BACKGROUND: Local nasal immunotherapy is accepted as an alternative to the injection route for allergic rhinitis. Despite this, little is known about the kinetics of the allergen after nasal delivery in allergic subjects. OBJECTIVE: We aimed at assessing the biodistribution of 123I-radiolabelled Par j 1 in Parietaria-allergic subjects, in comparison with healthy volunteers. METHODS: Purified Par j 1 was radiolabelled with 123I and sprayed into the nostrils of three control subjects and three Parietaria-allergic volunteers. Dynamic and static scintigraphic images of the head were recorded at serial times and blood samples were obtained to measure the plasma radioactivity, and to assess the presence of circulating radiolabelled species by gel chromatography. RESULTS: In Parietaria-sensitized subjects, the radiolabelled allergen was rapidly cleared from the nasal cavity and transported to pharynx, and little local persistence was seen. This differed from healthy subjects where nasal clearance of the tracer was slower and nasal radioactivity persisted up to 24 h. The increase in plasma radioactivity paralleled swallowing of the allergen in both groups, and plasma chromatographic profile did not differ between allergic and healthy volunteers. CONCLUSIONS: Sensitization to the allergen affects its local biodistribution. Gastrointestinal absorption is relevant also for the intranasal route.
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