A 5-Year Open-Label Follow-up of a Randomized Double-Blind Placebo-Controlled Trial of Intralymphatic Immunotherapy for Birch and Grass Allergy Reveals Long-term Beneficial Effects

Background: Intralymphatic immunotherapy (ILIT) is a novel, faster alternative to conventional allergen immunotherapy (AIT). Few previous studies have evaluated its long-term effects. The objective of the present study was to complete a 5-year follow-up of a randomized double-blind placebo-controlled trial of ILIT for a combination of birch and grass allergens. Methods: Fifty-eight patients with allergic rhinitis were treated with either placebo or a combination of ALK Alutard Birch and Grass 1000 SQ-U administered in 3 intralymphatic injections at 1-month intervals. A year after the vaccination, the symptoms induced by nasal provocation were significantly reduced. After 5-6 years, 20 out of 26 actively treated patients were followed up with a nasal provocation test (NPT) and seasonal registration of the combined symptom and medications score (CSMS), IgE and IgG4 levels in blood, and immunological markers in blood and lymph nodes and compared with 13 unvaccinated controls. Results: The reduction in the NPT response with ILIT at year 1 could not be convincingly reproduced at year 5. The new CSMS scores were markedly lower among the previously treated patients than among the control group. Furthermore, grass-specific IgG4 was increased, grass-specific IgE decreased, FcεR1 on basophils was reduced, and the fraction of memory T-cells in lymph nodes increased. Conclusion: The combination of seasonal clinical data and immunological parameters supports the notion of a long-lasting effect of ILIT. These data support the concept of ILIT as a good alternative to traditional AIT in pollen-induced allergic rhinitis.