A Synthetic Modified Live Chimeric Marker Vaccine against BVDV-1 and BVDV-2

Abstract

Bovine viral diarrhea virus (BVDV), a pestivirus which exists in the two distinct species BVDV-1 (syn. Pestivirus A) and BVDV-2 (syn. Pestivirus B), is the causative agent of one of the most widespread and economically important virus infections in cattle. For economic as well as for animal health reasons, an increasing number of national BVDV control programs were recently implemented. The main focus lies on the detection and removal of persistently infected cattle. The application of efficient marker or DIVA (differentiation of infected from vaccinated animals) vaccines would be beneficial for the eradication success in regions with a high BVDV prevalence to prevent fetal infection and it would allow serological monitoring of the BVDV status also in vaccinated farms. Therefore, a marker vaccine based on the cytopathic (cp) BVDV-1b strain CP7 was constructed as a synthetic backbone (BVDV-1b_synCP7). For serological discrimination of vaccinated from infected animals, the viral protein Erns was substituted by the heterologous Erns of Bungowannah virus (BuPV, species Pestivirus F). In addition, the vaccines were attenuated by a deletion within the type I interferon inhibitor Npro protein encoding sequence. The BVDV-2 vaccine candidate is based on the genetic sequence of the glycoproteins E1 and E2 of BVDV-2 strain CS8644 (CS), which were introduced into the backbone of BVDV-1b_synCP7_ΔNpro_Erns Bungo in substitution of the homologous glycoproteins. Vaccine virus recovery resulted in infectious cytopathic virus chimera that grew to titers of up to 106 TCID50/mL. Both synthetic chimera BVDV-1b_synCP7_ΔNpro_Erns Bungo and BVDV-1b_synCP7_ΔNpro_Erns Bungo_E1E2 BVDV-2 CS were avirulent in cattle, provided a high level of protection in immunization and challenge experiments against both BVDV species and allowed differentiation of infected from vaccinated cattle. Our study presents the first report on an efficient BVDV-1 and -2 modified live marker vaccine candidate and the accompanying commercially available serological marker ELISA system.

Bungowannah Pestivirus Chimeras as Novel Double Marker Vaccine Strategy against Bovine Viral Diarrhea Virus

“…The overall aim of this study was to develop a marker vaccine prototype for BVDV-1 using a novel approach based on a synthetic backbone strategy of a related pestivirus with chimeric protein expression that has successfully been employed previously [46]. The synthetic backbone strategy allows the rapid exchange, deletion or insertion of sequences or genes.…”

“…A recent study characterizing a CSF mutant virus has already shown that the deletion of N pro and the absence of the immunosuppressive function led to an attenuation in vivo [54]. Despite that, most of the N pro encoding sequences were deleted in our construct in order to further increase the safety for pregnant dams, a concept already applied for the commercial BVDV vaccine Bovela ® (Boehringer Ingelheim Vetmedica GmbH, Ingelheim/Rhein, Germany) and the previously described marker vaccine candidates BVDV-1b_synCP7_∆N pro _E rns Bungo and BVDV-1b_synCP7_∆N pro _E rns Bungo_E1E2CS [46]. Regarding the factor of the heterologous heterodimer of E1 and E2 that might negatively influence the in vitro growth of BuPV_∆N pro _E1E2 CP7, we selected the combined replacement of both proteins because of the high genetic diversity between BuPV and BVDV-1 and as the formation of E1-E2 heterodimers is essential for virus entry [55].…”

“…The E1 and E2 glycoprotein sequences of BuPV were substituted with the E1 and E2 encoding genomic region of BVDV-1b CP7 strain to obtain a BVDV-1 vaccine candidate. In line with a comprehensive vaccine strategy and the published BVDV-1 and BVDV-2 chimeric marker candidate vaccines [46], the viral IFN antagonist N pro was deleted with retaining only the first 12 aa to ensure a correct processing of the polyprotein in combination with a stable attenuation of the vaccine candidate. To discriminate vaccinated from BVDV-field infected animals, the genetic sequences of the glycoproteins E rns and the nonstructural protein NS3 of BuPV were retained (Figure 1).…”

“…Due to the high similarity in the genome organization of pestiviruses, individual genes are often interchangeable between different Pestivirus species. Several approaches have already shown the heterologous compatibility of pestivirus proteins resulting in the feasibility to generate pestiviral chimeras and their application for different purposes, for example, characterization of new viruses or viral proteins [43], development of serological assays for seroprevalence studies [44] and the development of marker vaccines [3,45,46]. As an example, the Suvaxyn CSF Marker ® vaccine (Zoetis Belgium SA, Louvain-la-Neuveb, Belgium) that contains live BVDV, which has been modified to replace the E2 gene of BVDV with the corresponding gene of CSFV, was market authorized in 2015.…”

Recent Advances on the Bovine Viral Diarrhea Virus Molecular Pathogenesis, Immune Response, and Vaccines Development

“…Due to the significance of PI animals for spreading the infection, the target of vaccination strategies against BVDV mainly focuses on fetal protection, in addition to preventing clinical disease and virus-induced immune dysregulation. Control vaccination programs against BVDV involved using different types of live attenuated, killed, and recombinant vaccines (132)(133)(134)(135)(136). Although several scientific reports suggested their ability to prevent the clinical BVDV manifestations in cattle, live attenuated and killed BVDV vaccines differ in their safety for the vaccination of different cattle populations.…”