Background: Various studies have shown the clinical efficacy of sublingual immunotherapy in grass pollen-induced rhinoconjunctivitis.
However, even short-term treatment with grass extracts might cause sensitizations to formerly unrecognized antigens.

Objective: To determine whether the antibody profiles are changing in patients receiving a defined grass pollen extract prior to and during the grass pollen season.

Methods: A randomized, double blind, placebo-controlled, multicenter phase II/III trial was started prior to the commencement of the grass pollen season. Patients with grass pollen allergy were randomly allocated to four groups, and received daily a standardized tablet at different doses. Treatment was started 8 weeks prior to the beginning of the pollen season and stopped at the end of the season. Blood samples were taken at the beginning of the study, at the beginning and the end of the pollen season, and one year after commencement of the study.

Results: At the beginning of the study, all patients tested positive for the major grass pollen allergens, but negative to the minor antigens.
In all patients, the degree of antibody reactivity rose considerably after starting active treatment and fell back to the initial values within one year. Immunoglobulin (Ig) E antibodies to the minor antigens remained negative, independent of treatment and seasonal exposure. In contrast to IgE, specific IgG antibodies to all allergens tested revealed no specific trend.

Conclusions: Immunotherapy with grass allergen tablets was accompanied by an increase in grass-specific IgE antibodies, which further
increased during pollen exposure, followed by a post-treatment drop in patient- and disease-specific antibodies. During this short course
of treatment, no patient developed any additional sensitizations.

Key words: Grass pollen allergy. Antibody profile. IgE. IgG. Sublingual immunotherapy. Tablet