Abstract
BackgroundAfrican horse sickness (AHS) is a severe arthropod-borne viral disease of equids, with a mortality rate of up to 95% in susceptible naïve horses. Due to safety concerns with the current live, attenuated AHS vaccine, alternate safe and effective vaccination strategies such as virus-like particles (VLPs) are being investigated. Transient plant-based expression systems are a rapid and highly scalable means of producing such African horse sickness virus (AHSV) VLPs for vaccine purposes.ResultsIn this study, we demonstrated that transient co-expression of the four AHSV capsid proteins in agroinfiltrated Nicotiana benthamiana dXT/FT plants not only allowed for the assembly of homogenous AHSV-1 VLPs but also single, double and triple chimeric VLPs, where one capsid protein originated from one AHS serotype and at least one other capsid protein originated from another AHS serotype. Following optimisation of a large scale VLP purification procedure, the safety and immunogenicity of the plant-produced, triple chimeric AHSV-6 VLPs was confirmed in horses, the target species.ConclusionsWe have successfully shown assembly of single and double chimeric AHSV-7 VLPs, as well as triple chimeric AHSV-6 VLPs, in Nicotiana benthamiana dXT/FT plants. Plant produced chimeric AHSV-6 VLPs were found to be safe for administration into 6 month old foals as well as capable of eliciting a weak neutralizing humoral immune response in these target animals against homologous AHSV virus.
Highlights
African horse sickness (AHS) is a severe arthropod-borne viral disease of equids, with a mortality rate of up to 95% in susceptible naïve horses
Transient capsid protein expression and assembly of chimeric AHS VLPs in plants In order to facilitate the assembly of African horse sickness virus-like particles (VLPs) in N. benthamiana dXT/ FT plant cells, sequences encoding the AHS structural capsid proteins VP2, VP5, VP3 and VP7 were codonoptimised for N. benthamiana expression and cloned into either the pEAQ-HT or pEAQ-express plant expression vectors [40]
In order to facilitate the assembly of the homogenous African horse sickness virus (AHSV)-1 VLPs, the pEAQHT-AHSV-1VP2, pEAQ-express-AHSV-1VP5 and pEAQ-express-AHSV-1VP7-AHSV-1VP3 plasmids were agroinfiltrated into N. benthamiana dXT/FT leaves in a ratio of 1:1:1
Summary
African horse sickness (AHS) is a severe arthropod-borne viral disease of equids, with a mortality rate of up to 95% in susceptible naïve horses. African horse sickness (AHS) is a devastating disease of equids causing severe morbidity in naïve horses with the mortality rate up to 95% [1]. The disease is included in the World Organisation for Animal Health (OIE) 2019 list of African horse sickness virus (AHSV), the causative agent of AHS, is an Orbivirus in the family Reoviridae and is transmitted to susceptible animals via Culicoides midges [4]. Like Bluetongue virus (BTV), the prototype Orbivirus [6], the subcore of AHSV is composed of 120 copies of structural protein VP3 and is covered by a layer of VP7 trimers forming the core particle.
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