VSG Coat
The surface of the trypanosome is covered by a dense coat of ~1x107 molecules of Variable Surface Glycoprotein (VSG). This coat enables an infecting T. brucei population to persistently evade the host's immune system, allowing chronic infection. The two properties of the VSG coat that allow immune evasion are:
- Shielding - the dense nature of the VSG coat prevents the immune system of the mammalian host from accessing the plasma membrane or any other invariant surface epitopes (such as ion channels, transporters, receptors etc.) of the parasite. The coat is uniform, made up of millions of copies of the same molecule; therefore the only parts of the trypanosome the immune system can 'see' are the N-terminal loops of the VSG that make up the coat.
- Periodic antigenic variation - the VSG coat undergoes frequent stochastic genetic modification - 'switching' - allowing variants expressing a new VSG coat to escape the specific immune response raised against the previous coat.
Read more about this topic: Trypanosoma Brucei
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