Allergic rhinitis and intralymphatic vaccination : immune response and tolerance

Abstract

The overall goal of this thesis was to study novel immunological mechanisms for the development of pollen-induced allergic rhinitis (AR) and to evaluate the clinical response in combination with immunological changes in AR patients treated with intralymphatic immunotherapy (ILIT).

In paper I, an increased fraction of neutrophils were detected in the nasal mucosa of AR patients compared with healthy controls. This accumulation was mainly due to a rise in a specific neutrophil subtype, CD16[high]CD62L[dim]. Studies of the biological functions revealed that CD16[high]CD62L[dim] neutrophils increased T-cell activation and induced eosinophil migration. Paper II investigated the expression of Notch receptors on CD4[+] T-cells and the presence of their corresponding ligands on epithelial cells and neutrophils. The fraction of CD4[+]Notch1[+] and CD4[+]Notch4[+] T-cells was higher in AR patients than in healthy controls. The expression levels of Notch ligand Jagged-1 (JAG-1) and Delta-like ligand-1 (DLL-1) were increased in nasal epithelial cells among AR patients. Likewise, neutrophils in nasal mucosa and blood displayed increased expression of JAG-1. Together this signals an increased activity in the Notch1/4 - JAG-1/DLL-1 pathways among allergic individuals suggesting that Notch signaling may participate in the regulation of T-cells in AR. In paper III the safety and efficacy of intralymphatic immunotherapy (ILIT) with two allergens given concomitantly were assessed. ILIT with two allergens appears to be a safe procedure with limited side effects. Allergen challenge, quality of life scores, and consumption of rescue medication indicated that ILIT reduced rhinitis symptoms. In patients treated with active ILIT timothy-specific IgG4, effector memory Tregs, Th1 central memory CD4[+] T-cells, and effector memory CD4[+] T-cells in the lymph nodes were increased after treatment, further supporting the rationale for this alternative administration route. Paper IV describes the outcome of two randomized, double-blinded, placebo-controlled trials. The first included patients that had recently ended three years of subcutaneous immunotherapy (SCIT), and the second contained patients without prior allergen-specific immunotherapy treatment. The dosage of 1000-3000-10000 SQ-U with one month in between was evaluated. This protocol was safe for patients previously treated with SCIT. The combined symptom and medication score (CSMS) was improved compared to the placebo group, and the timothy-specific IgG4 levels in the blood were doubled. In ILIT de novo, the first two patients that received active treatment developed severe adverse reactions at 5000 SQ-U. A modified up-dosing schedule, 1000-3000-3000 SQ-U, appeared safe but failed to improve the CSMS, quality of life, and nasal provocation response. Flow cytometry analyses could not detect T-cell changes, while lymph node-derived dendritic cells showed increased activation. In Paper V, patients treated with ILIT 5-6 years earlier returned for a follow-up visit to study the remaining clinical effects and persisting immunological changes. To gain statistical power, AR patients without previous AIT were included in the control group. The nasal provocation test displayed no difference between active ILIT and the control group. Still, the combined symptom and medication score were reduced in active ILIT compared to the control group. Timothy-specific IgE was decreased compared to pretreatment levels. Timothy-specific IgG4 and memory T-cells in lymph nodes were increased. Basophils displayed characteristics of reduced allergen sensitivity.

In summary: CD16[high]CD62L[dim] neutrophils may play a role in AR pathology by priming CD4[+] T-cells and enhancing eosinophil migration. Notch signaling appears to be another novel pathway for the development of pollen allergy involving T-cell regulation. These results suggest novel targets for the development of future AR therapy. In ILIT, two allergens can be concomitantly injected without risk of tangible side effects. In contrast, an increase in the dose, from 1000SQ-U to 5000SQ-U, is associated with a severe risk for anaphylactic reactions and should be avoided. A moderate dose increase to 3000SQ-U does not seem to improve the therapeutic outcome further. It is evident that the favorable effects of ILIT remain long after the last injection, but a booster might be needed after three to five years. Altogether the presented ILIT data further support the future use of ILIT in clinical praxis.