Pathogenesis of mucosal disease, a deadly disease of cattle caused by a pestivirus

BACKGROUND: Two biotypes of pestiviruses, cytopathogenic (cp) and non-cytopathogenic (noncp) viruses, are distinguished by their effects on tissue culture cells. In contrast to the bovine viral diarrhoea virus (BVDV) system, only a few cp border disease virus (BDV) and cp classical swine fever virus (CSFV) strains have been described. Antigenically closely related noncp and cp BVDV can be isolated from cattle with fatal mucosal disease (MD) and are called a virus pair. The generation of cp BVDV in an animal persistently infected with noncp BVDV is regarded as causative for the development of MD. OBJECTIVES: To analyse viral pairs of BVDV at the molecular level and thereby identify differences between the viruses of each pair. STUDY DESIGN: BVDV pairs were isolated from several animals coming down with MD; the genomes of the respective BVD viruses were sequenced on cDNA level. Studies concerning the polyprotein processing of each strain were carried out. RESULTS: Molecular analysis of BVDV pairs demonstrated a linkage between RNA recombination, generation of NS3 and the onset of fatal MD. CONCLUSION: The molecular analysis of BVDV pairs revealed that the respective cp strains arise by RNA recombination from noncp viruses