title: Preventing peptide-induced anaphylaxis: addition of C-terminal amino acids to produce a neutral isoelectric point.
abstract: BACKGROUND
  Progress in peptide immunotherapy for the treatment of autoimmune diseases has been hampered by reports of anaphylactic reactions in both mice and human subjects. Fatal anaphylaxis in nonobese diabetic (NOD) mice has been described after repeated subcutaneous insulin peptide B:9-23 immunizations. On the basis of observations that rapid systemic delivery of peptide to a sensitized mouse (eg, intravenous delivery) increases the anaphylactic response, it was hypothesized that slowing down the absorption of the peptide would prevent anaphylaxis.
  
  
  OBJECTIVE
  We sought to prevent anaphylaxis from B:9-23 peptide by altering the isoelectric point (pI) to neutral, thereby decreasing solubility and rate of absorption after subcutaneous injection.
  
  
  METHODS
  B:9-23 peptide was modified by the addition of 2 arginine (RR) amino acids to the C-terminus to create B:9-23RR, thereby increasing the pI from 5.4 to 7.0. Both native and modified B:9-23 peptide were tested for the ability to induce anaphylaxis in a NOD mouse model of self-peptide anaphylaxis.
  
  
  RESULTS
  This modification resulted in a peptide vaccine with decreased solubility when administered subcutaneously at a neutral pH. B:9-23RR significantly protected NOD mice from peptide-induced anaphylaxis compared with B:9-23 peptide. Furthermore, B:9-23RR peptide retains its ability to induce insulin autoantibodies and prevent diabetes in NOD mice.
  
  
  CONCLUSIONS
  The modification of the pI of a peptide vaccine might be a generalizable method to prevent anaphylaxis without changing the immunologic properties.
authors.affiliation: Section of Gastroenterology, Hepatology and Nutrition, The Children's Hospital, Denver, Colorado, USA. Edwin.liu@uchsc.edu
authors.forename: Edwin
authors.initials: E
authors.lastname: Liu
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Moriyama
authors.forename: Norio
authors.initials: N
authors.lastname: Abiru
authors.forename: Johanna
authors.initials: J
authors.lastname: Paronen
authors.forename: Devasenan
authors.initials: D
authors.lastname: Devendra
authors.forename: Fred D
authors.initials: FD
authors.lastname: Finkelman
authors.forename: George S
authors.initials: GS
authors.lastname: Eisenbarth
mesh_terms: D000595:Amino Acid Sequence; D000707:Anaphylaxis / Q000139:chemically induced / Q000517:prevention & control*; D000818:Animals; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007114:Immunization; D007328:Insulin / Q000008:administration & dosage / Q000009:adverse effects* / Q000737:chemistry / Q000276:immunology; D007526:Isoelectric Point; D051379:Mice; D016688:Mice, Inbred NOD; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000008:administration & dosage / Q000009:adverse effects* / Q000737:chemistry / Q000276:immunology
chemical_list: D007328:Insulin; D010446:Peptide Fragments; C097877:insulin B (9-23)