DNA damage drives antigen diversification in Trypanosoma brucei

Area of Science:

• Molecular Biology
• Immunology
• Parasitology

Background:

• Pathogens utilize antigenic variation to evade host immunity.
• African trypanosomes like Trypanosoma brucei rely on genomic diversification for immune evasion.
• Mechanisms of variant surface glycoprotein (VSG) gene diversification remain poorly understood due to limited experimental tools.

Purpose of the Study:

• To develop a sensitive method for measuring VSG diversification.
• To elucidate the molecular mechanisms underlying VSG gene generation in T. brucei.
• To investigate the role of DNA repair pathways in generating novel VSGs.

Main Methods:

• Development of a highly sensitive targeted sequencing approach.
• Induction of DNA double-strand breaks within VSG genes using Cas9.
• Analysis of recombination patterns and dependence on RAD51 and BRCA2.

Main Results:

• The developed sequencing method accurately measures VSG diversification.
• Cas9-induced DNA breaks trigger RAD51- and BRCA2-dependent VSG recombination.
• Generated VSGs are antigenically distinct, facilitating immune evasion.
• Recombination patterns mirror those observed during natural infection.

Conclusions:

• VSG diversification is mechanistically linked to DNA repair pathways.
• A novel experimental framework is established for studying antigen repertoire evolution.
• Understanding VSG diversification provides insights into pathogen immune evasion strategies.