Abstract
BackgroundBluetongue is a disease of domestic and wild ruminants caused by bluetongue virus serotypes (BTV), which have caused serious outbreaks worldwide. Commercially available vaccines are live-attenuated or inactivated virus strains: these are effective, but there is the risk of reversion to virulence or reassortment with circulating strains for live virus, and residual live virus for the inactivated vaccines. The live-attenuated virus vaccines are not able to distinguish naturally infected animals from vaccinated animals (DIVA compliant). Recombinant vaccines are preferable to minimize the risks associated with these vaccines, and would also enable the development of candidate vaccines that are DIVA-compliant.ResultsIn this study, two novel protein body (PB) plant-produced vaccines were developed, Zera®-VP2ep and Zera®-VP2. Zera®-VP2ep contained B-cell epitope sequences of multiple BTV serotypes and Zera®-VP2 contained the full-length BTV-8 VP2 codon-optimised sequence. In addition to fulfilling the DIVA requirement, Zera®-VP2ep was aimed at being multivalent with the ability to stimulate an immune response to several BTV serotypes. Both these candidate vaccines were successfully made in N. benthamiana via transient Agrobacterium-mediated expression, and in situ TEM analysis showed that the expressed proteins accumulated within the cytoplasm of plant cells in dense membrane-defined PBs. The peptide sequences included in Zera®-VP2ep contained epitopes that bound antibodies produced against native VP2. Preliminary murine immunogenicity studies showed that the PB vaccine candidates elicited anti-VP2 immune responses in mice without the use of adjuvant.ConclusionsThese proof of concept results demonstrate that Zera®-VP2ep and Zera®-VP2 have potential as BTV vaccines and their development should be further investigated.
Highlights
Bluetongue is a disease of domestic and wild ruminants caused by bluetongue virus serotypes (BTV), which have caused serious outbreaks worldwide
Zera®-VP2ep and Zera®-VP2 expression in N. benthamiana Zera®-VP2ep and Zera®-VP2 were successfully cloned into pEAQ-HT (George Lomonossoff, JII, Norwich) to generate pEAQ-HTZera®-VP2ep (Additional file 1: Figure S2a) and pEAQ-HTZera®-VP2 (Additional file 1: Figure S2c) and the recombinant constructs electroporated into Agrobacterium tumefaciens LBA4404
Plants were infiltrated at an OD600 of 0.5, 1.0 and 1.5 with recombinant Zera®VP2ep or Zera®-VP2 to examine the effects of A. tumefaciens cell concentration on recombinant protein expression levels
Summary
Bluetongue is a disease of domestic and wild ruminants caused by bluetongue virus serotypes (BTV), which have caused serious outbreaks worldwide. The live-attenuated virus vaccines are not able to distinguish naturally infected animals from vaccinated animals (DIVA compliant). Bluetongue (BT) is a non-contagious, arthropod-borne viral disease that affects ruminants [1]. The causative agent of BT is bluetongue virus (BTV), the type species of the genus Orbivirus in the family Reoviridae [4]. Since 1998 BTV has become one of the most widespread animal pathogens, as it has spread to areas that were previously free of the virus [6]. Outbreaks of BT occur when susceptible sheep are introduced into BTVendemic regions or when the virus spreads to naïve sheep populations at the interface of endemic and nonendemic regions [7]. In subsequent outbreaks the northernmost limits of BTV moved beyond 54 °N [2, 8]
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