Methods: One-hundred and two patients presenting allergic rhinitis with or without asthma were selected for a randomized double-blind, placebo-controlled trial and distributed into three groups: DPT (Dpt allergen extract, n=34), DPT+MRB (Dpt allergen plus mixed respiratory bacterial extracts, n=36), and Placebo (n=32). Clinical evaluation and immunological analyses were carried out before and after 12 and 18 months of treatment, including rhinitis/asthma symptom and medication scores, skin prick test (SPT) to Dpt extract, and measurements of Dpt-, Der p 1-, Der p 2-specific IgE, IgG4, and IgG1 in serum and -specific IgA in saliva and nasal lavage fluid.
Results: Clinical results showed a significant decline in rhinitis/asthma symptom scores in all groups, but medication use decreased only in active DPT group at 12 months. SPT results showed no significant changes and SLIT was generally safe, with no severe systemic reactions. SLIT using Dpt allergen alone induced increased serum IgG4 levels to Dpt, Der p 1 and Der p 2, and increased serum IgG1 and salivary IgA levels to Dpt and Der p 1. SLIT using DPT+MRB was able to decrease IgE levels, particularly to Der p 2, to increase salivary IgA levels to Der p 1, but had no changes on specific IgG4 and IgG1 levels.
Conclusions: Therefore, SLIT seems to be effective in ameliorating clinical symptoms, but only active SLIT was able to modulate the mucosal and systemic antibody responses. These findings support the role of specific serum IgG4 and IgG1, in addition to salivary IgA, as protective or blocking antibodies as well as biomarkers of tolerance that may be useful for monitoring activation of tolerance-inducing mechanisms during allergen immunotherapy.