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Crimean-Congo Haemorrhagic Fever virus (CCHFV) is a tick-born virus of the Nairovirus genus within the Bunyaviridae family. It is a virus with three segments of single-stranded, negative RNAs [7, 8, 32]. The three segments are named S (small, ~1.7 kb), M (middle, ~5.7 kb) and L (large, ~12 kb), principally encoding nucleocapsid protein (N protein, NP), glycoprotein and RNA-dependent RNA polymerase (RdRp), respectively [5, 7]. CCHFV has been found in more than 30 countries in Africa, Europe and Asia [23]. In China, it was first found in Xinjiang province in 1965 and outbreaks have been reported from time to time in Xinjiang [2, 21]. Apart from Xingjiang, CCHFV antibody positives were reported in animals or humans from several other provinces such as Yunnan, Qinghai and Sichuan [26, 34] and sporadic CCHF outbreaks have been recently reported in Turkey and Iran [3, 6, 22]. A CCHF outbreak poses a threat to public health because of the high mortality rate as well as the difficulties in treatment and prevention. 30-50% mortality is common and rates as high as 80% have also been reported [3, 13, 14, 32], mortality is related to the transmission routes and viral dose [3, 14, 32]. To date, the only known and used drug to treat CCHF is ribavirin [9] and there is no effective vaccine available against CCHFV [9].
Viral envelope proteins are the first-choice for vaccine design. However, they are more prone to mutation to evade the host immune system [11]. The nucleocapsid (N) proteins are normally comparatively abundant and conserved in viruses, therefore N proteins have been widely tested as protective immunogens. The N protein of the feline infectious peritonitis virus (FIPV) was found to induce protective immunity in cats [30]; the N protein of Influenza virus, Ebola virus and avian coronavirus can elicit a strong cellular immune response [12, 19, 33]. These results indicate the nucleocapsid protein is a promising candidate for vaccine deve-lopment [17, 29]. The N protein of CCHFV is highly immunogenic [25, 31]. In this paper, the N protein of CCHFV was expressed by the baculovirus expression system, which is a candidate for protein overex-pression and is extensively used for vaccine development. By Western blot and IEM analysis, it was shown that CCHFV N protein can automatically assemble into Virus-Like Particles (VLPs) when over expressed in insect cells.
Production of CCHF Virus-Like Particle by a Baculovirus-Insect Cell Expression System
- Received Date: 29 June 2011
- Accepted Date: 31 August 2011
Abstract: Crimean-Congo Haemorrhagic Fever Virus (CCHFV) is a tick-born virus of the Nairovirus genus within the Bunyaviridae family, which is widespread and causes high fatality. The nucleocapsid of CCHFV is comprised of N proteins that are encoded by the S segment. In this research, the N protein of CCHFV was expressed in insect cells using a recombinant baculovirus. Under an electron microscope, Virus-Like Particles (VLPs) with various size and morphology were observed in cytoplasmic vesicles in the infected cells. Sucrose-gradient purification of the cell lysate indicated that the VLPs were mainly located in the upper fraction after ultracentrifugation, which was confirmed by Western blot analysis and immuno-electron microscopy (IEM).