A double-blind, placebo-controlled immunotherapy dose-response study with standardized cat extract

Sublingual immunotherapy in pediatric allergic rhinitis and asthma: efficacy, safety, and practical considerations

Specific allergen immunotherapy (SIT) is the only disease-modifying treatment for allergic rhinitis and asthma. Subcutaneous immunotherapy (SCIT) is the only method with a US Food and Drug Administration (FDA)-approved formulation, but safety concerns limit administration to medical facilities. Sublingual immunotherapy (SLIT), under investigation in the United States, appears to have a more favorable safety profile, which may expand its use to populations generally not treated with SIT (eg, young children). This paper reviews SLIT studies that were specifically limited to the pediatric population. Most demonstrated evidence of clinical efficacy, but approximately 29% failed to demonstrate efficacy in symptom and medication scores in the first treatment year. Efficacy was seen in a broad range of allergen doses, but optimal dose range has not been established. SLIT appeared to be well tolerated in children as young as 2 years, but serious adverse reactions, including anaphylaxis, were reported. SLIT is a promising immunotherapy that may expand the population receiving SIT because of the convenience of home administration due to its favorable safety profile. However, questions remain unanswered, including optimal therapeutic dose.

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.

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.

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.

Accelerated immunotherapy schedules: review of efficacy and safety

OBJECTIVE

To provide a comprehensive evaluation of accelerated immunotherapy build-up schedules in terms of adverse reactions and clinical efficacy.

DATA SOURCES

Peer-reviewed studies and review articles were selected from the PubMed database for articles published in the years 1976 to 2006 using the following keywords: rush, cluster immunotherapy in combination with allergic rhinitis, asthma, Hymenoptera, and imported fire ant.

STUDY SELECTION

Studies were selected if they provided safety and efficacy information on accelerated allergen immunotherapy schedules. Most of the studies reviewed were double-blind, placebo controlled, but some open-observational studies were included if they provided immunotherapy safety or other information the author thought was relevant.

RESULTS

A wide range of systemic reactions were reported in the literature with inhalant allergens: ranging from 27% to 100% of the patients in rush immunotherapy studies and 0% to 79% of patients in the cluster studies. Predictors of systemic reactions with rush immunotherapy were forced expiratory volume in 1 second less than 80% of predicted and a high degree of skin test reactivity. Premedication clearly reduces the risk of systemic reactions with rush immunotherapy, but the effect on cluster schedules was not as clear.

CONCLUSION

Accelerated immunotherapy build-up schedules in selected patients may provide a rapid alternative to conventional build-up schedules without a significant increase in risk.

Basophil interleukin 4 and interleukin 13 production is suppressed during the early phase of rush immunotherapy

BACKGROUND

Studies using rush immunotherapy (RIT) have shown that rapid protection can be achieved using protocols allowing a fast increment of allergen dose. We examined the early effects of RIT on basophil numbers and expression of CD203c, production of interleukin (IL)-4 and IL-13 and histamine release by basophils in the peripheral blood of patients treated with immunotherapy and controls.

METHODS

Twelve patients treated with RIT and 4 untreated controls were included in the study. Any adverse events were evaluated during the incremental phase of RIT. Mononuclear cells were isolated before the start of RIT and 3 days, 1 week, 4 weeks and 3 months after the beginning of the treatment. Histamine release upon allergen stimulation, expression of CD203c and allergen-induced production of IL-4 and IL-13 by basophils were examined.

RESULTS

Significant decreases in blood basophil count (p = 0.02) were observed early in the treatment, returning to baseline values 1 week after the start of RIT. Similarly, histamine release decreased at day 3 (p = 0.02), but returned to pretreatment levels after 1 week. Also, the percentage of IL-4+ and IL-13+ basophils and levels of CD203c expression were markedly reduced early in the treatment. IL-4 and IL-13 production correlated with histamine release and CD203c expression. Histamine release and production of IL-4 and IL-13 by basophils before the treatment correlated with the severity of adverse events during the incremental phase of RIT.

CONCLUSION

We report the decrease in blood basophil numbers, their lower activation status and the reduced production of IL-4 and IL-13 early in the course of RIT. This early suppression of basophil activation could be one mechanism behind the protective effect of RIT.

Heat denaturation, a simple method to improve the immunotherapeutic potential of allergens

Allergen-specific immunotherapy (SIT) leads to a long-term amelioration of IgE- and Th2-mediated allergic diseases. However, SIT efficiency is low, with years of treatment along with frequent allergic side effects. The goal of this study was to reduce the side effects by destroying IgE-binding epitopes, i.e. by heat-denaturation, while preserving the therapeutic effect. Mice were immunised with bee venom, birch pollen, grass pollen or cat hair allergens, or with ovalbumin. Heat-denatured allergens bound less IgE but enhanced Th1-dependent IgG2a production as measured by ELISA. The strong IgG2a antibody responses also prevented allergic anaphylaxis in mice, as measured by body temperature drop after a challenge with a high allergen dose. We found that optimal heat-denaturation of allergens left a small proportion in the native conformation to sufficiently stimulate B cells, while non-B cell-mediated effects were probably amplified. The enhanced immunogenicity of heat-denatured allergens is likely explained by enhanced antigen presentation to T cells due to the particulate nature of heat-denatured proteins. This enables Th1 skewing of the immune response with strong production of IgG2a in mice. Therefore, heat-denaturation represents probably the simplest way to enhance the efficiency of SIT while reducing its side effects.

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.

High-dose allergen exposure leads to tolerance

Reports of decreased sensitization to cat allergen (Fel d 1) among individuals living with a cat or subjects exposed to high-dose cat allergen may be explained by the development of a form of high-dose tolerance resulting from natural exposure to an inhalant allergen. Although the epidemiological data regarding the relationship between exposure and sensitization to Fel d 1 are conflicting, the ability for high-dose Fel d 1 to induce a characteristic nonallergic immune response with a distinctive serum antibody profile has been established. Definition of this modified T-helper (Th)2 response to cat allergen, coupled with the renewed interest in regulatory T cells within the immunology field, has provided an avenue for exploring the mechanism by which IgE antibody-mediated responses are controlled. There is mounting evidence to suggest that the modified Th2 response is a variation of the allergic response and that the modified Th2-allergic axis is influenced by allergen dose and genetics. This article discusses putative immune mechanisms of tolerance within the context of an allergen-specific system. The relevance of high-dose allergen exposure and alternate factors such as endotoxin to the development of tolerance is considered. Fel d 1 exhibits unique molecular and immunological characteristics that may contribute to its tolerogenic properties. Major T-cell epitopes of Fel d 1 that preferentially induce regulatory factors have been defined. Furthermore, high-titer IgE antibody responses associated with atopic dermatitis are characterized by a defect in the T-cell repertoire that is specific to these epitopes. Identification of Fel d 1 epitopes that induce interleukin-10 may provide new targets for treatment.

Advances in upper airway diseases and allergen immunotherapy

Evidence of an increased prevalence of rhinitis in patients with asthma, and asthma in patients with rhinitis, supports the 1 airway concept. However, there are basic differences between the upper and lower airways, such as the virtual absence of remodeling in the nose compared with the bronchi, despite the presence of similar inflammation. Etiologic factors in chronic rhinosinusitis (CRS) attract increasing interest. Peripheral blood monocytes from patients with CRS release IL-4, IL-13, and IFN-gamma on stimulation with fungal antigens, especially those from Alternaria. This is not seen with cells from normal controls. However, a double-blind trial of intranasal amphotericin in CRS was negative. Evidence continues to accumulate of the pivotal role of regulatory T-lymphocytes secretion of IL-10 in the response to allergen immunotherapy. In patients with asthma and house dust mite allergy who are receiving appropriate pharmacotherapy and have instituted environmental controls, house dust mite immunotherapy provides marginal additional benefits in asthma control. Immunotherapy with cat dander extract at a maintenance dose containing 15 microg Fel d 1 produces a more consistent immunologic response than with maintenance doses containing 3.0 microg, whereas doses containing only 0.6 microg are no more effective than placebo. Sublingual immunotherapy for seasonal grass allergy can be safely administered by general practitioners, but symptom relief begins only in the second season of therapy. Sublingual immunotherapy for seasonal grass allergy in children reduced symptoms and onset of new asthma symptoms but, again, beginning only in the second year of treatment. A course of 6 weekly injections of ragweed Amb a 1 bound to cytosine phosphorothionate guanosine containing DNA produced a shift from T H 2 to T H 1 cytokine release both in peripheral blood cells and in the nose after allergen challenge. No symptom improvement was seen the first year, but symptoms were reduced the second year without further treatment.

The Safety of Immunotherapy in Patients with Allergic Asthma and Allergic Rhinitis

We studied systemic reactions associated with immunotherapy in a group of 50 patients with mean age 31.4 years. The group consisted of 36 women and 14 men who followed a three-year immunotherapy treatment with pollen and mite allergen extracts (HAL-Holland Corporation). A total number of 2550 injections were administered. Eight patients developed systemic reactions; 6 had allergic rhinitis and 2 allergic asthma. None developed severe anaphylaxis. Seven of the systemic reactions occurred immediately after injection while one was a late reaction manifested as generalized urticaria, local edema and rubor at the site of the injection. From the 7 patients who showed an immediate reaction, 5 developed generalized urticaria with local edema and rubor at the site of the injection, while 2 presented with bronchial spasm. We did not observe any reaction when the quantity of the extract injection was reduced by 50%. Our study points out that, in the vast majority of cases, immunotherapy is free of severe systemic reactions. Those that occur are associated with the injection of high-density extracts and none of them is severe.

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.

Dose dependence and time course of the immunologic response to administration of standardized cat allergen extract

BACKGROUND

The immunologic response to allergen immunotherapy with 3 serial 5-fold doses of cat extract has been studied after approximately 5 weeks of immunotherapy. The highest dose containing 15 mug of Fel d 1 produced the most consistent and favorable response. It is unknown whether the comparative response on reaching a maintenance dose is maintained with long-term maintenance therapy.

OBJECTIVE

The purpose of this investigation was to evaluate the immunologic responses with these 3 serial doses of cat hair and dander extract at baseline, after reaching the maintenance dose (approximately 5 weeks), and after 1 year of maintenance immunotherapy.

METHODS

Twenty-eight patients with cat allergy randomized in a double-blind study were assigned to one of 4 treatment groups: placebo or cat hair and dander extract containing 0.6 mug of Fel d 1, 3 mug of Fel d 1, and 15 mug of Fel d 1 at maintenance. Studies included skin prick tests and late cutaneous reactions with cat hair and dander extract, titrated nasal challenges with the extract, serum cat allergen-specific IgG4 and IgE measurement, and flow cytometric and ELISA analysis of whole blood and intranasal cytokines (TGF-beta, IL-10, IFN-gamma, IL-4, and IL-5).

RESULTS

Twenty-six subjects completed the study. After both 5 weeks and 1 year, significant and dose-dependent differences were seen with total symptom scores on nasal challenge ( P < .0001), with titrated skin prick testing with cat dander extract at 5 weeks ( P = .014) and 1 year ( P < .0001), and with cat-specific IgG4 measurement at 5 weeks ( P = .004) and 1 year ( P = .003). At 1 year, neither flow cytometry of whole blood nor ELISA evaluation of nasal cytokines demonstrated any significant differences among the treatment groups.

CONCLUSION

The response to titrated nasal allergen challenge, titrated skin prick testing, and allergen-specific IgG4 measurement to cat immunotherapy at 5 weeks is predictive of the response at 1 year.

Advances in upper airway diseases and allergen immunotherapy

Evidence for one airway continues to accumulate. Nasal allergen challenges increase lower airway inflammation, and nasal corticosteroid treatment reduces lower airway inflammation. Allergic respiratory inflammation might even spread systemically to involve nonrespiratory organs. Eosinophilic enteritis and eosinophilic esophagitis are reported during pollen seasons in patients with seasonal allergic rhinitis. Chronic hypertrophic sinusitis (CHS) is found in the majority of patients with asthma. Like asthma, the histology of CHS is characterized by epithelial damage, basement membrane thickening, and eosinophilic inflammation. The damaged epithelium might explain the acute bacterial exacerbations seen in patients with CHS. Studies have extended evidence of the safety and efficacy of the second- and third-generation antihistamines to younger children and to patients with perennial rhinitis but continue to show improvement of symptom scores over that seen with placebo of less than 20%. Studies on antihistamine use in the first trimester in nearly 500 women (65% taking loratadine) revealed no increase in the complications of pregnancy or congenital anomalies. Positive skin prick test responses to birch in asymptomatic young adults predicted later development of clinical allergic rhinitis. A dose response was demonstrated for immunotherapy with cat dander extract. The best results were in subjects receiving a dose containing 15 microg of the major cat allergen Fel d 1 (equivalent to approximately 2500 bioequivalent allergen units). Both topical intranasal immunotherapy and high-dose sublingual immunotherapy have been repeatedly proved to be safe and effective in double-blind, placebo-controlled studies. CD4+CD25+ regulatory T cells secreting IL-10, TGF-beta, or both appear important in normal individuals and in patients treated with allergen immunotherapy in maintaining or restoring normal T(H)1/T(H)2 balance and overall suppression of both phenotypes.

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.