Allergen immunotherapy in asthma: evidence for efficacy

Adjuvanted rush immunotherapy using CpG oligodeoxynucleotides in experimental feline allergic asthma

Allergic asthma is driven by relative overexpression of Th2 cell-derived cytokines in response to aeroallergens. In independent studies, both allergen-specific rush immunotherapy (RIT) and CpG oligodeoxynucleotides (ODN) showed promise in blunting eosinophilic inflammation in a model of feline allergic asthma. We hypothesized that RIT using allergen and CpG ODN would work synergistically to dampen the asthmatic phenotype in experimentally asthmatic cats. Twelve cats with asthma induced using Bermuda grass allergen (BGA) were studied. Of these, six were administered adjuvanted BGA RIT using CpG ODN #2142; six were administered placebo (saline) RIT and later crossed over to adjuvanted RIT. Over 2 days, subcutaneous CpG ODN (0.5ng/kg) with BGA (increasing doses every 2h from 20 to 200microg) was administered. Adverse events were recorded and compared with historical controls. Percentage of eosinophils in bronchoalveolar lavage fluid (BALF), % peripheral CD4+CD25+ T regulatory cells (Tregs), lymphocyte proliferation in response to ConA, and cytokine concentrations in BALF were measured over 2 months. Group mean BALF % eosinophils for the adjuvanted RIT cats were significantly lower at week 1 and month 1 (p=0.03 for both), and marginally significantly lower at month 2 (p=0.09) compared with placebo RIT cats. By the end of the study, 8/12 treated cats had BALF % eosinophils within the reference range for healthy cats. Adjuvanted RIT, but not placebo RIT, cats had significant decreases in the ConA stimulation index over time (p=0.05). BALF IL-4 concentrations were significantly higher at week 1 in adjuvanted RIT cats compared with baseline and month 2, and also with placebo RIT cats at week 1. No significant differences were detected between treatments or over time for IL-10 or IFN-gamma concentrations in BALF or for %Tregs cells in peripheral blood. Adjuvanted RIT using CpG ODN in experimental feline asthma dampens eosinophilic airway inflammation. Adverse effects associated with adjuvanted RIT were less severe compared with a historical, non-adjuvanted RIT protocol. The exact mechanism(s) by which adjuvanted RIT alters the aberrant allergic immune response were not elucidated in this study.

Rush immunotherapy in an experimental model of feline allergic asthma

Specific allergen immunotherapy represents the only curative treatment of allergy. No studies have evaluated its efficacy in feline allergic asthma. We hypothesized that an abbreviated course of immunotherapy (rush immunotherapy, RIT) would blunt eosinophilic airways inflammation in experimental feline asthma induced with Bermuda grass allergen (BGA). The 6-month study included asthmatic-RIT treated cats; asthmatic-no RIT treated cats; and non-asthmatic cats. RIT involved increasing parenteral doses (20-200 microg) of BGA over 2 days. Numbers of eosinophils in bronchoalveolar lavage fluid (BALF), serum and BALF immunoglobulins, lymphocyte blastogenesis assays, and cytokines in blood and BALF were evaluated. BALF eosinophils decreased (P=0.048) only in asthmatic-RIT treated cats (baseline 1.1 x 10(6); Month 6, 2.4 x 10(5)). Serum BGA-specific IgG was higher (P<0.001) at all time points after baseline within the asthmatic-RIT group, and was higher (P<0.001) than asthmatic-no RIT cats at Months 1 and 3. No differences (P=0.133) in BGA-specific IgE levels over time were noted among asthmatic-RIT cats, but this group had lower IgE levels (P<0.001) levels than asthmatic no-RIT cats at Months 3 and 6. Differences in BGA-specific IgA levels over time and between the two groups did not reach the traditional level of significance. The mean BGA stimulation index in the asthmatic-RIT cats was biologically insignificant at 6 months, reflecting BGA-specific lymphocyte hypoproliferation. Preliminary results of cytokine profiles were not significantly different; however, BAL cytokine profiles favoring a Th2 response prior to RIT shifted to increased IFN-g and IL-10 thereafter. RIT dampens eosinophilic airways inflammation in cats with experimental asthma. The mechanism of RIT may involve changes in allergen-specific immunoglobulins, induction of hyporesponsive lymphocytes, or alteration of cytokine profiles.

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.

Both allergen-specific CD4 and CD8 Type 2 T cells decreased in asthmatic children with immunotherapy

Allergen-specific immunotherapy (IT) has been used for the treatment of atopic diseases since the turn of this century. The precise working mechanisms, however, remain to be clarified. The aim of this study was to investigate the role of particular subsets of allergen-specific T cells in the non-atopic individuals, untreated asthmatic children and the asthmatic children receiving immunotherapy. We collected peripheral blood from 16 untreated asthmatic children and 17 asthmatic children receiving immunotherapy over one and half years. All the patients were sensitive to mite allergen. Peripheral blood mononuclear cells (PBMC) were isolated and, in vitro, stimulated with crude mite extract to enrich the mite-specific T-cell population. After 14 days, the enriched mite-specific T cells were stimulated with phorbol-12-myristate-13-acetate (PMA) and ionomycin for intracellular detection of cytokines such as IFN-gamma, IL-4 in CD4+ and CD8+ T lymphocytes. The data here demonstrated that the levels of mite-specific IgG4 and IgA increased significantly in asthmatic children after immunotherapy. In addition, both IL-4 expressing CD4+ and CD8+ T cells were significantly lower in asthmatic children after immunotherapy compared with those of before treatment and the normal control (p < 0.05). In contrast, the frequency of IFN-gamma expressing CD4+ and CD8+ T cells did not significantly differ between untreated and SIT-treated groups. All these data suggested that decreased Type 2 CD4+ and CD8+ T cells might be closely correlated with the regulatory mechanisms of immunotherapy.

Immunologic changes during immunotherapy in asthmatic children: increased IL-13 and allergen-specific IgG4 antibody levels

BACKGROUND

The prevalence of allergic diseases such as asthma, allergic rhinitis, and atopic diseases has increased in recent years. Immunotherapy with allergens is a treatment documented to have an effect on regulating cytokine production and allergen-specific antibody production.

OBJECTIVE

The aim of this study was to further investigate immunologic changes during immunotherapy and to explore the possible more efficient approach of immunotherapy.

METHODS

Asthmatic children receiving house dust mite immunotherapy were followed to learn immunologic parameters such as allergen-specific antibody levels, proliferative response of peripheral blood mononuclear cells, and cytokine change during immunotherapy.

RESULTS

The data suggested (1) IgG4 anti-mite antibody increased 8 months after immunotherapy while IgE antibody level remained the same; (2) allergen-induced, in vitro production of certain cytokines such as IL-4 and IL-10 decreased after immunotherapy; (3) IL-13 (which can induce IgG4 and IgE antibody production by B cells) increased after immunotherapy.

CONCLUSION

Although this needs more study, IL-13 might play an important role in the generation of IgG4-blocking antibody during immunotherapy.

Evaluation of household dust mite exposure and levels of specific IgE and IgG antibodies in asthmatic patients enrolled in a trial of immunotherapy

BACKGROUND

Monitoring the response to immunotherapy entails understanding exposure to relevant allergens. For the major indoor allergens, this requires sampling of dust from the patient's house. The objectives of this study were to measure indoor allergen levels during a controlled trial of dust mite immunotherapy for asthma and to relate these results to serum antibody levels.

METHODS

Eighty-eight asthmatic patients with mite allergy from seven geographic areas in the United States were enrolled in and completed a course of immunotherapy with Dermatophagoides extract or placebo control. Sensitization was evaluated by quantitative measurements of IgG and IgE antibodies. Dust samples were assayed for group I mite (Der p 1 and Der f 1), cat (Fel d 1), and cockroach (Bla g 1) allergens by monoclonal antibody-based ELISA.

RESULTS

Over the 4 years of the study, each of the houses had at least one sample that contained more than 2 micrograms of group I mite allergen per gram of dust. Mean mite allergen levels, however, varied over a wide range, from 0.2 microgram/gm or less to more than 50 micrograms/gm. IgE antibodies to mite were present in sera from 78% of the patients, whereas IgE antibodies to cat and cockroach allergens were found in sera from 34% and 11% of patients, respectively. Sixty-four percent of the patients had exposure and sensitization to mite, whereas the comparable figure for each of the other allergens was 5%.

CONCLUSIONS

Examination of the results suggested that allergen exposure, relative to a trial of immunotherapy, could be expressed as (1) the maximum level found in the house, (2) the percentage of sites having greater than 2 micrograms/gm, or (3) the mean value at the site with the maximum level. This report provides a background for evaluating the clinical results of immunotherapy in these patients and a model for the way in which sensitization and exposure should be monitored in studies of this kind.

Immunotherapy for childhood asthma: is there a rationale for its use?

OBJECTIVE

This paper reviews the literature regarding immunotherapy in the management of childhood asthma. Immunotherapy is a well established treatment of venom allergy and allergic rhinitis, however its use in asthma remains controversial.

DATA SOURCES

We reviewed the pediatric literature from 1966 to 1994 and evaluated the existing studies for clinical efficacy of immunotherapy in childhood asthma.

STUDY SELECTION

Only 12 purely pediatric studies existed over the time period that we reviewed. The studies used a variety of different antigens including house dust, house dust mite, grass, mold, cat, dog, and combinations of antigens.

RESULTS

In reviewing the studies, we assessed study duration, number of subjects, whether it was blinded, placebo controlled or open labeled, the measures of clinical efficacy and the assessments of specific and nonspecific bronchial reactivity. The studies were very heterogeneous, and therefore direct comparison and extrapolation of conclusions was difficult. The majority of the studies demonstrated either an improvement in asthmatic symptoms or a decrease in bronchial reactivity to the specific antigen employed, or both. The minority of studies demonstrated no clinical efficacy. The most consistent evidence of benefit was suggested in those trials employing house dust mite therapy, while immunotherapy for grass and cats demonstrated some benefit but the number of studies employing these treatments was very small. There are no trials that provide convincing evidence that immunotherapy with dog and mold antigens is effective for childhood reactive airway disease.

CONCLUSION

Asthma is a multifactorial disease with many triggers. In establishing a role for immunotherapy one must consider all the different aspects such as allergic triggers, environmental stresses, and viral infections. The literature is unclear as to when immunotherapy should be initiated for childhood asthma. While there are suggestions that immunotherapy should be considered for the child with mild or moderate asthma and dust mite sensitivity when pharmacotherapy is not efficacious, the immunomodulatory properties of immunotherapy may actually be more tailored for early intervention in asthma rather than for use once symptoms have occurred. More research is required in order to clarify whether immunotherapy should be recommended more often for the treatment of childhood asthma.

Effects of immunotherapy on symptoms, PEFR, spirometry, and airway responsiveness in patients with allergic asthma to house-dust mites (D. pteronyssinus) on inhaled steroid therapy

The present study was designed to investigate the effects of immunotherapy (IT) with an extract of Dermatophagoides pteronyssinus (Alergo-Merck Depot) during a 27-month period in patients with allergic asthma to house-dust mites. We included 11 patients (mean age 18 years) treated with a combination of IT and inhaled beclomethasone dipropionate (BDP) in comparison to another 11 (mean age 22 years) treated with BDP alone. We evaluated symptom scores, salbutamol use, peak expiratory flow rates (PEFR), spirometry, and bronchial hyperresponsiveness (BHR) during 18 months of therapy with BDP and in the 9 months after BDP interruption. The two kinds of treatment were efficient and comparable in relation to symptom score, salbutamol use, morning PEFR, FVC, and FEV1, but patients treated with IT and BDP had a faster improvement of BHR and PEFR variability. The interruption of BDP after 18 months of therapy was linked to an impairment of all end points, which were more pronounced in patients previously treated only with BDP. These findings suggest that in selected asthmatic patients allergic to house-dust mites, the association of IT and BDP is more effective than therapy with this inhaled steroid alone due to a faster and more striking improvement during the first months of treatment and to a lower rate of relapse after the interruption of therapy with BDP.

Functional endoscopic sinus surgery in patients with chronic sinusitis and asthma

Twenty asthma patients who underwent functional endoscopic sinus surgery for chronic sinusitis were studied. Medical records and questionnaire data for these 20 patients were studied regarding the impact of sinus disease and functional endoscopic sinus surgery on their asthma. We found that 95% reported that their asthma was worsened by their sinus disease (95% confidence interval, 0.74 to 0.99+), and 85% reported that functional endoscopic sinus surgery improved their asthma (0.60 to 0.97). Of the 13 patients who used both inhalers and systemic medication, 53.8% were able to eliminate some of their medication (0.21 to 0.79). Furthermore, 61.5% of these patients had a concomitant reduction in their inhaler use (0.28 to 0.85). All patients (six) who used only inhalers experienced a reduction in their inhaler use (0.54 to 1.00), and two patients were able to eliminate their inhalers completely. One of two patients who were steroid dependent was able to discontinue steroids after surgery. Of patients who used steroids intermittently (13), 53.8% were able to eliminate the use of steroids after surgery (0.21 to 0.79). Patients who required preoperative hospital admissions (4) and emergency room or urgent physician office visits (18) had a 75.0% and 81.3% (p < 0.001) reduction in visits, respectively, after surgery. Because 43% of the cost of asthma is the result of hospitalizations and emergency department/urgent physician office visits, a significant impact on health care costs can be realized with functional endoscopic sinus surgery in this patient population.

A new method, distribution-analyzing latex immunoassay (DALIA), to measure specific immunoglobulin G against mite and wheat allergen in human sera

A distribution-analyzing latex immunoassay (DALIA), based on the agglutination of latex particles coupled with mite or wheat allergen, was developed to determine allergen-specific IgG in human sera. The immune complex between chemically coupled-allergen latex and specific IgG was agglutinated specifically and efficiently by employing an IgM-type monoclonal second antibody with strong amplification activity. The extent of agglutination was evaluated by determining the relative ratio of volumes (RV) of agglutinates to residual nonagglutinating particles with a particle counter. This method exhibited a high sensitivity (detection limit < or = 5 units/ml) in the determination of allergen-specific IgG, and no influence of inhibitory factors such as competitive antibodies (specific-IgA, -IgM) and nonspecific IgG (< or = 320 mg/ml) was observed. The concentrations of specific IgG against mite allergen in the sera of 130 allergy patients with atopic dermatitis and 52 normal subjects were 22.3 +/- 12.3 and 16.5 +/- 4.2 units/ml, respectively, and the concentrations of specific IgG against wheat allergen in the same two groups were 5.4 +/- 4.2 and 2.1 +/- 2.2 units/ml, respectively. The coefficients of variation of intra- and interassay ranged from 3.4% to 11.2% in both cases. The present method is an excellent homogeneous immunoassay which may be used as a routine assay that can measure 50 samples per hour without prior treatment.

Booster immunotherapy (BIT)

This study tries to answer two questions: 1) how long does the therapeutic effect of successful immunotherapy (IT) last after termination of the treatment? and 2) what is the best treatment for recidivist patients? To answer the first question, we asked 108 patients with rye/grass pollen allergy who had previously undergone IT for 3-4 years and had responded well to treatment to complete a questionnaire on the course of their recovery after termination of the therapy. Evaluation of the answers revealed a recidivist rate of approximately 30% in the first 3 years. According to our results, the risk of a relapse after this period seems to be low. To answer the second question, we included 40 patients suffering from type I allergy to grass/rye pollen in a clinical study. Each of them had previously undergone specific IT with a grass pollen extract mixture and had terminated this therapy after 3-4 years practically free of symptoms during the grass pollen season. As the symptoms returned and increased from year to year after the end of IT, new therapeutic steps had to be considered. We investigated the efficacy of a short preseasonal injection treatment called "booster immunotherapy" (BIT). BIT was performed with two different injection-regimens, a low-dose schedule comprising six injections and a high-dose schedule with 11 injections, in both cases administered as a build-up regimen. In the next pollen season, 28/40 (70%) patients reported strong improvement or even complete remission of the allergy symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical pharmacology of asthma. Implications for treatment

The past 10 years have seen three important changes in the philosophy of managing asthma. First, histological studies using fibreoptic bronchoscopy have led to the recognition that asthma is an inflammatory condition of the bronchial mucosa and is not simply caused by smooth muscle spasm. Secondly, there has been some disenchantment with the long term use of regular beta 2-adrenergic agonists as these agents do not appear to control bronchial inflammation and have been associated with deaths from asthma. Thirdly, there has been a general shift away from physician-centred management towards patient-oriented management plans. These three separate strands have led to the development of regional and international consensus documents that emphasise the use of regular anti-inflammatory treatment to control bronchial inflammation and reduce symptoms. With the emphasis on finding the minimum amount of treatment, several traditional anti-asthma medications have been downgraded in importance. The introduction of self-management plans is to be welcomed, but it is important that these new strategies for treating asthma are properly evaluated so that the benefits they confer can be ascertained and maximised.

Childhood asthma: diagnosis and treatment

This discussion of asthma management should be regarded as providing guidelines, not dogma. The underlying principles of asthma management include recognition of the variability of the disease and the importance of the underlying inflammatory condition. Clinical assessment is not enough and objective monitoring with PEFR or spirometry provides important data. The treatment protocols require individualization. It is important that the patient and family are team members working together with the medical staff toward a goal of good asthma management. In the discussion of the management of asthma, much emphasis was placed on spirometry and home measurement of PEFR. Office use of spirometry is now the norm for asthma management. Providing asthmatic patients with peak flow meters and instructions in their use is part of the routine care of asthma. Instruction of the patient and family in the proper use of medications is paramount. The MDI devices need to be prescribed with careful instructions regarding their use. When the patient comes in for follow-up, part of the examination should include the patient's demonstration of how he uses this device. Discussion of the proper and safe use of bronchodilators is important. Overuse of inhaled bronchodilators may be a reflection of increasing asthma or, at the very least, evidence that the patient does not understand appropriate treatment of asthma. If a patient is dependent on regular use of an inhaled beta agent, it is likely that he would benefit from therapy directed at the underlying inflammation of asthma. The patient and the family should understand the purpose of each medication, the side effects, and the risks and benefits of their use. In particular, if steroid medications are necessary, the reasons for their use should be explained. Carefully matching the severity of the asthma with the therapeutic protocols provides an organized approach to asthma treatment. Avoiding triggers of asthma and controlling the environmental exposure to potential triggers leads to lower medication requirements and less lability. Offering the family written instructions to cope with changes in the child's condition, based on assessment of clinical and PEFR observations, allows them more autonomy and comfort in the day-to-day care of the asthmatic child.

Is the allergen-inhalation challenge predictive of the severity of seasonal asthmatic exacerbations?

Fifteen asthmatic patients sensitized to Parietaria pollen were studied. Before the pollen season they underwent an allergen-inhalation challenge which was preceded and followed by a methacholine-inhalation challenge. Pollen count, symptom score, and drug consumption were monitored daily throughout the study. A severity score was obtained by adding symptom score and drug consumption. Patients underwent a third methacholine challenge during the pollen season, after they had been exposed to a high atmospheric concentration of pollen. The severity score during the first period of the pollen season was significantly correlated with both the early and the late asthmatic responses to the allergen observed before the season (r2 = 0.50; P < 0.005). Bronchial sensitivity to methacholine was significantly increased both after allergen challenge and after seasonal exposure, but these increases correlated neither with each other nor with the severity score. We conclude that bronchial responses to experimental exposure to allergens, but not the changes in nonspecific airway responsiveness, can, in part, predict the severity of asthma exacerbation during the pollen season.

Management of chronic asthma

The treatment of asthma is changing to reflect the importance of inflammation in the disease pathogenesis. Medicines that alter the inflammatory response are the cornerstone of therapy for patients with persistent symptoms. Bronchodilators are important in acute care, but in chronic illness they are adjuvant therapy. Patient education is essential for successful outcome.

Allergens and asthma

This article presents the studies that show that asthma in children is strongly associated with sensitization to dust mite and other indoor allergens. In addition, the recent evidence that this association reflects a causal relationship between allergen exposure and asthma is reviewed. The relevance of quantitative measurements of the major indoor allergens (dust mite, cockroach, and cat) in the houses of children with asthma is discussed. Finally, the increasing evidence that avoidance measures can be an effective treatment for asthma is considered together with the details about avoidance protocol for dust mite and cat allergen.

Allergen immunotherapy. Review of efficacy and current practice

The modern use of allergen immunotherapy is described. Evidence for efficacy in inhalant allergy and insect sting allergy is reviewed. Current indications for allergen immunotherapy are discussed.

Bronchial asthma

Asthma is one of the most common respiratory problems in modern industrialized countries, affecting over 5% of the population. It affects all age groups from infants to senior citizens, and mortality rates from asthma appear to be increasing during the past few years in the United States as well as in other industrialized countries. Asthma tends to occur in families, associated with other allergic disease, and may be induced by a wide variety of environmental antigens, most commonly inhaled allergens such as pollen and dust. Bronchial challenge with a specific allergen results in an early bronchospastic response with a relatively brief duration, and in a significant number of patients there is a late response with onset after 3 to 4 hours, lasting hours to days. This late response is associated with a bronchial hypersensitivity reaction, which is demonstrable by nonspecific challenge testing in the laboratory. During the period of bronchial hyperresponsiveness patients are prone to develop attacks following exposure to a wide variety of "triggers," including cold air, fumes, or cigarette smoke. The current approach to management of patients with asthma emphasizes prevention, with avoidance of specific allergens when possible, and chronic use of anti-inflammatory agents including corticosteroids and cromolyn sodium. The goal is to decrease the bronchial hyperresponsiveness. Management of the acute asthma attack consists of bronchodilator therapy, primarily with inhaled beta-adrenergic agonists, and administration of oral or systemic corticosteroids if the attack is not rapidly relieved. Additional therapeutic agents including theophylline and anticholinergics may be useful in some situations. Response to therapy during the first couple of hours in the emergency room is the most important predictor of the course of the acute attack, and patients who have not responded significantly after 2 hours of maximum therapy are candidates for hospital admission or prolonged emergency room observation. The goal of acute therapy is to wean the patient from intravenous drugs and place him or her on rapidly tapering doses of oral prednisone while initiating a vigorous program of preventive therapy. Follow-up observation, both in the office and in the patient's home, is vital and involves extensive patient education and objective testing of peak airflow. In general, the course of asthma is relatively benign compared with other obstructive airway diseases; however, significant mortality exists, especially in older patients and those with late-onset asthma.