Variant antibody identification by peptide mapping

During development of CGP56901, a monoclonal antibody (MAb) specific for a unique epitope on human IgE, the protein A-purified IgG from one of the can didate production cell lines, showed an additional minor heavy chain (H-cha in) band with a molecular weight slightly lower than that of the principal H-chain band on SDS-PAGE. The N-terminal amino acid sequence of this minor H-chain species indicated that at least the first 30 amino acids were ident ical to those of the antibody light-chain (L-chain) variable domain. More d etailed studies using peptide mapping and amino acid sequencing analysis co nfirmed a crossover event between the V genes of the antibody. The position is between Arg(108) Of the L chain and Ala(124) Of the H chain. This cross over resulted in a Variant H chain, which had 16 fewer amino acid residues than the normal CGP56901 H chain. These results show that peptide mapping i s a useful "first-line" analytical tool in the characterization of the qual ity of the monoclonal antibody. (C) 1999 John Wiley & Sons, Inc.