Variable surface glycoprotein

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Variable surface glycoprotein

Existing structural data : 1VSG , 2VSG

Identifier
External IDs
Occurrence
Parent taxon 5702

The variable surface glycoprotein ( glycoprotein with a variable surface ) is formed by trypanosomes in order to subvert the host's immune response through immune evasion. It is a very effective adaptation mechanism of the pathogen to the complex processes of the immune system of vertebrates . The host's immune system is paralyzed by constantly being presented with new antigen variants .

The variable surface glycoprotein is a surface antigen that covers the entire surface of the parasite . The glycoprotein exists as a homodimer , the identical subunits of which each have a molecular mass of about 60,000 Daltons . The C-terminal ends are fixed in the cell membrane via a glycosylphosphatidylinositol (GPI) anchor . There is only one variant of the variable surface glycoprotein which surrounds the parasite membrane as a dense, 12-15 nm thick "coat" with approximately 10 8 identical copies (corresponds to 5 × 10 7 homodimers). This coat fulfills several functions:

  • It focuses the host's specific immune response on exactly one antigen variant.
  • It masks other antigenic membrane components from the host's immunocompetent cells.
  • It acts as a diffusion barrier for macromolecules , preventing the host's complement system from coming into contact with the pathogen's cell membrane.

The defense shield also means a restriction for the parasite: the exocytosis and endocytosis of the pathogen is limited to certain areas at the base of the flagellum , the so-called flagellum pocket.

Variable surface glycoprotein is likely encoded in the pathogen's DNA by more than 1,000 different genes, which can produce a corresponding number of variants. As the pathogen multiplies in the host, new variable surface glycoprotein variants are continuously expressed. Every peak of parasitemia marks the predominance of a new serological type, against which the immune system directs its antibody production. If a pathogen variant is under control, the next generation develops against which these antibodies are ineffective.

Web links

Individual evidence

  1. ↑ P. Vincendeau, B. Bouteille: Immunology and immunopathology of African trypanosomiasis. In: Anais da Academia Brasileira de Ciências. Volume 78, Number 4, December 2006, pp. 645-665, ISSN  0001-3765 . PMID 17143404 . PDF .
  2. ↑ SJ Black, P. Guirnalda, D. Frenkel, C. Haynes, V. Bockstal: Induction and regulation of Trypanosoma brucei VSG-specific antibody responses. In: Parasitology. Volume 137, Number 14, December 2010, pp. 2041-2049, ISSN  1469-8161 . doi: 10.1017 / S003118200999165X . PMID 20025827 .
This text is based in whole or in part on the entry Variable surface glycoprotein in Flexikon , a wiki from DocCheck . The takeover took place on July 23, 2004 under the then valid GNU license for free documentation .