Allergy immunotherapy: Future directions for the 2020s.

Allergy immunotherapy (AIT), whether administered as subcutaneous immunotherapy or as sublingual immunotherapy (SLIT), is an effective treatment for sensitization to inhalant allergens. There remain, however, some important unresolved issues, such as the need for compelling evidence for or against the efficacy of treatment with multiple unrelated allergen extracts and optimal dosing with SLIT-liquid preparations. Both methods of AIT involve prolonged periods of treatment to achieve persisting benefit. This can be inconvenient and expensive, and failure to complete the period of prescribed treatment is common with both methods. New approaches are being developed and studied to make AIT more effective, safer, or more convenient. Among these approaches are using alternative routes of administration; using adjuvants, including vitamin D, Toll-like receptor ligand agonists, biologics, or probiotics; introducing additional SLIT tablets; defining the patterns of major and minor allergen sensitivity of patients and the content of allergen extracts to better match sensitization with treatment; and treating cats to reduce their allergen release. The allergen molecules themselves are being altered to make them less reactive with specific immunoglobulin E, both by creating allergoids and by using recombinant technology to produce modified allergen molecules. Which, if any, of these new approaches will become part of AIT practice in the next decade depends in part on their efficacy and in part on the availability of the resources to adequately study them.