Structural basis for HIV-1 neutralization by a gp41 fusion intermediate-directed antibody

Area of Science:

• Immunology
• Virology
• Structural Biology

Background:

• Developing an effective human immunodeficiency virus-1 (HIV-1) vaccine is a critical global health priority.
• The HIV-1 gp41 inner-core trimer is a conserved target for therapeutic intervention due to its essential role in viral fusion.

Purpose of the Study:

• To determine the structural basis of interaction between the HIV-1 gp41 inner-core mimetic (5-helix) and the cross-neutralizing antibody D5.
• To elucidate the mechanisms by which D5 neutralizes HIV-1 and to identify key residues involved in this process.

Main Methods:

• X-ray crystallography was used to determine the 2.0-Å resolution crystal structure of the D5 antibody fragment complexed with 5-helix.
• Kinetic analysis of D5 mutants was performed to assess the impact of specific residue interactions on antibody binding and neutralization.

Main Results:

• The crystal structure revealed critical interactions between the D5 CDR H2 loop and the gp41 hydrophobic pocket, as well as a large pocket within D5 accommodating core gp41 residues.
• Kinetic analysis indicated that the persistence of D5 at the fusion intermediate state is essential for effective HIV-1 neutralization.

Conclusions:

• The study validates the gp41 N-peptide trimer fusion intermediate as a viable target for developing neutralizing antibodies against HIV-1.
• The findings provide a structural template for the rational design of more potent and broadly neutralizing antibodies for HIV-1 vaccine development.