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Intranasal Exposure to Rift Valley Fever Virus Live-Attenuated Strains Leads to High Mortality Rate in Immunocompetent Mice

Rift Valley fever virus (RVFV) is an arthropod-borne virus that can cause severe illness in both ruminants and humans. The virus can be transmitted by an arthropod bite or contact with contaminated fluids or tissues. Two live-attenuated vaccines, Smithburn (SB) and Clone 13 (Cl.13), are used during epizootic events in Africa. However, they induce significant adverse effects limiting their use in the field. In our study, we infected immunocompetent mice with SB or Cl.13 by a subcutaneous or an intranasal inoculation. Interestingly, we found that, unlike the subcutaneous infection, the intranasal inoculation led to a high mortality rate of infected mice. Moreover, we found high viral titers in the brain of both the SB- and Cl.13-infected mice. Overall, this study unveils a correlation between the pathogenicity and the route of administration of both SB and Cl.13, with the intranasal inoculation leading to a stronger neurovirulence and higher mortality rate than the subcutaneous infection. 

Read the paper publlished in Viruses