Utility of silver birch and house dust mite extracts derived from licensed sublingual tablets for nasal allergen challenge

BackgroundNasal allergen challenge (NAC) is used to investigate the effects of allergen exposure and assess treatment efficacy in allergic rhinitis (AR). This study aims to establish dose-responses to NAC using licensed silver birch (SB) pollen and house dust mite (HDM) sublingual tablets as sources of the allergen extracts in participants with AR.MethodsSixteen volunteers with HDM-induced perennial AR and 15 volunteers with SB pollen-induced seasonal rhinitis underwent a graded up-dosing NAC with extracts derived from HDM allergen (Acarizax (R)) and SB (Itulazax (R)) tablets, respectively. Total nasal symptom score (TNSS, range 0-12) and peak nasal inspiratory flow (PNIF) were recorded before, at 10 min and at the end of the NAC. The dose of each allergen that provoked a TNSS of at least 7 ("provoking dose 7") in most allergic participants was identified. NACs using the "provoking dose 7" were performed on 5 non-allergic individuals to test for irritant effects. The "provoking dose 7" of HDM extract was used in a subgroup of two SB allergic, non-HDM allergic, volunteers, and vice versa for SB extract, to test for allergen specificity of the responses.ResultsMost patients experienced a TNSS of at least 7/12 at a median concentration of 1500 AU/mL for both SB pollen and HDM. The average decline in PNIF at this dose was 63.15% for SB and 63.99% for HDM. NACs using the 1500 AU/mL concentrations were performed on 5 non-allergic individuals with no symptomatic or PNIF response. 1500 AU/mL of HDM extract produced no symptoms in SB allergics nor 1500 AU/mL SB extract in HDM allergics.ConclusionFor both SB and HDM extracts, the optimal allergen dose for NAC to cause a moderate-severity response ("provoking dose 7/12") was 1500 AU/mL. Licensed sublingual allergen tablets provide a readily available and inexpensive source of SB and HDM extracts for use in future interventional studies in AR.