Arch Virol (1998) 143: 1295–1309
Isolation and characterization of cytopathogenic classical
swine fever virus (CSFV)
, M. Büttner, and G. Meyers
Federal Research Centre for Virus Diseases of Animals, Tübingen,
Federal Republic of Germany
Accepted February 19, 1998
Summary. Two new classical swine fever virus (CSFV) isolates obtained from
naturally infected swine were found to exhibit a cytopathogenic (cp) phenotype.
According to their reactivity with monoclonal antibodies (mabs) the isolates
cpBW1 and cpMVP1 were classiﬁed as antigenic types “Lothringen’92” and
“Flandern’90”, respectively. In Northern blot analyses and PCR assays CSFV
RNA of subgenomic length was detected in infected cells indicating the presence
of defective interfering particles. Nucleotide sequencing of cDNA fragments ob-
tained by reverse transcription (RT)-PCR allowed to localize in the genomes of
the cpMVP1 and cpBW1 DIs deletions of 4,764 and 4,746, respectively. From
the latter isolate a noncytopathogenic (noncp) biotype was obtained by cloning in
cell culture. CSFV cpBW1 and a noncp isolate were used separately for infection
of pigs. Viremia occurred much quicker after infection with cp virus and clinical
signs were more prominent compared to animals infected with noncp virus.
Three closely related virus species, bovine viral diarrhea virus (BVDV), border
disease virus (BDV) of sheep and classical swine fever virus (CSFV), form the
genus pestivirus within the family Flaviviridae . Pestiviruses represent
important pathogens of animals which cause severe losses in lifestock farming.
An interesting biological characteristic of these positive strand RNA viruses is
the existence of noncytopathogenic (noncp) and cytopathogenic (cp) biotypes
among all pestiviruses. Cytopathogenic pestiviruses emerge from noncp viruses
by mutational events and may be considered genetic accidents [22, 23]. At least
for BVDV the cp biotype has a major disadvantage for long term survival in vivo
Present address: Staatliches Veterinäruntersuchungsamt Krefeld, Krefeld, Germany.