Design and Pilot Scale Production of an Alternative Non-Live Attenuated BTV Vaccine in Yeast

Bluetongue (BT) is an infectious disease of domestic and wild ruminants caused by Bluetongue virus (BTV), an arbovirus of the Orbivirus genus within Sedoreoviridae family. It’s primarily transmitted by biting midges of the Culicoides genus. BTV poses a significant threat to the livestock industry, particularly sheep. To date, a total of 36 serotypes of BTV have been characterized worldwide, causing periodic outbreaks, occurring most frequently in the Mediterranean basin. The control of BT disease is based on vaccination and several vaccines have been developed. Live attenuated vaccines and inactivated vaccines are widely used to prevent BT. However, despite their demonstrated efficacy, those vaccines have several limitations, including safety concerns and incomplete cross-protection among BTV serotypes. Recombinant subunit BT vaccines based on BTV structural proteins or virus-like particle vaccines (VLPs) may solve some of these limitations. In this study, we aim to design and develop vaccines that constitute an alternative to conventional attenuated vaccines. For this, we intend to express the VP2 and VP5 BTV antigens in Saccharomyces cerevisiae, a GRAS microorganism, by fusing the antigens to the secretion and cell wall retention signals of the Pir4 yeast cell wall protein. The VP2 and VP5 BTV structural proteins will be expressed in S. cerevisiae, targeting them to the yeast cell surface, or to the culture medium. The possibility of obtaining virus-like particles (VLPs), mimicking the virus, will also be studied.

Given that the research is currently underway, cloning, gene confirmation, sequencing and transformation of the constructs into the yeast expression system have been successfully completed. The confirmation of VP2, VP5, VLPs expression and assembly is currently under investigation, using immunofluorescence and Western blot analysis. The assessment of antigenicity and evaluation of the potential immunogenicity will be performed to validate the activity of the vaccine candidate in animals.