Variation from Cytopathogenic Biotype to Non-Cytopathogenic Biotype is Correlated with the Deletion of Cellular Sequence from Bovine Viral Diarrhea Viruses.

Abstract

ABSTRACT. Non-cytopathogenic (NCP) viruses of bovine viral diarrhea (BVD) virus were detected at a low ratio by the reverse plaque formation method from virus samples after several plaque clonings of cytopathogenic (CP) BVD viruses; NADL and Osloss strains. This phenomenon suggests that the NCP BVD viruses are produced at a low ratio during the propagation of CP BVD viruses in vitro. To investigate the differences between the parent CP BVD virus and the NCP BVD virus as a real progeny, the regions flanking the insertion of cellular mRNA in the p125 domain of NADL and Osloss strains were amplified by RT-PCR and cloned into pGEM 3Z plasmid vector, and then sequenced. Consequently, it was confirmed that sequences of cellular mRNA insertion of CP BVD viruses, NADL and Osloss strains, were completely and exactly deleted from the NCP BVD viruses which were real progeny of CP BVD viruses, NADL and Osloss strains. These results suggest that NCP BVD viruses may revert from CP biotype to NCP biotype by the deletion of cellular mRNA insertion in the viral genome of CP BVD viruses (NADL and Osloss strains). proposed that a NCP BVD virus mutated to a CP BVD virus by taking up cellular sequences during a recombination event in persistently infected animals [21,22]. This hypothesis, however, was challenged by observations that some CP BVD viruses lacked the insertion in their genomes [7,9,12]. Therefore, the understanding of the cytopathogenicity of the BVD virus seems far from complete. Recently, NCP BVD viruses were isolated from CP BVD virus stocks and each virus stock of CP BVD virus contained simultaneously two kinds of NCP BVD viruses showing a different manner of interference [24]. It was speculated that the mutation from the CP biotype to the NCP biotype occurred during the propagation of CP BVD viruses in vitro. This paper deals with the possibility that the reversion of BVD virus from CP biotype to NCP biotype is caused by the deletion of cellular mRNA insertion in viral genome of CP BVD viruses; NADL and Osloss strains. MATERIALS AND METHODS Viruses and cells:The NADL [13] and Osloss strains [26] of CP BVD virus and derivative NCP BVD viruses (NADL-END + , NADL-END -, Osloss-END + and Osloss-END -strains) newly isolated from plaque cloned NADL and Osloss strains in our laboratory were used in this study. The NADL strain originated from the American Type Culture Collection (Rockville, MD, U.S.A.), and the Osloss strain was kindly provided by Prof. B. Liess, Institute for Virology, Hannover Veterinary School, Germany. Stock viruses were propagated in bovine testicle (BT) cell cultures and stored at 80°C. The BT cells were grown in Eagle's minimum essential medium (MEM) containing 10% fetal

Cytopathogenicity of Classical Swine Fever Viruses that do not Show the Exaltation of Newcastle Disease Virus is Associated with Accumulation of NS3 in Serum-Free Cultured Cell Lines

“…The noncp pestiviruses replicate without inducing a cytopathic effect (CPE), while cp viruses cause lysis of appropriate cultured cells. Cytopathogenic viruses are frequently reported for BVDV and some cp BVDVs have insertions of cellular sequences, duplication of the viral genome, or contain defective interfering (DI) particles [16,20,21]. Most CSFV field isolates that show the exaltation of Newcastle disease virus (END) phenomenon [8] are noncp in porcine cell cultures.…”

Characterization of Classical Swine Fever Virus Associated with Defective Interfering Particles Containing a Cytopathogenic Subgenomic RNA Isolated from Wild Boar.

“…Some preparations of cp BVDVs have insertions of cellular sequences, duplication of the viral genome in their genome, or defective interfering (DI) particles [17,22]. Recently, it has been reported that some strains of CSFV, which do not show the exaltation of Newcastle disease virus (END) phenomenon [10] but show intrinsic interference [5], inducing CPE in some swine kidney cell lines [24,26].…”

Segregation of Bovine Viral Diarrhea Virus Isolated in Japan into Genotypes.

“…Bovine testicle (BT) cells used for propagation of viruses, viral titration and serum neutralizing test were grown in Eagle's minimum essential medium supplemented with 10% fetal calf serum (GM) [18]. All cell cultures and fetal calf serum were determined to be free of BVDV before use by RT-PCR [14].…”