Variable region light chain genes encoding human antibodies to HIV-1

Area of Science:

• Immunology
• Molecular Biology
• Virology

Background:

• Previous studies indicated skewed heavy chain variable (VH) gene repertoires in human antibodies against HIV, with gp120 binding to VH3 gene products.
• The specific roles of light chain (VL) genes in the anti-HIV antibody response remained less understood.

Purpose of the Study:

• To analyze the light chain variable region genes (VL) used in human monoclonal antibodies targeting HIV-1 proteins (p25, gp41, gp120).
• To investigate potential biases in VL gene usage and the mutational patterns within these genes and their CDR3 regions.

Main Methods:

• Analysis of VL gene repertoires from human monoclonal antibodies against HIV-1 proteins.
• Comparison of VL gene mutation rates and patterns with corresponding VH genes.
• Examination of diversification and selection events in the third hypervariable regions (CDR3) of VL chains.

Main Results:

• Unlike VH genes, VL gene usage in anti-HIV antibodies did not show a family bias.
• A trend towards using VL genes from the downstream kappa locus was observed.
• VL genes exhibited lower mutation rates than VH genes, with no clustering of mutations in hypervariable regions.
• Light chain CDR3 regions showed significant diversification, including untemplated nucleotide additions, truncations, and somatic mutations, leading to length heterogeneity and potential selection of specific amino acids.

Conclusions:

• The light chain CDR3 regions of anti-HIV antibodies are highly diversified and appear to be under positive selection.
• These CDR3 regions play a critical role in dictating the specificity of certain anti-HIV antibodies, bearing hallmarks of antigenic selection.