Author:

Keywords:

AIDS Vaccines, Antibodies, Antigens, CD4, Base Sequence, Binding Sites, HIV Envelope Protein gp120, HIV-1, Humans, Kinetics, Molecular Sequence Data, Mutation, Peptide Library, Sequence Homology, Nucleic Acid, Single-Chain Antibodies, Science & Technology, Life Sciences & Biomedicine, Biochemistry & Molecular Biology, HUMAN-IMMUNODEFICIENCY-VIRUS, HUMAN MONOCLONAL-ANTIBODY, FUSION INHIBITOR T-20, SUBTYPE-B, PASSIVE-IMMUNIZATION, TYPE-1 INFECTION, DOMAIN ANTIBODY, HIGH-AFFINITY, ENV CLONES, RECEPTOR, CD4 Antigens, 03 Chemical Sciences, 06 Biological Sciences, 11 Medical and Health Sciences, 31 Biological sciences, 32 Biomedical and clinical sciences, 34 Chemical sciences

Abstract:

Recently, we described llama antibody fragments (VHH) that can neutralize human immunodeficiency virus, type 1 (HIV-1). These VHH were obtained after selective elution of phages carrying an immune library raised against gp120 of HIV-1 subtype B/C CN54 with soluble CD4. We describe here a new, family-specific approach to obtain the largest possible diversity of related VHH that compete with soluble CD4 for binding to the HIV-1 envelope glycoprotein. The creation of this family-specific library of homologous VHH has enabled us to isolate phages carrying similar nucleotide sequences as the parental VHH. These VHH displayed varying binding affinities and neutralization phenotypes to a panel of different strains and subtypes of HIV-1. Sequence analysis of the homologs showed that the C-terminal three amino acids of the CDR3 loop were crucial in determining the specificity of these VHH for different subtype C HIV-1 strains. There was a positive correlation between affinity of VHH binding to gp120 of HIV-1 IIIB and the breadth of neutralization of diverse HIV-1 envelopes. The family-specific approach has therefore allowed us to better understand the interaction of the CD4-binding site antibodies with virus strain specificity and has potential use for the bioengineering of antibodies and HIV-1 vaccine development.