title: Biochemical and biological characterization of a dodecameric CD4-Ig fusion protein: implications for therapeutic and vaccine strategies.
abstract: Drug toxicities associated with HAART lend urgency to the development of new anti-HIV therapies. Inhibition of viral replication at the entry stage of the viral life cycle is an attractive strategy because it prevents de novo infection. Soluble CD4 (sCD4), the first drug in this class, failed to suppress viral replication in vivo. At least three factors contributed to this failure: sCD4 demonstrated poor neutralizing activity against most primary isolates of HIV in vitro; it demonstrated an intrinsic capacity to enhance viral replication at low concentrations; and it exhibited a relatively short half-life in vivo. Many anti-gp120 monoclonal antibodies, including neutralizing monoclonal antibodies also enhance viral replication at suboptimal concentrations. Advances in our understanding of the events leading up to viral entry suggest strategies by which this activity can be diminished. We hypothesized that by constructing a sCD4-based molecule that is large, binds multiple gp120s simultaneously, and is highly avid toward gp120, we could remove its capacity to enhance viral entry. Here we describe the construction of a polymeric CD4-IgG1 fusion protein. The hydrodynamic radius of this molecule is approximately 12 nm. It can bind at least 10 gp120 subunits with binding kinetics that suggest a highly avid interaction toward virion-associated envelope. This protein does not enhance viral replication at suboptimal concentrations. These observations may aid in the design of new therapeutics and vaccines.
authors.affiliation: Laboratory of Immunoregulation, NIAID, and the Molecular Interactions Resource Division of Bioengineering and Physical Science, National Institutes of Health, Bethesda, Maryland 20892, USA. jarthos@nih.gov
authors.forename: James
authors.initials: J
authors.lastname: Arthos
authors.forename: Claudia
authors.initials: C
authors.lastname: Cicala
authors.forename: Tavis D
authors.initials: TD
authors.lastname: Steenbeke
authors.forename: Tae-Wook
authors.initials: TW
authors.lastname: Chun
authors.forename: Charles
authors.initials: C
authors.lastname: Dela Cruz
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Hanback
authors.forename: Prateeti
authors.initials: P
authors.lastname: Khazanie
authors.forename: Daniel
authors.initials: D
authors.lastname: Nam
authors.forename: Peter
authors.initials: P
authors.lastname: Schuck
authors.forename: Sara M
authors.initials: SM
authors.lastname: Selig
authors.forename: Donald
authors.initials: D
authors.lastname: Van Ryk
authors.forename: Margery A
authors.initials: MA
authors.lastname: Chaikin
authors.forename: Anthony S
authors.initials: AS
authors.lastname: Fauci
mesh_terms: D016915:AIDS Vaccines / Q000276:immunology / Q000378:metabolism* / Q000627:therapeutic use; D000911:Antibodies, Monoclonal / Q000276:immunology; D001704:Biopolymers; D016860:CD4 Immunoadhesins / Q000276:immunology / Q000378:metabolism*; D015496:CD4-Positive T-Lymphocytes / Q000821:virology; D002478:Cells, Cultured; D002850:Chromatography, Gel; D018920:Coculture Techniques; D015699:HIV Envelope Protein gp120 / Q000276:immunology; D015497:HIV-1 / Q000276:immunology / Q000502:physiology; D006801:Humans; D008561:Membrane Fusion / Q000276:immunology; D009500:Neutralization Tests; D014779:Virus Replication / Q000276:immunology
chemical_list: D016915:AIDS Vaccines; D000911:Antibodies, Monoclonal; D001704:Biopolymers; D016860:CD4 Immunoadhesins; D015699:HIV Envelope Protein gp120