Toxoplasma Gondii Induces Blood-Brain Barrier Dysfunction in a Human Stem Cell- Derived Model

Abstract

Background:

Toxoplasma gondii is a single-celled obligate intracellular parasite commonly found in cat feces and animal issues and is known to cause cerebral infections in immune- compromised individuals and neonates. Once ingested, T. gondii reaches the host's blood supply and reaches the brain, where infection ensues. However, it remains unclear how T. gondii crosses the blood-brain barrier to reach the brain. In this study, we utilize a human stem cell-derived BBB model with near in vivo properties to investigate the effects of T. gondii on critical barrier properties that permit entry into the brain parenchyma.

Methods:

Human-induced pluripotent stem cells (iPSCs) were used to derive brain microvascular endothelial cells (BMECs). BMECs were exposed to tachyzoites, the infectious rapid replicating stage of T. gondii, at a multiplicity of infection (MOI) of 0.1 and 1.0 for 24 hours. Following exposure, several critical barrier properties were monitored, including trans- endothelial electrical resistance (TEER) and tight junction analysis.

Results:

BMECs treated with both MOI of 0.1 and 1.0 showed a significant reduction in all three tight junction proteins (Claudin-5, Occludin, and ZO-1), as indicated by an increase in discontinuous junctions and a decrease in area fraction index. Barrier integrity is directly associated with tight junctional continuity and localization. Furthermore, tachyzoites at an MOI of 0.1 and 1.0 demonstrated a reduction in barrier tightness, as observed by a decrease in TEER.

Conclusion and Potential Impact:

These results indicate that T. gondii may, in part, have access to the brain by inducing disruption in tight junction proteins, thus increasing barrier leakiness via a para-cellular route. These data may help guide future investigations on T. gondii's ability to evoke blood-brain barrier dysfunction and reach the vulnerable brain tissue.