Madsen K G, Hansen C M, Madsen E S, Strandbygaard B, Bøtner A, Sørensen K J
Danish Veterinary Institute for Virus Research Lindholm, Kalvehave, Denmark.
Arch Virol. 1998;143(9):1683-700. doi: 10.1007/s007050050409.
Vaccine-like viruses of American type of porcine reproductive and respiratory syndrome virus (PRRSV) were detected in serum samples by RT-PCR. The viruses were analysed by nucleotide sequencing of the genomic region encoding open reading frames 2 to 7. During the ongoing study of Danish isolates of PRRSV by means of nucleotide sequencing, RT-PCR reactions and subsequent nucleotide sequencing showed the presence of American type PRRSV in Danish breeding herds. Most likely, these atypical viruses originated from boars vaccinated with live vaccine of American type (MLV RespPRRS), which were taken to artificial insemination centres and there brought together with unvaccinated boars already at the centres. The nucleotide sequences of three Danish viruses of American type PRRSV were compared to those of known PRRSV isolates. The nucleotide sequence identities of the atypical Danish isolates were between 99.2-99.5% to the vaccine virus RespPRRS and 99.0-99.3% to VR2332 which are the parental virus to the vaccine virus. Phylogenetic analysis including field isolates of American type supports the conclusion that the introduction of American type PRRSV in Denmark was due to spread of vaccine virus.
通过逆转录聚合酶链反应（RT-PCR）在血清样本中检测到美国型猪繁殖与呼吸综合征病毒（PRRSV）的类疫苗病毒。通过对编码开放阅读框2至7的基因组区域进行核苷酸测序来分析这些病毒。在对丹麦PRRSV分离株进行核苷酸测序的持续研究过程中，RT-PCR反应及随后的核苷酸测序显示丹麦种猪群中存在美国型PRRSV。极有可能的是，这些非典型病毒源自接种了美国型活疫苗（MLV RespPRRS）的公猪，这些公猪被送往人工授精中心，并在那里与已在中心的未接种疫苗的公猪混在一起。将三株丹麦美国型PRRSV病毒的核苷酸序列与已知PRRSV分离株的序列进行了比较。非典型丹麦分离株与疫苗病毒RespPRRS的核苷酸序列同一性在99.2%至99.5%之间，与疫苗病毒的亲本病毒VR2332的同一性在99.0%至99.3%之间。包括美国型田间分离株在内的系统发育分析支持了丹麦引入美国型PRRSV是由于疫苗病毒传播这一结论。
