Affinity maturation of a high-affinity human monoclonal antibody against the third hypervariable loop of human immunodeficiency virus: use of phage display to improve affinity and broaden strain reactivity.

Important note: Information in this article was accurate in 1996. The state of the art may have changed since the publication date.

J Mol Biol. 1996 Feb 16;256(1):77-88. Unique Identifier : AIDSLINE MED/96190953
Thompson J; Pope T; Tung JS; Chan C; Hollis G; Mark G; Johnson KS; Cambridge Antibody Technology Ltd, Melbourn Cambridgeshire, UK.

Abstract: The present study set out to investigate whether phage display could be used to improve the properties of a high-affinity human monoclonal antibody directed against the third hypervariable loop (V3 loop) of human immunodeficiency virus (HIV). The aim was to increase affinity through slowing the dissociation rate (off-rate constant of koff), whilst retaining the ability of this antibody to bind diverse V3 loop sequences. When reformatted as a scFv, the antibody fragment retained the properties of the parental IgG, including the ability to neutralise virus. Heavy and light chains were sequentially replaced with repertoires of variable domains from non-immunised human donors followed by selection on biotinylated synthetic peptide. All selected variants derived from the same germline as the parental antibody. Variants of the light chain provided little if any improvement, whereas two residue changes in VHCDR2 and one in VHFR3 resulted in a reduced koff from gp120 protein of the MN strain (MNgp120) and synthetic V3 loop peptides as measured by surface plasmon resonance using the BIAcore instrument (Pharmacia Biosensor). VHCDR3 was modified using synthetic oligonucleotides and several clones with reduced koff identified, a number of different substitutions occurring at a single residue position. The residues in the heavy chain identified as reducing koff were simultaneously randomised by site-directed mutagenesis, resulting in scFv variants with koff slowed up to sevenfold. Far from compromising recognition of variant loops, binding to these sequences was improved; the koff from synthetic peptides modelled on V3 loop variants being slowed to a degree similar to that observed with MNgp120. All four changes were located towards either extremes of CDRs 2 and 3, suggesting that the mechanism of improvement may be one of alternation of loop conformation. This work illustrates that phage display can be used to tailor the properties of a therapeutic monoclonal antibody in a predefined fashion.

Keywords: Amino Acid Sequence *Antibodies, Monoclonal/CHEMISTRY/GENETICS/METABOLISM Antibody Affinity/GENETICS Base Sequence Cloning, Molecular Coliphages/GENETICS DNA/GENETICS Human *HIV Antibodies/CHEMISTRY/GENETICS/METABOLISM HIV Envelope Protein gp120/GENETICS/*IMMUNOLOGY HIV-1/GENETICS/*IMMUNOLOGY IgG/CHEMISTRY/GENETICS/METABOLISM Immunoglobulins, Heavy-Chain/CHEMISTRY/GENETICS/METABOLISM Immunoglobulins, Light-Chain/CHEMISTRY/GENETICS/METABOLISM In Vitro Kinetics Molecular Sequence Data Mutagenesis, Site-Directed Neutralization Tests Peptide Fragments/GENETICS/*IMMUNOLOGY Protein Conformation JOURNAL ARTICLE
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M9681176

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