title: Increasing the serum persistence of an IgG fragment by random mutagenesis.
abstract: The major histocompatibility complex (MHC) class I-related receptor FcRn is involved in regulating serum gammaglobulin (IgG) levels in mice. With the aim of increasing the serum half-life of a recombinant murine Fc gamma 1 fragment, the affinity for binding to FcRn at pH 6.0 has been increased by random mutagenesis of Thr252, Thr254, and Thr256 followed by selection using bacteriophage display. These residues were chosen as they are in proximity to the FcRn-IgG (Fc) interaction site. Two mutants with higher affinity (due to lower off-rates) than the wild-type Fc have been isolated and analyzed in pharmacokinetic studies in mice. The mutant with the highest affinity has a significantly longer serum half-life than the wild type fragment, despite its lower off-rate from FcRn at pH 7.4. The results provide support for the involvement of FcRn in the homeostasis of serum IgGs in mice. The indications that a homologous FcRn regulates IgG levels in humans suggest that this approach has implications for increasing the serum persistence of therapeutic antibodies.
authors.affiliation: Department of Microbiology, University of Texas Southwestern Medical Center, Dallas 75235-8576, USA.
authors.forename: V
authors.initials: V
authors.lastname: Ghetie
authors.forename: S
authors.initials: S
authors.lastname: Popov
authors.forename: J
authors.initials: J
authors.lastname: Borvak
authors.forename: C
authors.initials: C
authors.lastname: Radu
authors.forename: D
authors.initials: D
authors.lastname: Matesoi
authors.forename: C
authors.initials: C
authors.lastname: Medesan
authors.forename: R J
authors.initials: RJ
authors.lastname: Ober
authors.forename: E S
authors.initials: ES
authors.lastname: Ward
mesh_terms: D000818:Animals; D001483:Base Sequence; D001709:Biotechnology; D006207:Half-Life; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007128:Immunoglobulin Fragments / Q000097:blood* / Q000235:genetics*; D007074:Immunoglobulin G / Q000097:blood* / Q000235:genetics*; D051379:Mice; D016296:Mutagenesis; D009838:Oligodeoxyribonucleotides / Q000235:genetics; D015202:Protein Engineering; D017452:Receptors, IgG / Q000235:genetics / Q000378:metabolism
chemical_list: D007128:Immunoglobulin Fragments; D007074:Immunoglobulin G; D009838:Oligodeoxyribonucleotides; D017452:Receptors, IgG