Grass pollen immunotherapy for hayfever is associated with increases in local nasal but not peripheral Th1:Th2 cytokine ratios

T-cell responses induced by allergen-specific immunotherapy

Allergen-specific immunotherapy is recognized as a highly effective practice in the treatment of patients with severe allergic rhinitis and/or asthma and is recommended by World Health Organization as an integrated part of allergy management strategy. Several studies have shown that allergen-specific immunotherapy, based on the administration of increasing doses of allergen, achieves a hyposensitization and reduces both early and late responses occurring during the natural exposure to the allergen itself. This is the unique antigen-specific immunomodulatory treatment in current use for human diseases. Successful immunotherapy is associated with reductions in symptoms and medication scores and improved quality of life. After interruption it usually confers long-term remission of symptoms and prevents the onset of new sensitizations in children up to a number of years. Subcutaneous immunotherapy usually suppresses the allergen-induced late response in target organs, likely due to the reduction of the infiltration of T cells, eosinophils, basophils, mast cells and neutrophils. In addition to the reduction of cells of allergic inflammation, immunotherapy also decreases inflammatory mediators at the site of allergen exposure. This review provides an update on the immunological T cell responses induced by conventional subcutaneous and sublingual immunotherapy, and gives a unifying view to reconciling the old dualism between immunoredirecting and immunoregulating mechanisms.

[Allergen-specific Immunotherapy for children and adolescents - a review on available products in Austria]

A pediatric consensus report on allergen-specific immunotherapy for children and adolescents is presented for Austria. Products on the market in Austria are presented and categorised according to studies performed on the target population of children and adolescents, their effectiveness and indication. In general, more clinical studies on children and adolescents are mandatory for most of the available allergen-specific immunotherapeutics. In addition, the use of allergen-specific immunotherapy in general should be promoted as the exclusive treatment with long-lasting effects in type I allergies in particular in children.

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.

Biomarkers for allergen immunotherapy in cedar pollinosis

To initiate, monitor, and complete effective immunotherapy, biomarkers to predict and visualize the immune responses are needed. First, we need to identify the right candidate for immunotherapy. Secondly, the immune responses induced by immunotherapy should be monitored. For the first objective, analysis of polymorphisms of candidate genes may be helpful, but still be in development. Regarding biomarkers for immune responsese, there are numerous reports that evaluate immunotherapy-induced immune changes such as suppression of effector cells, deviation to Th1 cytokine production, and induction of regulatory T cells. No standardized methods, however, have been established. Among them, a functional assay of blocking IgG activity, the IgE-facilitated allergen binding assay, may be useful. We quantitated induced expression of an activation marker, CD203c, on basophils and found that the assay efficiently predicts sensitivity to particular allergen and severity of the allergen-induced symptoms. In patients who received rush immunotherapy for Japanese cedar pollinosis, reduction in CD203c expression after the therapy was observed, suggesting the utility of the test for monitoring immunotherapy.

Complementary roles for lipid and protein allergens in triggering innate and adaptive immune systems

BACKGROUND

Recent advances in allergy research mostly focussed on two major headings: improving protein allergen purification, which is aimed towards a better characterization of IgE- and T-cell reactive epitopes, and the potential new role for unconventional innate and regulatory T cells in controlling airway inflammation. These advancements could appear to be in conflict each other, as innate T cells have a poorly-defined antigen specificity that is often directed toward nonprotein substances, such as lipids.

METHOD

To reconcile these contrasting findings, the model of cypress pollinosis as paradigmatic for studying allergic diseases in adults is suggested.

RESULTS

The biochemical characterization of major native protein allergens from undenatured pollen grain demonstrated that the most relevant substance with IgE-binding activity is a glycohydrolase enzyme, which easily denaturizes in stored grains. Moreover, lipids from the pollen membrane are implicated in early pollen grain capture and recognition by CD1(+) dendritic cells (DC) and CD1-restricted T lymphocytes. These T cells display Th0/Th2 functional activity and are also able to produce regulatory cytokines, such as IL-10 and TGF-beta. CD1(+) immature DCs expand in the respiratory mucosa of allergic subjects and are able to process both proteins and lipids.

CONCLUSION

A final scenario may suggest that expansion and functional activation of CD1(+) DCs is a key step for mounting a Th0/Th2-deviated immune response, and that such innate response does not confer long-lasting protective immunity.

New visions in specific immunotherapy in children: an iPAC summary and future trends

Specific immunotherapy is indicated for confirmed immunoglobulin E-mediated airway diseases using standardized allergen products with documented clinical efficacy and safety. For decades the subcutaneous route of administration (SCIT) has been the gold standard. Recently, the sublingual immunotherapy (SLIT) has also been investigated in children. SCIT, especially with grass and birch pollens but also house dust mites, is an effective treatment in children with allergic rhinitis and asthma when a significant part of their symptoms are caused by these allergens. A long-term effect up to 12 yr after discontinuation of SCIT with timothy allergen has been shown. Efficacy and safety of SLIT in pollen allergic rhinoconjunctivitis have been demonstrated in adults. The evidence in children is a little less convincing, and more data is needed. The clinical relevance, long-term results and the size of the effect, as well as the dose, the treatment regimen and duration has not been sufficiently elaborated. It is demonstrated that SCIT has the potential for preventing the development of asthma in children with allergic rhinoconjunctivitis. Also one randomized study indicates a preventive effect of SLIT in children on the development of asthma. At present, there are no studies who clearly demonstrates either a long-term effect or a preventive effect on the development of asthma of SLIT in children. The areas with lack of evidence should be addressed in well performed prospective, randomized long-term studies both with SCIT and SLIT. This review was initiated by iPAC (international Pediatric Allergy and Asthma Consortium) and aims to review current knowledge related to specific immunotherapy in childhood, and to identify needs for future research in this field.

How strong is the evidence that immunotherapy in children prevents the progression of allergy and asthma?

PURPOSE OF REVIEW

The purpose of this review is to describe the scientific evidence that specific immunotherapy can prevent the development of asthma in patients suffering from rhinoconjunctivitis as well as reduce the number of new allergies developing.

RECENT FINDINGS

Proposed strategies for the prevention of the development of allergic rhinoconjunctivitis and asthma include allergen avoidance, pharmacological treatment (antihistamines and steroids) and specific immunotherapy. Long-term follow-up on immunotherapy studies demonstrates that specific immunotherapy for 3 years shows persistent long-term effects on clinical symptoms after termination of treatment and long-term, preventive effects on later development of asthma in children with seasonal rhinoconjunctivitis. It is so far the only treatment for allergic diseases that has been shown to be able to prevent worsening of disease and development of asthma. Also, specific immunotherapy seems to reduce the development of new allergic sensitivities as measured by the skin prick test as well as specific IgE measurements.

SUMMARY

Specific immunotherapy is the only treatment that interferes with the basic pathophysiological mechanisms of the allergic disease and thereby carries the potential for changes in the long-term prognosis of respiratory allergy. Specific immunotherapy should be recognized not only as first-line therapeutic treatment for allergic rhinoconjunctivitis, but also as secondary preventive treatment for respiratory allergic diseases.

The facilitated antigen binding (FAB) assay--a protocol to measure allergen-specific inhibitory antibody activity

Specific allergen immunotherapy is an effective treatment for IgE-mediated allergic disease and involves T- and B-cell mediated events. IgE receptors on the surface of antigen-presenting cells facilitate the presentation of allergens in the presence of specific IgE antibody resulting in T-cell activation. Interference with these IgE-dependent mechanisms by 'blocking' IgG antibodies may downregulate T-cell responses and manifest as a reduction in allergic responses in vivo. The vigor of proliferative responses by T-cell clones is representative of the binding of allergen-IgE complexes to B cells. Therefore, a simplified assay can be employed that measures the binding of allergen-IgE complexes to B cells instead of a more complex assay involving proliferative assays using antigen-specific T-cell clones. Allergen-IgE complexes can be easily detected by flow cytometry and this simplified technique is called the IgE-facilitated allergen binding (IgE-FAB) assay which is described in this chapter.

CD4+ T cell-specific deletion of IL-4 receptor alpha prevents ovalbumin-induced anaphylaxis by an IFN-gamma-dependent mechanism

IL-4Ralpha-mediated STAT6 activation serves an essential role in various animal models of allergy and asthma at both the sensitization and effector phases. IL-4 and IL-13 signaling via the IL-4Ralpha chain exacerbates murine anaphylaxis, but the cell-specific requirements for IL-4Ralpha expression are unclear. The purpose of this study was to elucidate the mechanisms of systemic anaphylaxis to OVA in gene-targeted mice with a deletion of the IL-4Ralpha chain in the macrophage/neutrophil or CD4+ T lymphocyte population. Results demonstrated that anaphylaxis in this model was entirely dependent upon the FcgammaRII/III and was associated with mast cell degranulation. Expression of the IL-4Ralpha on CD4+ T cells, but not macrophages or neutrophils, was critical for severe anaphylaxis, characterized by diarrhea, hypothermia, and death. Ab depletion experiments demonstrated that IFN-gamma protected against mortality and severe intestinal pathology despite the presence of Ag and specific Ab. This protection was associated with reduced levels of mast cell protease, a marker of mast cell degranulation, suggesting that IFN-gamma may inhibit mast cell degranulation in vivo. These data suggest that it may be possible to limit the severity of anaphylaxis using rational therapies designed to increase numbers of IFN-gamma-producing cells by targeting IL-4Ralpha signaling in CD4+ T lymphocytes.

Immunotherapy with allergen peptides

Specific allergen immunotherapy (SIT) is disease-modifying and efficacious. However, the use of whole allergen preparations is associated with frequent allergic adverse events during treatment. Many novel approaches are being designed to reduce the allergenicity of immunotherapy preparations whilst maintaining immunogenicity. One approach is the use of short synthetic peptides which representing dominant T cell epitopes of the allergen. Short peptides exhibit markedly reduced capacity to cross link IgE and activate mast cells and basophils, due to lack of tertiary structure. Murine pre-clinical studies have established the feasibility of this approach and clinical studies are currently in progress in both allergic and autoimmune diseases.

Immunology of anaphylaxis: lessons from murine models

The use of animal models is increasing, and mice are suitable animals to use in exploring systemic anaphylaxis based on the similarity between human and mouse immune systems. Two anaphylaxis pathways have been characterized in mice, which may help in understanding some of the discrepancies found in humans. In addition, cytokine studies are raising new concepts that may put together some of the puzzling mechanisms described in this disease. Finally, the study of the mechanisms that parasitic infections use to evade the human immune system and the scene in which a parasite induces clinical anaphylaxis are opening new insights in the immunology pathways and new strategies to fight against this exclusive disease.

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.

Defining the T cell antigen proteome of wasp venom

BACKGROUND

While modulation of T cell function is believed to be important in the successful acquisition of clinical tolerance during venom immunotherapy, little is known of the role of wasp venom specific T cell antigens.

OBJECTIVE

We sought comprehensively to characterize the T cell proteome for wasp venom to facilitate the future development of T cell-based immunotherapeutic approaches.

METHODS

Using peripheral blood mononuclear cells from wasp venom-allergic individuals and IL-4 ELISPOT analysis, we characterized T cell responses to whole venom and gel filtration/ion exchange-fractionated venom. Reactive fractions were purified and identified using highly sensitive electrospray ion-trap mass spectrometry.

RESULTS

Wasp venom-allergic individuals have detectable whole wasp venom-specific T cells directly ex vivo, which show rapid IL-4 effector function. T cell responses to gel filtration/ion exchange fractionated venom were dominated by responses to phospholipase A(1), hyaluronidase and antigen 5.

CONCLUSION

Although it is likely that there are many T cell antigens within wasp venom, the main responses are to proteins coincident with the known IgE-binding proteins.

Peptide immunotherapy for allergic diseases

Specific allergen immunotherapy has been widely practised for almost 100 years. Whilst this approach is disease-modifying and efficacious, the use of whole allergen preparations is associated with an unacceptably high prevalence of allergic adverse events during treatment. Many approaches to reduce the allergenicity of immunotherapy preparations whilst maintaining immunogenicity are under development. One such approach is the use of short synthetic peptides which represent major T-cell epitopes of the allergen. Major potential advantages of this approach include markedly reduced capacity to cross-link immunoglobulin-E and activate mast cells and basophils, and ease of manufacture and standardization. Promising results in preclinical studies have led to the translation of this approach to clinical studies in humans. Peptide immunotherapy is currently under development for allergic and autoimmune diseases.

Allergen injection immunotherapy for seasonal allergic rhinitis

BACKGROUND

Allergic rhinitis is the most common of the allergic diseases. Despite improved understanding of the pathophysiology of allergic rhinitis and advances in its pharmacological treatment, its prevalence has increased worldwide. For patients whose symptoms remain uncontrolled despite medical treatment, allergen injection immunotherapy is advised. An allergen-based treatment may reduce symptoms, the need for medication and modify the natural course of this disease.

OBJECTIVES

To evaluate the efficacy and safety of subcutaneous specific allergen immunotherapy, compared with placebo, for reducing symptoms and medication requirements in seasonal allergic rhinitis patients.

SEARCH STRATEGY

We searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 1 2006), MEDLINE (1950 to 2006), EMBASE (1974 to 2006), Pre-MEDLINE, KOREAMED, INDMED, LILACS, PAKMEDINET, Scisearch, mRCT and the National Research Register. The date of the last search was February 2006.

SELECTION CRITERIA

All studies identified by the searches were assessed to identify randomised controlled trials involving participants with symptoms of seasonal allergic rhinitis and proven allergen sensitivity, treated with subcutaneous allergen specific immunotherapy or corresponding placebo.

DATA COLLECTION AND ANALYSIS

Two independent authors identified all studies reporting double-blind, placebo controlled randomised trials of specific immunotherapy in patients with seasonal allergic rhinitis due to tree, grass or weed pollens. Two authors independently performed quality assessment of studies. Data from identified studies were abstracted onto a standard extraction sheet and subsequently entered into RevMan 4.2.8. Analysis was performed using the Standardised Mean Difference (SMD) method and a random-effects model; P values < 0.05 were considered statistically significant. The primary outcome measures were symptom scores, medication use, quality of life and adverse events.

MAIN RESULTS

We retrieved 1111 publications of which 51 satisfied our inclusion criteria. In total there were 2871 participants (1645 active, 1226 placebo), each receiving on average 18 injections. Duration of immunotherapy varied from three days to three years. Symptom score data from 15 trials were suitable for meta-analysis and showed an overall reduction in the immunotherapy group (SMD -0.73 (95% CI -0.97 to -0.50, P < 0.00001)). Medication score data from 13 trials showed an overall reduction in the immunotherapy group (SMD of -0.57 (95% CI -0.82 to -0.33, p<0.00001)). Clinical interpretation of the effect size is difficult. Adrenaline was given in 0.13% (19 of 14085 injections) of those on active treatment and in 0.01% (1 of 8278 injections) of the placebo group for treatment of adverse events. There were no fatalities.

AUTHORS' CONCLUSIONS

This review has shown that specific allergen injection immunotherapy in suitably selected patients with seasonal allergic rhinitis results in a significant reduction in symptom scores and medication use. Injection immunotherapy has a known and relatively low risk of severe adverse events. We found no long-term consequences from adverse events.

T lymphocytes expressing CCR3 are increased in allergic rhinitis compared with non-allergic controls and following allergen immunotherapy

BACKGROUND

In T cell-associated allergic inflammation, homing of T-helper 2 (Th2) effector cells to mucosal sites may be influenced by chemokine receptor expression. Previous studies have identified CCR3 and CCR4 as putative markers of Th2 cells and CCR5 and CXCR3 as markers of Th1 cells. The aim of this study was to assess differential chemokine receptor expression from symptomatic atopic grass pollen-sensitive subjects, compared with patients on high-dose allergen injection immunotherapy (IT) and healthy controls.

METHODS

We examined chemokine receptor expression (CCR1-7 and CXCR1-4) by flow cytometry of peripheral blood CD4+ and CD8+ T cells. We also depleted peripheral blood mononuclear cell (PBMC) populations of CCR3+ CD4+ cells by magnetic bead separation and cells were stimulated with grass pollen allergen for 6 days. Cytokine production was measured by enzyme-linked immunosorbent assay.

RESULTS

On freshly isolated PBMC, atopic individuals exhibited increased numbers of CCR3+ CD4+ cells compared with normal controls (P < 0.01). CCR3 expression in IT patients was reduced compared with matched atopic rhinitic controls (P < 0.05) and comparable with that observed in normal subjects. Depletion of CCR3+ CD4+ cells from allergen-stimulated PBMC cultures resulted in decreased interleukin (IL)-5 production compared with whole CD4+ populations (P < 0.05). Freshly isolated CCR3+ CD4+ cells have significantly higher intracellular IL-4 and lower IFN-gamma levels than CCR3- CD4+ cells. CD4+ T cells cultured from both peripheral cells and nasal biopsies demonstrated increased expression of CCR3 in the presence of IL-4 (P < 0.05).

CONCLUSION

CCR3+ CD4+ T cells are increased in allergic rhinitis, are reduced by allergen IT, have a Th2 phenotype and contribute to allergen-specific responses. Strategies against CCR3+ T cells may be effective in human allergic diseases.

Inhibition of IL-4/IL-13 does not enhance the efficacy of allergen immunotherapy in murine allergic airway inflammation

BACKGROUND

Successful allergen-specific immunotherapy (SIT) is associated with reduced Th2 cytokine production and the induction of IL-10-producing regulatory T cells. To improve treatment efficacy, we investigated the impact of an IL-4/IL-13 inhibitor during SIT.

METHODS

BALB/c mice were sensitized intranasally with ovalbumin (OVA) for 4 weeks. Subsequently, they were subjected to intranasal SIT, with OVA being administered at doses increasing from 1 mug to 1 mg over 3 weeks with or without an IL-4/IL-13 inhibitor. Serum OVA-specific antibodies were measured and bronchoalveolar lavage (BAL) fluids were checked for airway eosinophilia. Subsequently, lung tissue was examined histologically for inflammatory infiltrates. Cytokines were detected in BAL fluids and spleen cell cultures. Furthermore, CD4 CD25 double-positive spleen T cells were checked for intracellular IL-10 production by flow cytometry.

RESULTS

OVA sensitization resulted in persistent IgE synthesis and an eosinophil-rich allergic airway inflammation combined with increased IL-4 and IL-5 levels. Therefore, intranasal SIT could efficiently reverse the allergic phenotype. This was associated with decreased IL-4 and IL-5 levels, and increased IL-10 levels in BAL fluids as well as increased amounts of IL-10-producing CD25+ regulatory T cells. However, mice treated with the IL-4/IL-13 inhibitor during SIT did not produce significantly different results .

CONCLUSION

The use of an IL-4/IL-13 inhibitor as an adjuvant for SIT did not enhance anti-allergic effects. Thus, the observed reversal of Th2 responses during SIT may not be the keystone for successful therapy, but rather other factors, e.g. IL-10-producing regulatory T cells, may be crucial.

The IgE-facilitated allergen binding (FAB) assay: validation of a novel flow-cytometric based method for the detection of inhibitory antibody responses

The IgE-facilitated allergen binding (IgE-FAB) assay represents an in vitro model of facilitated allergen presentation. Allergen-IgE complexes are incubated with an EBV-transformed B cell line and complexes bound to CD23 on the surface of cells are detected by flow cytometry. The addition of serum from patients who have received allergen-specific immunotherapy has been shown previously to inhibit allergen-IgE complex binding to CD23 on B cells. In this study, we describe the characterisation and analytical validation of the grass pollen-specific IgE-FAB assay according to guidelines from the International Conference on Harmonisation. We established the intra- and inter-assay variability of IgE-FAB and have defined the detection limits of this assay. We have also demonstrated assay linearity and robustness. Using the results from a randomised double-blind placebo-controlled trial of grass pollen immunotherapy (n=33), we have defined the clinical sensitivity and specificity of the IgE-FAB assay using ROC curve analysis. In conclusion, the IgE-FAB assay is reproducible, robust, sensitive and a specific method suitable as a tool for monitoring inhibitory antibody function from patients receiving allergen immunotherapy.

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.

Mechanisms of allergen-specific immunotherapy: T-regulatory cells and more

Activation-induced cell death, anergy, or immune response modulation by regulatory T cells (Treg cells) are essential mechanisms of peripheral T-cell tolerance. Genetic predisposition and environmental instructions tune thresholds for the activation of T cells, other inflammatory cells, and resident tissue cells in allergic diseases. Skewing allergen-specific effector T cells to a Treg-cell phenotype seems to be crucial in maintaining a healthy immune response to allergens and successful allergen-specific immunotherapy. The Treg-cell response is characterized by an abolished allergen-specific T-cell proliferation and the suppressed secretion of T-helper 1- and T-helper 2-type cytokines. Suppressed proliferative and cytokine responses against allergens are induced by multiple suppressor factors, including cytokines such as interleukin-10 (IL-10) and transforming growth factor beta (TGF-beta), and cell surface molecules such as cytotoxic T-lymphocyte antigen-4, programmed death-1, and histamine receptor 2. The increased levels of IL-10 and TGF-beta produced by Treg cells potently suppress IgE production while simultaneously increasing the production of noninflammatory isotypes IgG4 and IgA, respectively. In addition, Treg cells directly or indirectly suppress the activity of effector cells of allergic inflammation, such as mast cells, basophils, and eosinophils. In conclusion, peripheral tolerance to allergens is controlled by multiple active suppression mechanisms on T cells, regulation of antibody isotypes, and suppression of effector cells. The application of current knowledge of Treg cells and related mechanisms of peripheral tolerance may soon lead to more rational and safer approaches to the prevention and cure of allergic disease.

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.

IgG-blocking antibodies inhibit IgE-mediated anaphylaxis in vivo through both antigen interception and Fc gamma RIIb cross-linking

Although it has long been hypothesized that allergen immunotherapy inhibits allergy, in part, by inducing production of IgG Abs that intercept allergens before they can cross-link mast cell Fc epsilonRI-associated IgE, this blocking Ab hypothesis has never been tested in vivo. In addition, evidence that IgG-allergen interactions can induce anaphylaxis by activating macrophages through Fc gammaRIII suggested that IgG Ab might not be able to inhibit IgE-mediated anaphylaxis without inducing anaphylaxis through this alternative pathway. We have studied active and passive immunization models in mice to approach these issues and to determine whether any inhibition of anaphylaxis observed was a direct effect of allergen neutralization by IgG Ab or an indirect effect of cross-linking of Fc epsilonRI to the inhibitory IgG receptor Fc gammaRIIb. We demonstrate that IgG Ab produced during the course of an immune response or administered passively can completely suppress IgE-mediated anaphylaxis; that these IgG blocking Abs inhibit IgE-mediated anaphylaxis without inducing Fc gammaRIII-mediated anaphylaxis only when IgG Ab concentration is high and challenge allergen dose is low; that allergen epitope density correlates inversely with the allergen dose required to induce both IgE- and Fc gammaRIII-mediated anaphylaxis; and that both allergen interception and Fc gammaRIIb-dependent inhibition contribute to in vivo blocking Ab activity.

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.

Cytokine gene transcription in feline nasal tissue with histologic evidence of inflammation

OBJECTIVE

To correlate gene transcription of cytokines and chemokines with histologic inflammation in nasal biopsy specimens of cats.

ANIMALS

25 study cats and 4 specific pathogen-free cats.

PROCEDURE

One nasal biopsy specimen from each cat was submitted for routine histologic evaluation; a second was submitted for evaluation by use of a quantitative real-time polymerase chain reaction analysis with a fluorogenic probe (ie, TaqMan) for detection of cytokines and chemokines (interleukin [IL]-4, IL-5, IL-6, IL-10, IL-12 p40, IL-16, IL-18, interferon [IFN]I-gamma, tumor necrosis factor [TNF]-alpha, and the regulated on activation normal T cell expressed and secreted [RANTES] protein). Specimens were grouped histologically by degree of inflammation (none, mild, moderate, or severe). Linearized TaqMan signals for each gene were compared among histologic groups.

RESULTS

Nasal biopsy specimens from specific pathogen-free cats were histologically normal, and cytokine transcription was low in these samples. As nasal inflammation in study cats worsened from absent (n = 3) to mild (4) to moderate (8) or severe (10), progressively and significantly increasing transcription of IL-6, IL-10, IL-12 p40, IFN-gamma, TNF-alpha, and the RANTES protein was detected. Transcription of IL-4, IL-5, IL-16, and IL-18 did not correlate with worsened histologic inflammation.

CONCLUSIONS AND CLINICAL RELEVANCE

Transcription of specific cytokines and chemokines in nasal tissue of cats progressively increased with severity of histologic evidence of inflammation, and IL-6, IL-10, IL-12 p40, IFN-gamma, TNF-alpha, and the RANTES protein were markers of inflammation. Our data suggest that the nasal cavity of cats is biased toward a Th1 cytokine profile that is augmented by inflammation.

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.

Peptide-based therapeutic vaccines for allergic and autoimmune diseases

Allergic and autoimmune diseases are forms of immune hypersensitivity that increasingly cause chronic ill health. Most current therapies treat symptoms rather than addressing underlying immunological mechanisms. The ability to modify antigen-specific pathogenic responses by therapeutic vaccination offers the prospect of targeted therapy resulting in long-term clinical improvement without nonspecific immune suppression. Examples of specific immune modulation can be found in nature and in established forms of immune desensitization. Understanding and exploiting common mechanisms such as the ability to induce antigen-specific regulatory cells should allow the development of effective therapeutic strategies for both forms of immunopathology. Targeting pathogenic T cells using vaccines consisting of synthetic peptides representing T cell epitopes is one such strategy that is currently being evaluated with encouraging results. Future challenges in the development of therapeutic vaccines include selection of appropriate antigens and peptides, optimization of peptide dose and route of administration and identifying strategies to induce bystander suppression.

Immunotherapy in the age of anti-IgE

Recent results of allergen immunotherapy research have continued to validate efficacy and have also demonstrated a truly preventive aspect for this treatment. This review summarizes the basic principles of effective allergen immunotherapy and highlights some of the advances that have been published in the past year. These studies show that allergen immunotherapy, when done appropriately and properly, not only causes a decrease in symptoms and use of medication as well as an improved quality of life, but that the progression of disease from allergic rhinitis to asthma is substantially decreased and the development of new allergies is diminished. In addition, laboratory studies continue to demonstrate significant changes in the immune system with a shift in the immune pathway from TH2 toward a TH1 response. The impact of anti-IgE as a therapeutic agent with allergen immunotherapy is also be reviewed.

Potential role of interleukin-10-secreting regulatory T cells in allergy and asthma

Allergic diseases are caused by aberrant T-helper-2 immune responses in susceptible individuals. Both naturally occurring CD4(+)CD25(+) regulatory T cells and inducible populations of antigen-specific interleukin-10-secreting regulatory T cells inhibit these inappropriate immune responses in experimental models. This article discusses the evidence that regulatory T-cell function might be impaired in allergic and asthmatic disease and that certain therapeutic regimens might function, at least in part, to promote regulatory T-cell generation. Current research strategies seek to exploit these observations to improve the generation of allergen-specific regulatory T-cell populations with the potential to provide the safe and long-term alleviation of disease symptoms.

T cell epitope immunotherapy induces a CD4+ T cell population with regulatory activity

BACKGROUND

Synthetic peptides, representing CD4(+) T cell epitopes, derived from the primary sequence of allergen molecules have been used to down-regulate allergic inflammation in sensitised individuals. Treatment of allergic diseases with peptides may offer substantial advantages over treatment with native allergen molecules because of the reduced potential for cross-linking IgE bound to the surface of mast cells and basophils.

METHODS AND FINDINGS

In this study we address the mechanism of action of peptide immunotherapy (PIT) in cat-allergic, asthmatic patients. Cell-division-tracking dyes, cell-mixing experiments, surface phenotyping, and cytokine measurements were used to investigate immunomodulation in peripheral blood mononuclear cells (PBMCs) after therapy. Proliferative responses of PBMCs to allergen extract were significantly reduced after PIT. This was associated with modified cytokine profiles generally characterised by an increase in interleukin-10 and a decrease in interleukin-5 production. CD4(+) cells isolated after PIT were able to actively suppress allergen-specific proliferative responses of pretreatment CD4(neg) PBMCs in co-culture experiments. PIT was associated with a significant increase in surface expression of CD5 on both CD4(+) and CD8(+) PBMCs.

CONCLUSION

This study provides evidence for the induction of a population of CD4(+) T cells with suppressor/regulatory activity following PIT. Furthermore, up-regulation of cell surface levels of CD5 may contribute to reduced reactivity to allergen.

Lack of detectable alterations in immune responses during sublingual immunotherapy in children with seasonal allergic rhinoconjunctivitis to grass pollen

BACKGROUND

Recent work indicates that subcutaneous specific immunotherapy induces specific T-cell anergy, a shift in the TH1/TH2 ratio, and antibody production in favor of IgG4. There are few data on sublingual immunotherapy (SLIT), especially in children.

METHODS

We assessed the proliferation of peripheral blood mononuclear cells ((3)H-thymidine incorporation) and secretion of interleukin (IL)-4, interferon (IFN)gamma and IL-5 (ELISA) after in vitro stimulation with allergen or phytohemagglutinin (PHA) in 29 children with allergic rhinoconjunctivitis receiving SLIT with grass pollen before, and after 1 and 2 years of treatment in a multicenter placebo-controlled study on the efficacy of the treatment. Further, non-specific intracellular production of IL-4, IL-13, IFNgamma, IL-2, IL-10 and IL-5 (FACS) and serum total and specific IgE and IgG4 (ELISA) were analyzed.

RESULTS

Proliferation and IL-4 and IL-5 secretion after stimulation with allergen or PHA did not differ between the groups. In addition, we observed no effect of SLIT on intracellular cytokine production. IFNgamma secretion after allergen coculture was comparable between the groups. Following PHA stimulation, IFNgamma secretion was significantly higher in the SLIT group after 1 year, and a trend was observable already before and after 2 years of treatment, probably due to the inhomogeneity in the groups despite randomization (for age and asthma). No significant changes were observed for sIgE/sIgG4 ratios over time either in or between the groups.

CONCLUSION

During 2 years of SLIT in children with a positive effect on rescue medication use, we observed no significant effects on in vitro T-cell immune responses or immunoglobulins. So far, pediatric studies demonstrating stable effects of SLIT on such reactions are missing, probably due to limited effects of SLIT on systemic immunologic reactions.

Induction of T 'regulatory' cells by standardized house dust mite immunotherapy: an increase in CD4+ CD25+ interleukin-10+ T cells expressing peripheral tissue trafficking markers

BACKGROUND

Clinically effective subcutaneous allergen-specific immunotherapy (SIT) is associated with altered circulating T cell cytokine production and altered local cytokine responses with increased IL-10 following allergen challenge in target organs.

OBJECTIVE

This study aimed to elucidate mechanisms for these T cell changes, by examining surface expression of markers for peripheral tissue trafficking on circulating cytokine-positive T cells following standardized house dust mite- (HDM-) SIT.

METHODS

A randomized conventional HDM immunotherapy study was performed on a panel of 12 HDM-allergic subjects. Nine subjects received treatment with conventional HDM immunotherapy using a standardized extract and three subjects were treated by standard pharmacotherapy alone. Symptom and medication scores and allergen-induced cutaneous late-phase responses were assessed before and 9 months after institution of therapy. Before and at 3 and 9 months of SIT, peripheral blood mononuclear cells were cultured for 14 days with HDM extract and CD4+ and CD8+ T cell expression of CD62L, CD49d and CCR5 and production of IL-10, IFN-gamma and IL-4 were analysed by flow cytometry. Allergen-specific T cell proliferation was assessed by 3H-thymidine incorporation.

RESULTS

At 9 months, all SIT-treated patients showed reduced symptom scores and late-phase cutaneous responses to HDM compared with baseline levels. The proportions of CD4+ T cells which were IL-10+ were increased (P < 0.01), and the proportions of CD4+ and CD8+ T cells which were IL-4+ decreased (P < 0.05) compared with baseline. CD4+ and CD8+ T cell IFN-gamma production, expression of surface markers for peripheral tissue trafficking and allergen-specific proliferation remained unchanged during SIT treatment. However, increased proportions of CD4+CD62L(-), CD4+CD49d(hi), CD4+CCR5+ T cells expressing IL-10 were detected at 9 months of SIT compared with baseline (P < 0.05). IL-10 staining co-localized with CD4+CD25+ T cells.

CONCLUSION

Clinically effective subcutaneous immunotherapy with a standardized HDM Dermatophagoides pteronyssinus preparation results in decreased numbers of IL-4+ T cells and expansion of CD4+IL-10+ T cells expressing a peripheral tissue trafficking phenotype. The co-localization of IL-10+ staining to CD4+CD25+ T cells is consistent with the induction of a T regulatory cell population by SIT.

Tregs and allergic disease

Allergic diseases such as asthma, rhinitis, and eczema are increasing in prevalence and affect up to 15% of populations in Westernized countries. The description of Tregs as T cells that prevent development of autoimmune disease led to considerable interest in whether these Tregs were also normally involved in prevention of sensitization to allergens and whether it might be possible to manipulate Tregs for the therapy of allergic disease. Current data suggest that Th2 responses to allergens are normally suppressed by both CD4+CD25+ Tregs and IL-10 Tregs. Furthermore, suppression by these subsets is decreased in allergic individuals. In animal models, Tregs could be induced by high- or low-dose inhaled antigen, and prior induction of such Tregs prevented subsequent development of allergen sensitization and airway inflammation in inhaled challenge models. For many years, allergen-injection immunotherapy has been used for the therapy of allergic disease, and this treatment may induce IL-10 Tregs, leading to both suppression of Th2 responses and a switch from IgE to IgG4 antibody production. Improvements in allergen immunotherapy, such as peptide therapy, and greater understanding of the biology of Tregs hold great promise for the treatment and prevention of allergic disease.

Increased allergen concentration enhances IFN-gamma production by allergic donor T cells expressing a peripheral tissue trafficking phenotype

BACKGROUND

Clinically effective allergen-specific immunotherapy correlates with decreased circulating allergen-specific IL-4+ T cells but increased IFN-gamma+ cells at sites of allergen challenge. Whether immunotherapy promotes trafficking of IFN-gamma+ T cells to peripheral tissues is unknown. As aeroallergen is administered at higher concentrations during immunotherapy than those encountered naturally, the effect of allergen concentration on adhesion molecule (CD62L and CD49d) and chemokine receptor (CCR3 and CCR5) expression by peripheral-blood T cells was analysed in parallel with cytokine production.

METHODS

House dust mite-allergic donor peripheral blood mononuclear cells were cultured for 14 days with different allergen concentrations. Cytokine profiles of were analysed by flow cytometry.

RESULTS

Cultures stimulated with 100 microg/ml house dust mite extract compared with 1 microg/ml had increased proportions and numbers of CD62Llo, CD49dhi or CCR5+ T cells expressing IFN-gamma. CCR3-positive CD4+ and CD8+ T cell numbers were very low and did not differ between cultures. In contrast the proportions of 'peripheral tissue trafficking' CD4+ T cells expressing IL-4 were decreased in cultures stimulated with high in comparison with low allergen concentration.

CONCLUSION

These results indicate the importance of achieving high allergen doses during immunotherapy to promote IFN-gamma production and expression of a 'peripheral tissue trafficking' phenotype by allergen-specific CD4+ and CD8+ T cells. The net change in cytokine milieu at sites of allergen encounter would then down-regulate clinical manifestations of allergic disease.

Adjuvants for allergen immunotherapy: experimental results and clinical perspectives

PURPOSE OF REVIEW

Inclusion of adjuvants in immunotherapy vaccines are important to enhance immune responses to allergens. This article will cover the recent advances in adjuvant formulations described in published articles primarily over the past 2 years.

RECENT FINDINGS

Traditionally, allergen immunotherapy preparations utilize aluminium hydroxide as an adjuvant. These have generally proved efficacious and have a good safety profile. However, recent advances in the understanding of immunological mechanisms underlying immunotherapy and in the design of new adjuvants may allow a more rational approach to adjuvant use. One approach is to use adjuvants such as immunostimulatory sequences or monophosphoryl lipid A, which can deviate allergy-associated Th2 immune responses towards a Th1 phenotype. Both of these adjuvants have been used in pilot controlled clinical trials which have demonstrated clinical efficacy and the induction of protective IgG antibodies. Other approaches to improve immunotherapy vaccines include microencapsulation of allergen to allow delivery of the allergen directly to the gut in order to induce immunological tolerance and vaccination with heat-killed mycobacteria.

SUMMARY

There is great interest in newly designed adjuvants to improve the efficacy and safety of allergen immunotherapy. A better understanding of immunological mechanisms and further clinical trials utilizing new adjuvants are needed.

Tregs and allergic disease

Allergic diseases such as asthma, rhinitis, and eczema are increasing in prevalence and affect up to 15% of populations in Westernized countries. The description of Tregs as T cells that prevent development of autoimmune disease led to considerable interest in whether these Tregs were also normally involved in prevention of sensitization to allergens and whether it might be possible to manipulate Tregs for the therapy of allergic disease. Current data suggest that Th2 responses to allergens are normally suppressed by both CD4+CD25+ Tregs and IL-10 Tregs. Furthermore, suppression by these subsets is decreased in allergic individuals. In animal models, Tregs could be induced by high- or low-dose inhaled antigen, and prior induction of such Tregs prevented subsequent development of allergen sensitization and airway inflammation in inhaled challenge models. For many years, allergen-injection immunotherapy has been used for the therapy of allergic disease, and this treatment may induce IL-10 Tregs, leading to both suppression of Th2 responses and a switch from IgE to IgG4 antibody production. Improvements in allergen immunotherapy, such as peptide therapy, and greater understanding of the biology of Tregs hold great promise for the treatment and prevention of allergic disease.

Allergy Vaccine Engineering: Epitope Modulation of Recombinant Bet v 1 Reduces IgE Binding but Retains Protein Folding Pattern for Induction of Protective Blocking-Antibody Responses

Human type 1 immediate allergic response symptoms are caused by mediator release from basophils and mast cells. This event is triggered by allergens aggregating preformed IgE Abs bound to the high-affinity receptor (FcepsilonRI) on these cells. Thus, the allergen/IgE interaction is crucial for the cascade leading to the allergic and anaphylactic response. Two genetically engineered forms of the white birch pollen major allergen Bet v 1 with point mutations directed at molecular surfaces have been characterized. Four and nine point mutations led to a significant reduction of the binding to human serum IgE, suggesting a mutation-induced distortion of IgE-binding B cell epitopes. In addition, the mutated allergens showed a decrease in anaphylactic potential, because histamine release from human basophils was significantly reduced. Retained alpha-carbon backbone folding pattern of the mutated allergens was indicated by x-ray diffraction analysis and circular dichroism spectroscopy. The rBet v 1 mutants were able to induce proliferation of T cell lines derived from birch pollen allergic patients. The stimulation indices were similar to the indices of nonmutated rBet v 1 and natural Bet v 1 purified from birch pollen. The ability of anti-rBet v 1 mutant specific mouse IgG serum to block binding of human serum IgE to rBet v 1 demonstrates that the engineered rBet v 1 mutants are able to induce Abs reactive with nonmodified Bet v 1. rBet v 1 mutants may constitute vaccine candidates with improved efficacy/safety profiles for safer allergy vaccination.

Is immunotherapy effective in allergic disease?

PURPOSE OF REVIEW

The purpose of this review is to summarize the basic principles of effective immunotherapy, and to highlight some of the advances that have been published in the past year.

RECENT FINDINGS

Recent findings show that immunotherapy, when performed appropriately and properly, not only causes a decrease in symptoms, use of medication and an improved quality of life, but also that the shift from allergic rhinitis to asthma is substantially decreased and the development of new allergies is diminished. In addition, laboratory studies continue to demonstrate significant changes in the immune system moving the patient towards a non-allergic immune function T helper type 2 cell to T helper type 1 cell shift.

SUMMARY

In summary, recent research clearly continues to demonstrate the efficacy of immunotherapy not only as a therapeutic agent but as a preventive one as well.

Immunotherapy in children

PURPOSE OF REVIEW

Specific allergen immunotherapy although being performed for almost 100 years, is still being addressed in clinical trials. In children the sublingual allergen application has gained considerable interest.

RECENT FINDINGS

Controlled long-term trials suggest that specific allergen immunotherapy has the capacity to modify the natural history of allergic airway disease by reducing the incidence of new sensitivities non-specifically, reducing allergic symptoms years after discontinuation and preventing the incidence of asthma. The current evidence on sublingual immunotherapy is not sufficient to recommend this mode of treatment in clinical practice yet.

SUMMARY

Specific allergen immunotherapy should be considered in children in whom IgE-mediated allergic symptoms cannot be adequately controlled by symptomatic treatment.

Cytokine expression in allergic inflammation: systematic review of in vivo challenge studies

BACKGROUND

Allergic inflammatory responses are driven by cells of the immune system that rely on cytokines to regulate the activity of other immune and structural cells.

OBJECTIVE

To review published studies to (1) identify cytokines consistently increased after allergen challenge in atopic patients and (2) investigate temporal variation in cytokine expression.

METHODS

A PUBMED systematic search was used to extract data from studies involving analysis of cytokine expression in fluids or biopsies following in vivo allergen challenge in atopic patients.

RESULTS

Data were extracted from 82 studies. There were no consistent reports of cytokine protein increase in fluids of patients at 0-1 h after challenge. At 4-12 h, the chemokines eotaxin, macrophage inflammatory protein-1alpha, RANTES (regulated on activation normal T cell expressed and secreted) and interleukin (IL)-8 have all been consistently reported to be up-regulated. At 18-24 h after challenge, the lymphokines IL-4, IL-5 and IL-13, as well as the pro-inflammatory cytokines granulocyte-macrophage colony-stimulating factor, tumour necrosis factor-alpha and IL-6 are consistently increased when compared with the respective control value. There were no reports of up-regulation in interferon-gamma protein and mRNA and in IL-2 mRNA.

CONCLUSION

The expression of granulocyte-macrophage colony-stimulating factor is consistently increased in tissues at 4-12 h after challenge. The influence of this cytokine on antigen capture and presentation by dendritic cells should be further investigated. Additionally, allergen challenge studies are needed that investigate the expression of macrophage-derived chemokine and thymus-regulated and activation-regulated chemokine in tissues of atopic patients. Blocking the effects of these lymphocyte-specific chemokines might provide new therapeutic approaches for the control of allergic inflammation.

Increased expression of allergen-induced in vitro interleukin-10 and interleukin-18 mRNA in peripheral blood mononuclear cells of allergic rhinitis patients after specific immunotherapy

BACKGROUND

During specific pollen immunotherapy (SIT) there is a local mucosal shift from Th2- to Th1- type cytokine predominance, with IL-12 having a major role in this shift. IL-10-induced tolerance is supposed to be a key phenomenon in venom immunotherapy (VIT). However, the role of Th1-promoting cytokines, on the one hand, and the role of regulatory cytokines, on the other hand, have not been studied in parallel during SIT.

OBJECTIVE

This study was undertaken to analyse the allergen-induced in vitro mRNA expression of Th1-type effector cytokine IL-18 and regulatory cytokines IL-10 and TGF-beta during SIT in peripheral blood mononuclear cells (PBMC) of allergic rhinitis (AR) patients.

METHODS

Thirty patients with AR undergoing pollen SIT and 10 patients with AR who were not treated with SIT were included in the study. The symptoms and medications were registered post-seasonally before the beginning of SIT and after 1 year of therapy. PBMC samples were collected and stimulated with pollen allergen extract prior to the treatment, at the maintenance phase in 12 patients and after 1 year of the treatment. The cytokine mRNA expression was assessed using kinetic real-time RT-PCR (TaqMan).

RESULTS

There was a clear increase in the treated AR patients, in comparison with untreated AR patients, in the expression of both IL-10 (mean change from baseline (SEM): 3.1 (0.8) vs. -0.3 (0.3), P<0.002, Mann-Whitney U-test) and IL-18 (2.7 (0.9) vs. -0.2 (0.6), P<0.03) mRNA after 1 year. The clearest increase in IL-10 mRNA expression was seen in patients who did not benefit at all (6.0 (2.3), P<0.001 vs. untreated) and the least increase in patients that had the greatest reduction of symptoms (0.8 (0.6), n.s. vs. untreated) at 1 year. The clearest increase in IL-18 mRNA expression was seen in patients with moderate outcome (3.4 (1.6), P<0.04 vs. untreated). In intermediate samples, taken when the maintenance dose was reached, the peak expression of allergen-induced IL-10 mRNA was associated with the most favourable outcome of SIT (P=0.01, Fisher exact test). A similar trend was seen in IL-18 mRNA expression.

CONCLUSIONS

The results suggest that an early and transient increase in allergen-specific IL-10 and IL-18 mRNA expression in PBMC is essential for the therapeutic outcome after 1 year of SIT.

A Role for IL-10-Mediated HLA-DR7-Restricted T Cell-Dependent Events in Development of the Modified Th2 Response to Cat Allergen

Although high dose exposure to inhaled cat allergen (Fel d 1) can cause a form of tolerance (modified Th2 response), the T cell mechanism for this phenomenon has not been studied. T cell responses to Fel d 1 were characterized in both allergic (IgE(pos)) and modified Th2 (IgE(neg)IgG(pos)) responders as well as serum Ab-negative controls (IgE(neg)IgG(neg)). Fel d 1 stimulated high levels of IL-10 in PBMC cultures from all individuals, with evidence of Th2 and Th1 cytokine skewing in allergic and control subjects, respectively. Using overlapping peptides, epitopes at the N terminus of Fel d 1 chain 2 were shown to stimulate strong T cell proliferation and to preferentially induce IL-10 (peptide 2:1 (P2:1)) or IFN-gamma (P2:2) regardless of the allergic status of the donor. Injection of cat extract during conventional immunotherapy stimulated expansion of IL-10- and IFN-gamma-producing chain 2 epitope-specific T cells along with increased Fel d 1-specific serum IgG and IgG4 Ab. Six of 12 modified responders expressed the major HLA-DRB1 allele, *0701, and both P2:1 and P2:2 were predicted ligands for this allele. Cultures from DR7-positive modified responders produced the highest levels of IL-10 to P2:1 in addition to other major and minor epitopes within chains 1 and 2. In the presence of anti-IL-10 mAb, both T cell proliferation and IFN-gamma production were enhanced in a Fel d 1- and epitope-specific manner. We conclude that IL-10-producing T cells specific for chain 2 epitopes are relevant to tolerance induction, and that DR7-restricted recognition of these epitopes favors a modified Th2 response.

Grass Pollen Immunotherapy Induces Mucosal and Peripheral IL-10 Responses and Blocking IgG Activity

T regulatory cells and IL-10 have been implicated in the mechanism of immunotherapy in patients with systemic anaphylaxis following bee stings. We studied the role of IL-10 in the induction of clinical, cellular, and humoral tolerance during immunotherapy for local mucosal allergy in subjects with seasonal pollinosis. Local and systemic IL-10 responses and serum Ab concentrations were measured before/after a double-blind trial of grass pollen (Phleum pratense, Phl P) immunotherapy. We observed local increases in IL-10 mRNA-positive cells in the nasal mucosa after 2 years of immunotherapy, but only during the pollen season. IL-10 protein-positive cells were also increased and correlated with IL-10 mRNA(+) cells. These changes were not observed in placebo-treated subjects or in healthy controls. Fifteen and 35% of IL-10 mRNA signals were colocalized to CD3(+) T cells and CD68(+) macrophages, respectively, whereas only 1-2% of total CD3(+) cells and 4% of macrophages expressed IL-10. Following immunotherapy, peripheral T cells cultured in the presence of grass pollen extract also produced IL-10. Immunotherapy resulted in blunting of seasonal increases in serum allergen Phl p 5-specific IgE, 60- to 80-fold increases in Phl p 5-specific IgG, and 100-fold increases in Phl p 5-specific IgG4. Post-immunotherapy serum exhibited inhibitory activity, which coeluted with IgG4, and blocked IgE-facilitated binding of allergen-IgE complexes to B cells. Both the increases in IgG and the IgG "blocking" activity correlated with the patients' overall assessment of improvement. Thus, grass pollen immunotherapy may induce allergen-specific, IL-10-dependent "protective" IgG4 responses.

Mite antigens enhance ICAM-1 and induce VCAM-1 expression on human umbilical vein endothelium

Although sublingual allergen-specific immunotherapy has been proved to be effective in the treatment of allergic diseases, controversy surrounds the means by which such a local therapy can induce systemic immunological changes. Adhesion molecules are critical in the regulation of leukocyte traffic. It has been hypothesized that allergenic extract, administered locally, may induce an up-regulation of the mucosal vessel vascular adhesion molecules (CAMs) resulting in local recruitment of circulating inflammatory cells. In the present study we investigated whether the mite antigens, Der p1 and Der p2, can modulate CAM expression of human endothelial cells (HEC). To do this, slices of whole human umbilical cord vein underwent short-term (8 hours) cultures in the presence or absence of mite antigen (baseline, unstimulated controls). Cryostatic sections of the specimens were then evaluated immunohistochemically for expression of intercellular adhesion molecule (ICAM-1) and vascular cell adhesion molecule (VCAM-1) molecules. The results revealed that while Der p1 is capable of significantly up-regulating ICAM-1 and VCAM-1 on HEC, Der p2 antigen moderately up-regulates ICAM-1 expression but is ineffective in modulating VCAM-1. Although preliminary, these results clearly support the hypothesis that at least some of the effects of sublingual immunotherapy may derive from inflammatory cell recruitment at the site of allergen release.

In vitro allergen-induced mRNA expression of signaling lymphocytic activation molecule by PBMC of patients with allergic rhinitis is increased during specific pollen immunotherapy

BACKGROUND

Specific immunotherapy (SIT) acts by inducing a shift from T(H)2 to T(H)1 cell response on mucous membranes, reducing allergic inflammation. New genes expressed primarily in T(H)1-type cells have been found. Of these genes, signaling lymphocytic activation molecule (SLAM) promotes T-cell proliferation and IFN-gamma production. Nothing is known about its role in T(H)2-T(H)1 switch during SIT.

OBJECTIVE

We sought to analyze the mRNA expression of SLAM and other T(H)1-associated genes, interleukin-12 receptor beta2 (IL-12Rbeta2) and T-box expressed in T cells (T-bet), and compare them with the clinical outcome of the therapy.

METHODS

PBMC from 30 patients allergic to pollen undergoing SIT were collected during the therapy. Control PBMC were collected from 10 patients with allergic rhinitis not participating in SIT and from 10 nonallergic subjects. Cells were stimulated in vitro with pollen allergen extracts. SLAM, IL-12Rbeta2, and T-bet mRNA expressions were studied by real-time quantitative RT-PCR technique (Taqman). Symptom scoring and medication scoring were registered before commencement of SIT and after 1 year of the therapy.

RESULTS

Before the treatment, in vitro allergen-induced SLAM mRNA expression in PBMC was significantly lower in the patients with allergic rhinitis than in the healthy control subjects. After 1 year of the treatment, SLAM mRNA expression was increased in the patients undergoing SIT and was associated with IFN-gamma mRNA expression and inversely associated with the symptom improvement. At the maintenance dose, an increase in SLAM mRNA expression was associated with the clinical symptom improvement at 1 year. No changes were seen in IL-12Rbeta(2) or T-bet mRNA expressions.

CONCLUSIONS

SLAM mRNA expression in PBMC is modulated during the course of SIT, and an early and transient increase of SLAM mRNA expression is associated with clinical symptom improvement.

T-cell immunotherapy of allergic disease: the role of CD8+ T cells

PURPOSE OF REVIEW

The scope of this review is to place recent advances in T-cell immunotherapy into an account of our understanding of the potential role of CD8+ T cells in the pathogenesis of allergic disease.

RECENT FINDINGS

Studies over the last year suggest that changes in CD8+ T-cell function may represent key events in successful T-cell immunotherapy. The first human human leukocyte antigen class I allergen epitopes have now been described and will provide further insights into the role of allergen-specific CD8+ T cells.

SUMMARY

The coupling of recent technical advances in the study of antigen-specific T cells with the knowledge of human allergen class I epitopes will promote rapid progress in the field, with potential consequences for the diagnosis, monitoring and immunotherapeutic treatment of affected individuals.