A randomized controlled trial of sublingual immunotherapy for Japanese cedar pollinosis

Japanese cedar pollen represents an important and unique allergen. Sublingual immunotherapy (SLIT) has been suggested to be a highly effective route of desensitization against a variety of allergens. However, little information is available about its use in cedar pollen allergy.

A blinded randomized, placebo-controlled trial employing SLIT for cedar pollinosis was conducted over a period of 6 months. Sixty-seven subjects were enrolled and the symptom scores during the pollen season were evaluated by a symptom diary, measurement of cedar-specific IgE and IgG4, and determination of Cry j-specific Th2 clones before SLIT and before and after the pollen season.

No major adverse effects were observed in either group. The serum-specific IgG4 activity increased significantly after SLIT in the active group. The active group also exhibited significantly lower symptom scores compared to the placebo. The specific Th2 clone sizes were not significantly different between the groups before the pollen season. However, an increase in the clone size was observed after the pollen season in the placebo group, but not in the active group.

Use of SLIT for Japanese cedar pollinosis was found to be safe and associated with an increase in cedar-specific IgG4 levels. Such therapy inhibited the increase in Cry j-specific Th2 clone size induced by pollen exposure. Finally, use of SLIT resulted in significant improvement of the clinical symptoms of cedar pollinosis in this patient population. These observations suggest that SLIT may offer another safe approach to the management of cedar pollinosis.