Opriessnig T, Halbur P G, Yoon K-J, Pogranichniy R M, Harmon K M, Evans R, Key K F, Pallares F J, Thomas P, Meng X J
Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa 50011, USA.
J Virol. 2002 Dec;76(23):11837-44. doi: 10.1128/jvi.76.23.11837-11844.2002.
The objectives of this study were to compare the molecular and biological characteristics of recent porcine reproductive and respiratory syndrome virus (PRRSV) field isolates to those of a modified live virus (MLV) PRRS vaccine and its parent strain. One hundred seventeen, 4-week-old pigs were randomly assigned to six groups. Group 1 (n = 20) served as sham-inoculated negative controls, group 2 (n = 19) was inoculated with Ingelvac PRRS MLV vaccine, group 3 (n = 20) was inoculated with the parent strain of the vaccine (ATCC VR2332), group 4 (n = 19) was inoculated with vaccine-like PRRSV field isolate 98-38803, group 5 (n = 19) was inoculated with PRRSV field isolate 98-37120, and group 6 (n = 20) was inoculated with known high-virulence PRRSV isolate ATCC VR2385. The levels of severity of gross lung lesions (0 to 100%) among the groups were significantly different at both 10 (P < 0.0001) and 28 days postinoculation (p.i.) (P = 0.002). At 10 days p.i., VR2332 (26.5% +/- 4.64%) and VR2385 (36.4% +/- 6.51%) induced gross lesions of significantly greater severity than 98-38803 (0.0% +/- 0.0%), 98-37120 (0.8% +/- 0.42%), Ingelvac PRRS MLV (0.9% +/- 0.46%), and negative controls (2.3% +/- 1.26%). At 28 days p.i., 98-37120 (17.2% +/- 6.51%) induced gross lesions of significantly greater severity than any of the other viruses. Analyses of the microscopic-interstitial-pneumonia-lesion scores (0 to 6) revealed that VR2332 (2.9 +/- 0.23) and VR2385 (3.1 +/- 0.35) induced significantly more severe lesions at 10 days p.i. At 28 days p.i., VR2385 (2.5 +/- 0.27), VR2332 (2.3 +/- 0.21), 98-38803 (2.6 +/- 0.29), and 98-37120 (3.0 +/- 0.41) induced significantly more severe lesions than Ingelvac PRRS MLV (0.7 +/- 0.17) and controls (0.7 +/- 0.15). The molecular analyses and biological characterizations suggest that the vaccine-like isolate 98-38803 (99.5% amino acid homology based on the ORF5 gene) induces microscopic pneumonia lesions similar in type to, but different in severity and time of onset from, those observed with virulent strains VR2385 and the parent strain of the vaccine. Our data strongly suggest that isolate 98-38803 is a derivative of Ingelvac PRRS MLV and that the isolate is pneumovirulent.
本研究的目的是比较近期猪繁殖与呼吸综合征病毒（PRRSV）田间分离株与一种改良活病毒（MLV）PRRS疫苗及其亲本毒株的分子和生物学特性。117头4周龄仔猪被随机分为6组。第1组（n = 20）作为假接种阴性对照，第2组（n = 19）接种英特威PRRS MLV疫苗，第3组（n = 20）接种疫苗的亲本毒株（ATCC VR2332），第4组（n = 19）接种疫苗样PRRSV田间分离株98 - 38803，第5组（n = 19）接种PRRSV田间分离株98 - 37120，第6组（n = 20）接种已知高毒力PRRSV分离株ATCC VR2385。接种后10天（P < 0.0001）和28天（P = 0.002）时，各组间肺脏大体病变严重程度（0至100%）差异显著。接种后10天，VR2332（26.5% ± 4.64%）和VR2385（36.4% ± 6.51%）诱导的大体病变严重程度显著高于98 - 38803（0.0% ± 0.0%）、98 - 37120（0.8% ± 0.42%）、英特威PRRS MLV（0.9% ± 0.46%）和阴性对照（2.3% ± 1.26%）。接种后28天，98 - 37120（17.2% ± 6.51%）诱导的大体病变严重程度显著高于其他任何病毒。对微观间质性肺炎病变评分（0至6）的分析显示，接种后10天，VR2332（2.9 ± 0.23）和VR2385（3.1 ± 0.35）诱导的病变显著更严重。接种后28天，VR2385（2.5 ± 0.27）、VR2332（2.3 ± 0.21）、98 - 38803（2.6 ± 0.29）和98 - 37120（3.0 ± 0.41）诱导的病变显著比英特威PRRS MLV（0.7 ± 0.17）和对照（0.7 ± 0.15）更严重。分子分析和生物学特性表明，疫苗样分离株98 - 38803（基于ORF5基因的氨基酸同源性为99.5%）诱导的微观肺炎病变类型与强毒株VR2385和疫苗亲本毒株相似，但严重程度和发病时间不同。我们的数据强烈表明，分离株98 - 38803是英特威PRRS MLV的衍生物，且该分离株具有肺毒力。
