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.

A New PCR-RFLP for Species-Specific Diagnosis of South American Animal Trypanosomiasis

“…In cattle, impairment of body condition was also observed in most (61%) of the animals infected by T. theileri. These clinical and hematological features of this infection corroborate the hypothesis that presumes the opportunistic behavior of this parasite in cattle (Lee et al, 2013). However, a specific test able to differentiate this species will avoid unnecessary treatments for this non-pathogenic Trypanosome.…”

“…vivax, T. evansi, T. simiae and T. brucei brucei. In South America, the absence of the cyclic vector (tsetse fly) has limited the number of species involved in the domestic ruminant sickness, with only T. vivax and T. evansi being identified (Desquesnes et al, 2013). T. theileri infection has also been reported in Africa and South America, however its pathogenicity in domestic large ruminants is still under study (Lee et al, 2013).…”

What is your diagnosis? Bovine synovial fluid

“…The life cycle of T theileri in the mammalian host is not fully understood; however, both epimastigote and trypomastigotes can be found in the peripheral blood. Recent evidence suggests amastigotes may be found intracellularly, and the parasite is capable of attaching to and invading both phagocytic and nonphagocytic mammalian cells . T theileri may cause long‐lasting latent infections with low levels of parasitemia, but infections are typically associated with mild or no clinical signs .…”

“…Recent evidence suggests amastigotes may be found intracellularly, and the parasite is capable of attaching to and invading both phagocytic and nonphagocytic mammalian cells . T theileri may cause long‐lasting latent infections with low levels of parasitemia, but infections are typically associated with mild or no clinical signs . It is speculated that infections may become apparent with concomitant disease or immunosuppression, and cases of abortion, peritonitis, and suppurative meningoencephalitis associated with T theileri have been reported.…”

“…1 T theileri may cause long-lasting latent infections with low levels of parasitemia, but infections are typically associated with mild or no clinical signs. 1 It is speculated that infections may become apparent with concomitant disease or immunosuppression, and cases of abortion 2 , peritonitis 3 , and suppurative meningoencephalitis 4 associated with T theileri have been reported. Prevalence studies in North America are dated; however, a higher prevalence of T theileri infections have been documented in beef than dairy cows, and in pregnant than nonpregnant cows.…”