Photo-inactivated allergens. II. Clinical experience with house dust allergen in pulmonary function tests and in immunotherapy

Injection 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 methods of delivery, we updated the 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 2005, Dissertation Abstracts and Current Contents.

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

MAIN RESULTS

Eighty-eight trials were included (13 new trials). There were 42 trials of immunotherapy for house mite allergy; 27 pollen allergy trials; 10 animal dander allergy trials; two Cladosporium mould allergy, two latex and six trials looking at multiple allergens. Concealment of allocation was assessed as clearly adequate in only 16 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 -0.59, 95% confidence interval -0.83 to -0.35) and it would have been necessary to treat three patients (95% CI 3 to 5) with immunotherapy to avoid one deterioration in asthma symptoms. Overall it would have been necessary to treat four patients (95% CI 3 to 6) 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. If 16 patients were treated with immunotherapy, one would be expected to develop a local adverse reaction. If nine patients were treated with immunotherapy, one would be expected to develop a systemic reaction (of any severity).

AUTHORS' 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 local or systemic adverse effects (such as anaphylaxis) must be considered.

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.

Suppression of IgE antibodies with conjugates of haptens or allergens and synthetic hydrophilic polymers

A variety of allergens and allergenic haptens can be converted to nonimmunologenic and tolerogenic derivatives by conjugation to nonimmunogenic, hydrophilic, synthetic polymers, such as mPEG, PVA, and PVP. The resulting conjugates of common allergens and of small molecules, such as those responsible for drug allergies, can potentially be used therapeutically for the specific suppression of the IgE antibodies that mediate the corresponding allergic manifestations of the immediate type. All these conjugates exert their immunosuppressive effect in mice by activating suppressor T cells; hapten-PVA and hapten-PVP conjugates--as distinct from antigen-mPEG conjugates--also appear to inactive the hapten-specific B cell population.

Animal dander allergy

In a group of twenty-three atopic patients skin tests were performed with the dander allergens of horse, cat and guinea-pig, and with house dust and Timothy pollen allergens. A good agreement was observed between positive skin reactions and the results of RAST with these various allergens. In a number of cases, positive skin reactions were not related to the clinical histories. Likewise, positive RAST scores in several instances proved clinically meaningless. In patients with history-related skin reactions better correlation with RAST was observed. In such patients, skin reactions with photo-inactivated allergens remained strongly positive.