VSG meaning in Medical ?

Answer:

What is Variable Surface Glycoprotein mean?

Variant surface glycoprotein (VSG) is a ~60kDa protein which densely packs the cell surface of protozoan parasites belonging to the genus Trypanosoma. This genus is notable for their cell surface proteins. They were first isolated from Trypanosoma brucei in 1975 by George Cross. VSG allows the trypanosomatid parasites to evade the mammalian host's immune system by extensive antigenic variation. They form a 12–15 nm surface coat. VSG dimers, ~90% of all cell surface protein. It also makes up ~10% of total cell protein. For this reason, these proteins are highly immunogenic and an immune response raised against a specific VSG coat will rapidly kill trypanosomes expressing this variant. However, with each cell division there is a possibility that the progeny will switch expression to change the VSG that is being expressed. VSG has no prescribed biochemical activity.

The parasite has a large cellular repertoire of antigenically distinct VSGs (~1500/2000 complete and partial (pseudogenes)) located in telomeric and subtelomeric arrays (on megabase chromosomes or minichromosomes). VSGs are expressed from a bloodstream expression site (BES, ES) in a polycistron by RNA polymerase I (recruited to a ribosomal-type promoter) with other ES-associated genes (ESAGs), of which transferrin receptor (Tfr: ESAG6, ESAG7) is one. Only one VSG gene is expressed at a time, as only one of the ~15 ES are active in a cell. 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. This coat replacement process is critical for the survival of recently switched cells because initial VSGs remain targets for the escalating host Ab response. Mosaic VSG genes can be created by homologous recombination of a partial VSG gene from an array. This partial gene may replace any portion of the residing VSG gene, creating a new mosaic VSG. VSG half-life measurements suggest that initial VSGs may persist on the surface of genetically switched trypanosomes for several days. It remains unclear whether the regulation of VSG switching is purely stochastic or whether environmental stimuli affect switching frequency. The fact that switching occurs in vitro suggests that there is at least some host-independent, stochastic element to the process.

The antigenic variation causes cyclical waves of parasitemia, which is one of the characteristics of Human African Trypanosomiasis. The cyclical process take 5-8 days. This occurs because a diverse range of coats expressed by the trypanosome population means that the immune system is always one step behind: it takes several days for an immune response against a given VSG to develop, giving the population time to diversify as individuals undergo further switching events. The repetition of this process prevents the extinction of the infecting trypanosome population, allowing chronic persistence of parasites in the host and enhancing opportunities for transmission.

reference

Full Form	Category
Viscous Semi-Geostrophic	Academic & Science
Velocidad de Sedimentacion Globular	Academic & Science
Vanderbilt Student Government	Academic & Science
Visualization Sciences Group	Academic & Science
Lugansk	Airport Code
Venue Services Group	Business
Vesalius Student Government	Community
Video Sound And Graphics	Computing
Virtual Security Gateway	Computing
Variable Spaced Grating	Electronics
Virgin Sun Grown	General
Vegetarian Society of Georgia	General
Vertical Sleeve Gastrectomy	General
Virtualized Services Gateway	General
Variant surface glycoproteins	General
Vachio Solutions Group	General
Vietnam Studies Group	General
Vector Signal Generator	General
Viscous Speed Governors	General
Vegetarian Starter Guide	General
Van Side Glass	General
Variable Speed Governor	General
Vehicle Simulation Game	General
Vehicle Service Group	Governmental
VASCO DA GAMA	Indian Railway Station
Variable Surface Glycoprotein	Medical
Veterinary Specialist Group	Medical
Vena Saphena Graft	Medical
Virtual Support Group	Military and Defence
Vibration Shutout Grip	Military and Defence
Lugansk, Ukraine	Regional