The haploid trypomastigote-like gametes can interact with each other via their flagella and undergo cell fusion (the process is called syngamy). Trypanosoma gambiense is digenetic; i.e., it completes its life cycle in two hosts. The mammalian bloodstream forms are notable for their cell surface proteins, variant surface glycoproteins, which undergo remarkable antigenic variation, enabling persistent evasion of host adaptive immunity leading to chronic infection. , The parasite was discovered in 1894 by Sir David Bruce, after whom the scientific name was given in 1899.. The trypanosome haptoglobin-hemoglobin receptor is an elongated three a-helical bundle with a small membrane distal head. The kinetoplast lies near the basal body with which it is indistinguishable under microscope. The disease symptoms occur in two stages. , The mitochondrial genome is found condensed into the kinetoplast, an unusual feature unique to the kinetoplastid protozoans. , The surface of the trypanosome is covered by a dense coat of ~5 x 106 molecules of variant surface glycoprotein (VSG). HAT is transmitted by the tsetse fly Glossina spp. In the salivary glands, some parasites detach and undergo transformation into short and stumpy trypomastigotes. Trypanosoma brucei is a species of parasitic protozoan that causes African trypanosomiasis, also known also as African sleeping sickness.Its two recognized subspecies are Trypanosoma brucei rhodesiense (southern and eastern Africa) and Trypanosoma brucei gambiense (central and western Africa).  After ingestion by the parasite, the TLF-1 particle is trafficked to the lysosome wherein Apo1 is activated by a pH mediated conformational change. It is caused by infection with protozoan parasites belonging to the genus Trypanosoma.They are transmitted to humans by tsetse fly (Glossina genus) bites which have acquired their infection from human beings or from animals harbouring human pathogenic parasites. ; the etiologic agents are two subspecies of Trypanosoma brucei (World Health Organization, 2020a).  Because host immunity against a specific VSG does not develop immediately, some parasites will have switched to an antigenically-distinct VSG variant, and can go on to multiply and continue the infection. Its cell membrane (called pellicle) encloses the cell organelles, including the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, and ribosomes. This releases ApoL1 from the HDL particle to insert in the lysosomal membrane. While the principal vectors of T. b. rhodesiense, causing East African sleeping sickness, are G. morsitans, G. pallidipes, and G. Swynnertoni.  It is evolving asexually and its genome shows the Meselson effect. These rapidly divide to become epimastigotes. , The short and stumpy trypomastigotes are taken up by tsetse fly during blood meal. The events of reproduction are:, In the 1980s, DNA analyses of the developmental stages of T. brucei started to indicate that the trypomastigote in the tsetse fly undergoes meiosis, i.e. SYNONYM OR CROSS REFERENCE: African trypanosomiasis, Human African trypanosomiasis (HAT), sleeping sickness, African sleeping sickness, African lethargy, Trypanosoma brucei gambiense, Trypanosoma brucei rhodesiense Footnote 1-3. , Expression of VSG genes occurs through a number of mechanisms yet to be fully understood. T. brucei is one of only a few pathogens known to cross the blood brain barrier.  The long slender forms are able to penetrate the blood vessel endothelium and invade extravascular tissues, including the central nervous system (CNS). However, with each cell division there is a possibility that one or both of the progeny will switch expression to change the VSG that is being expressed. It is estimated up to 10% of the T. brucei genome may be made up of VSG genes or pseudogenes. gambiense.  The first is a parasite of non-human vertebrates, while the latter two are the known parasites of humans. The amoeba is one of the most common sarcodines. Trypanosoma Brucei.  This is due to a thymidine to cytosine mutation at the second codon position.  This coat enables an infecting T. brucei population to persistently evade the host's immune system, allowing chronic infection. The rupture of the erythrocytes results in the release of free haem into the blood where it is bound by haptoglobin. VSG genes are typically located in the subtelomeric regions of the chromosomes, which makes it easier for them to be silenced when they are not being used.. Along the body surface, the flagellum is attached to the cell membrane forming an undulating membrane. . , All T. b. gambiense are resistant to killing by a serum component — trypanosome lytic factor (TLF) of which there are two types: TLF-1 and TLF-2. Representative protozoans. The flagellum is bound to the cytoskeleton of the main cell body by four specialised microtubules, which run parallel and in the same direction to the flagellar tubulin.  The discovery of sexual reproduction in T. brucei supports the hypothesis that meiosis and sexual reproduction are ancestral and ubiquitous features of eukaryotes.  It has a low sequence homology with the VSGc (<25%).  This gene is not found in T. b. T. brucei is responsible for African trypanosomiasis, or sleeping sickness (q.v. ), which occurs in equatorial Africa in two forms, both transmitted by the tse-tse fly (Glossina).  VSG silencing is largely due to the effects of histone variants H3.V and H4.V. The intermediate host is blood sucking insect […]  TLF-2 enters trypanosomes independently of TbHpHbR.