Packaging of Rift Valley fever virus pseudoviruses and establishment of a neutralization assay method

Li, Yuetao; Zhao, Yongkun; Wang, Cuiling; Zheng, Xuexing; Wang, Hualei; Gai, Weiwei; Jin, Hongli; Yan, Feihu; Qiu, Boning; Gao, Yuwei; Li, Nan; Yang, Songtao; Xia, Xianzhu

Rift Valley fever virus (RVFV) is an RNA virus in the Phlebovirus genus of the Bunyaviridae family [10] . In particular, RVFV is a high-risk pathogen that can induce fatal encephalitis and hemorrhagic fever in humans and ruminants [5, 11] . Due to its strong pathogenicity and fast dissemination, RVFV has attracted considerable worldwide attention. Currently, viral isolation, hemagglutination inhibition assays, enzyme-linked immunosorbent assays (ELISAs), agar gel immunodiffusion assays, immunofluorescence assays, radioimmunoassays, and complement fixation assays are the primary methods used to detect RVFV [16, 17] . Additionally, clinical detection of anti-RVFV antibodies is primarily accomplished by using the ELISA method [16] . Commonly used coating antigens include the envelope protein (Gn) and inactivated RVFV. However, this method can only preliminarily detect antibody levels in humans, and those results do not truly reflect whether the antibodies have pathogen-neutralizing, anti-RVFV, and anti-infection functions. Therefore, the virus neutralization assay has become an important clinical method for measuring antibody activity and evaluating immune status in humans. The neutralization assay typically uses natural viruses, which can cause infections in the assay operators and pose a risk of viral spread; thus, this assay is considered very dangerous. To avoid the potential risks associated with the neutralization assay, the present study used a lentiviral packaging system and targeted RVFV structural proteins to construct RVFV pseudoviruses to replace live viruses. The pseudoviruses were then used to establish an RVFV neutralization assay method to allow effective evaluation of human antibody titers.