BackgroundMany ruminant diseases of viral aetiology can be effectively prevented using appropriate vaccination measures.For diseases such as Rift Valley fever (RVF) the long inter-epizootic periods make dynavap o rings routine vaccination programs unfeasible.Coupling RVF prophylaxis with seasonal vaccination programmes by means of multivalent vaccine platforms would help to reduce the risk of new RVF outbreaks.Methodology/principal findingsIn this work we generated recombinant attenuated Rift Valley fever viruses (RVFVs) encoding in place of the virulence factor NSs either the VP2 capsid protein or a truncated form of the non-structural NS1 protein of bluetongue virus serotype 4 (BTV-4).The recombinant viruses were able to carry and express the heterologous BTV genes upon consecutive passages in arm tray for wheelchair cell cultures.
In murine models, a single immunization was sufficient to protect mice upon RVFV challenge and to elicit a specific immune response against BTV-4 antigens that was fully protective after a BTV-4 boost.In sheep, a natural host for RVFV and BTV, both vaccines proved immunogenic although conferred only partial protection after a virulent BTV-4 reassortant Morocco strain challenge.Conclusions/significanceThough additional optimization will be needed to improve the efficacy data against BTV in sheep, our findings warrant further developments of attenuated RVFV as a dual vaccine platform carrying heterologous immune relevant antigens for ruminant diseases in RVF risk areas.