Invited Speaker

Acanthamoeba and Blood-brain Barrier: The Breakthrough
Naveed Khan, Parisa Mortazavi, Selwa Alsam, James Sissons, Kwang Sik Kim, Graham Goldsworthy and Edward L. Jarroll
UK

Acanthamoeba granulomatous encephalitis is a fatal human infection. However, its pathogenesis and pathophysiology remain unclear. Haematogenous spread is a key step in the development of Acanthamoeba granulomatous encephalitis, but it is not clear how circulating amoebae cross the blood-brain barrier to enter the central nervous system to produce disease. Using the primary human brain microvascular endothelial cells (HBMEC), which constitute the blood-brain barrier, here it is shown that Acanthamoeba abolishes the HBMEC transendothelial electrical resistance. Using transcytosis assays, it was observed that Acanthamoeba transcytose across the HBMEC monolayers. The primary interactions of Acanthamoeba with the HBMEC resulted in increased protein tyrosine phosphorylations and the activation of RhoA, suggesting host-parasite cross-talk. Western blotting assays revealed that Acanthamoeba degraded occludin and zonula occludens-1 proteins in a Rho kinase-dependent manner resulting in blood-brain barrier perturbations. Using adhesion assays, it was observed that parasite adhesion to and cytotoxicity of HBMEC is mediated by a mannose-binding protein that is expressed on the surface of Acanthamoeba and presents a potential targets for therapeutic interventions. Furthermore, Acanthamoeba - mediated HBMEC cell death was inhibited, in a concentration-dependent manner, using LY294002 i.e., a PI3K inhibitor. HBMEC transfected with dominant-negative PI3K (Δp110K) were significantly less susceptible to Acanthamoeba-mediated HBMEC cell death (P<0.01). Future studies will continue to identify both host and parasite factors involved in the pathogenesis and pathophysiology of Acanthamoeba encephalitis. Knowledge of such factors is crucial for the rational development of therapeutic interventions against this fatal brain infection.