title: Trypanosoma brucei brucei traverses different biological barriers differently and may modify the host plasma membrane in the process.
abstract: Trypanosoma brucei are extracellular hemoflagellate protozoan parasites and one of the causative agents of a devastating zoonotic disease called African Trypanosomiasis. In humans, the disease is caused by Trypanosoma brucei rhodensiense and Trypanosoma brucei gambiense, which cross the blood brain barrier (BBB) causing neurological disorders which culminate in death if untreated. In some domestic animals and laboratory rodents, Trypanosoma brucei brucei causes a disease similar to that in humans. The mechanism by which Trypanosoma brucei brucei invade biological barriers including the BBB has not been fully elucidated. To further address this issue, Mardin Dardy Canine Kidney II (MDCKII) and Human dermal microvascular endothelial cell (HDMEC) monolayers were grown to confluence on transwell inserts to constitute in vitro biological barriers. MDCKII cells were chosen for their ability to form tight junctions similar to those formed by the BBB endothelial cells. Labeled trypanosomes were placed in the upper chamber of transwell inserts layered with confluent MDCKII/HDMEC monolayers and their ability to cross the monolayer over time evaluated. Our results show that only 0.5-1.25% of Trypanosoma brucei brucei were able to migrate across the monolayers after 3 h. By employing immune-staining and confocal microscopic analysis we observed that trypanosomes were located at the tight junctions and inside the cell in the MDCK II monolayers indicating that they crossed the monolayer using both the paracellular and transcellular routes. Our observations also showed that there seemed to be no obvious degradation of junction proteins Zonula Ocludens-1, Occludin and Ecadherin. In the HDMEC cell monolayer, our scanning electron microscopy data showed that Trypanosoma brucei brucei is able to modulate the plasma membrane to form invaginations similar to cuplike structures formed by Tlymphocytes. However these structures seemed to be independent of vascular adhesion molecules suggesting that they could be more like the membrane ruffles formed by certain intracellular bacteria during invasion. Taken together, our data reveal a mechanism by which Trypanosoma brucei brucei is able to cross different biological barriers including the BBB without causing any obvious damage.
authors.affiliation: State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue-yang Road, 200031, Shanghai, China; Molecular Biology Laboratory, School of Biotechnical, Biosecurity and Laboratory Sciences, College of Veterinary Medicine, Animal Resources and Biosecurity, Makerere University, P. O. Box 7062, Kampala, Uganda. Electronic address: moniyanja@yahoo.com.
authors.forename: Monica
authors.initials: M
authors.lastname: Namayanja
authors.affiliation: State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue-yang Road, 200031, Shanghai, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Dai
authors.affiliation: Molecular Biology Laboratory, School of Biotechnical, Biosecurity and Laboratory Sciences, College of Veterinary Medicine, Animal Resources and Biosecurity, Makerere University, P. O. Box 7062, Kampala, Uganda.
authors.forename: Barbara
authors.initials: B
authors.lastname: Nerima
authors.affiliation: Molecular Biology Laboratory, School of Biotechnical, Biosecurity and Laboratory Sciences, College of Veterinary Medicine, Animal Resources and Biosecurity, Makerere University, P. O. Box 7062, Kampala, Uganda.
authors.forename: Enock
authors.initials: E
authors.lastname: Matovu
authors.affiliation: Centre for Parasitic Organisms, School of Life Sciences, Sun Yat-Sen University, Guangzhou, 510276, China.
authors.forename: Zhao-Rong
authors.initials: ZR
authors.lastname: Lun
authors.affiliation: Molecular Biology Laboratory, School of Biotechnical, Biosecurity and Laboratory Sciences, College of Veterinary Medicine, Animal Resources and Biosecurity, Makerere University, P. O. Box 7062, Kampala, Uganda.
authors.forename: George W
authors.initials: GW
authors.lastname: Lubega
authors.affiliation: State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue-yang Road, 200031, Shanghai, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Zhengjun
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000469:parasitology* / Q000648:ultrastructure; D002460:Cell Line; D002462:Cell Membrane / Q000469:parasitology / Q000648:ultrastructure; D004285:Dogs; D005407:Flagella / Q000502:physiology / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D006801:Humans; D061985:Madin Darby Canine Kidney Cells / Q000469:parasitology* / Q000648:ultrastructure; D051379:Mice; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D011817:Rabbits; D051381:Rats; D062725:Tight Junction Proteins / Q000737:chemistry; D019108:Tight Junctions / Q000469:parasitology; D014346:Trypanosoma brucei brucei / Q000502:physiology* / Q000648:ultrastructure; D014353:Trypanosomiasis, African / Q000469:parasitology* / Q000473:pathology
chemical_list: D062725:Tight Junction Proteins
keywords: 'Possible cuplike structures'; Biological barriers; Paracellular; Plasma membrane modification; Transcellular; Trypanosoma brucei brucei