used as an immunotherapy; however, recently, sublingual administration has come to be considered a safer and convenient alternative administration route of allergens. In this review, we focus on the safety and protocol of subcutaneous and sublingual immunotherapy against seasonal allergic rhinitis. We also describe an approach to selecting allergens for the vaccine so as to avoid secondary sensitization and adverse events. The biomarkers and therapeutic mechanisms for immunotherapy are not fully understood. We discuss the therapeutic biomarkers that are correlated with the improvement of clinical symptoms brought about by immunotherapy as well as the involvement of Tr1 and regulatory T cells in the therapeutic mechanisms. Finally, we focus on the current immunotherapeutic approach to treating Japanese cedar pollinosis, the most prevalent pollinosis in Japan, including sublingual immunotherapy with standardized extract, a transgenic rice-based edible vaccine, and an immunoregulatory liposome encapsulating recombinant fusion protein.

Sublingual grass pollen immunotherapy is associated with increases in sublingual Foxp3-expressing cells and elevated allergen-specific immunoglobulin G4, immunoglobulin A and serum inhibitory activity for immunoglobulin E-facilitated allergen binding to B cells

BACKGROUND

The mechanisms of sublingual immunotherapy (SLIT) are less well understood than those of subcutaneous immunotherapy (SCIT).

OBJECTIVES

To determine the effects of grass-pollen SLIT on oral mucosal immune cells, local regulatory cytokines, serum allergen-specific antibody subclasses and B cell IgE-facilitated allergen binding (IgE-FAB).

METHODS

Biopsies from the sublingual mucosa of up to 14 SLIT-treated atopics, nine placebo-treated atopics and eight normal controls were examined for myeloid dendritic cells (mDCs) (CD1c), plasmacytoid dendritic cells (CD303), mast cells (AA1), T cells (CD3) and Foxp3 using immunofluorescence microscopy. IL-10 and TGF-beta mRNA expression were identified by in situ hybridization. Allergen-specific IgG and IgA subclasses and serum inhibitory activity for binding of allergen-IgE complexes to B cells (IgE-FAB) were measured before, during and on the completion of SLIT.

RESULTS

Foxp3(+) cells were increased in the oral epithelium of SLIT- vs. placebo-treated atopics (P=0.04). Greater numbers of subepithelial mDCs were present in placebo-treated, but not in SLIT-treated, atopics compared with normal controls (P=0.05). There were fewer subepithelial mast cells and greater epithelial T cells in SLIT- compared with placebo-treated atopics (P=0.1 for both). IgG(1) and IgG(4) were increased following SLIT (P<0.001). Peak seasonal IgA(1) and IgA(2) were increased during SLIT (P<0.05). There was a time-dependent increase in serum inhibitory activity for IgE-FAB in SLIT-treated atopics.

CONCLUSIONS

SLIT with grass pollen extract is associated with increased Foxp3(+) cells in the sublingual epithelium and systemic humoral changes as observed previously for SCIT.

Mechanisms of sublingual immunotherapy

Allergen-specific sublingual immunotherapy is now recognized to be an efficacious and well-tolerated treatment for allergic rhinitis. Emerging treatment strategies are also aimed at the primary treatment of allergic asthma, particularly allergy to house dust mites. Knowledge of the exact mechanisms of action of sublingual immunotherapy is at a basic level, although there appear to be similarities to the immunological changes seen in subcutaneous immunotherapy. An improved understanding should allow the development of more effective treatment programs and widen the potential use of this form of immunotherapy. This review discusses the possible mechanism of action of sublingual immunotherapy, including data from animal and clinical studies, while comparing this with the current understanding of subcutaneous immunotherapy.

An update on the safety of specific immunotherapy

PURPOSE OF REVIEW

As allergen sublingual immunotherapy becomes more widely used in Europe and draws the attention of physicians of the USA, it is important to compare and contrast the safety aspects of this therapy versus allergen subcutaneous immunotherapy.

RECENT FINDINGS

There are reports of severe systemic reactions associated with sublingual immunotherapy, but no fatalities. There are various studies of systemic reactions, including those that result in death, associated with subcutaneous immunotherapy over its nearly 100-year worldwide experience. Local reactions are common to both forms of the treatment.

SUMMARY

If both forms of therapy are equally effective, a cost (including safety aspects) -benefit analysis of sublingual immunotherapy versus subcutaneous immunotherapy is necessary to determine how best to incorporate both forms of specific immunotherapy into the management of allergic patients. Adherence to published guidelines will reduce the likelihood of adverse reactions.

Sublingual immunotherapy for allergic respiratory diseases: an evaluation of meta-analyses

BACKGROUND

Five published meta-analyses (MAs) seem to prove the efficacy of sublingual immunotherapy in allergic asthma and rhinoconjunctivitis.

OBJECTIVE

We aimed to assess the consistency, magnitude, and robustness of the results of these MAs.

METHODS

The data reported in the MAs were checked with the data reported in the original studies. Funnel plots were performed to test for potential publication bias, and the trim-and-fill method was used to assess and correct the estimate of the effects if asymmetry was present.

RESULTS

The 5 MAs included 43 studies; 17 were used in more than one MA. There were discrepancies among the MAs in the data reported from the same original studies: the MAs reported different estimates for the same outcome or the same estimates for different outcomes in 16 of those 17 studies. The MAs evaluated 15 main outcomes, 10 of which showed benefits that reached statistical significance. Funnel plots showed asymmetry in 7 outcomes, and correction by using the trim-and-fill method led to a decrease in their effect estimates and even to a loss of statistical significance in 4 of the previously significant outcomes. There was inconsistency among the MAs in the benefits when considering age, disease, allergen, or symptoms and medication use.

CONCLUSION

Because of discrepancies, inconsistencies, and lack of robustness, the MAs on sublingual immunotherapy do not provide enough evidence to support its current routine management in patients with allergic asthma or rhinoconjunctivitis. Sensitivity to potential publication bias should be tested and reported in all MAs.

Administration regimens for sublingual immunotherapy to pollen allergens: what do we know?

The modalities of administration of sublingual immunotherapy (SLIT), including dosing, build-up phase, duration of the treatment, and frequency of the maintenance dose are largely variable. In the case of pollen (SLIT), the complexity increases, since preseasonal, coseasonal and pre-coseasonal regimens can be used. The administration regimens are of relevance from a practical point of view, but can also have economic implications. We review herein the available literature (randomized double blind controlled studies) on pollen SLIT, in order to derive experimentally-supported suggestions about the regimens of administration that should be preferred.

Evaluation of subcutaneous versus mucosal (intranasal) allergen-specific rush immunotherapy in experimental feline asthma

Rush immunotherapy (RIT) is effective for the treatment of experimental feline allergic asthma. In humans, the safety profile of immunotherapy is improved by delivering allergen by a mucosal route. We hypothesized that mucosal (intranasal) RIT would have similar efficacy to subcutaneous RIT with improved safety. Twelve cats sensitized and challenged with Bermuda grass allergen (BGA) were randomized to receive subcutaneous (SC) or intranasal (IN) RIT. Increasing doses of BGA (20-200 microg) were administered over 24h followed by 200 microg BGA weekly as maintenance. Adverse reactions were recorded. Clinical respiratory scores after BGA aerosol challenge, bronchoalveolar lavage fluid (BALF) % eosinophils, and cytokine concentrations were measured before RIT (day 1) and at months 1, 3 and 6 (M1, M3, M6). More adverse events were recorded with SC RIT (n=12) compared with IN RIT (n=6). Respiratory scores were lower by M6 compared with D1 in both the groups. The % BALF eosinophils declined significantly after RIT for both groups (mean+/-SEM, SC RIT D1 62+/-12, M6 9+/-4; IN RIT D1 54+/-9, M6 14+/-6). The BALF IL-4:IFN-gamma ratio significantly decreased over time in the IN RIT group (mean+/-SEM, D1 2.4+/-0.2, M6 1.0+/-0.2). While both protocols decreased eosinophilic airway inflammation, the SC RIT protocol did not cause life-threatening adverse events and demonstrated more consistent resolution of clinical signs after allergen challenge. Either protocol could be considered for the treatment of feline allergic asthma.

Efficacy and safety of specific immunotherapy with a high-dose sublingual grass pollen preparation: a double-blind, placebo-controlled trial

BACKGROUND

Sublingual immunotherapy (SLIT) is increasingly being used for the treatment of allergic rhinitis, but there are conflicting study results demonstrating clinically relevant efficacy.

OBJECTIVE

To show clinical efficacy and safety of a new high-dose grass pollen preparation for SLIT.

METHODS

In a 2-year, double-blind, placebo-controlled trial, 185 subjects with rhinitis or rhinoconjunctivitis, with or without asthma, were treated with a recently developed, high-dose, 6-grass pollen mixture for SLIT once daily.

RESULTS

The primary end point, a combined symptom-medication score, showed almost no change in the placebo group during a 42-day evaluation period in the grass pollen season from 2003 to 2005, whereas active treatment was associated with a significant and clinically relevant improvement (full analysis set, P = .01; main data set, P = .002). The effect was irrespective of asthma diagnosis. Allergen-specific IgE showed no difference in both groups, and specific IgG4 and IgG1 increased with active treatment in the first and second study years compared with placebo, clearly indicating the immunogenic effect of the active treatment. The SLIT was well tolerated. No serious adverse drug reactions occurred.

CONCLUSIONS

High-dose, sublingual, specific immunotherapy with an extract of a 6-grass pollen mixture showed a significant and clinically relevant improvement in subjects with grass pollen-associated rhinitis or rhinoconjunctivitis, with or without asthma. The treatment with the sublingual solution was well tolerated.

Two year follow-up of immunological response in mite-allergic children treated with sublingual immunotherapy. Comparison with subcutaneous administration

Although the efficacy of allergen-specific sublingual immunotherapy (SLIT) is now accepted, the underlying mechanisms remain elusive. Such mechanisms are better documented in the case of subcutaneous immunotherapy (SCIT). In order to understand the T-lymphocyte response in patients receiving SLIT, we compared children with respiratory disease monosensitized to Dermatophagoides pteronyssinus receiving SLIT or SCIT over a 2-yr period. Peripheral blood was obtained before beginning immunotherapy, and after 3 months, 1 yr and 2 yr. Total IgE, specific IgE and IgG4 to D. pteronyssinus were determined in serum. T-cell markers (CD3, CD4, CD8, CD25) and intracellular cytokine production (TNF-alpha, IL-2, IL-4 and IFN-gamma) were determined in peripheral blood mononuclear cells (PBMC) by flow cytometry. No differences between SCIT and SLIT were detected in the clinical variables or in the subjective evaluation. Although an increase in specific IgE and IgG4 was only detected in SCIT, a significant decrease in the specific IgE/IgG4 ratio was found in both groups. SCIT and SLIT experienced an increase in the CD4/CD8 ratio over time, but an increase in the CD4(+)CD25(+) and a decrease in the CD8(+)CD25(+) subsets were only found with SCIT. A slight shift from a Th2 to a Th1 pattern, measured by the IFN-gamma/IL-4 ratio, was only detected in the CD4 T cells with SCIT. A decrease in both groups was found in TNF-alpha and IL-2 production over time. Children with respiratory allergic diseases receiving SCIT or SLIT had a different immunologic response in peripheral blood during treatment, though the clinical improvement was similar. Whether SLIT induces a mucosal protective response should be studied.

Is sublingual immunotherapy the final answer? Implications for the allergist

Sublingual immunotherapy (SLIT) is now accepted as a viable alternative to the traditional injection route based on more than 40 clinical trials and several meta-analyses of efficacy. In addition, the safety profile is very favorable, also in younger children. Although some aspects need to be further clarified (eg, optimal doses, patient selection, and mechanisms of action), SLIT can be currently regarded as an additional therapeutic option that allergists have available. The main distinctive feature of SLIT is certainly its tolerability, safety, and convenience for the patient. Nonetheless, as happens with injection immunotherapy, it is mandatory that the prescription of SLIT is made by a trained specialist, and that a detailed diagnosis is made before prescribing it.

Sublingual grass allergen tablet immunotherapy provides sustained clinical benefit with progressive immunologic changes over 2 years

BACKGROUND

This is an interim analysis of a randomized, double-blind, placebo-controlled phase III trial with 3 years of daily treatment with grass tablet immunotherapy (GRAZAX; ALK-Abelló A/S, Hørsholm, Denmark) or placebo, followed by 2 years of follow-up to assess the persistent efficacy.

OBJECTIVE

We sought to evaluate the efficacy and safety of specific immunotherapy with grass allergen tablets compared with placebo after treatment covering 2 consecutive grass pollen seasons.

METHODS

The interim analyses included 351 adult participants with moderate-to-severe allergic rhinoconjunctivitis caused by grass pollen. Participants were treated with active (n = 189) or placebo (n = 162) tablets for an average of 22 months. All participants were allowed to use symptomatic rescue medication.

RESULTS

The primary efficacy analysis showed highly significant mean reductions of 36% in rhinoconjunctivitis symptom score (P < .0001; median reduction, 44%) and 46% in rhinoconjunctivitis medication score (P < .0001; median reduction, 73%) in the active group relative to the placebo group. Mean rhinoconjunctivitis quality of life was 33% better (P < .0001; median, 40%). Clinical improvements were paralleled by significant changes in allergen-specific immunoglobulins. The treatment was well tolerated, and adverse events led to withdrawal in less than 1% of participants. There were no serious adverse events related to treatment.

CONCLUSION

Grass allergen tablet immunotherapy showed progressive immunologic changes and highly significant efficacy over 2 years of continued treatment.

Sublingual-swallow immunotherapy with standardized 3-grass pollen extract: a double-blind, placebo-controlled study

BACKGROUND

Sublingual immunotherapy (SLIT) is accepted as a safe and effective route for the treatment of grass pollen allergy, but clarification of its clinical and biological efficacy requires more study.

OBJECTIVE

To evaluate the efficacy, safety, and compliance of SLIT with a standardized 3-grass pollen extract in patients with grass pollen seasonal allergic rhinoconjunctivitis, with or without mild asthma.

METHODS

This multicenter, randomized, double-blind study included 127 patients (aged 12-41 years; mean age, 24.9 years) with grass pollen seasonal allergic rhinoconjunctivitis, with or without mild asthma. They received either SLIT with a high-dose, standardized, 3-grass pollen extract or placebo for 10 months before and during the grass pollen season. The efficacy evaluation compared weekly clinical scores (defined as the sum of the symptom score and rescue medication score) to measure rhinoconjunctivitis and asthma for the first 8 weeks of the pollen season. We also evaluated safety and compliance and measured changes in anti-Dactylis specific IgG4 antibody levels.

RESULTS

There was a trend in favor of the study group in the mean adjusted clinical score. The groups were not comparable on inclusion (P = .02): the SLIT group included more subjects with asthma and had a higher mean IgG4 serum level. Additional exploration according to subgroups with and without asthma found that among the patients without asthma, the SLIT group had a significantly better clinical score (P = .045). Anti-Dactylis specific IgG4 levels increased significantly in the SLIT group.

CONCLUSION

SLIT with a standardized, high-dose, 3-grass pollen extract is safe and significantly improves the clinical score in patients with hay fever and without asthma during the pollen season.

A randomized controlled trial of sublingual immunotherapy for Japanese cedar pollinosis

BACKGROUND

Japanese cedar pollen represents an important and unique allergen. Sublingual immunotherapy (SLIT) has been suggested to be a highly effective route of desensitization against a variety of allergens. However, little information is available about its use in cedar pollen allergy.

METHODS

A blinded randomized, placebo-controlled trial employing SLIT for cedar pollinosis was conducted over a period of 6 months. Sixty-seven subjects were enrolled and the symptom scores during the pollen season were evaluated by a symptom diary, measurement of cedar-specific IgE and IgG4, and determination of Cry j-specific Th2 clones before SLIT and before and after the pollen season.

RESULTS

No major adverse effects were observed in either group. The serum-specific IgG4 activity increased significantly after SLIT in the active group. The active group also exhibited significantly lower symptom scores compared to the placebo. The specific Th2 clone sizes were not significantly different between the groups before the pollen season. However, an increase in the clone size was observed after the pollen season in the placebo group, but not in the active group.

CONCLUSION

Use of SLIT for Japanese cedar pollinosis was found to be safe and associated with an increase in cedar-specific IgG4 levels. Such therapy inhibited the increase in Cry j-specific Th2 clone size induced by pollen exposure. Finally, use of SLIT resulted in significant improvement of the clinical symptoms of cedar pollinosis in this patient population. These observations suggest that SLIT may offer another safe approach to the management of cedar pollinosis.

Sublingual immunotherapy reduces allergic symptoms in a mouse model of rhinitis

BACKGROUND

Sublingual immunotherapy (SLIT) is a clinically effective treatment in both pollen and house dust mite-induced rhinitis and asthma. However, the mechanisms by which this is accomplished are not clear.

OBJECTIVE

The objective of the current study was to establish a mouse model of rhinitis in order to study the effect and mechanisms of SLIT.

METHODS

Mice were sensitized by intraperitoneal injections of alum-adsorbed Phleum pratense extract. Sensitized mice were SLIT-treated and subsequently challenged intranasally and analysed for clinical symptoms, antibody levels, eosinophilia and T cell response.

RESULTS

Intranasal challenge of sensitized mice led to the development of rhinitis characterized by significantly increased sneezing and influx of eosinophils into the nose. Levels of specific IgE were fivefold increased in nasopharyngeal lavage (NAL) fluid and more than doubled in serum. Furthermore, a T-helper type 2 (Th2) like T cell response was observed in local draining lymph nodes. SLIT treatment of sensitized mice reduced sneezing, eosinophilia and IgE levels in the NAL by more than 50%. Moreover, serum levels of IgE and IgG1 as well as T cell response in the draining lymph nodes were also significantly reduced. Treatment for a shorter time or with a lower dose only led to minor reductions of the clinical and immunological parameters, indicating that the effect of SLIT is time and dose dependent.

CONCLUSION

In the present study, we have established a mouse model displaying the hallmarks of allergic rhinitis using a clinically relevant allergen. Using this model, we have demonstrated that SLIT treatment is able to reduce allergic symptoms in a time- and dose-dependent manner.

Allergen-induced in vitro expression of IL-18, SLAM and GATA-3 mRNA in PBMC during sublingual immunotherapy

BACKGROUND

Signalling lymphocytic activation molecule (SLAM) and interleukin (IL)-18 induce interferon (IFN)-gamma production from Th1 cells. The allergen-induced SLAM and IL-18 mRNA expressions are increased during subcutaneous immunotherapy (SCIT), but nothing is known about their role during sublingual immunotherapy (SLIT). Transcription factor GATA-3 is associated with Th2 cells but its role in SCIT and SLIT is yet unexplored. This study was undertaken to analyse the allergen induced in vitro mRNA expression of IL-18, SLAM and GATA-3 in peripheral blood mononuclear cells (PBMC) of children with allergic rhinitis (AR) during SLIT.

METHODS

Ten patients with AR undergoing pollen SLIT with a weekly dose of 200,000 SQ-U, 10 with 24,000 SQ-U of mixture of Betula verrucosa, Corylus avellana and Alnus glutinosa and 10 with placebo were included. Peripheral blood mononuclear cell were stimulated with birch extract prior to, after 1 and 2 years of the treatment. The mRNA expression was assessed using kinetic real-time RT-PCR (TaqMan); Applied Biosystems, Foster City, CA, USA).

RESULTS

The expression of IL-18 mRNA was increased in the high-dose group in comparison to the placebo group after 1 year of therapy (P = 0.028) and had an inverse correlation with the late phase skin reaction after the second study year (r = -0.41, P = 0.041). SLAM mRNA expression increased in the high-dose group from baseline to 1 year (P = 0.028) and correlated with IL-10 (r = 0.96, P < 0.0001) and transforming growth factor-beta (r = 0.80, P = 0.0037) mRNA expression. No significant changes were seen in GATA-3 mRNA expression.

CONCLUSIONS

During SLIT, IL-18 and SLAM are upregulated, suggesting that the Th2 type inflammatory response is downregulated during SLIT by increased Th1 type response.

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.

Sublingual immunotherapy in sensitized mice

BACKGROUND

Many studies have demonstrated immunologic changes induced by sublingual immunotherapy (SLIT), but the definitive mechanism of action needs further investigation.

OBJECTIVE

To study the immunologic response induced by SLIT in sensitized mice.

METHODS

Timothy grass (Phleum pratense)-sensitized mice received SLIT for 2, 4, or 6 weeks at 3 different concentrations, including a buffer control. Serum samples and washes of the lungs (bronchoalveolar lavage [BAL]) and the nasal passages (nasal lavage [NAL]) were analyzed for allergen-specific antibodies. T cells were isolated from the spleen and cervical lymph nodes for the analysis of proliferation and cytokine production.

RESULTS

Sublingual immunotherapy in sensitized mice resulted in a 30-fold increase in antigen specific IgA levels in BAL and NAL fluid compared with buffer-treated mice, whereas antigen specific IgE was undetectable in BAL and NAL fluid in animals treated with SLIT. Furthermore, IgA levels were proportional to the dose and duration of SLIT. Levels of specific IgA in serum correlated with levels in BAL and NAL fluid. Serum IgA levels were proportional to the duration of allergen exposure to the oral mucosa. Conversely, no changes in serum levels of IgE and IgG were induced by SLIT. Proliferation of T cells was increased in mice treated with SLIT compared with nontreated mice.

CONCLUSION

High levels of IgA in serum and in BAL and NAL fluid of mice treated with SLIT demonstrate that SLIT induces a mucosal, nonallergic response in sensitized mice.

Sublingual immunotherapy: update 2006

PURPOSE OF REVIEW

Sublingual immunotherapy is currently accepted as a viable therapeutic option, and is widely used in many European countries. In the past 2 years, new data concerning clinical, immunological and practical aspects of sublingual immunotherapy have been published, and many critical points have been addressed.

RECENT FINDINGS

In addition to the new data on clinical efficacy, the most recent studies have shown that, similar to the injection route, sublingual immunotherapy can also prevent the onset of new sensitizations and the onset of asthma. Moreover, several postmarketing surveys have confirmed the satisfactory safety profile, even in very young children, and compliance has been measured. The good safety profile has also suggested the possibility of using sublingual immunotherapy without the updosing phase. Finally, the mechanisms of action have been systematically investigated and the biodistribution of sublingual allergens has been further clarified.

SUMMARY

More new data on sublingual immunotherapy are rapidly appearing in the international literature. These data consistently confirm the value of this treatment and show that sublingual immunotherapy is a viable and useful form of immunotherapy.

Allergen immunotherapy: where is it now?

The scientific basis and the proof of clinical effectiveness of allergen immunotherapy administered by subcutaneous injection (SCIT) are well established. It is effective treatment for sensitivity to Hymenoptera venom and for allergic rhinitis and allergic asthma. SCIT administered in the proper setting reduces the development of new sensitivities and progression from rhinitis to asthma. Further, the beneficial effects persist long after completion of a course of treatment. Although many people enjoy the benefits of SCIT, extension of its use to the many others who might be candidates for this treatment is limited by its drawbacks of safety concerns and the inconvenience of repeated clinic visits over several years to receive the injections. There are many attempts underway to improve on the safety and convenience while still retaining the benefits of SCIT. These include approaches using current allergen extracts, especially by administering them sublingually. Alternatively, through recombinant technology, extracts are being modified to reduce their allergenicity without reducing their immunogenicity. They are being linked to immunostimulatory DNA sequences that will modify their in vivo processing resulting in an enhanced nonallergic response or they are being incorporated into fusion proteins with inhibitory properties for mast cells and basophils.

Standardized training for healthcare professionals and its impact on patients with perennial rhinitis: a multi-centre randomized controlled trial

BACKGROUND

Perennial rhinitis is common and often results in substantial, potentially avoidable, impairment of quality of life. Quality of rhinitis care has been shown to be sub-optimal in general practice. Rigorous evaluation of educational interventions for healthcare professionals using randomized controlled trials is very uncommon.

OBJECTIVE

To evaluate the effectiveness of standardized allergy training for healthcare professionals on patients' disease-specific quality of life.

METHODS

Patients with clinician diagnosed perennial rhinitis and/or a prescription for relevant nasal medication were recruited from general practice. Following baseline measurement of quality of life using the validated rhino-conjunctivitis questionnaire (RQLQ), patients were centrally randomized to receive care from an allergy-trained primary healthcare professional or routine care. RQLQ was measured again at 13 months after randomization.

RESULTS

Process measures revealed that the training was well received. 202 patients were included in the intention-to-treat analysis and 157 in the per-protocol analysis. There was a 0.23 greater mean improvement in quality-of-life scores in the intervention group when compared with controls (P=0.08) in the intention-to-treat analysis, this increasing to a 0.3 greater mean improvement if confined to a per-protocol analysis (P=0.05). The intention-to-treat analysis showed that 39/101 (39%) in the intervention group showed a clinically significant > or =0.5 improvement in RQLQ compared with 28/101 (28%) of controls (risk difference=11%, number needed to treat=9, P=0.1).

CONCLUSIONS

Standardized allergy education given to primary healthcare professionals leads to modest improvements in disease-specific quality of life in patients with perennial rhinitis.

Evaluation of serum IgG4 antibodies specific to grass pollen allergen components in the follow up of allergic patients undergoing subcutaneous and sublingual immunotherapy

BACKGROUND

A number of reports suggest that induction of IgG 'blocking antibodies' may be important for successful allergen immunotherapy. Nevertheless, a significant increase in specific IgG and IgG4 antibodies has not been consistently demonstrated for sublingual immunotherapy (SLIT).

METHODS

The present observation included three groups of grass pollen allergic patients all submitted to three different allergen immunotherapeutic regimens in an open, non-placebo controlled clinical study: (i) 16 patients underwent a modified 'cluster' regimen of weekly injections of a standardized aluminium-absorbed Phleum pratense extract for 5 weeks, followed by 3 weeks of maintenance injections. (ii) Fifteen patients were treated with standardized timothy grass pollen-allergen oral vaccine. In the first session of a SLIT protocol without up-dosing, each patient received 2.4 ml of sublingual vaccine containing about 57 microg of Phl p 5 and received a maintenance dose of 24 microg of Phl p 5 once a day for 120 days. (iii) Fourteen subjects were treated with a standardized allergen extract containing 5-grass pollen mixture; a SLIT protocol was performed without up-dosing, administering a dose corresponding to about 10.0 microg/ml grass-pollen Group 5 and a maintenance dose of 4 microg of grass-pollen Group 5 once a day for 135 days. Patients' sera were characterized in detail by determining IgG4 antibodies to rPhl p 1, 2, 5, 6, 7, 11, 12 and nPhl p 4 and eosinophil cationic protein before the start of immunotherapy and during the peak of pollen season.

RESULTS

No relevant systemic side effects were registered in patients treated with the modified cluster subcutaneous immunotherapy (SCIT) protocol and the two SLIT protocols without build-up phase. After SCIT all patients had high titres of serum allergen-specific IgG4 antibodies. High-dose SLIT led to an IgG4 increase comprising 25% of the SCIT level, while low-dose SLIT increased to 4% of the SCIT. Furthermore, the increase of specific IgG antibodies corresponds to a decrease of serum ECP during allergen exposure.

CONCLUSIONS

These preliminary data seem to indicate that: (i) pre-seasonal high-dose SLIT protocol without build-up phase is safe and well-tolerated by allergic patients; (ii) compared to IgG4 levels induced by SCIT, only a high-dose SLIT regimen results in an appreciable serum specific IgG4 increase.

New insights in sublingual immunotherapy

Sublingual immunotherapy (SLIT) is accepted in the official documents and is currently used in many European countries. In recent years, new clinical data on efficacy and safety have been published, including meta-analyses in adults and children and surveys of safety in children younger than age 5 years. Moreover, it has been shown that, similar to the injection route, SLIT can prevent the onset of new sensitizations and the onset of asthma. Additionally, the mechanisms of action are beginning to be systematically studied. Some points need further investigation, such as the effect in asthma, the mechanisms of action, and the optimal dose to be administered.

Immunological mechanisms of allergen-specific immunotherapy

Allergen-specific immunotherapy has been carried out for almost a century and remains one of the few antigen-specific treatments for inflammatory diseases. The mechanisms by which allergen-specific immunotherapy exerts its effects include the modulation of both T-cell and B-cell responses to allergen. There is a strong rationale for improving the efficacy of allergen-specific immunotherapy by reducing the incidence and severity of adverse reactions mediated by IgE. Approaches to address this problem include the use of modified allergens, novel adjuvants and alternative routes of administration. This article reviews the development of allergen-specific immunotherapy, our current understanding of its mechanisms of action and its future prospects.

Clinical efficacy and safety of sublingual immunotherapy with tree pollen extract in children

BACKGROUND

Subcutaneous immunotherapy has been the principal approach of immunotherapy in the treatment of allergic diseases. Several clinical studies with birch, alder or hazel pollen extract conducted as subcutaneous immunotherapy have been published suggesting a well-tolerated and clinically effective treatment. Only a few clinical studies of sublingual immunotherapy (SLIT) with these allergens have been published. This study investigated the clinical efficacy, safety and dose-response relationship of SLIT in children suffering from rhinoconjunctivitis with/without asthma.

METHODS

Eighty-eight children (5-15 years) with a history of tree pollen-induced allergic rhinoconjunctivitis with/without seasonal asthma for >or=2 years were included. Allergy to tree pollen was confirmed by positive skin-prick test, positive specific IgE and positive conjunctival provocation test. The extract used was a glycerinated mixture of Betula verrucosa, Corylus avellana and Alnus glutinosa 100,000 SQ-U/ml. Children were randomized into three groups receiving SLIT 5 days a week for up to 18 months; dose group 1: accumulated weekly dose of 24,000 SQ-U; dose group 2: accumulated weekly dose of 200,000 SQ-U; and placebo.

RESULTS

In the birch pollen season, dose group 2 showed a significant reduction of symptom (P = 0.01) and medication scores (P = 0.04) compared with placebo. Dose group 1 showed a significant reduction of symptom scores (P = 0.03). There were no statistical differences between dose groups 1 and 2. All children tolerated the treatment well.

CONCLUSION

SLIT with tree pollen extract provided dose-dependent benefits in tree pollen-allergic children in terms of significantly reduced symptoms and medication use. The treatment was well tolerated.

Sublingual immunotherapy of allergic diseases

The only disease-modifying treatment that is available for allergic patients is allergen-specific immunotherapy. Two competing application forms are used: subcutaneous immunotherapy, which has been used for > 90 years, and a relatively new immunotherapy where the allergen is applied sublingually. Numerous studies have shown efficacy for subcutaneous immunotherapy and have identified possible mechanisms that are responsible for the observed reduction in allergic responses. In contrast, the efficacy of sublingual immunotherapy has not been documented to the same degree and the responsible immunological mechanisms have not yet been clearly defined. This review focuses on the published clinical and experimental data on sublingual immunotherapy and points at possible mechanisms of how sublingual immunotherapy may differ from subcutaneous immunotherapy in its mode of action, and also discusses the potential advantages and pit falls of both therapies.

Sublingual immunotherapy with Dermatophagoides monomeric allergoid down-regulates allergen-specific immunoglobulin E and increases both interferon-gamma- and interleukin-10-production

BACKGROUND

The clinical efficacy and safety of sublingual immunotherapy (SLIT) for aeroallergens has been demonstrated in several trials, whereas the immunological changes induced by this treatment, which may account for the clinical improvement, are still unclear.

OBJECTIVE

To investigate the effects of a successful SLIT on the in vitro allergen-driven T cell response and cytokine secretion as well as on the serum levels of chemokines and of IgE, IgG1 and IgG4 antibodies (Abs).

MATERIALS AND METHODS

Twenty-five Dermatophagoides pteronyssinus (Dp)-sensitive patients with perennial rhinitic and/or rhinitic and asthmatic symptoms were randomized into two groups (13 untreated (UT) and 12 SLIT-treated) for a 1 year and half study. The proliferative response of peripheral blood mononuclear cell (PBMC) to purified Der p1 allergen, their cytokines (IFN-gamma, IL-4, IL-10 and TGF-beta) production and serum levels of chemokines associated with T helper type 1 (Th1) (CXCL10) or T helper type 2 (Th2) (CCL22) responses and of Dp-specific IgE, IgG1 and IgG4 Abs were evaluated before and after 6 months of treatment.

RESULTS

SLIT induced a significant reduction of symptom medication scores after 6, 12 and 18 months of treatment in comparison with UT patients. SLIT-treated patients showed a significant decrease in serum levels of DP-specific IgE Abs, whereas total IgE, and specific IgG1 and IgG4 Abs remained unchanged. The proliferative response of allergen-specific T cells to Der p1 in vitro after 6 months of treatment was reduced, while no effect was observed on T cell proliferation to recall antigen (streptokinase). Moreover, Der p1-driven IFN-gamma and IL-10 were significantly increased in culture supernatants of PBMC from 6 month-treated patients in comparison with those detected at the beginning of therapy.

CONCLUSIONS

These data suggest that the allergen-driven enhancement of IL-10- and IFN-gamma-producing T cells precedes and associates with SLIT-induced down-regulation of specific IgE, thus providing a rationale to explain the clinical benefit of SLIT in allergic patients.

Novel ways for immune intervention in immunotherapy: mucosal allergy vaccines

Allergen-specific immunotherapy is currently the only curative treatment for allergy. Subcutaneous immunotherapy (SCIT) has been successfully used to treat patients who are allergic to insect venom, house dust mites, or tree or grass pollens. In the context of potentially severe, albeit infrequent, side effects associated with SCIT, mucosal routes of administration are being investigated to conduct allergenic desensitization. This article reviews recent developments in the field of nasal, oral, and sublingual immunotherapy as they relate to safety, clinical efficacy, and immune mechanisms of action. Implications for the design and development of improved allergy vaccines that could be used through such nonparenteral routes are discussed. Specifically, allergen presentation platforms and adjuvants facilitating the targeting of immune cells at mucosal surfaces to promote tolerance induction are reviewed.

Sublingual immunotherapy: a comprehensive review

Sublingual immunotherapy (SLIT) has been used with increasing frequency in Europe and is viewed with increasing interest by allergists in the United States. To address this interest, a Joint Task Force of the American College of Allergy, Asthma and Immunology and the American Academy of Allergy, Asthma and Immunology's Immunotherapy and Allergy Diagnostic Committees reviewed the available literature on SLIT and prepared this report. The task force concluded that despite clear evidence that SLIT is an effective treatment, many questions remained unanswered, including effective dose, treatment schedules, and overall duration of treatment. Until these have been determined, an assessment of the cost/benefit ratio of the treatment cannot be made. SLIT does appear to be associated with few serious side effects, but it has not been administered in high-risk asthmatic patients, nor in the studies reviewed has it been administered as a mixture of non-cross-reacting allergens. Furthermore, there is currently no allergy extract approved for this use in the United States, nor is there a Current Procedural Terminology code for billing purposes. All of these factors should be given careful consideration by anyone contemplating initiating SLIT treatment for their allergic patients.

Absence of systemic immunologic changes during dose build-up phase and early maintenance period in effective specific sublingual immunotherapy in children

BACKGROUND

Sublingual immunotherapy (SLIT) has been reported to be a safe treatment for inhalant allergies in children. Yet the immunologic mechanisms resulting in clinical improvement are poorly understood.

OBJECTIVE

To identify early systemic immunologic changes during the first 8 weeks of clinically effective SLIT to grass pollen, tree pollen or house dust mite in paediatric patients with allergic rhinoconjunctivitis and/or asthma.

METHODS

Peripheral blood mononuclear cells and plasma samples of 13 children with reduced symptoms after 1 year of SLIT were obtained before therapy and at 2 and 8 weeks after the initiation of SLIT. Allergen-specific lymphocyte proliferation assays were performed, and allergen-induced cytokine production (IL-2, IL-4, IL-10, IFN-gamma, and TGF-beta(1)) was measured by ELISA and flow cytometry. Allergen-specific IgE, IgG1, IgG4, and IgA levels in plasma samples were determined in ELISA.

RESULTS

During the first 8 weeks of successful SLIT, allergen-specific lymphoproliferation (n=13) as well as levels of allergen-specific intracellular (n=8) and secreted cytokines (n=9) did not change significantly. In addition, no alterations in levels of allergen-specific Igs (n=7) were observed.

CONCLUSION

We could not find any early systemic immunologic changes during the first 8 weeks of clinically effective SLIT to inhalant allergens in paediatric patients with allergic rhinoconjunctivitis and/or asthma.

Update on sublingual immunotherapy

OBJECTIVE

To obtain a current understanding of the mechanisms, clinical indications, efficacy, and safety of sublingual immunotherapy (SLIT) for the treatment of children and adults with allergic rhinitis, asthma, and allergic conjunctivitis.

METHODS

A MEDLINE and Index Medicus search for peer-reviewed articles on SLIT was performed.

RESULTS

Since the approval of SLIT by the World Health Organization in 1988, the efficacy and safety of SLIT have been confirmed in several new double-blind, placebo-controlled studies for monosensitized patients who are allergic to house dust mites, grass pollens, ragweed, and birch pollen. Documented immunologic responses to SLIT have included a decrease in serum eosinophilic cationic protein and interleukin 13 (IL-13) levels, an elevation in IL-12 levels, a reduction in late-phase responses, and increases in IgG4/IgE ratios. A Cochrane review of 22 studies confirmed the efficacy and safety of SLIT for patients with allergic rhinitis. A long-term asthma study showed sustained efficacy 5 years after discontinuing the vaccine. The safety of SLIT has been confirmed in postmarketing studies, and severe systemic adverse effects have never been reported. In view of its safety profile, SLIT is taken by the patient at home (away from specialized centers), and no specialized resuscitation facilities are required.

CONCLUSION

SLIT is a safe and effective therapeutic option for patients with allergic rhinitis and asthma. Because of its efficacy, safety, and ease of administration, it has been accepted in Europe, Southern Africa, Australasia, Southeast Asia, and the Middle East as a promising therapeutic option that can significantly alter the natural history of allergic disease without the risks of injection immunotherapy.

Mouse allergen-specific immunoglobulin G and immunoglobulin G4 and allergic symptoms in immunoglobulin E-sensitized laboratory animal workers

BACKGROUND

High levels of allergen-specific IgG have been associated with clinical efficacy in immunotherapy studies, but whether this antibody isotype is associated with clinical tolerance in the setting of environmental exposure remains unclear.

OBJECTIVE

To determine if mouse allergen-specific IgG (mIgG) and IgG4 (mIgG4) levels are associated with mouse-related symptoms among IgE-sensitized laboratory workers.

METHODS

Fifty-eight workers with either skin test or serologic evidence of IgE-mediated mouse sensitization were studied. Symptom data were obtained by a questionnaire. Serum levels of mouse-specific IgG, IgG4, and IgE were quantified by a solid-phase antigen-binding assay (IgG) and RAST (IgG4 and IgE), and the relationships between mouse-specific serologic responses and mouse-related symptoms were analysed.

RESULTS

Twenty-three (39.7%) participants reported mouse-related symptoms. Mouse-specific IgG and IgG4 levels were not associated with mouse-related symptoms among the study population as a whole. Among the 29 (50%) participants with detectable mouse-specific IgE (mIgE), higher mouse-specific IgG and IgG4 levels were associated with a decreased risk of symptoms, after adjusting for mIgE level (odds ratio (OR) 0.3, 95% confidence interval (CI): 0.1-1.4, and OR 0.3, 95% CI: 0.04-2.6, respectively). Higher levels of mIgG and mIgG4 remained associated with a decreased risk of symptoms after additional adjustment for sex and handling of mice (OR 0.1, 95% CI: 0.02-0.7, and OR 0.2, 95% CI: 0.02-2.1, respectively). Higher mIgG : IgE and mIgG4 : IgE ratios were also associated with a decreased risk of symptoms after adjusting for these confounders (OR 0.1, 95% CI: 0.02-0.7, and OR 0.2, 95% CI: 0.02-0.92, respectively).

CONCLUSION

Among workers with detectable mIgE, higher mIgG and mIgG4 levels are associated with a decreased risk of mouse-related symptoms. High serum levels of mIgG or mIgG4 may be markers for clinical tolerance among laboratory mouse workers with detectable mIgE, but these findings need to be confirmed in larger, prospective studies.

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.