Composition and stability of allergenic extracts made from gamma-irradiated rye grass (Lolium perenne) pollen

Background Phenol is commonly added to allergenic extracts as a bacteriosta tic agent, but it is poisonous and also detrimental to proteins, which acce lerates extract degradation. Sterilization by gamma-irradiation of the sour ce material could be an alternative to the use of phenol. Objective To analyse the potential effects of gamma-irradiation of pollen o n the composition, potency, and stability of the resulting extract, and com pare them with those of phenol. Methods Ryegrass (Lolium perenne) pollen was sterilized by gamma-irradiatio n at a dose of 25 kGy. Extracts prepared from the irradiated pollen were th en compared by electrophoresis techniques and RAST inhibition to extracts, without or with 0.5% phenol, from nonirradiated pollen. In addition, proteo lytic activity was compared in extracts from irradiated and nonirradiated p ollen. To evaluate the stability of extracts on storage, they were analysed after forced degradation for up to 7 days at 37 degrees C. Results When fresh extracts were analysed, there were no noticeable differe nces between the three types, as judged by immunoblotting and PAST inhibiti on experiments. However, on storage, extracts from irradiated pollen appear ed to be superior to extracts from nonirradiated pollen, as some proteins w ere more stable in the former. This could be related to the lower proteolyt ic activity we have also observed in extracts from irradiated pollen. In co ntrast, extracts containing phenol degraded much faster, as proven by all o ur methods of investigation. Conclusion Gamma-irradiation of pollen did not influence the IgE-binding ca pacity of the resulting extracts, but did yield extracts with somewhat impr oved stability, probably by reducing the proteolytic activity. It may be co ncluded that gamma-irradiation of the source material represents a good alt ernative to the use of phenol for the preparation of allergenic extracts.