Abstract
Rift Valley fever (RVF) is a zoonotic arboviral disease that causes recurrent epidemics in Africa that may trigger fatal neurological disorders. However, the mech anisms of neuroinvasion by which the RVF virus (RVFV) reaches the human central nervous system (CNS) remain poorly characterized. In particular, it is not clear how RVFV is able to cross the human blood-brain barrier (hBBB), which is a neurovascular endothelium that protects the brain by regulating brain and blood exchanges. To explore these mechanisms, we used an in vitro hBBB model to mimic in vivo hBBB selectiveness and apicobasal polarity. Our results highlight the ability of RVFV to cross the hBBB by direct infection in a non-structural protein S (NSs)-independent but strain-dependent manner, leading to astrocyte and pericyte infections. Interestingly, RVFV infection did not induce hBBB disruption and was associated with progressive elimination of infected cells with no impairment of the tight junction protein scaffold and barrier function. Our work also shows that NSs, a well described RVFV virulence factor, limited the establishment of the hBBB-induced innate immune response and subsequent lymphocyte recruitment. These results provide in vitro confirmation of the ability of RVFV to reach human CNS by direct infection of the hBBB without altering its barrier function, and provide new directions to explore human RVFV neurovirulence and neuroinvasion mechanisms.