African Trypanosome Interactions With an in Vitro Model of the Human Blood–brain Barrier

Abstract

The neurological manifestations of sleeping sickness in man are attributed to the penetration of the blood-brain barrier (BBB) and invasion of the central nervous system by Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense. However, how African trypanosomes cross the BBB remains an unresolved issue. We have examined the traversal of African trypanosomes across the human BBB using an in vitro BBB model system constructed of human brain microvascular endothelial cells (BMECs) grown on Costar Transwell inserts. Human-infective T. b. gambiense strain IL 1852 was found to cross human BMECs far more readily than the animal-infective Trypanosoma brucei brucei strains 427 and TREU 927. Tsetse fly-infective procyclic trypomastigotes did not cross the human BMECs either alone or when coincubated with bloodstreamform T. b. gambiense. After overnight incubation, the integrity of the human BMEC monolayer measured by transendothelial electrical resistance was maintained on the inserts relative to the controls when the endothelial cells were incubated with T. b. brucei. However, decreases in electrical resistance were observed when the BMEC-coated inserts were incubated with T. b. gambiense. Light and electron microscopy studies revealed that T. b. gambiense initially bind at or near intercellular junctions before crossing the BBB paracellularly. This is the first demonstration of paracellular traversal of African trypanosomes across the BBB. Further studies are required to determine the mechanism of BBB traversal by these parasites at the cellular and molecular level.

An optimized in vitro blood–brain barrier model reveals bidirectional transmigration of African trypanosome strains

“…A tenfold increase of the trypanosomal inoculum resulted in an increased transmigration of T. b. brucei and T. b. rhodesiense, but not of T. b. gambiense, indicating that a certain density of parasites has to be reached in order to achieve maximum transmigration rates. The invasion process occurs by opening of the tight junctions without the destruction or degradation of tight junction proteins, and trypanosomes transmigrate through the BBB paracellularly (Grab et al, 2004). Opening of the tight junctions has been proven by real-time TEER (transendothelial electrical resistance) measurements, which revealed a transient loss of barrier integrity during transmigration (Grab et al, 2004).…”

“…For African trypanosomes paracellular transmigration of endothelia has been reported as well (Grab et al, 2004). To investigate whether paracellular transmigration of macrophages has synergistic effects on the transmigration of trypanosomes, as shown for lymphocytes in a rodent model (Masocha et al, 2004), the transmigration of J774 murine macrophages alone and together with T. b. brucei TC221 was examined.…”

“…The invasion process occurs by opening of the tight junctions without the destruction or degradation of tight junction proteins, and trypanosomes transmigrate through the BBB paracellularly (Grab et al, 2004). Opening of the tight junctions has been proven by real-time TEER (transendothelial electrical resistance) measurements, which revealed a transient loss of barrier integrity during transmigration (Grab et al, 2004). A comparable transmigration mechanism is known from the paracellular exvasation process of leukocytes, which are able to cross endothelial barriers without cellular damaging.…”

Amyloid β Interaction with Receptor for Advanced Glycation End Products Up-Regulates Brain Endothelial CCR5 Expression and Promotes T Cells Crossing the Blood-Brain Barrier

“…The HBMEC monolayer cultured on Transwell insert has been broadly used as an in vitro BBB model (28,48,49). Based on the BBB model, we previously showed that A␤-induced CCR5 expression was related to T cells crossing the HBMEC monolayer (28).…”

Neuropathology of Naturally OccurringTrypanosoma evansiInfection of Horses

“…38 Several studies have demonstrated that the use of subtherapeutic doses of diminazene aceturate may prolong survival of horses experimentally infected by T. brucei spp., but it is associated with subsequent invasion of the central nervous system by trypanosomes and production of necrotizing encephalitis. 14,18,19,26,28,34,39,44 Diminazene aceturate clears trypanosomes from tissues except in the central nervous system, 17 because the drug does not cross the blood-brain barrier (BBB). 19,31 Thus, trypanosomes in the central nervous system survive antitrypanosomal therapy, and with a change in their surface glycoproteins may lead to new parasitemias.…”