RNA polyrnerase 1-mediated expression of viral RNA for the rescue of infectious virulent and avirulent Rift Valley fever viruses

Rift Valley fever Virus (RVFV, Bunyaviridae, Phlebovirtis) is a mosquito-transmitted arbovirus that causes human and animal diseases in sub-Saharan Africa and was introduced into tire Arabian Peninsula ill 2000. Here, we describe a method of reverse genetics to recover infectious RVFV from transfected plasmids based Oil the use Of the cellular RNA polymerase I promoter to synthesize viral transcripts. We compared its efficiency with a system using T7 RNA polymerase and found that both are equally efficient for the rescue of RVFV generating titers of approx. 10(7) to 10(8) pfu/ml. We used the RNA polymerase 1-based system to rescue both attenuated MP12 and virulent ZH548 strains as well as chimeric MP12-ZH548 viruses, and in addition RVFV expressing reporter proteins. (C) 2008 Elsevier Inc. All rights reserved.