Polyethylene glycol-modified ragweed pollen extract in rhinoconjunctivitis

Abstract

Sixty-two ragweed-sensitive adult subjects volunteered to take part in a 2-year, placebo-controlled efficacy study of polyethylene glycol (PEG)-modified ragweed extract, in ragweed pollen-induced rhinoconjunctivitis. At the beginning of the study, subjects were stratified according to skin sensitivity to ragweed extract and PEG-modified ragweed and the severity of hay fever in the previous year. There was random allocation of half to active treatment and half to placebo treatment. Before the first ragweed pollen season the 36 most sensitive subjects received 10 weekly injections (group 1), and the remaining 26 received six injections (group 2). Before the second season all subjects received 10 injections. Doses increased by half a log concentration each week unless there were adverse reactions. The mean total dose received by group 1 in year 1 was 385 μg of protein (28.9 μg AgE) and received by group 2 was 218 μg of protein (16.4 μg AgE). In year 2 the mean total dose was 1829 jug (137.2 μg AgE). Sixty-six percent of injections elicited no reaction or a mild local reaction; the remaining injections produced local redness and swelling more than 2 inches in diameter. Four percent of injections produced systemic symptoms. PEG-modified ragweed stimulated increases in ragweed specific IgG antibody both years, but increases in ragweed specific IgE antibody were significant only in group 1 in year 1. The magnitude of the IgG antibody changes was directly related to the total dose injected. At the beginning of the second year, PEG-modified ragweed-treated subjects still had elevated IgG antibody levels. In the first year the subjects who had received 10 PEG-modified ragweed injections improved in symptoms and medications; however, in subjects who received only six injections there was no difference between active and placebo treatment. In year 2 the actively treated group had significantly less symptoms and needed less medication, and the improvement was significantly better than that observed during the first year. The results indicate that PEG-modified ragweed, administered in sufficient doses, is effective in reducing symptoms of ragweed-induced rhinoconjunctivitis and that the effect may be additive when it is administered over consecutive years.