title: Gamma ray sterilization of delta inulin adjuvant particles (Advax™) makes minor, partly reversible structural changes without affecting adjuvant activity.
abstract: We earlier identified a developmental series of seven isoforms/polymorphs of microparticulate inulin by comparing non-covalent bonding strengths. Their pharmaceutical utility lies in the modulation of cellular immunity, exploited as vaccine adjuvants (Advax™) especially for delta inulin (DI). As such particles cannot be sterilized by filtration we explore the effect of (60)Co gamma radiation (GR) on inulin isoforms, particularly DI. Its adjuvant activity and overt physical properties were unaffected by normal GR sterilizing doses (up to 25kGy). Heating irradiated isoform suspensions near their critical dissolution temperature revealed increased solubility deduced to reflect a single lethal event in one component of a multi-component structure. Local oxidative effects of GR on DI were not found. The observed DI loss was almost halved by re-annealing at the critical temperature: surviving inulin chains apparently reassemble into smaller amounts of the original type of structure. Colorimetric tetrazolium assay revealed increases in reducing activity after GR of raw inulin powder, which yielded DI with normal physical properties but only 25% normal recovery yet 4× normal reducing ability, implying final retention of some GR-changed inulin chains. These findings suggest minimal inulin chain cleavage and confirm that GR may be a viable strategy for terminal sterilization of microparticulate inulin adjuvants.
authors.affiliation: Vaxine Pty Ltd., Flinders Medical Centre, Bedford Park, Adelaide 5042, Australia; Cancer Research Laboratory, Australian National University Medical School, The Canberra Hospital, Canberra 2605, Australia; John Curtin School of Medical Research, Australian National University, Canberra 2601, Australia. Electronic address: peter.cooper@anu.edu.au.
authors.forename: P D
authors.initials: PD
authors.lastname: Cooper
authors.affiliation: The Mawson Institute, University of South Australia, Adelaide 5095, Australia.
authors.forename: T G
authors.initials: TG
authors.lastname: Barclay
authors.affiliation: The Mawson Institute, University of South Australia, Adelaide 5095, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Ginic-Markovic
authors.affiliation: Vaxine Pty Ltd., Flinders Medical Centre, Bedford Park, Adelaide 5042, Australia; Department of Diabetes and Endocrinology, Flinders Medical Centre/Flinders University, Adelaide 5042, Australia. Electronic address: nikolai.petrovsky@flinders.edu.au.
authors.forename: N
authors.initials: N
authors.lastname: Petrovsky
mesh_terms: D000276:Adjuvants, Immunologic / Q000737:chemistry*; D000818:Animals; D005260:Female; D005720:Gamma Rays; D007444:Inulin / Q000737:chemistry*; D051379:Mice; D008807:Mice, Inbred BALB C; D020033:Protein Isoforms / Q000737:chemistry; D013242:Sterilization / Q000379:methods*
chemical_list: D000276:Adjuvants, Immunologic; D020033:Protein Isoforms; D007444:Inulin
keywords: AI-2; Adjuvant; BP; British Pharmacopoeia; DI; DP; DPn; EDTA; EI; GI; GR; Immunity; Inulin; PBS; Polymorph; RI; RT; SD; Sterilization; Tc; USP; United States Pharmacopoeia; Vaccine; alpha-2 inulin; critical temperature of an isoform/polymorphic variant; degree of polymerization; delta inulin; epsilon inulin; ethylene diamine tetra acetate; gamma inulin; gamma radiation; kGy; kilogray; number average degree of polymerization; phosphate buffered saline; refractive index; room temperature (20–21°C); standard deviation