Allergen-Specific Immunotherapy for Respiratory Allergy
Allergen-Specific Immunotherapy for Respiratory Allergy
Among the treatments available for respiratory allergy, which include allergen avoidance and pharmacotherapy, specific immunotherapy (SIT) is the only treatment able to not only act on the symptoms of allergy but also act on the causes. SIT is the practice of administering gradually increasing doses of the specific causative allergen to reduce the clinical reactivity of allergic subjects and was introduced one century ago. SIT remained an empirical treatment for more than 40 years, but the first controlled trial in 1954 paved the way for the scientific era. At present, SIT may be administered in two forms: subcutaneous (SCIT) and sublingual immunotherapy (SLIT). A large number of trials, globally analyzed in several meta-analyses, evaluated the efficacy and safety of SCIT and SLIT in allergic rhinitis and asthma. Current available data give solid evidence to the clinical efficacy of both SCIT and SLIT in allergic rhinitis and asthma. Providing the recommended doses and administration schedules are adhered to, the safety and tolerability are very good; however, adverse systemic reactions remain a drawback for SCIT. After one century of use, accumulating evidence surrounds SIT and the central role in the management of respiratory allergy.
Sensitization to environmental inhalant allergens, such as pollens, house dust mites, animal epithelia and moulds, is clinically expressed by rhinitis, conjunctivitis and asthma. The treatment of respiratory allergy is based on allergen avoidance (which is only rarely feasible), drug therapy and allergen-specific immunotherapy (SIT), but only the latter is able to act on the causes as well as the symptoms of allergy. Moreover, SIT has a preventative role against new sensitizations and development of asthma in allergic rhinitis patients. SIT is the practice of administering gradually increasing doses of the specific causative allergen to reduce the clinical reactivity of allergic subjects. It was introduced one century ago, but remained a merely empirical treatment until 1954, when the first controlled trial was published. Until the 1980s, the only way to administer SIT was by the injective, subcutaneous route, but the introduction in the market of new, highly biologically potent allergen extracts raised the issue of safety because of a series of fatal systemic reactions. To improve the safety, other routes of administration were investigated, such as oral immunotherapy and local nasal immunotherapy. However, the former was found to be ineffective despite administering very high allergen doses, while the latter showed clinical efficacy but had a poor tolerability, with nasal reactions to each administration of the extract. In 1986, the sublingual route was proposed for the first time as an alternative route of administration and in the following years after it proved to be an effective and safe treatment for respiratory allergy and thus is the true alternative to the injection route. To date, a very large number of trials provided a solid evidence for efficacy of both subcutaneous immunotherapy (SCIT), and sublingual immunotherapy (SLIT), which was accurately examined by a meta-analysis.
This article aims to provide the reader a comprehensive view on the characteristics of SCIT and SLIT, with a particular focus on their respective advantages and limitations.
Abstract and Introduction
Abstract
Among the treatments available for respiratory allergy, which include allergen avoidance and pharmacotherapy, specific immunotherapy (SIT) is the only treatment able to not only act on the symptoms of allergy but also act on the causes. SIT is the practice of administering gradually increasing doses of the specific causative allergen to reduce the clinical reactivity of allergic subjects and was introduced one century ago. SIT remained an empirical treatment for more than 40 years, but the first controlled trial in 1954 paved the way for the scientific era. At present, SIT may be administered in two forms: subcutaneous (SCIT) and sublingual immunotherapy (SLIT). A large number of trials, globally analyzed in several meta-analyses, evaluated the efficacy and safety of SCIT and SLIT in allergic rhinitis and asthma. Current available data give solid evidence to the clinical efficacy of both SCIT and SLIT in allergic rhinitis and asthma. Providing the recommended doses and administration schedules are adhered to, the safety and tolerability are very good; however, adverse systemic reactions remain a drawback for SCIT. After one century of use, accumulating evidence surrounds SIT and the central role in the management of respiratory allergy.
Introduction
Sensitization to environmental inhalant allergens, such as pollens, house dust mites, animal epithelia and moulds, is clinically expressed by rhinitis, conjunctivitis and asthma. The treatment of respiratory allergy is based on allergen avoidance (which is only rarely feasible), drug therapy and allergen-specific immunotherapy (SIT), but only the latter is able to act on the causes as well as the symptoms of allergy. Moreover, SIT has a preventative role against new sensitizations and development of asthma in allergic rhinitis patients. SIT is the practice of administering gradually increasing doses of the specific causative allergen to reduce the clinical reactivity of allergic subjects. It was introduced one century ago, but remained a merely empirical treatment until 1954, when the first controlled trial was published. Until the 1980s, the only way to administer SIT was by the injective, subcutaneous route, but the introduction in the market of new, highly biologically potent allergen extracts raised the issue of safety because of a series of fatal systemic reactions. To improve the safety, other routes of administration were investigated, such as oral immunotherapy and local nasal immunotherapy. However, the former was found to be ineffective despite administering very high allergen doses, while the latter showed clinical efficacy but had a poor tolerability, with nasal reactions to each administration of the extract. In 1986, the sublingual route was proposed for the first time as an alternative route of administration and in the following years after it proved to be an effective and safe treatment for respiratory allergy and thus is the true alternative to the injection route. To date, a very large number of trials provided a solid evidence for efficacy of both subcutaneous immunotherapy (SCIT), and sublingual immunotherapy (SLIT), which was accurately examined by a meta-analysis.
This article aims to provide the reader a comprehensive view on the characteristics of SCIT and SLIT, with a particular focus on their respective advantages and limitations.