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Bulletin No. 15 - Summer 2003
VirologyPorcine Reproductive and Respiratory Syndrome (PRRS)
NIELSEN HS, LIU G, NIELSEN J, OLEKSIEWICZ MB, B?TNER A, STORGAARD T, FAABERG KS
Generation of an infectious clone of VR-2332, a highly virulent North American-type isolate of porcine reproductive and respiratory syndrome virus
Journal of Virology 2003 77: 3702-3711
After establishing a cDNA clone of the European-type Lelystad virus, a first cDNA clone of the pathogenic North American PRRS isolate VR-2332 was successfully assembled. The infectious virus was recovered with its capped RNA tranfected into BHK-21C cells. The clone was completely sequenced and 11 differences were noted between the sequence of the full-length DNA clone and that of the parental VR-2332 DNA. The parental VR-2332 strain and the clone-derived virus exhibited similar characteritics: same cell trophism, same growth kinetics in Mark-145 cells and similar clinical signs in pigs infected with the infectious clone or the parental strain (classical blue discoloration of ears). Also the infected pigs seroconverted but seroconversion kinetics were lower for the cloned virus and lower titers were recorded in MarK-145 cells infected with the cloned virus. The first cDNA clone of the American PRRSV strain will help understand the molecular mechanisms of the virulent virus and give rise to new recombinant vaccines.
