Identification of HIV-1 Envelope Mutations that Enhance Entry Using Macaque CD4 and CCR5

Area of Science:

• Virology
• Immunology
• Structural Biology

Background:

• Rhesus macaques are crucial animal models for HIV-1 vaccine research, but most transmitted HIV-1 strains poorly infect macaque cells due to species-specific restrictions.
• A key restriction is a mutation in macaque CD4, which reduces HIV-1 Envelope (Env)-mediated viral entry compared to human CD4.
• Previous studies identified Env gp120 mutations that enhance binding to macaque CD4, but further exploration is needed.

Purpose of the Study:

• To identify novel Env mutations that promote HIV-1 entry into cells expressing macaque receptors.
• To understand the structural and functional impact of these mutations on viral entry and sensitivity to neutralizing antibodies.

Main Methods:

• Utilized deep mutational scanning to screen thousands of Env point mutants for enhanced HIV-1 entry via macaque receptors.
• Analyzed mutations in the N-terminal heptad repeat (NHR) and C-terminal heptad repeat (CHR) regions of gp41.
• Assessed the impact of identified mutations on viral entry into cells with human and macaque CD4 and CCR5 receptors.

Main Results:

• Identified numerous uncharacterized amino acid mutations in gp41's NHR and CHR regions that increased entry into macaque cells by up to 9-fold.
• Observed modest increases (up to 1.5-fold) in infection of cells with human CD4 and CCR5.
• Found that these NHR/CHR mutations enhanced sensitivity to MPER-targeting neutralizing antibodies and cold inactivation, suggesting a shift towards an intermediate trimer conformation.

Conclusions:

• The identified gp41 NHR/CHR mutations significantly enhance HIV-1 entry into macaque cells, offering valuable insights for improving the macaque model for HIV-1 vaccine development.
• These findings contribute to a deeper understanding of the relationship between HIV-1 Env structure, function, and receptor interactions.
• The mutations may inform the design of novel vaccine strategies targeting specific Env conformations.