How many VSG genes are there?
The VSG coat determines the antigenic phenotype of the parasite and protects invariant constituents of the outer membrane from the immune system. Each parasite genotype contains a repertoire of around 1000 different VSG genes.
What is VSGs?
A vertical sleeve gastrectomy (VSG) is a minimally invasive procedure during which the size of your stomach is reduced to three or four ounces. This limits the amount of food you can eat to help you lose weight. After a VSG, levels of ghrelin — a hunger hormone — also drop, so your appetite is initially reduced.
How does expressing a different VSG allow T brucei to evade the immune system?
Trypanosoma brucei parasites successfully evade the host immune system by periodically switching the dense coat of variant surface glycoprotein (VSG) at the cell surface. Each parasite expresses VSGs in a monoallelic fashion that is tightly regulated.
What is VSG switching?
VSG expression is ‘switched’ by homologous recombination of a silent basic copy gene from an array (directed by homology) into the active telomerically-located expression site. During this transition, trypanosomes simultaneously display both pre- and post-switch VSGs on their surface.
What parasite causes African sleeping sickness?
African Trypanosomiasis, also known as “sleeping sickness”, is caused by microscopic parasites of the species Trypanosoma brucei. It is transmitted by the tsetse fly (Glossina species), which is found only in sub-Saharan Africa.
Who is at risk for African sleeping sickness?
Who is at risk for African sleeping sickness? The only people at risk for African sleeping sickness are those who travel to Africa. That’s where the tsetse fly is found. The parasites that cause the disease are passed on only by the tsetse fly.
How do African trypanosomes avoid the immune system?
During infection of a mammalian host, African trypanosomes are in constant contact with the host’s immune system. These protozoan parasites are infamous for their ability to evade the immune responses by periodically switching their major variant surface glycoprotein (VSG), a phenomenon called antigenic variation.
What is VSG biology?
Variant surface glycoprotein (VSG) is a ~60kDa protein which densely packs the cell surface of protozoan parasites belonging to the genus Trypanosoma. VSG allows the trypanosomatid parasites to evade the mammalian host’s immune system by extensive antigenic variation.
What are VSGs in trypanosomes?
Variant Surface Glycoproteins (VSGs) VSGs allow trypanosomes to remain undetected by the adaptive immune system almost indefinitely and escape the complement system. Ten million identical VSGs form homodimers with one another and cover the parasite’s cell membrane like a dense homogenous forest.
Is the VSG coat of Trypanosoma brucei an impenetrable barrier?
Variations on the statement “the variant surface glycoprotein (VSG) coat that covers the external face of the mammalian bloodstream form of Trypanosoma brucei acts a physical barrier” appear regularly in research articles and reviews. The concept of the impenetrable VSG coat is an attractive one, as …
Is Trypanosoma brucei unique or conserved-among-trypanosomatids?
The features first identified in T. brucei extend from unique to conserved-among-trypanosomatids to conserved-among … Studies on Variant Surface Glycoproteins (VSGs) and antigenic variation in the African trypanosome, Trypanosoma brucei, have yielded a remarkable range of novel and important insights.
What are trypanosomes?
Trypanosomes are flagellated protozoan parasites belonging to the genus Trypanosoma, family Trypanosomatidae. They live in the blood and other body fluids of vertebrate hosts, where some of them cause disease.