Abstract
Cytopathogenic (cp) pestiviruses frequently emerge in cattle that are persistently infected with the bovine viral diarrhea virus (BVDV) as a consequence of RNA recombination and mutation. They induce apoptosis in infected tissue cultures, are highly attenuated in the immunocompetent host, and unable to establish persistent infections after diaplacental infections. Cp strains of BVDV have been used as naturally attenuated live vaccines and for species-specific plaque reduction tests for the indirect serological detection of BVDV. Here, we present a genetically engineered cp strain of the classical swine fever virus (CSFV). Cytopathogenicity of the strain was induced by the insertion of ubiquitin embedded in a large NS3 to NS4B duplication. The CSFV RNA genome was stabilized by the inactivation of the NS2 autoprotease, hindering the deletion of the insertion and the reversion to a wild-type genome. Additional insertion of a mCherry gene at the 5′-end of the E2 gene allowed fluorescence-verified plaque reduction assays for CSFV, thus providing a novel, cost-efficient diagnostic tool. This genetically stabilized cp CSFV strain could be further used as a basis for potential new modified live vaccines. Taken together, we applied reverse genetics to rationally fixate a typical cp NS3 duplication in a CSFV genome.
Highlights
Replicon with the CP Rit insertion (Ubi*) at the 50 -end of the open reading frame (ORF) to test the activity of this ubiquitin insertion as a processing signal for classical swine fever virus (CSFV) NS3
Infected cattle but have never been isolated from CSFV infected pigs [60]. This circumstance may be explained by the fact that cp strains of bovine viral diarrhea virus (BVDV) arise from mutations in persistently infected, immunotolerant animals from their ncp progenitor viruses
CSFV infections are rather rare in pigs, and most persistently infected (PI) piglets die quickly due to the higher virulence of CSFV
Summary
Academic Editors: Paul Becher, Norbert Tautz and Nicolas Ruggli. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The classical swine fever virus (CSFV) is the causative agent of classical swine fever (CSF), formerly termed hog cholera. CSFV has been eradicated in most developed countries, but despite longstanding eradication efforts by the OIE Health), CSF is still an economically important disease. Recent outbreaks of CSFV in the domestic pig population and/or endemic situations in known wild boar reservoirs are reported from Africa, Asia, the Caribbean, Central and South America and Europe [1,2,3]
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