Facilitated Allergen Binding (FAB) Is a Meaningful Immunological Biomarker for Monitoring Immediate Clinical Efficacy in Short-Term Peptide Allergen Immunotherapy

Rationale: Short-term peptide-allergen-immunotherapy is a novel approach for treating allergic rhinoconjunctivitis. We investigated whether changes in mucosal reactivity to allergen exposure after this short-term therapy are detectable in the immunological parameters of sIgG4 and the functional blocking antibody response measured by facilitated allergen binding (FAB).

Methods: Data was collected from a DBPC dose-finding study in 198 patients who received placebo or a peptidase-hydrolysate of grass-pollen peptides at 5 visits over 4 weeks at cumulative doses of up to 370µg (EudraCT-No:2013-005445-37). Conjunctival allergen challenge was used as a surrogate marker of efficacy before and after immunotherapy. We have shown that this parameter has a predictive value for patients’ symptoms and medication needs during the pollen season. Serum samples were taken to determine sIgG4 and FAB.

Results: Patients exhibiting diminished reactivity and tolerating an at least 10-fold higher concentration of the conjunctival challenge solution showed a significantly greater increase in FAB (20.01% ± 16.706) than patients who did not improve (p = 0.01); The immediate change in sIgG4 observed in the improved patients was not significant (p = 0.233). Also, patients showing no reaction to the highest conjunctival allergen concentration had significantly higher FAB values (p = 0.034) than patients who still reacted to one of the allergen challenge dilutions; the immediate induction of sIgG4 found in the non-reacting patients was not significant (p = 0.797).

Conclusions: After 4 weeks of peptide allergen immunotherapy, the immediate appearance of FAB can be correlated with a meaningful clinical parameter of therapeutic efficacy.