Polymerized whole ragweed: A two-year follow-up of patients treated with an improved method of immunotherapy

Abstract

We have previously reported, in a 1-yr study, the effectiveness of polymerized ragweed (PRW) as an improved method of immunotherapy for patients suffering from ragweed hay fever. In that study, treatment with PRW was found to be superior to treatment with monomer ragweed extract (MRW) because of the reduced allergenicity of the PRW. The current study is a 2-yr follow-up of nine patients treated with PRW and nine patients treated with MRW. After 1 yr of immunotherapy, both MRW- and PRW-treated patients received 9,000 protein nitrogen units (PNU) and after a second year of maintenance therapy both groups received a cumulative dose of 15,000 PNU. Serum blocking antibody against ragweed antigen E (AgE) was measured periodically during the study. After 1 yr of immunotherapy, blocking antibody in the PRW- and MRW-treated groups was similar with respective means of 1,300 and 1,500 ng AgE bound per milliliter of serum. At the end of 2 yr of therapy, these serum AgE binding activities rose to 2,700 and 4,100, respectively. No significant local or systemic reactions occurred in the PRW-treated group during the year of maintenance therapy. However, large local reactions prevented three of the nine patients treated with MRW from achieving a monthly maintenance schedule. A significant decrease in rhinitis symptoms was noted in both treated groups as compared with the season before immunotherapy and also to a group of patients untreated with immunotherapy during the 1978 ragweed season.