Background:
African trypanosomes are pathogens transmitted by the tsetse fly and are responsible for Human African Sleeping Sickness. The mechanism for the how the trypanosomes cross the blood brain barrier or how the microvascular flow in the brain affect this is unknown. We hypothesized that flow conditions at the blood brain barrier affect Trypanosome entry through the endothelial barrier.

Material and Methods:
Human brain microvessel endothelial cells (HBMEC) were cultured on Electric Cell-Substrate Impedance Sensing flow chambers, which can detect transendothelial electrical resistance (TEER). HBMEC are exposed to 2 or 14 dynes/cm2 shear in the presence or absence of trypanosomes for up to 24 hrs.

Result:
When trypanosomes were added to HBMEC exposed to 2 dynes/cm2, TEER dropped from 1800 to 1200. When flow rate was 14 dynes/cm2, TEER increased back to 1800, but after several hours, the trypanosomes still were able to penetrate.

Conclusion:
Under low laminar flow conditions, the trypanosomes were able to pass through the blood brain barrier within hours of infection. Under high levels of shear stress, the blood brain barrier was better maintained and did not allow tyrpanosome penetration until several hours.