What is antigenic variation in trypanosomes?
Trypanosome persistence in the mammal is due to antigenic variation, which involves changes in the identity of the variant surface glycoprotein (VSG) that forms a dense cell surface coat to shield invariant surface antigens from immune recognition.
What is the importance of VSG in trypanosomes?
A variant surface glycoprotein (VSG) coat covering the membrane of African trypanosomes protects them from lytic factors in human plasma and allows them to escape the host immune reaction.
How many variant surface glycoprotein genes are expressed at once?
one VSG gene
The VSG is central to antigenic variation; one VSG gene is expressed at any one time and there is a low frequency stochastic switch to expression of a different VSG gene.
What is the significance of the stumpy form of a trypanosome?
In the blood, trypanosomes exhibit two developmental forms: the slender form and the stumpy form. The slender form proliferates in the bloodstream, establishes the parasite numbers and avoids host immunity through antigenic variation. The stumpy form, in contrast, is non-proliferative and is adapted for transmission.
What causes antigenic variation?
Antigenic variation can occur by altering a variety of surface molecules including proteins and carbohydrates. Antigenic variation can result from gene conversion, site-specific DNA inversions, hypermutation, or recombination of sequence cassettes.
What is VSG Why is it important in pathogenesis caused by Trypanosoma?
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.
What does surface glycoprotein do?
Surface location of the S glycoprotein renders it a direct target for host immune responses, making it the main target of neutralizing antibodies. In the light of its crucial roles in viral infection and adaptive immunity, the S protein is the focus of most vaccine strategies as well as therapeutic interventions.
What is a glycoprotein where are they found in human cells list some of their functions?
Glycoproteins function in the structure, reproduction, immune system, hormones, and protection of cells and organisms. Glycoproteins are found on the surface of the lipid bilayer of cell membranes.
What is the life cycle of Trypanosoma?
The life cycle of Trypanosoma cruzi involves two intermediate hosts: the invertebrate vector (triatomine insects) and the vertebrate host (humans) and has three developmental stages namely, trypomastigotes, amastigotes and epimastigotes [8].
What are Metacyclic Trypomastigotes?
Metacyclogenesis is the transformation of epimastigote forms (noninfective) to trypomastigotes, which are metacyclic forms that are capable of infecting mammalian cells when released into the feces.
Antigenic variation is one of several resources by which trypanosomes manipulate their hosts. VSG of trypanosomes constitutes the main antigenic molecule exposed in the surface of these blood parasites.
What is the vector of trypanosomiasis?
Trypanosoma brucei rhodesienseand T. brucei gambiense, the causative agents of Human African Trypanosomiasis, are transmitted by tsetse flies. Within the vector, the parasite undergoes through transformations that prepares it to infect the human host.
How do trypanosomes infect humans?
Diversity of TrypanosomaSpecies and Hosts Most species of trypanosome are incompetent to infect man; they infect animals, mainly through their natural insect vector, the tsetse fly.
What can we learn from Trypanosoma brucei variation?
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. The features first identified in T. bruceiextend from unique to conserved-among-trypanosomatids to conserved-among-eukaryotes.