Sterilization of therapeutic immunoadsorbents by ionizing radiation

The application of ionizing radiation (gamma-rays from 60Co) to sterilize therapeutic immunoadsorbents (IA)s was investigated. The IAs were porous bead carriers immobilizing anti-IgE antibodies and were irradiated in both the freeze-dried and precipitated (wet) states. The IgE removal (%), the IgE adsorption capacity of IA, was acceptable in terms of practical use even after an irradiation dose of 2.5 Mrad in the precipitated state; the anti-IgE antibody itself lost much of its activity, possibly because of intermolecular crosslinking of antibody molecules, after being irradiated with a dose at least of 0.5 Mrad. In the freeze-dried state only IA consisting of CPG-1400 could tolerate a dose of 2.5 Mrad. Dose-survival curves were obtained using Bacillus pumilus spores in both the freeze-dried and precipitated IAs and the D-values were calculated to be respectively 0.27 and 0.31 Mrad. Thus, ionizing radiation may be applicable for sterilizing IAs in the precipitated state and in the freeze-dried state for an IA consisting of CPG-1400 although the initial bioburden on IA should be low.