中文摘要：

猪繁殖与呼吸综合征病毒（PRRSV）GD07株在Marc-145细胞中在添加或不添加猪干扰素-β（swIFN—p）免疫压力条件下连续传代，将获得的新毒株进行病毒生物学分析、序列测定和IFN～pmRNA水平检测。结果显示，传代后病毒效价逐渐降低，swlFN-β对自然传代和免疫压力下传代毒株的抑制作用下降，且对swlFN—β免疫压力下传代毒株的抑制作用下降的程度较大。序列分析表明，ORF3和ORF5序列的变异导致氨基酸发生变异。荧光定量RT—PCR检测表明，swlFN-β免疫压力下传代病毒感染Marc-145细胞的IFN—pmRNA水平低于自然传代毒株的相应指标，两者均远低于poly（I：C）刺激细胞后的IFN-βmRNA水平。结果表明，swIFN-β免疫压对PRRSV的遗传变异有正向加速作用。

英文摘要：

The highly pathogenic porcine reproductive and respiratory syndrome virus Guangdong （PRRSV-GD07） strain was continuously propagated in Marc-145 cell with or without addition of swine in- terferon-p（swIFN-β） for 50 passages to develop PRRSV-GD-IFNF. and PRRSV-GDF. Infected cells were collected for extraction of viral RNA after every 10 passages, and viral biology, sequence and host IFN-β mRNA level were analyzed. In result, the viral titer and sensitivity to swIFN-β decreased gradually after several passages, especially PRRSV-GD07 strain with swIFN@ ORF3 and ORF5 genes were amplified,cloned and sequenced. Sequencing analysis indicated that the strains after propagation with or without swIFN-β had some nucleic acid mutations. IFN-β mRNA level in Marc-145 cells with swIFN-β was lower than that without swIFN-β and both were far less than IFN-β mRNA level in the cells with poly （I： C）. These results demonstrated that molecular variation of PRRSV-GD07 strain was accelerated under swine interferon-β immune pressure.