In vivo and in vitro immunological changes induced by a short course of grass allergy immunotherapy tablets.

BACKGROUND The fast-dissolving grass allergy immunotherapy tablet (grass AIT), Grazax, has proven effective in grass pollen-induced rhinoconjunctivitis. OBJECTIVE To investigate the immunological and cutaneous changes induced after a short course with grass AIT. METHODS We performed a randomized, double-blind placebo-controlled trial with 78 patients randomly assigned to receive either grass AIT or placebo in a 2:1 ratio. Treatment lasted at least 8 weeks before the grass pollen season (GPS), and continued until the season finished. Specific immunoglobulin (Ig) G4, IgE, and IgE-blocking factor to Phleum pratense were measured at the beginning of the trial and at different intervals during treatment. Immediate and delayed skin tests with P pratense were also performed. Safety endpoints were defined in terms of adverse events reported. RESULTS A total of 75 patients completed the trial (50 active and 25 placebo). P pratense IgG4, IgE, and IgE-blocking factor in actively treated patients increased significantly from baseline to the start of the GPS compared to placebo (P > .001, P = .017, and P = .005, respectively). The immediate cutaneous response was reduced during therapy in actively treated subjects, whereas placebo-treated subjects showed a decrease only after the start of the GPS. The delayed response to the intradermal test in grass AIT-treated subjects diminished, although not in a significantly different way from the placebo-treated subjects. CONCLUSION Treatment with grass AIT for grass pollen allergic rhinoconjunctivitis induces immunological changes after only 1 month of treatment.