HIV-1 gp140 epitope recognition is influenced by immunoglobulin DH gene segment sequence

Area of Science:

• Immunology
• Molecular Biology
• Evolutionary Biology

Background:

• The Complementarity Determining Region 3 (CDR-H3) of the immunoglobulin (Ig) H chain is crucial for antigen binding.
• Amino acids from diversity (DH) gene segments form the CDR-H3, with their reading frame (RF) influencing amino acid composition and hydrophobicity.
• Evolutionary selection has conserved DH RF hydrophobicity signatures across jawed vertebrates.

Purpose of the Study:

• To investigate how evolutionary constraints on DH germ line sequence influence epitope recognition.
• To test if altering DH sequence preference impacts antibody binding to HIV-1 envelope epitopes.

Main Methods:

• Generated genetically modified mice with altered DH gene segment usage (preferential RF2 or inverted RF1).
• Immunized mice with gp140 from HIV-1 JR-FL.
• Assessed antibody binding to HIV-1 epitopes using enzyme-linked immunosorbent assay (ELISA) and peptide microarray.

Main Results:

• Serum reactivity to key epitopes varied significantly based on the DH sequence used in CDR-H3.
• Antibodies from mice with arginine-enriched CDR-H3 showed broader hydrophobicity binding but lower intensity compared to tyrosine- or valine-enriched CDR-H3.
• Tyrosine incorporation is promoted by RF1, while RF2 or inverted RF1 enrich for valine or arginine.

Conclusions:

• DH germ line sequence patterns significantly influence epitope recognition and antibody binding affinity.
• These findings may explain the necessity of extensive somatic mutation for effective antibody neutralization in HIV-infected individuals.