Neutralizing monoclonal antibodies against human immunodeficiency virus type 2 gp120

Area of Science:

• Virology
• Immunology
• Vaccine Development

Background:

• The external envelope protein (gp120) of human immunodeficiency virus type 2 (HIV-2ROD) plays a crucial role in viral entry and infectivity.
• Understanding the immunogenic and neutralizing epitopes on HIV-2 gp120 is essential for developing effective vaccines and therapies.
• The V3 variable domain and C3 conserved domain of gp120 are key targets for antibody-mediated neutralization.

Purpose of the Study:

• To generate and characterize monoclonal antibodies (MAbs) against specific domains of the HIV-2ROD gp120.
• To assess the neutralizing capabilities of these MAbs against HIV-2 infection.
• To investigate the mechanisms of MAb-mediated inhibition, including effects on CD4-gp120 binding and viral fusion.

Main Methods:

• Immunization of mice with synthetic peptides corresponding to the V3 or C3 domains of HIV-2 gp120.
• Generation and characterization of monoclonal antibodies (MAbs) using binding assays (surface immunofluorescence, Western immunoblot) and neutralization assays.
• Epitope mapping of MAb-binding sites and assessment of their impact on CD4-gp120 interactions.

Main Results:

• A MAb (B2C) targeting the V3 domain neutralized HIV-2 infection in an isolate-specific manner and bound to infected cells.
• The B2C epitope was mapped to a 6-amino-acid peptide within the V3 domain, containing the core sequence His-Tyr-Gln.
• MAbs against the C3 domain showed weak neutralization and limited inhibition of CD4-gp120 binding, suggesting their epitopes were less accessible.

Conclusions:

• The V3 region of HIV-2ROD contains a type-specific, fusion-inhibiting neutralizing epitope, analogous to HIV-1.
• The V3 sequence of HIV-2 represents a potential target for the development of animal models for HIV vaccine research.
• Different mechanisms may contribute to B2C-mediated neutralization, beyond simple inhibition of CD4-gp120 binding.