[Peptides from the principal neutralizing and CD4-binding domain: similar immunoreactive properties and structure...

Area of Science:

• Immunology
• Virology
• Structural Biology

Background:

• Human immunodeficiency virus (HIV) proteins gp120 and gp41 are primary targets for immune responses in HIV infection.
• Understanding the binding sites for CD4 receptor and induction of virus-neutralizing antibodies (VNA) is crucial for AIDS research.
• gp120 contains regions for inducing type-specific neutralizing antibodies (PND) and binding to CD4 (CD4-BR).

Purpose of the Study:

• To investigate the relationship between immune responses to PND and CD4-BR regions of HIV gp120.
• To analyze the cross-reactivity and structural similarities between PND and CD4-BR.

Main Methods:

• ELISA assays using synthetic peptide fragments from PND and CD4-BR regions (BRU and MN strains) with sera from HIV-infected individuals.
• Cross-linked immunoreactivity experiments with rabbit antisera against PND and CD4-BR peptides.
• Peptide homology analysis and assessment of lysine residue acetylation effects.

Main Results:

• A synchronized immune response was observed between antibodies targeting PND and CD4-BR peptides (correlation coefficient r = 0.82).
• Cross-reactivity was confirmed between rabbit antibodies raised against PND and CD4-BR peptides.
• Peptide analysis revealed common structural elements, particularly a high content of positively charged amino acids, in both regions.

Conclusions:

• The immune responses to PND and CD4-BR are interrelated, suggesting shared epitopes or structural features.
• Positively charged amino acids in PND and CD4-BR may play a role in the gp120-CD4 interaction.
• Acetylation of lysine residues abolished peptide reactivity, highlighting the importance of these charged residues.