Differences in clinical and immunologic reactivity of patients allergic to grass pollens and to multiple-pollen species. II. Efficacy of a double-blind, placebo-controlled, specific immunotherapy with standardized extracts

Hypoallergenic derivatives of major grass pollen allergens for allergy vaccination

Grass pollen-induced hay-fever and allergic asthma represent a major health problem in industrialized countries. Whereas the symptoms of these allergic conditions can be controlled by pharmacotherapy, specific immunotherapy vaccination is the only causative approach towards the treatment of these type 1 allergies. Specific immunotherapy is based on administration of increasing amounts of the disease-causing allergens in the form of allergen-containing extracts. However, the extracts used for immunotherapy consist of allergenic and non-allergenic components and may induce severe anaphylactic side-effects upon therapeutic administration. With recent developments in molecular biology of pollen allergens it has become feasible to produce modified hypoallergenic derivatives of recombinant allergens with abrogated or greatly reduced likelihood of anaphylactic side-effects as compared to extract-based treatments. We have demonstrated this concept through reducing the anaphylactic potential of major rye grass pollen allergens by introducing a few point mutations which leave the overall structural fold of the molecule unaltered. These modified forms are expected to make allergen-specific immunotherapy more widely used in the future.

Allergen immunotherapy for asthma

BACKGROUND

Allergen specific immunotherapy has long been a controversial treatment for asthma. Although beneficial effects upon clinically relevant outcomes have been demonstrated in randomised controlled trials, there remains a risk of severe and sometimes fatal anaphylaxis. The recommendations of professional bodies have ranged from cautious acceptance to outright dismissal. With increasing interest in new allergen preparations and new methods of delivery, it was time to conduct another systematic review of allergen specific immunotherapy for asthma.

OBJECTIVES

The objective of this review was to assess the effects of allergen specific immunotherapy for asthma.

SEARCH STRATEGY

We searched the Cochrane Airways Group trials register up to June 2001, MEDLINE, Dissertation Abstracts, Current Contents and reference lists of articles.

SELECTION CRITERIA

Randomised controlled trials using various forms of allergen specific immunotherapy to treat asthma and reporting at least one clinical outcome.

DATA COLLECTION AND ANALYSIS

Three reviewers independently assessed eligibility of studies for inclusion. Two reviewers independently performed quality assessment of studies.

MAIN RESULTS

Seventy-five trials were included (52 of 54 previously included trials and 23 new trials). A total of 3,506 participants (3,188 with asthma) were involved. There were 36 trials of immunotherapy for house mite allergy; 20 pollen allergy trials; ten animal dander allergy trials; two Cladosporium mould allergy, one latex and six trials looking at multiple allergens. Concealment of allocation was assessed as clearly adequate in only 15 of these trials. Significant heterogeneity was present in a number of comparisons. Overall, there was a significant reduction in asthma symptoms and medication and improvement in bronchial hyper-reactivity following immunotherapy. There was a significant improvement in asthma symptom scores (standardised mean difference -0.72, 95% confidence interval -0.99 to -0.33) and it would have been necessary to treat 4 (95%CI 3 to 5) patients with immunotherapy to avoid one deterioration in asthma symptoms. Overall it would have been necessary to treat 5 (95%CI 4 to 6) patients with immunotherapy to avoid one requiring increased medication. Allergen immunotherapy significantly reduced allergen specific bronchial hyper-reactivity, with some reduction in non-specific bronchial hyper-reactivity as well. There was no consistent effect on lung function.

REVIEWER'S CONCLUSIONS

Immunotherapy reduces asthma symptoms and use of asthma medications and improves bronchial hyper-reactivity. One trial found that the size of the benefit is possibly comparable to inhaled steroids. The possibility of adverse effects (such as anaphylaxis) must be considered.

Immunotherapy with keyhole lampet hemocyanin-conjugated decapeptide vaccine in cypress pollen allergy

BACKGROUND

Cupressaceae pollen allergy is a world-wide pollinosis but immunotherapy has rarely been tested. Immunotherapy is usually allergen-specific but new forms may be targeted towards IgE.

OBJECTIVES

A randomized, double-blind, placebo-controlled trial was carried out to assess the efficacy of a vaccine made of keyhole lampet hemocyanin (KLH)-conjugated decapeptide from the Fc(epsilon4) domain of the IgE in cypress pollinosis.

METHODS

Sixty patients with cypress pollen allergy were studied. They were included on a suggestive clinical history, positive skin tests and nasal challenge to cypress pollen extract. Three intramuscular injections of the vaccine (250 microg) or placebo were administered monthly with a booster injection 5 to 8 weeks later. The primary end-point criterion was the threshold dose inducing a positive nasal challenge. The secondary end-point was the symptom-medication scores measured when cypress pollen grains were over 50 grains/m3.

RESULTS

Nasal challenge before treatment was non-significantly different between the placebo and vaccine groups. After treatment there was no significant difference between the two groups. Pollen counts were over 50 grains/m3 for 8 weeks during the trial. There was no significant difference in total symptom scores between the placebo and vaccine groups. The vaccine was safe.

CONCLUSIONS

The KLH-conjugated decapeptide vaccine was not effective in cypress pollen allergy.

Development of new IgE specificities to allergenic components in birch pollen extract during specific immunotherapy studied with immunoblotting and Pharmacia CAP System

BACKGROUND

New IgE sensitizations to proteins in allergen extracts have been shown to occur during allergen-specific immunotherapy (IT). However little is known about the kinetics of the changes in antibody reactivities.

METHODS

Twenty-four allergic children and adults were treated with birch pollen rush IT (RIT). Fifteen matched patients served as allergic controls. Sera were obtained at regular intervals for up to three years and analyzed with immunoblotting and Pharmacia CAP System with recombinant (r) birch pollen allergens (rBet v 1, rBet v 2, and rBet v 4).

RESULTS

All birch-allergic patients had specific IgE to the major birch pollen allergen Bet v 1, but only three had IgE to rBet v 2 and/or rBet v 4 at the beginning of the study. New IgE sensitizations developed in 65% of the birch RIT-treated patients when studied by immunoblotting. Twenty-nine percent of the patients developed new sensitizations to rBet v 2 and/or rBet v 4 during RIT as measured by Pharmacia CAP System. Generally, new specific IgE reactivities occurred after at least one year of RIT, and only at low levels (< 1 kUA/l).

CONCLUSIONS

Sensitization to additional allergenic pollen components frequently occurs during prolonged birch RIT. However, the IgE levels are low and the clinical relevance is not known.

Efficacy of combination treatment with anti-IgE plus specific immunotherapy in polysensitized children and adolescents with seasonal allergic rhinitis

BACKGROUND

Specific immunotherapy (SIT) and treatment with monoclonal anti-IgE antibody have complementary modes of action.

OBJECTIVE

The purpose of this study was to determine whether combined therapy could provide better efficacy than either treatment alone.

METHODS

We conducted a randomized, double-blinded trial to assess the efficacy and safety of subcutaneously administered anti-IgE (omalizumab) or placebo in children and adolescents with seasonal allergic rhinitis in both a birch pollen season and a grass pollen season (sequential seasons together lasting an average of 84 days). There were 4 treatment arms. Each subject was started on SIT-birch or SIT-grass, and anti-IgE or placebo was started before and maintained during the anticipated pollen seasons (a total of 24 weeks). The primary efficacy variable was symptom load, the sum of daily symptom severity score plus rescue medication use.

RESULTS

A total of 221 subjects (intent-to-treat population) aged 6 to 17 years were analyzed for efficacy. Combination therapy reduced symptom load over the 2 pollen seasons by 48% (P <.001) over SIT alone. When analyzed separately by season, the 2 groups receiving unrelated SIT were considered placebo controls. In the grass season, symptom loads were as follows: unrelated (birch) SIT + placebo, 0.89 (reference value); unrelated (birch) SIT + anti-IgE, 0.49 (-45%); SIT-grass + placebo, 0.61 (-32%); SIT-grass + anti-IgE, 0.26 (-71%).

CONCLUSION

Anti-IgE therapy conferred a protective effect independent of the type of allergen. Additional clinical benefit was demonstrated in both pollen seasons, whether there was coverage by SIT or not. This combination might prove useful for the treatment of allergic rhinitis, particularly for polysensitized patients.

Mucosal tolerance as therapy of type I allergy: intranasal application of recombinant Bet v 1, the major birch pollen allergen, leads to the suppression of allergic immune responses and airway inflammation in sensitized mice

BACKGROUND

Several studies have demonstrated that mucosal administration of soluble antigens can prevent the onset or reduce the severity of certain autoimmune diseases or allergies. Few studies exist showing the efficacy of mucosal tolerance for therapy of such diseases.

OBJECTIVE

The aim of the present study was to modulate an allergic immune response by intranasal antigen administration in an already sensitized organism.

METHODS

A murine model of allergic asthma to birch pollen (BP) and its major allergen Bet v 1 was utilized. Sensitized mice were intranasally treated with recombinant (r)Bet v 1 in different concentrations and at different intervals. On the day the mice were killed, blood and bronchoalveolar lavage fluids were taken and immediate type I skin tests were performed. T cell proliferation and cytokine production (interleukin (IL)-5, interferon (IFN)-gamma) were measured in spleen and lung cell cultures.

RESULTS

Mucosal treatment with rBet v 1 (3 x 50 microg in 4 day intervals) led to a reduction of type I skin reactions, suppressed immunoglobulin (Ig)G1/IgE antibody levels and markedly decreased IL-5 and IFN-gamma production in vitro in spleen and lung cell cultures. Moreover, lung inflammation (i.e. eosinophilia and IL-5 levels in bronchoalveolar lavage fluids) was significantly suppressed by the treatment.

CONCLUSION

Our results demonstrate that intranasal treatment with rBet v 1 reduced systemic allergic immune responses as well as airway inflammation in BP-sensitized mice. We therefore suggest that mucosal tolerance induction with recombinant allergens could be a promising concept for the therapy of allergic diseases.

The ACVD task force on canine atopic dermatitis (XXIV): allergen-specific immunotherapy

Allergen-specific immunotherapy (ASIT) has been used for years to treat dogs with atopic dermatitis (AD) and humans with atopic diseases. The efficacy of ASIT has been well documented for humans with respiratory atopic diseases and stinging insect allergy, but its effectiveness seems more controversial for patients with AD. In spite of insufficient evidence derived from randomized controlled trials, multiple open studies and a large body of clinical observations suggest that ASIT is effective in controlling the clinical signs of dogs with AD. As a result of the scarcity of evidence from controlled trials, the true efficacy of ASIT, and the optimal protocols for allergen dose and frequency of injection are currently unknown. Allergen-specific immunotherapy nevertheless may be included in the treatment of canine AD because of its potential advantages and limited disadvantages compared to other forms of therapy. There is no evidence, however, for the preference of any specific treatment protocol. The predictive value of historical, clinical and immunologic features related to the efficacy of ASIT in dogs with AD are discussed in this paper. Adverse reactions, and the requirements for monitoring of patients receiving ASIT, then are reviewed and detailed. Finally, this review highlights aspects of ASIT where further research and controlled studies are needed.

Prevention of new sensitizations in monosensitized subjects submitted to specific immunotherapy or not. A retrospective study

BACKGROUND

Specific immunotherapy is the only currently available allergen-orientated treatment able to modify the natural history of respiratory allergic diseases. Safety and clinical efficacy of this treatment are well documented, but evidence about the ability to reduce new sensitizations is still poor.

OBJECTIVE

We report a retrospective study conducted in order to assess the prevention of new sensitizations in monosensitized subjects treated with specific immunotherapy vs. monosensitized patients treated with anti-allergic drugs.

METHODS

8396 monosensitized patients with respiratory symptoms were selected according to an open, retrospective design. Group A included 7182 patients submitted to specific immunotherapy (and anti-allergic drugs when needed) for 4 years and then treated with drugs for at least 3 years. Group B included 1214 patients treated only with drugs for at least 7 years. All patients underwent prick test with a standard panel of allergens and total and specific IgE determination before and after 4 years of treatment and again 3 years later.

RESULTS

Groups were well balanced. Polysensitized subjects were 23.75% in Group A and 68.03% in Group B after 4 years (P < 0.0001) and 26.95% and 76.77%, respectively, after 7 years (P < 0.0001). Asthmatic subjects were more prone to develop polysensitization in comparison to subjects suffering only from rhinitis (32.14% instead of 27.29% after 4 years, 36.5% instead of 31.33% after 7 years; P < 0.0001). Specific IgE decreased by 24.11% in Group A and increased by 23.87% in Group B (P < 0.0001). Total IgE decreased by 17.53% in Group A and increased by 13.71% in Group B (P < 0.0001).

CONCLUSIONS

Specific immunotherapy was observed retrospectively to reduce new sensitizations in monosensitized subjects suffering from respiratory allergic diseases.

The consideration of immunotherapy in the treatment of allergic asthma

BACKGROUND

Immunotherapy (IT) has undergone rigorous trials to evaluate its therapeutic benefit in the treatment of allergic respiratory disease. The tools of molecular biology have provided a framework with which to begin to understand the mechanistic effects of IT on the underlying inflammatory component of allergic respiratory disease.

RESULTS

The clinical relevance of these observations belies our understanding of allergic inflammation as the subsoil for the development of abnormal airway physiology, heightened bronchial reactivity, and the development of chronic asthmatic symptomatology.

CONCLUSIONS

IT provides the potential to downregulate this inflammatory cascade, reduce IgE antibody production, and attenuate symptoms. Conceptually, early intervention of allergic disease holds the most promise as a therapeutic intervention capable of arresting the progression of the disease, altering the severity of the disease, and/or preventing the development of the respiratory disease process.

Immunotherapy with a calcium phosphate-adsorbed five-grass-pollen extract in seasonal rhinoconjunctivitis: a double-blind, placebo-controlled study

BACKGROUND

Calcium phosphate-adsorbed allergen extracts are used for subcutaneous immunotherapy to avoid the use of aluminium adjuvants.

OBJECTIVES

A double-blind, placebo-controlled study was performed in order to confirm the safety and assess the efficacy of a standardized five-grass-pollen extract adsorbed onto calcium phosphate for specific immunotherapy (IT).

METHODS

Twenty-nine patients with seasonal rhinoconjunctivitis were randomized to receive either the active preparation (16 patients) or placebo (13 patients), in a 1-year study. During the increasing dose phase, an extract ranging from 0.1 IR per ml to 50 IR per ml was administered at a rate of one subcutaneous injection per week until a maintenance dose was reached. The patients were assessed by symptom diary and rescue medications during seasonal exposure and specific nasal and skin reactivity before and after IT. Immunological parameters (specific IgE and IgG4 antibodies) were assessed before, during and after IT.

RESULTS

The overall symptoms score (mean AUC) was not significantly different between the IT group and the placebo group during grass-pollen exposure (49.6 vs. 56, respectively). The total medication score (mean AUC) was significantly lower in the IT group than in the placebo group (11 vs. 41, P < 0.01, Mann-Whitney U-test). The cumulative symptom/medication score was significantly lower in the IT group than in the placebo group (64.5 vs. 102.3, P < 0.05, U-test). A significant increase in nasal reactivity threshold was observed after IT in the IT group (21. 4 IR/mL before IT vs. 63.4 IR/mL after IT, P < 0.01, Wilcoxon), whereas no significant changes were observed in the placebo group (31.0 IR/mL before IT vs. 37.7 IR/mL after IT). IT induced a significant reduction in grass pollen cutaneous reactivity in the actively treated group (P < 0.001). A significant increase in serum-specific IgG4 antibody response was observed in the IT group (3.1% before IT vs. 10.1% after IT, P < 0.001). Nine patients in the IT group developed moderate immediate systemic reactions vs. two patients in the placebo group.

CONCLUSION

Specific immunotherapy with calcium phosphate-adsorbed standardized grass pollen extract was safe and effective for the treatment of patients with seasonal allergic rhinoconjunctivitis.

Pollen-specific rush immunotherapy: clinical efficacy and effects on antibody concentrations

BACKGROUND

Studies of rush immunotherapy (RIT) with standardized extracts for the treatment of seasonal pollen allergy are few, especially for birch-pollen RIT.

OBJECTIVE

The study was performed to investigate the efficacy of RIT with standardized birch- or timothy-pollen extracts. Further, the serum antibody levels were evaluated for correlation with clinical efficacy.

METHODS

This open, longitudinal study included 30 allergic patients treated with RIT and 16 allergic patients serving as a control group. The therapy was continued for 3 years and blood samples were collected at regular intervals for antibody measurements using the Pharmacia CAP System.

RESULTS

The RIT was generally well tolerated. An increase in the total and specific IgE concentrations during the early months of RIT was observed, followed by decreased levels. Specific IgG and IgG4 increased continuously for 2 years. The symptom and medication scores were significantly decreased, compared with preRIT, at both the first and third pollen seasons after the start of RIT treatment (P < .0001 and P < .001, respectively). The clinical improvement during RIT was significantly greater compared with the control group (P < .05). The decreased medication and the symptom improvement during the third year of RIT correlated with the relative decrease in specific IgE (rs = .52, P < .05) and with the specific IgG4 level before the start of RIT (rs= -.68, P < .01), respectively.

CONCLUSIONS

Our study indicates that RIT with standardized birch- or timothypollen extracts is clinically effective and safe. Measurements of specific antibody levels during treatment may be helpful in monitoring RIT.

The efficacy of immunotherapy in an experimental murine model of allergic asthma is related to the strength and site of T cell activation during immunotherapy

In the present study, the relation between the efficacy of immunotherapy, and the strength and site of T cell activation during immunotherapy was evaluated. We used a model of allergic asthma in which OVA-sensitized and OVA-challenged mice display increased airway hyperresponsiveness, airway inflammation, and Th2 cytokine production by OVA-specific T cells. In this model, different immunotherapy strategies, including different routes of administration, or treatment with entire OVA or the immunodominant T cell epitope OVA(323-339), or treatment with a peptide analogue of OVA(323-339) with altered T cell activation capacity were studied. To gain more insight in how immunotherapy affects allergen-specific T cells, the site of Ag-specific T cell activation and the magnitude of the T cell response induced during different immunotherapy strategies were determined using an adoptive transfer model. Our data suggest that amelioration of airway hyperresponsiveness and inflammation is associated with the induction of a strong, synchronized, and systemic T cell response, resulting in a decreased OVA-specific Th2 response. In contrast, deterioration of the disease after immunotherapy is associated with the induction of a weak nonsynchronized T cell response, resulting in the enhancement of the OVA-specific Th2 response after challenge.

Allergen-specific immunotherapy in birch- and grass-pollen-allergic rhinitis. I. Efficacy estimated by a model reducing the bias of annual differences in pollen counts

BACKGROUND

Evaluation of the efficacy of allergen-specific immunotherapy (IT) with pollen extracts is complicated by annual variation in pollen intensity. Our study aimed to evaluate the efficacy of birch and grass IT, taking into consideration these variations.

METHODS

After 1 year of observation, 52 patients with rhinoconjunctivitis and allergy to birch as well as grass pollen were allocated to double-blinded clustered IT with aluminum-adsorbed extract produced from either birch (Betula verrucosa) pollen or grass (PIleum pratense) pollen. After 1 year of treatment, the patients continued IT with their original extract and also received the other extract. During the three consecutive pollen seasons, the rhinoconjunctivitis symptom score and the use of antihistamines, eye-drops, and oral prednisolone were recorded. Longitudinal data analysis was used to investigate the relation between different pollen counts and the magnitude of clinical efficacy.

RESULTS

An effect of IT was found on symptom score, antihistamine intake, and eye-drop use for both birch and grass (P values <0.05). The mean reduction in symptom score/medication by IT ranged from 24% to 95%, depending on mean seasonal pollen counts. A minimum mean seasonal grass-pollen count of 20-30 pollen grains m3 was required for the efficacy of grass IT to emerge.

CONCLUSIONS

A model was developed for evaluation of efficacy in longitudinal IT studies, taking the differences in annual pollen counts into consideration. The model showed a significant beneficial role of pollen IT in rhinoconjunctivitis patients allergic to birch and grass pollen.

The consideration of immunotherapy in the treatment of allergic asthma

Immunotherapy has undergone rigorous trials to assess its therapeutic benefit in the treatment of allergic respiratory disease. The tools of molecular biology have provided a framework with which to begin to understand the mechanistic effects of immunotherapy on the underlying inflammatory component of allergic respiratory disease. The clinical relevance of these observations belies our understanding of allergic inflammation as the subsoil for the development of abnormal airway physiology, heightened bronchial reactivity, and the development of chronic asthmatic symptoms. Immunotherapy provides the potential to downregulate this inflammatory cascade, reduce IgE antibody production, and attenuate symptoms. Conceptually, early intervention of allergic disease holds the most promise as a therapeutic intervention capable of arresting the progression of the disease, altering the severity of the disease, and/or preventing the development of the respiratory disease process.

Economic evaluation of specific immunotherapy versus symptomatic treatment of allergic rhinitis in Germany

OBJECTIVE

To use published data to compare the economic consequences of specific immunotherapy (SIT) lasting 3 years with those of continuous symptomatic treatment in patients with either pollen or mite allergy.

DESIGN AND SETTING

The evaluation was conducted from the following 3 perspectives in Germany: (i) society; (ii) healthcare system; and (iii) statutory health insurance (SHI) provider. A modelling approach was used which was based on secondary analysis of existing data. The follow-up period was 10 years. The break-even point of cumulated costs, their difference per patient and the additional cost per additional patient free from asthma symptoms [incremental cost-effectiveness ratio (ICER)] were used as target variables, each from the viewpoint of SIT. The types of costs were direct and indirect (society), direct (healthcare system) and those incurred by SHI (i.e. expenses). In the base-case analysis, the average values of the clinical parameters and average case-related costs/expenses were applied.

MAIN OUTCOME MEASURES AND RESULTS

The break-even point was reached between year 6 and year 8 after the start of therapy, resulting in net savings of between 650 and 1190 deutschmarks (DM) per patient after 10 years. The ICERs of SIT were between -DM3640 and -DM7410, depending on study perspective and nature of the allergy (1990 values for symptomatic treatment and treatment of asthma, 1995 values for SIT; DM1 approximately $US0.58). The sensitivity analysis demonstrated the robustness of the model and its results. First, all the independent variables of the model were varied. Secondly, the influence of the model variables was quantified using a deterministic model. SIT was more likely to result in net savings than in additional costs. An economic parameter (cost for symptomatic treatment) had the highest influence on the results.

CONCLUSIONS

This evaluation showed that SIT for 3 years is economically advantageous in patients who are allergic to pollen or mites and whose symptoms are inadequately controlled by continuous symptomatic treatment. After 10 years, the administration of SIT leads to net savings from the perspectives of society, the healthcare system and SHI (third-party payer) in Germany.

Oligodeoxynucleotides containing CpG motifs induce IL-12, IL-18 and IFN-gamma production in cells from allergic individuals and inhibit IgE synthesis in vitro

The effects of phosphorothioate oligonucleotides containing CpG motifs (CpG-ODN) on cultured cells from allergic patients and non-atopic individuals were investigated. In peripheral blood mononuclear cells (PBMC) CpG-ODN led to a significant increase of IFN-gamma. By intracellular cytokine staining, IFN-gamma production could be attributed to NK cells and inhibition experiments indicated an IL-12-dependent mechanism. Moreover, CpG-ODN increased mRNA expression of IL-12 and IL-18 in PBMC. In this respect, no significant difference between allergic and non-atopic individuals was observed. Monocyte-derived dendritic cells were identified as one IL-12- and IL-18-producing source. In addition, stimulation of PBMC derived from atopic patients with CpG-ODN led to a considerable increase of polyclonal IgG and IgM synthesis. In contrast, the production of total IgE was suppressed. CpG-ODN induced a significant rise of IgG and IgM specific for allergens to which the patients were sensitized, whereas allergen-specific IgE levels remained unchanged. Our data suggest that CpG-ODN display a strong influence on the ongoing immune response and might represent potential adjuvants for specific immunotherapy of type I allergy.

Comparison between nasal provocation tests and skin tests in patients treated with loratadine and cetirizine

BACKGROUND

The effect of H1-blockers may differ depending on the target organ.

OBJECTIVE

A double-blind, placebo-controlled study was carried out to compare the effect of a 7-day treatment with loratadine (10 mg daily) or cetirizine (10 mg daily) on nasal challenge with grass pollen grains and skin tests with allergen or histamine.

METHODS

Twenty-four patients were enrolled, but the analysis was carried out on 23. Nasal challenge was carried out by using 5-fold increasing numbers of pollen grains. Skin prick tests were done with serial concentrations of allergens and 1 concentration of histamine. Patients were tested in a cross-over design, with each treatment being administered for the previous 7 days and with a 2-week washout period.

RESULTS

By comparison with placebo, loratadine and cetirizine increased significantly the threshold number of pollen grains required to induce a positive nasal challenge (P <.001). There was no difference between loratadine and cetirizine. Skin test responses to allergen were significantly reduced by loratadine and cetirizine by comparison with placebo. Skin test responses to histamine were significantly decreased by the 2 H1-blockers, but they were more profoundly decreased by cetirizine than by loratadine.

CONCLUSIONS

Both H1-blockers reduced similarly allergen-induced skin test and nasal challenge responses. Cetirizine was more effective on histamine skin test responses.

Immune responses after immunization with plasmid DNA encoding Bet v 1, the major allergen of birch pollen

BACKGROUND

Immunization with plasmid DNA encoding various antigens is a promising method in vaccine research. Recent studies also indicate that DNA-based immunization might represent a potential approach in allergen-specific immunotherapy.

OBJECTIVE

In this study we have characterized the immune responses induced by recombinant Bet v 1a and plasmid DNA encoding for Bet v 1a, the major allergen of birch pollen in a mouse system.

METHODS

Balb/c mice were injected intraperitoneally with recombinant Bet v 1a and intradermally with plasmid DNA encoding for the gene of Bet v 1a (pCMV-Bet). In addition, the effect of immunostimulatory DNA sequences was investigated by appending CpG motifs to the gene of Bet v 1a, coinjecting CpG-oligodeoxynucleotides together with the pCMV-Bet construct, or both. IgE and IgG antibody responses, as well as IgG subclasses, were measured by ELISA in sera after each immunization. IFN-gamma and IL-4 levels were also measured by ELISA in sera and supernatants of allergen-stimulated spleen cells.

RESULTS

The primary humoral response to a single treatment with pCMV-Bet was very weak, but the reaction could be boosted to higher levels by 2 additional injections. On the other hand, proliferation assays of spleen cells and measurements of cytokine levels already indicated a cellular response after the first injection of plasmid DNA. After 2 immunizations with pCMV-Bet, the ratio of IgG1 to IgG2a pointed to a TH1 subclass profile. IgE was not detectable in any group at any time during the immune reaction. Accordingly, IL-4 levels were markedly reduced in the serum, as well as in the supernatants, of stimulated spleen cells. Animals immunized with pCMV-Bet containing appended CpG motifs at the 3' end of the Bet v 1a gene and/or with the CpG-ODN GCTAGACGTTAGCGT plus pCMV-Bet displayed reduced humoral responses against Bet v 1a when compared with animals injected with pCMV-Bet alone. The levels of IFN-gamma measured after allergen stimulation of isolated spleen cells were significantly higher in animals immunized with pCMV-Bet plus CpG motifs than with pCMV-Bet alone. Immunization with recombinant Bet v 1a protein elicited a strong TH2 -type response, including IgE production, a high titer of IgG1, and IL-4 production in both serum and supernatants of proliferation cultures.

CONCLUSION

In contrast to immunization with protein, DNA immunization induces a strong TH1 -type response against a relevant inhalant allergen. Our data support the concept of developing a novel type of allergen immunotherapy based on plasmid DNA immunization.

The paradigm of Th1 and Th2 cytokines: its relevance to autoimmunity and allergy

In the past few years, considerable evidence has accumulated to suggest the existence of functionally polarized responses by the CD4+ T helper (Th)--and the CD8+ T cytotoxic (Tc)-cell subsets that depend on the cytokines they produce. The Th1 and Th2 cellular immune response provide a useful model for explaining not only the different types of protection, but also the pathogenic mechanisms of several immunopathological disorders. The factors responsible for the polarization of specific immune response into a predominant Th1 or Th2 profile have been extensively investigated in mice and humans. Evidence has accumulated from animal models to suggest that Th1-type lymphokines are involved in the genesis of organ-specific autoimmune diseases, such as experimental autoimmune uveitis, experimental allergic encephalomyelitis, or insulin-dependent diabetes mellitus. Accordingly, data so far available in human diseases favor a prevalent Th1 lymphokine profile in target organs of patients with organ-specific autoimmunity. By contrast, Th2-cell predominance was found in the skin of patients with chronic graft-versus host disease, progressive systemic sclerosis, systemic lupus erythematosus, and allergic diseases. The Th1/Th2 concept suggests that modulation of relative contribution of Th1- or Th2-type cytokines regulate the balance between protection and immunopathology, as well as the development and/or the severity of some immunologic disorders. In this review, we have discussed the paradigm of Th1 and Th2 cytokines in relation to autoimmunity and allergy.

Heat-Killed Listeria monocytogenes as an Adjuvant Converts Established Murine Th2-Dominated Immune Responses into Th1-Dominated Responses

We investigated the capacity of heat-killed Listeria monocytogenes (HKL), a potent stimulator of the innate immune system, as a vaccine adjuvant to modify both primary and secondary Ag-specific immune responses. Mice immunized with the Ag keyhole limpet hemocyanin (KLH) mixed with HKL generated a KLH-specific primary response characterized by production of Th1 cytokines and large quantities of KLH-specific IgG2a Ab. Moreover, administration of KLH with HKL as an adjuvant reversed established immune responses dominated by the production of Th2 cytokines and high levels of KLH-specific IgE and induced a Th1-type response with high levels of IFN-γ and IgG2a and low levels of IgE and IL-4. Neutralization of IL-12 activity at the time of HKL administration blocked the enhancement of IFN-γ and reduction of IL-4 production, indicating that IL-12, induced by HKL, was responsible for the adjuvant effects on cytokine production. These results suggest that HKL as an adjuvant during immunization can successfully bias the development of Ag-specific cytokine synthesis toward Th1 cytokine production even in the setting of an ongoing Th2-dominated response. Thus, HKL may be clinically effective in vaccine therapies for diseases such as allergy and asthma, which require the conversion of Th2-dominated immune responses into Th1-dominated responses.

Changes in skin-test reactivity do not correlate with clinical efficacy of H1-blockers in seasonal allergic rhinitis

New-generation H1-blockers may possess antiallergic properties, and their effect may differ, depending on the target organ. A double-blind, placebo-controlled, parallel-group study was carried out during the pollen season to compare the clinical effect on nasal and conjunctival symptoms of astemizole (10 mg o.d.) and loratadine (10 mg o.d.) with their effect on skin-test reactivity to allergen and histamine. Thirty-eight patients (12-56 years of age) were studied. Nasal and ocular symptoms were recorded daily from days 4 to 7. Skin prick tests with serial concentrations of allergens and one concentration of histamine were carried out before and at the end of the 7-day treatment period. Parallel-line bioassay, analysis of variance, and covariance were used to analyze skin test data. Loratadine and astemizole significantly decreased symptoms from baseline (P < 0.004 and P < 0.006). Skin-test reactivity to allergen and histamine was more profoundly decreased by astemizole than loratadine. The histamine covariant was more important in the allergen effect of astemizole than in that of loratadine. Two H1-blockers having the same clinical effect on nasal and ocular symptoms during the pollen season have totally different effects on skin-test reactivity. Skin-test reactivity to allergen or histamine is not predictive of the clinical efficacy of H1-blockers during seasonal allergic rhinitis.

Effect of seasonal exposure to pollen on nonspecific interleukin-4, interleukin-5, and interferon-gamma in vitro release by peripheral blood mononuclear cells from subjects with pollinosis

The immune response to environmental allergens depends on both genetic and environmental factors. Allergen exposure triggers the activation of allergen-specific Th2 cells in allergic patients, as well as increased Th2-type cytokine mRNA expression and eosinophil recruitment. Nevertheless, different patterns of release of cytokines could explain the heterogeneity of atopic response. In our study, 25 patients with pollinosis and 15 healthy donors were selected to characterize their release of Th2 (interleukin [IL]-4 and IL-5) and Th1 (interferon-gamma [IFN-gamma]) cytokines, both during and outside the pollen season. Peripheral blood mononuclear cells from patients and controls were isolated, cultured in the presence of phorbol-12-myristate-13-acetate plus ionomycine, and phytohemagglutinin (PHA), and cytokine release was assessed by titration in the supernatants. Both IL-4 and IL-5 showed higher levels during than outside the pollen season in pollinic patients (P<0.05) after nonspecific stimuli, whereas IFN-gamma levels were significantly lower during than outside the pollen season only after culture with PHA. Significant differences were not observed in the control group. Our results are consistent with the hypothesis that release of cytokines by peripheral blood mononuclear cells from patients with pollinosis depends on environmental exposure to sensitizing pollens, and that influence can be revealed by in vitro nonspecific stimulation. Nevertheless, the heterogeneity in results suggests that the use of mitogens to assess Th1/Th2 dominance may need careful evaluation.

Effects of adjuvants on the immune response to allergens in a murine model of allergen inhalation: cholera toxin induces a Th1-like response to Bet v 1, the major birch pollen allergen

Based on the fact that type I allergies are frequently elicited by inhalant allergens, we have established a model of aerosol inhalation leading to allergic sensitization in BALB/c mice. Using this model we studied the effects of aluminium hydroxide (Al(OH)3), known to enhance IgE antibody responses, compared with cholera toxin (CT), a potent mucosal adjuvant, on the immune response to birch pollen (BP) and its major allergen Bet v 1. Two groups of BALB/c mice were either systemically immunized with recombinant Bet v 1 in Al(OH)3 and subsequently aerosol exposed to BP allergen, or aerosolized with BP and CT. IgE-mediated skin reactions were only elicited in the mice which had received Bet v 1/Al(OH)3. Allergen-specific serum IgE and IgG1 antibodies dominated in the Al(OH)3 group, IgG2a antibody levels to BP and rBet v 1 were markedly higher in the sera of mice exposed to CT with the allergen. IgA antibodies were only detected in the bronchial lavage of the CT-treated group. Moreover, the latter group displayed consistently higher T cell proliferative responses to BP and interferon-gamma production in vitro. Thus, the systemic immunization with rBet v 1 in Al(OH)3 before inhalation of the BP extract promoted a Th2-like immune response, while CT mixed with the aerosolized BP extract rather induced a Th1-like immune response. In an attempt to reverse these ongoing immune responses we could achieve a shift towards a Th0 response. Immunization with BP extract without adjuvant treatment led to undetectable antibody or cellular immune responses. We conclude from the present study that the induction of an immune response to BP allergen after aerosol inhalation can be directed towards a Th1- or a Th2-like response. Once established, the immune response can be modulated.

Immunological changes during specific immunotherapy of grass pollen allergy: reduced lymphoproliferative responses to allergen and shift from TH2 to TH1 in T-cell clones specific for Phl p 1, a major grass pollen allergen

BACKGROUND AND OBJECTIVE

The mechanisms operative in specific immunotherapy (SIT) of Type I allergy are not completely understood. In the present study we evaluated immunological changes during SIT in pollinosis.

METHOD

Eight patients suffering from pollinosis (monosensitized to grass pollen) were treated with conventional SIT. All subjects had IgE specific for Phl p 1, a major allergen of timothy grass. In vitro changes in the immunological reactivity to grass pollen extract and to recombinant Phl p 1 were evaluated. Subjects were examined at three occasions: before, after 3 months and after 1 year of SIT.

RESULTS

Serological analysis revealed a marked increase of grass pollen- and Phl p 1-specific IgG, titres of specific IgE did not change significantly. Lymphoproliferative responses to grass pollen extract and rPhl p 1 were reduced already after 3 months of treatment. Accordingly, the cloning efficiency for Phl p 1-specific T-cell clones (TCC) dropped markedly in all patients. The majority of allergen-specific TCC raised before SIT revealed a TH2-like pattern of cytokine production, TCC established after SIT revealed TH1 characteristics. This shift was due to a decrease in IL-4 rather than an increase in IFN-production by T cells. Investigations of the epitopes recognized by T cells before and after SIT did not reveal the outgrowth of new ('protecting') specificities. We could not observe induction of allergen-specific CD8+ lymphocytes (supressor cells).

CONCLUSION

Our data indicate that -- on the level of TH lymphocytes -- SIT induces tolerance to the allergen and a modulation of the cytokine pattern produced in response to allergen stimulation.

A double-blind, placebo-controlled study of immunotherapy with grass-pollen extract Alutard SQ during a 3-year period with initial rush immunotherapy

Thirty patients with asthma and/or monosensitized allergic rhinitis caused by grass pollen whose ages ranged from 15 to 35 years were selected. Two groups were established at random: an active group and a placebo group, and a double-blind study was done on treatment with immunotherapy for a period of 3 continuous years, with initiation doses administered according to the rush immunotherapy technique. Grass-pollen allergen extract Alutard SQ and histamine as a placebo were used. The objective parameters of efficacy evaluated were end-point cutaneous tests, conjunctival provocation, bronchial provocation, and symptom/medication scores, as well as specific immunoglobulin determinations. The statistical evaluation of the results was significant for the differences existing between the initial and final time of the active group, and there were significant differences between the two groups for all of the parameters considered. We found no relationship between clinical improvement and the range of specific immunoglobulin E values. Regarding the safety of the treatment, systemic adverse effects were manifested only in the initial phase (rush immunotherapy), and were easily controlled by treatment. We conclude that the efficacy and safety of immunotherapy with grass pollen make it possible to consider this treatment fundamental in these patients.

Dissection of immunoglobulin E and T lymphocyte reactivity of isoforms of the major birch pollen allergen Bet v 1: potential use of hypoallergenic isoforms for immunotherapy

We dissected the T cell activation potency and the immunoglobulin (Ig) E-binding properties (allergenicity) of nine isoforms of Bet v 1 (Bet v 1a-Bet v 1l), the major birch pollen allergen. Immunoblot experiments showed that Bet v 1 isoforms differ in their ability to bind IgE from birch pollen-allergic patients. All patients tested displayed similar IgE-binding patterns toward each particular isoform. Based on these experiments, we grouped Bet v 1 isoforms in three classes: molecules with high IgE-binding activity (isoforms a, e, and j), intermediate IgE-binding (isoforms b, c, and f), and low/no IgE-binding activity (isoforms d, g, and 1). Bet v 1a, a recombinant isoform selected from a cDNA expression library using IgE immunoscreening exhibited the highest IgE-binding activity. Isoforms a, b, d, e, and 1 were chosen as representatives from the three classes for experimentation. The potency of each isoallergen to activate T lymphocytes from birch pollen-allergic patients was assayed using peripheral blood mononuclear cells, allergen-specific T cell lines, and peptide-mapped allergen-specific T cell clones. Among the patients, some displayed a broad range of T cell-recognition patterns for Bet v 1 isoforms whereas others seemed to be restricted to particular isoforms. In spite of this variability, the highest scores for T cell proliferative responses were observed with isoform d (low IgE binder), followed by b, 1, e, and a. In vivo (skin prick) tests showed that the potency of isoforms d and 1 to induce typical urticarial type 1 reactions in Bet v 1-allergic individuals was significantly lower than for isoforms a, b, and e. Taken together, our results indicate that hypoallergenic Bet v 1 isoforms are potent activators of allergen-specific T lymphocytes, and Bet v 1 isoforms with high in vitro IgE-binding activity and in vivo allergenicity can display low T cell antigenicity. Based on these findings, we propose a novel approach for immunotherapy of type I allergies: a treatment with high doses of hypoallergenic isoforms or recombinant variants of atopic allergens. We proceed on the assumption that this measure would modulate the quality of the T helper cell response to allergens in vivo. The therapy form would additionally implicate a reduced risk of anaphylactic side effects.

Treatment of allergic rhinitis

An increased understanding of the pathophysiology of allergic rhinitis can provide a logical basis for improved therapeutic strategies tailored individually to each patient. The first recommendation is the avoidance of possible or verified allergens. If this does not provide significant relief or is impractical, then immunotherapy plays a preventative role in some patients and it has been shown to be effective in certain cases. Initially, most patients try new nonsedating antihistamines, sometimes combined with a short course of topical vasoconstrictors. When nasal obstruction is a problem, a steroid spray is preferred. It is often necessary to add topical treatment for eye symptoms, e.g. antihistamine or cromoglycate eyedrops. In severe cases simultaneous administration of nasal corticosteroids and nonsedating antihistamines may achieve optimal control of symptoms. Cromolyn derivates are also effective in mild or moderate rhinoconjunctivitis and are especially recommended in the treatment of children. Systemic corticosteroid therapy should be reserved for the rare patient with extreme symptoms, and limited to short courses. Recent studies have shown that if patients are provided with appropriate medication, education and instruction, symptoms of allergic rhinitis can be well controlled with minimum impairment of quality of life.

Seasonal variations of interleukin-4 and interferon-gamma release by peripheral blood mononuclear cells from atopic subjects stimulated by polyclonal activators

IgE synthesis is controlled by interleukin (IL)-4 and interferon (IFN)-gamma, but there is heterogeneity in the IL-4 response depending on the sensitization of patients and natural allergen exposure. In patients sensitized to various allergens, we studied the synthesis of IL-4, IFN-gamma, and IgE to determine to what extent their in vitro immune response may be influenced by pollen season, depending on their sensitization. We studied 12 nonallergic individuals, seven patients sensitized to cypress pollen, 12 sensitized to grass pollen, 14 sensitized to several pollens, and 42 patients with polysensitization. The release of IL-4 and IFN-gamma from peripheral blood mononuclear cells stimulated by polyclonal agents (calcium ionophore A23187 and phorbol myristate acetate) was measured by ELISA. The spontaneous and IL-4-induced release of IgE was measured by ELISA. In patients with cypress pollen allergy, IL-4 and IgE release were significantly lower than in patients with other allergies. In the pollen-sensitized group, IL-4 and IgE release were significantly higher during the pollen season than out of it. No variation in IL-4 or IgE release was observed in the polysensitized group. IFN-gamma production was not affected by the pollen season. These data show that the seasonal variations of IL-4 and IgE synthesis differ according to the sensitization of patients.

T-cell epitopes of Phl p 1, major pollen allergen of timothy grass (Phleum pratense): evidence for crossreacting and non-crossreacting T-cell epitopes within grass group I allergens

BACKGROUND

The use of peptides representing T-cell epitopes of allergens is a modern concept for improvement of specific immunotherapy. A prerequisite for this approach is the identification of T-cell epitopes of atopic allergens.

METHODS

T-cell lines and 40 T-cell clones (TCC) specific for Phl p 1, the group I allergen of timothy grass (Phleum pratense), were established from the peripheral blood of nine patients allergic to grass pollen and mapped for epitope specificity by using overlapping dodecapeptides. Phenotype and cytokine production profile of TCC were investigated. Representative TCC were analyzed for HLA-restriction, T-cell receptor V beta gene usage, and crossreactivity with grass pollen extracts from Dactylis glomerata, Poa pratensis, Lolium perenne, Secale cereale, and selected amino acid sequence-derived peptides.

RESULTS

Patients displayed IgE binding to all grass species investigated. Forty TCC were established. Fifteen T-cell epitopes could be identified on Phl p 1. Of 40 TCC, 39 displayed the helper cell (Th) phenotype; one clone was CD8+. Specific stimulation induced a Th2-like type of cytokine production in 20 of 39 TCC. Crossreactivity studies revealed crossreacting and non-crossreacting T-cell epitopes.

CONCLUSION

Phl p 1, a major grass pollen allergen, harbors multiple T-cell epitopes. Species-specific and crossreacting T-cell epitopes exist among group I allergens of grasses. Epitope recognition patterns could not be correlated with particular HLA haplotypes. A restricted T-cell receptor V beta gene usage was not observed.