Rift Valley fever virus (RVFV) is an arthropod-borne virus (arbovirus) responsible for a severe zoonotic disease affecting a wide range of domestic and wild ruminants as well as humans. RVFV is endemic in many African countries and has also caused outbreaks in Madagascar and Arabian Peninsula. With regard to its wide geographical distribution, its potential to emerge in a new area, and its capability to trigger major health and economic crisis, it is essential to study and better understand several aspects of its life cycle and, in particular, its interactions with mammalian hosts and arthropod vectors. To do so, it is key for researchers to be able to amplify in vitro viral strains isolated from the field and determine accurately the viral titers of RVFV stocks. In this chapter, we present protocols that can be easily implemented to produce and titrate RVFV stocks in your laboratory.

Rift Valley fever virus (RVFV) causes severe disease in humans and ungulates. The virus can be transmitted by mosquitoes, direct contact with infected tissues or fluids, or aerosol, making it a significant biological threat for which there is no approved vaccine or therapeutic. Herein we describe the evaluation of DEF201, an adenovirus-vectored interferon alpha which addresses the limitations of recombinant interferon alpha protein (cost, short half-life), as a pre- and post-exposure treatment in a lethal hamster RVFV challenge model. DEF201 was delivered intranasally to stimulate mucosal immunity and effectively bypass any pre-existing immunity to the vector. Complete protection against RVFV infection was observed from a single dose of DEF201 administered one or seven days prior to challenge while all control animals succumbed within three days of infection. Efficacy of treatment administered two weeks prior to challenge was limited. Post‑exposure, DEF201 was able to confer significant protection when dosed at 30 min or 6 h, but not at 24 h post-RVFV challenge. Protection was associated with reductions in serum and tissue viral loads. Our findings suggest that DEF201 may be a useful countermeasure against RVFV infection and further demonstrates its broad-spectrum capacity to stimulate single dose protective immunity.