Functional integrity of intravenous immunoglobulin following irradiation with a virucidal dose of gamma radiation

Although intravenous immunoglobulins (IVIG) and other plasma therapeutics have had a relatively good safety record, improved methods for viral clearance are constantly being evaluated and incorporated into new manufacturing processes. Gamma irradiation has been used routinely to assure sterility of healthcare products and medical devices, but it has not been applied successfully as a viral inactivation method for biologics. We examine whether virucidal doses of gamma irradiation (50 kGy) can be delivered to a manufacturing intermediate form of IVIG, a fractionated plasma paste, with negligible effect on structural and functional integrity of purified IgG product. Immunoglobulins from paste were examined for radiation-induced damage by SDS-PAGE and ELISAs utilizing viral antigens specific for rubella, CMV and mumps. Fc domain integrity was assessed by immunoblotting, quantitatively comparing the binding of irradiated and non-irradiated materials to cell surface Fcγ receptors, and by employing quantitative RT-PCR to study the kinetics of accumulation of mRNA for the immune modulatory cytokines IL-1α, IL-1β, IL-4, IL-8, IFNγ, and TNFα. The results demonstrate that Fab and Fc domains of IVIG remain essentially intact and functional after gamma irradiation to virucidal doses, suggesting that this method could be used to enhance the safety of IVIG products.