Detergent Micelle Conjugates Containing Amino Acid Monomers Allow
Purification of Human IgG near Neutral pH
Abstract
Industrial scale production of therapeutic monoclonal antibodies (mAbs)
is commonly achieved with Protein A chromatography, a process that
requires exposure of the antibody to strongly acidic conditions during
the eluting step. Exposure to acid inactivates virus contaminants but
may, in parallel, lead to antibody aggregation that must be eliminated
or kept at acceptably low levels. This report seeks to provide a
practical method for overcoming a long-standing problem. We show how
Brij-O20 detergent micelles, conjugated by the amphiphilic
[(bathophenanthroline)3:Fe2+] complex in the presence of amino acid
monomers: phenylalanine (Phe), tyrosine (Tyr), tryptophan (Trp),
isoleucine (Ile) or valine (Val), efficiently capture polyclonal human
IgG (hIgG) at neutral pH and allow its recovery by extraction either at
pH 4 (85-97% yield) or at pH 6.3 (72-84% yield). Of the five amino
acid monomers surveyed, Phe or Tyr produced the highest overall process
yield at both pH 4 and 6.3. The monomeric state of the purified hIgG’s
was confirmed by dynamic light scattering (DLS). Potential advantages of
the purification method are discussed.