Determination of the clearance factor for transmissible spongiform encephalopathy agents during the manufacturing process of polygeline

Objective:To determine the safety of polygeline, a gelatine-derived plasma substitute produced from bovine bones, in terms of safety for bovine spongi form encephalopathy (BSE) by evaluating the ability of the manufacturing pr ocess of polygeline to eliminate agents related to transmissible spongiform encephalopathy (TSE) through the validation of three main production steps . Design: Laboratory scale experimental process tin duplicate) using 20% hams ter-adapted 263K scrapie-infected brain homogenate as infective titrated so urce (10(9) LD50/ 2 ml), added to each material before being processed and titrated in hamsters. Experiment 1: time/temperature dependency of gelatine autoclaving. Experiment 2: cross-linking and distillation. Experiment 3: f inal sterilization. Monitoring period: 1 year with daily animal clinical ob servation Histology of all brains. Setting: LCG-RBM laboratories, Italy; st rict GLP compliance. Measurements and results: Heating the gelatine (at conditions lower than th ose used in production process) was very effective in inactivating the infe ctivity of TSE agents. Clearance factors were reproducible, dependent upon time and temperature, reaching a total theoretical process clearance in the range of 9.2-13.8 [6.9 +/- 2.3 (+ 4.6)] log(10) LD50. Conclusions: These experimental results provide further important data conf irming the safety of the procedural steps; this complements the safety due to the careful sourcing of the raw material. There is high assurance that t here is no significant risk of TSE transmission to humans by the therapeuti c administration of polygeline.