Establishment of an in vitro human blood-brain barrier model for antiviral screening against neurotropic viruses.

BACKGROUND: Neurotropic viruses infect the central nervous system (CNS) resulting in severe neurological and long-term complications, including permanent cognitive impairments. However, for many of these neurotropic viruses, like tick-borne encephalitis virus (TBEV), there are no clinically approved antiviral drugs. The blood-brain barrier (BBB) is a key entry point for neurotropic viruses, as well as a barrier for drug delivery to the brain. To aid in the identification of BBB-penetrating antivirals we established a BBB-permeable antiviral screening assay (BASA). METHODS: BASA combines antiviral assays with an in vitro BBB transwell model consisting of primary human brain microvascular endothelial cells (HMBEC) and pericytes (HBMVP). The combination of our in vitro BBB transwell model with astrocyte-enriched cell cultures provided a tri-culture model to investigate TBEV infection at the BBB. RESULTS: The suitability of BASA for identifying BBB-permeable antivirals was validated by testing clinically approved anti-human immunodeficiency virus (HIV) drugs with known CNS-penetrating properties. Infection experiments reveal that TBEV crosses the intact BBB to infect astrocytic target cells. Through the application of BASA, we identify a novel BBB-permeable antiviral against TBEV (compound 3d). CONCLUSIONS: We establish a modular assay system for the early evaluation of CNS penetration potential of novel antiviral compounds. The development of tools like ours can help promote early-stage preclinical optimization of dedicated therapeutics against neurotropic viruses, while reducing the need for animal experiments.