Affinity Purification of Human Immunoglobulins A, G, and M by Hexamer Peptide Ligand

Antibody-based therapeutics account for a third of all new treatments in USA and the size of the therapeutic antibody market is projected to reach over 30 billion per year by 2010. Although most of antibodies in the market and in the clinical development are immunoglobulin-G-based drugs, more and more attention has been paid to immunoglobulins A and M for their potential as mucosal vaccines and therapeutic agents. A family of linear hexamer peptides, exhibiting the ability to recognize and bind immunoglobulin G (IgG) through its Fc portion, has been previously identified through a three-step screening of a synthetic solid phase peptide ligand library. Among them, peptide ligand HWRGWV also exhibits the ability to bind IgA and IgM with different affinities because of different structures and interactions. Chromatographic resins containing HWRGWV ligand at different peptide densities have been extensively characterized for their applicability in affinity chromatography for the downstream processing of human immunoglobulins A, G, and M. The ligand shows the ability to purify hIgA, hIgG, and hIgM from complete mammalian cell culture medium containing 10% fetal calf serum and 5% tryptose phosphate broth with high recovery and purity. The influence of the elution pH and salt concentration, and the possibility for one step purification of hIgA, hIgG, hIgM mixture were also investigated.&'