Broadly cross-reactive HIV-1-neutralizing human monoclonal Fab selected for binding to gp120–CD4–CCR5 complexes

doi:10.1073/pnas.102562599

Broadly cross-reactive HIV-1-neutralizing human monoclonal Fab selected for binding to gp120–CD4–CCR5 complexes

^*Departments of Immunology and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037; ^§Laboratory of Experimental and Computational Biology, National Cancer Institute–Frederick, National Institutes of Health, Frederick, MD 21702-1201; ^¶Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814-4799; and ^‖Department of Pediatrics, Tulane University Medical Center, 1430 Tulane Avenue, New Orleans, LA 70112

Edited by Peter S. Kim, Merck and Co., Inc., West Point, PA, and approved March 22, 2002 (received for review October 22, 2001)

Abstract

HIV-1 entry into cells involves formation of a complex between gp120 of the viral envelope glycoprotein (Env), a receptor (CD4), and a coreceptor, typically CCR5. Here we provide evidence that purified gp120_JR-FL–CD4–CCR5 complexes exhibit an epitope recognized by a Fab (X5) obtained by selection of a phage display library from a seropositive donor with a relatively high broadly neutralizing serum antibody titer against an immobilized form of the trimolecular complex. X5 bound with high (nM) affinity to a variety of Envs, including primary isolates from different clades and Envs with deleted variable loops (V1, -2, -3). Its binding was significantly increased by CD4 and slightly enhanced by CCR5. X5 inhibited infection of peripheral blood mononuclear cells by a selection of representative HIV-1 primary isolates from clades A, B, C, D, E, F, and G with an efficiency comparable to that of the broadly neutralizing antibody IgG1 b12. Furthermore, X5 inhibited cell fusion mediated by Envs from R5, X4, and R5X4 viruses. Of the five broadly cross-reactive HIV-1-neutralizing human monoclonal antibodies known to date, X5 is the only one that exhibits increased binding to gp120 complexed with receptors. These findings suggest that X5 could possibly be used as entry inhibitor alone or in combination with other antiretroviral drugs for the treatment of HIV-1-infected individuals, provide evidence for the existence of conserved receptor-inducible gp120 epitopes that can serve as targets for potent broadly cross-reactive neutralizing antibodies in HIV-1-infected patients, and have important conceptual and practical implications for the development of vaccines and inhibitors.

AIDS‖antibody‖vaccines‖inhibitors

Footnotes

↵ † M.M., S.K.P., and Y.S. contributed equally to this work.
↵ ‡ Present address: BioCytex, 140, Chemin de L'Armée d'Afrique, 13010 Marseille, France.
↵ ** Present address: Genmab, Jenalaan 18a, 3584 CK, Utrecht, The Netherlands.
↵ ‡‡ To whom reprint requests should be addressed at: Laboratory of Experimental and Computational Biology, National Cancer Institute–Frederick, National Institutes of Health, Building 469, Room 246, P.O. Box B, Miller Drive, Frederick, MD 21702-1201. E-mail: dimitrov{at}ncifcrf.gov.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations:

sCD4,

soluble CD4;

dsCCR5,

detergent-solubilized CCR5