title: The Role of Protein Excipient in Driving Antibody Responses to Erythropoietin.
abstract: Human serum albumin (HSA) is an excipient present in formulations of several recombinant protein products that are approved for clinical use. We investigated the relative contributions of HSA and HSA particles to the generation of antibody responses against recombinant human erythropoietin (rhEPO) and the excipient HSA itself. Protein samples were characterized before injection for quantities of monomeric proteins, soluble protein aggregates, and nano- and micron-sized particles. rhEPO, containing various concentrations of HSA particles, were injected three times a week for 8 weeks into mice. Hematocrits and the production of anti-rhEPO and anti-HSA antibodies were determined at various time points. Levels of antibodies against rhEPO in mice injected with HSA-containing rhEPO were higher than those in mice treated with HSA-free rhEPO. Mice injected with formulations that contained particles of HSA produced strong anti-HSA antibody responses; whereas these responses were greatly reduced when particle-free formulations were administered. In contrast, anti-rhEPO antibody responses were not affected by the presence of particles.
authors.affiliation: Department of Pharmaceutical Sciences, University of Colorado Denver, Anschutz Medical Campus, Aurora, Colorado 80045.
authors.forename: Merry
authors.initials: M
authors.lastname: Christie
authors.affiliation: Global Biologics Research and Development, Hospira, Lake Forest, Illinois 60045.
authors.forename: David
authors.initials: D
authors.lastname: Peritt
authors.affiliation: Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado 80045.
authors.forename: Raul M
authors.initials: RM
authors.lastname: Torres
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, Boulder, Colorado 80309.
authors.forename: Theodore W
authors.initials: TW
authors.lastname: Randolph
authors.affiliation: Department of Pharmaceutical Sciences, University of Colorado Denver, Anschutz Medical Campus, Aurora, Colorado 80045. Electronic address: john.carpenter@ucdenver.edu.
authors.forename: John F
authors.initials: JF
authors.lastname: Carpenter
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology*; D000917:Antibody Formation / Q000276:immunology*; D000068817:Epoetin Alfa / Q000276:immunology; D004921:Erythropoietin / Q000276:immunology*; D005079:Excipients / Q000008:administration & dosage*; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D011994:Recombinant Proteins / Q000276:immunology*; D012709:Serum Albumin / Q000276:immunology*
chemical_list: D000906:Antibodies; D005079:Excipients; D011994:Recombinant Proteins; D012709:Serum Albumin; D004921:Erythropoietin; D000068817:Epoetin Alfa
keywords: excipients; immune response; particle size; protein aggregation; proteins