Very few substitutions in a germ line antibody are required to initiate significant domain exchange

J Virol. 2010 Oct;84(20):10700-7. doi: 10.1128/JVI.01111-10. Epub 2010 Aug 11.


2G12 is a broadly neutralizing anti-HIV-1 monoclonal human IgG1 antibody reactive with a high-mannose glycan cluster on the surface of glycoprotein gp120. A key feature of this very highly mutated antibody is domain exchange of the heavy-chain variable region (V(H)) with the V(H) of the adjacent Fab of the same immunoglobulin, which assembles a multivalent binding interface composed of two primary binding sites in close proximity. A non-germ line-encoded proline in the elbow between V(H) and C(H)1 and an extensive network of hydrophobic interactions in the V(H)/V(H)' interface have been proposed to be crucial for domain exchange. To investigate the origins of domain exchange, a germ line version of 2G12 that behaves as a conventional antibody was engineered. Substitution of 5 to 7 residues for those of the wild type produced a significant fraction of domain-exchanged molecules, with no evidence of equilibrium between domain-exchanged and conventional forms. Two substitutions not previously implicated, A(H14) and E(H75), are the most crucial for domain exchange, together with I(H19) at the V(H)/V(H)' interface and P(H113) in the elbow region. Structural modeling gave clues as to why these residues are essential for domain exchange. The demonstration that domain exchange can be initiated by a small number of substitutions in a germ line antibody suggests that the evolution of a domain-exchanged antibody response in vivo may be more readily achieved than considered to date.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Antibodies, Monoclonal / chemistry
  • Antibodies, Monoclonal / genetics*
  • Antibodies, Monoclonal / immunology*
  • Antibodies, Neutralizing / chemistry
  • Antibodies, Neutralizing / genetics*
  • Antibodies, Neutralizing / immunology*
  • Broadly Neutralizing Antibodies
  • HIV Antibodies / chemistry
  • HIV Antibodies / genetics*
  • HIV Antibodies / immunology*
  • HIV Envelope Protein gp120 / chemistry
  • HIV Envelope Protein gp120 / immunology*
  • HIV-1 / chemistry
  • HIV-1 / immunology*
  • Humans
  • Immunoglobulin Variable Region / chemistry
  • Immunoglobulin Variable Region / genetics
  • Immunoglobulin Variable Region / immunology
  • Models, Molecular
  • Molecular Sequence Data
  • Polysaccharides / chemistry
  • Polysaccharides / immunology
  • Protein Structure, Tertiary
  • Sequence Homology, Amino Acid


  • 2G12 monoclonal antibody
  • Antibodies, Monoclonal
  • Antibodies, Neutralizing
  • Broadly Neutralizing Antibodies
  • HIV Antibodies
  • HIV Envelope Protein gp120
  • Immunoglobulin Variable Region
  • Polysaccharides
  • gp120 protein, Human immunodeficiency virus 1