Characterization and HIV-1 fusion inhibitory properties of monoclonal Fabs obtained from a human non-immune phage library selected against diverse epitopes of the ectodomain of HIV-1 gp41

J Mol Biol. 2005 Nov 11;353(5):945-51. doi: 10.1016/j.jmb.2005.09.044. Epub 2005 Sep 30.


Using a human non-immune phage library comprising more than 10(9) functional human antibody specificities in Fab format, we have been able to select a set of eight monoclonal Fabs targeted against diverse epitopes of the ectodomain of gp41 from HIV-1. The antigens used for panning the antibodies comprised two soluble, disulfide-linked, trimeric polypeptides derived from gp41, N(CCG)-gp41 and N35(CCG)-N13. The former comprises an exposed trimeric coiled-coil of the N-helices of gp41 fused in helical phase to the minimal thermostable ectodomain of gp41, while the latter comprises only the trimeric coiled-coil of N-helices. The selected Fabs were probed by Western blot analysis against four antigens: N(CCG)-gp41, N35CCG-N13, N34CCG (a smaller version of N35CCG-N13), and the minimal thermostable ectodomain core of gp41 in its six-helix bundle conformation (6-HB). Three classes of Fabs were found: class A (two Fabs) interact predominantly with the 6-HB; class B (four Fabs) interact with both the 6-HB and the internal trimeric coiled-coil of N-helices; and class C (two Fabs) interact specifically with the internal trimeric coiled-coil of N-helices. The IC50 values for the Fabs, expressed as bivalent mini-antibodies, ranged from 6 microg/ml to 60 microg/ml in a quantitative vaccinia virus-based reporter gene assay for HIV-1 envelope-mediated cell fusion using the envelope from the HIV-1 T tropic strain LAV. The two most potent fusion inhibitors belonged to class B. This panel of Fabs provides a set of useful probes for studying HIV-1 envelope-mediated cell fusion and may serve as a basis for developing Fab-based anti-HIV-1 therapeutics.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural

MeSH terms

  • Anti-HIV Agents
  • Antibodies, Monoclonal / immunology
  • Antibodies, Monoclonal / pharmacology
  • Antibodies, Viral / pharmacology
  • Antigens, Viral / chemistry
  • Antigens, Viral / immunology
  • Epitopes / immunology
  • HIV Envelope Protein gp41 / immunology*
  • HIV-1 / drug effects*
  • HIV-1 / immunology
  • HIV-1 / physiology
  • Humans
  • Immunoglobulin Fab Fragments / immunology
  • Immunoglobulin Fab Fragments / pharmacology*
  • Membrane Fusion / drug effects*
  • Peptide Library
  • Protein Structure, Tertiary


  • Anti-HIV Agents
  • Antibodies, Monoclonal
  • Antibodies, Viral
  • Antigens, Viral
  • Epitopes
  • HIV Envelope Protein gp41
  • Immunoglobulin Fab Fragments
  • Peptide Library