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J. Virol., 01 1998, 380-387, Vol 72, No. 1
JJ Meulenberg, JN Bos-de Ruijter, R van de Graaf, G Wensvoort and RJ Moormann
The 5'-terminal end of the genomic RNA of the Lelystad virus isolate (LV)
of porcine reproductive and respiratory syndrome virus was determined. To
construct full-length cDNA clones, the 5'-terminal sequence was ligated to
cDNA clones covering the complete genome of LV. When RNA that was
transcribed in vitro from these full-length cDNA clones was transfected
into BHK-21 cells, infectious LV was produced and secreted. The virus was
rescued by passage to porcine alveolar lung macrophages or CL2621 cells.
When infectious transcripts were transfected to porcine alveolar lung
macrophages or CL2621 cells, no infectious virus was produced due to the
poor transfection efficiency of these cells. The growth properties of the
viruses produced by BHK-21 cells transfected with infectious transcripts of
LV cDNA resembled the growth properties of the parental virus from which
the cDNA was derived. Two nucleotide changes leading to a unique PacI
restriction site directly downstream of the ORF7 gene were introduced in
the genome- length cDNA clone. The virus recovered from this mutated cDNA
clone retained the PacI site, which confirmed the de novo generation of
infectious LV from cloned cDNA. These results indicate that the infectious
clone of LV enables us to mutagenize the viral genome at specific sites and
that it will therefore be useful for detailed molecular characterization of
the virus, as well as for the development of a safe and effective live
vaccine for use in pigs.
Copyright © 1998, American Society for Microbiology
Infectious transcripts from cloned genome-length cDNA of porcine reproductive and respiratory syndrome virus
Institute for Animal Science and Health, Lelystad, The Netherlands. J.J.M.Meulenberg@id.dlo.nl
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