Hv. Bjorklund et al., MOLECULAR CHARACTERIZATION OF THE 3'-NONCODING REGION OF CLASSICAL SWINE FEVER VIRUS-VACCINE STRAINS, Virus genes, 16(3), 1998, pp. 307-312
The genomes of classical swine fever virus (CSFV) vaccine strains are
poorly characterized, and the mechanisms for their attenuation remain
unknown. The aim of the present study was to characterize the 3' nonco
ding region (3' NCR) of a number of attenuated vaccine strains of CSFV
in order to examine changes in the viral genome after attenuation. Th
e results showed that the 3' NCR:s of Porcivac, Rovac, Russian LK and
original Chinese vaccine strain contain insertions very similar to tha
t present in the published nucleotide sequence of the C-strain. Phylog
enetic analysis showed that the vaccine strains Porcivac, Rovac and Ru
ssian LK vaccine were closely related to each other, but that these th
ree strains showed a distant relationship with two tested variants of
the Chinese vaccine strain (C-strain and original Chinese vaccine). Th
e 3' NCR insertion is not likely to be a marker for attenuation of the
virus, since many CSFV vaccine strains do not contain the insertion.
The fact that the insertions occur in lapinized vaccine strains sugges
ts that these genetic segments were incorporated during the adaptation
of the virus to the rabbit host system.