Characterization of HIV-1 neutralization escape mutants

Area of Science:

• Virology
• Immunology
• Molecular Biology

Background:

• Monoclonal antibodies (MAbs) targeting the V3 neutralization epitope of human immunodeficiency virus type 1 (HIV-1) are crucial for therapeutic strategies.
• Selection pressure from neutralizing MAbs can lead to the emergence of drug-resistant HIV-1 variants.

Purpose of the Study:

• To investigate the molecular mechanisms underlying HIV-1 neutralization escape.
• To identify specific mutations conferring resistance to V3-specific neutralizing MAbs.

Main Methods:

• Infection of MT4 cells with molecularly cloned HIV-1 in the presence of a neutralizing MAb.
• Epitope mapping to the V3 region (amino acids 305-321).
• Immunofluorescence assays to assess MAb binding.
• Polymerase chain reaction (PCR) amplification, cloning, and sequencing of viral RNA.
• Differential hybridization using specific oligonucleotides.

Main Results:

• Selection of HIV-1 plaques resistant to MAb neutralization.
• Identification of a C-to-G base pair change at position 6663 in variant 110.5/1, predicting an Arg to Gly substitution at amino acid 308.
• Reduced binding capacity of HIV-1 variants to the selecting MAb.
• Demonstration that the Arg308Gly substitution significantly reduces the potency of a linear peptide in blocking MAb neutralization.
• Identification of homozygous 308Gly subclones.

Conclusions:

• Amino acid residue 308 within the V3 loop is critical for the binding of the specific monoclonal antibody.
• The Arg308Gly substitution confers resistance to neutralization by this MAb.
• Mutations distant from the MAb binding site may also influence neutralization by V3 loop-targeting antibodies.