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"Researchers have uncovered a key mechanism used by the parasite that causes African sleeping sickness to evade antibodies... Trypanosoma brucei “constantly changes a surface coat made up of millions of copies of a single protein.” ..."
"... Using a mouse model, the researchers showed that Trypanosoma brucei essentially plays a game of hide-and-seek by setting up shop in its hosts’ tissues, allowing it to constantly change its protective surface coat and evade antibodies. ...
The T. brucei parasite constantly changes a surface coat made up of millions of copies of a single protein—the variant surface glycoprotein (VSG). Once one VSG has been recognized by a host’s antibody response, the parasite has already “switched” to a new one, which the immune system hasn’t spotted yet. By changing which of these variant genes is active, the parasite can alter its appearance enough to evade its host’s immune response for long periods. ..."
From the abstract:
"The protozoan parasite Trypanosoma brucei evades clearance by the host immune system through antigenic variation of its dense variant surface glycoprotein (VSG) coat, periodically ‘switching’ expression of the VSG using a large genomic repertoire of VSG-encoding genes. Recent studies of antigenic variation in vivo have focused near exclusively on parasites in the bloodstream, but research has shown that many, if not most, parasites reside in the interstitial spaces of tissues. We sought to explore the dynamics of antigenic variation in extravascular parasite populations using VSG-seq7, a high-throughput sequencing approach for profiling VSGs expressed in populations of T. brucei. Here we show that tissues, not the blood, are the primary reservoir of antigenic diversity during both needle- and tsetse bite-initiated T. brucei infections, with more than 75% of VSGs found exclusively within extravascular spaces. We found that this increased diversity is correlated with slower parasite clearance in tissue spaces. Together, these data support a model in which the slower immune response in extravascular spaces provides more time to generate the antigenic diversity needed to maintain a chronic infection. Our findings reveal the important role that extravascular spaces can have in pathogen diversification."
Discovery Illuminates How Sleeping Sickness Parasite Outsmarts Immune Response "Parasite spread by tsetse flies persists in hosts by hiding in tissues and evading antibodies"
Tissue spaces are reservoirs of antigenic diversity for Trypanosoma brucei (no public access, but article above contains link to PDF)
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