DNA damage drives antigen diversification in Trypanosoma brucei - Nature

"The African trypanosome Trypanosoma brucei uses an especially sophisticated system of antigenic variation, periodically 'switching' expression of a surface coat consisting of 10 7 copies of a single, immunogenic protein known as the variant surface glycoprotein (VSG)."

"During an infection, each T. brucei parasite expresses a single VSG at a time from one of about 15 telomeric bloodstream expression sites (BESs), while the remaining VSG-encoding genes are stored in other expression sites, subtelomeric arrays and minichromosomes."

"Although gene conversion-based switching allows for the activation of VSGs outside of a BES, analysis of the T. brucei genome has shown that only around 20% of the VSGs in the parasite genome are full-length genes encoding a functional VSG protein."

Trypanosoma brucei employs antigenic variation to evade host immunity by periodically switching its variant surface glycoprotein (VSG). This unicellular parasite expresses a single VSG from one of about 15 active bloodstream expression sites while the rest remain silenced. Although the parasite has thousands of VSGs, only about 20% are full-length genes capable of functional expression. The remaining 80% are pseudogenes or fragments, limiting the potential for immune evasion through in situ switching alone.

Read at Nature