A monoclonal Fab derived from a human nonimmune phage library reveals a new epitope on gp41 and neutralizes diverse human immunodeficiency virus type 1 strains.
A monoclonal Fab (Fab 3674) selected from a human nonimmune phage library by panning against the chimeric construct N(CCG)-gp41 (which comprises an exposed coiled-coil trimer of gp41 N helices fused in the helical phase onto the minimal thermostable ectodomain of gp41) is described. Fab 3674 is shown to neutralize diverse laboratory-adapted B strains of human immunodeficiency virus type 1 (HIV-1) and primary isolates of subtypes A, B, and C in an Env-pseudotyped-virus neutralization assay, albeit with reduced potency (approximately 25-fold) compared to that of 2F5 and 4E10. Alanine scanning mutagenesis maps a novel epitope to a shallow groove on the N helices of gp41 that is exposed between two C helices in the fusogenic six-helix bundle conformation of gp41. Bivalent Fab 3674 and the C34 peptide (a potent fusion inhibitor derived from the C helix of gp41) are shown to act at similar stages of the fusion reaction and to neutralize HIV-1 synergistically, providing additional evidence that the epitope of Fab 3674 is new and distinct from the binding site of C34.
Gustchina
Elena
E
Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0820, USA.
Louis
John M
JM
Lam
Son N
SN
Bewley
Carole A
CA
Clore
G Marius
GM
D019943:Amino Acid Substitution / Q000235:genetics; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000914:Antibodies, Viral / Q000276:immunology*; D002460:Cell Line; D018604:Epitope Mapping; D000939:Epitopes / Q000276:immunology*; D015723:Gene Library; D015700:HIV Envelope Protein gp41 / Q000276:immunology*; D015497:HIV-1 / Q000276:immunology*; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000235:genetics* / Q000276:immunology*; D016297:Mutagenesis, Site-Directed; D009500:Neutralization Tests
D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D000939:Epitopes; D015700:HIV Envelope Protein gp41; D007140:Immunoglobulin Fab Fragments; C514787:gp41 protein, Human immunodeficiency virus 1