House dust mite allergy and treatments
The prevalence of allergic asthma, the most common allergic disease, increased dramatically in the last 20 years. This exacerbated immune-mediated disorder is characterized by chronic airway inflammation, mucus production, and variable airflow obstruction with airways hyperresponsiveness (AHR). House dust mites (HDM) can be considered as one of the most important provider of inhalant allergens within the world and the mite sensitization affects more than 20% of the population from industrialized countries, including Thailand.
As it is clearly established that allergen-specific Th2 cells play the central role for the mediation of this chronic inflammatory response, the aim of a vaccine against HDM allergy could be the induction of allergen-specific Th1 or Treg cells to prevent or to skew the Th2 response into a protective one.
Conventional allergen-specific immunotherapy (SIT) is, up to now, the unique immune-modifying therapy that has been recommended for the specific treatment of HDM allergy. When effective, such immunotherapy triggers Th1 or Treg cytokines (IFNg, IL-10, TGFb) as well as blocking allergen-specific IgG4 antibodies to down-regulate the Th2-biased allergic response. However, such treatment presents some disadvantages and is sometimes risky. Indeed, SIT involves 50-80 subcutaneous (SCIT) or sublingual (SLIT) administration of HDM allergen extracts using incremental regimes within 1 to 3 years. The other main limiting factor in SIT is anaphylactic side-effects, which vary in incidence from 0.1-5% of individuals (prime/boosting of specific IgE response by using natural allergen displaying IgE reactivity) and the triggering of new allergic responses against allergens for which patients were not sensitized prior to these treatments. Moreover, there are issues about the production, standardization and composition of the HDM allergen extracts. Notably, it is well known that some important HDM allergens are present in very tiny amounts in such allergen extracts.
Because of these above disadvantages, innovative and more effective therapies are urgently required. Thanks to the great advances in molecular allergology and immunology, new anti-allergy vaccines are currently developed to treat HDM allergy and asthma.