title: Evidence of intracellular stages in Trypanosoma (Megatrypanum) theileri in non-phagocytic mammalian cells.
abstract: Trypanosoma (subgenus Megatrypanum) theileri was first identified over one hundred years ago, and is a widespread parasite in cattle. Its life cycle within the mammalian host has rarely been reported. Whether there is an intracellular stage in tissues is unknown and such a stage has not been demonstrated experimentally. Intriguingly, using Giemsa staining with light microscopy and transmission electron microscopy examination, we found that the parasite was able not only to attach to cells but also to invade several phagocytic and non-phagocytic mammalian cells. Based on these findings, we conducted further investigations using a special antibody in immunofluorescence confocal images. Moreover, we examined a series of possible events of cell invasion in T. theileri. The results revealed that GM1, a marker of membrane rafts, was implicated in the mechanism of entry by this parasite. After incubation with tissue culture trypomastigotes, the gelatinolytic activity was significantly increased and accumulated at the attachment sites. Using ultrastructural localization detection by CytoTracker live imaging and confocal immunofluorescence microscopy, we found that lysosome fusion and the autophagy pathway were engaged in invaginating processes. T. theileri amastigotes also invaded cells and were enclosed by the lysosomes. Furthermore, tissue-cultured trypomastigotes were found to be capable of triggering intracellular free Ca(2+) transients and TGF-β-signaling. Our findings that intracellular amastigote stages exist in mammalian cells infected with T. theileri and that the invasion processes involved various host cell components and cell signalings were extremely surprising and warrant further investigation.
authors.affiliation: Department of Medical Education and Research, Taichung Veterans General Hospital, 160, Sec. 3, Taichung 40705, Taiwan. leeyenf@yahoo.com.tw
authors.forename: Yen-Feng
authors.initials: YF
authors.lastname: Lee
authors.forename: Ching-Chang
authors.initials: CC
authors.lastname: Cheng
authors.forename: Jiun-Sheng
authors.initials: JS
authors.lastname: Chen
authors.forename: Nai-Nu
authors.initials: NN
authors.lastname: Lin
authors.forename: Yi-Wen
authors.initials: YW
authors.lastname: Hung
authors.forename: Jiunn-Min
authors.initials: JM
authors.lastname: Wang
authors.forename: Wu-Chun
authors.initials: WC
authors.lastname: Tu
authors.forename: Kwong-Chung
authors.initials: KC
authors.lastname: Tung
authors.forename: Yung-Tsung
authors.initials: YT
authors.lastname: Chiu
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D006224:Cricetinae; D003593:Cytoplasm / Q000469:parasitology*; D051147:Ganglioside Galactosyltransferase / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D017125:Genes, Protozoan / Q000235:genetics; D006790:Host-Parasite Interactions; D008247:Lysosomes / Q000469:parasitology; D051379:Mice; D046529:Microscopy, Electron, Transmission; D010586:Phagocytes / Q000469:parasitology; D010802:Phylogeny; D051381:Rats; D015398:Signal Transduction; D014345:Trypanosoma / Q000145:classification / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D014352:Trypanosomiasis / Q000469:parasitology* / Q000473:pathology
chemical_list: D051147:Ganglioside Galactosyltransferase; D002118:Calcium