Abstract
Bluetongue is a severe, economically important disease of ruminants that is widely distributed in tropical and temperate regions around the world. It is associated with major production losses, restrictions of animal movements and trade, as well as costs associated with developing and implementing effective surveillance and control measures. Mammalian hosts infected with bluetongue virus (BTV) generate a protective neutralising antibody response targeting the major BTV outer-capsid protein and serotype-specific antigen, VP2. BTV VP2 proteins that have been expressed in plants are soluble, with a native conformation displaying neutralising epitopes and can assemble with other BTV structural proteins to form virus-like particles (VLPs).His-tagged VP2 proteins of BTV serotypes 4 and 8 were transiently expressed in Nicotiana benthamiana then purified by immobilised metal affinity chromatography (IMAC). Antisera from IFNAR −/− mice prime/boost vaccinated with the purified proteins, were shown to contain VP2-specific antibodies by Indirect ELISA (I-ELISA), western blotting and serum neutralisation tests (SNT). Vaccinated mice, subsequently challenged with either the homologous or heterologous BTV serotype, developed viraemia by day 3 post-infection. However, no clinical signs were observed in mice challenged with the homologous serotype (either prime-boost or single-shot vaccinated), all of which survived for the duration of the study. In contrast, all of the vaccinated mice challenged with a heterologous serotype, died, showing no evidence of cross-protection or suppression of viraemia, as detected by real-time RT-qPCR or virus isolation. The induction of protective, serotype-specific neutralising antibodies in IFNAR −/− mice, indicates potential for the use of plant-expressed BTV VP2s as subunit vaccine components, or as a basis for serotype-specific serological assays.
Highlights
Bluetongue virus (BTV) infects a wide range of domesticated and wild ruminants, causing the severe clinical disease ‘bluetongue’ (BT) primarily in naïve sheep and some deer species [1,2,3]
This paper describes vaccination/challenge studies showing that VP2 of BTV-4 and BTV-8 expressed in tobacco plants (Nicotiana benthamiana) can be used to raise neutralising antibodies and a protective response in IFNARÀ/À mice
His-tagged rVP2s of BTV-4 and BTV-8, expressed at high levels ($1.5 mg/mL each) in tobacco plants and immobilised metal affinity chromatography (IMAC) purified, were soluble suggesting that they retain a native conformation
Summary
Bluetongue virus (BTV) infects a wide range of domesticated and wild ruminants, causing the severe clinical disease ‘bluetongue’ (BT) primarily in naïve sheep and some deer species [1,2,3]. Bluetongue outbreaks in non-endemic regions of the world, as well as those caused by exotic BTV strains/serotypes in endemic regions, can cause major economic losses. These include fatalities (mainly among sheep), loss of productivity and reproductive. The BTV genome is composed of ten linear segments of dsRNA, encoding seven structural proteins (VP1–VP7) and five non-structural proteins (NS1–NS5) [8,9].
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