Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames, Iowa, USA.
Aptimmune Biologics, St. Louis, Missouri, USA.
J Clin Microbiol. 2021 Feb 18;59(3). doi: 10.1128/JCM.01757-20.
The MARC-145 cell line is commonly used to isolate porcine reproductive and respiratory syndrome virus (PRRSV) for diagnostics, research, and vaccine production, but it yields frustratingly low success rates of virus isolation (VI). The ZMAC cell line, derived from porcine alveolar macrophages, has become available, but its utilization for PRRSV VI from clinical samples has not been evaluated. This study compared PRRSV VI results in ZMAC and MARC-145 cells from 375 clinical samples (including 104 lung, 140 serum, 90 oral fluid, and 41 processing fluid samples). The PRRSV VI success rate was very low in oral fluids and processing fluids regardless of whether ZMAC cells or MARC-145 cells were used. Success rates of PRRSV VI from lung and serum samples were significantly higher in ZMAC than in MARC-145 cells. Lung and serum samples with threshold cycle ( ) values of <30 had better VI success. PRRSV-2 in genetic lineages 1 and 8 was isolated more successfully in ZMAC cells than in MARC-145 cells, whereas PRRSV-2 in genetic lineage 5 was isolated in the two cell lines with similar success rates. For samples with positive VI in both ZMAC and MARC-145 cells, 14 of 23 PRRSV-2 isolates had similar titers in the two cell lines. A total of 51 of 95 (53.7%) ZMAC-obtained PRRSV-2 or PRRSV-1 isolates grew in MARC-145 cells, and all 46 (100%) MARC-145-obtained isolates grew in ZMAC cells. In summary, ZMAC cells allow better isolation of a wide range of PRRSV field strains; however, not all of the ZMAC-obtained PRRSV isolates grow in MARC-145 cells. This report provides important guidelines to improve isolation of PRRSV from clinical samples for further characterization and/or for producing autogenous vaccines.
MARC-145 细胞系常用于分离猪繁殖与呼吸综合征病毒（PRRSV），用于诊断、研究和疫苗生产，但病毒分离（VI）的成功率却令人沮丧地低。ZMAC 细胞系源自猪肺泡巨噬细胞，现已可获得，但尚未评估其用于从临床样本中分离 PRRSV VI 的效果。本研究比较了 ZMAC 和 MARC-145 细胞从 375 份临床样本（包括 104 份肺组织、140 份血清、90 份口腔液和 41 份加工液样本）中分离 PRRSV VI 的结果。无论使用 ZMAC 细胞还是 MARC-145 细胞，口腔液和加工液中的 PRRSV VI 成功率都非常低。ZMAC 细胞中肺和血清样本的 PRRSV VI 成功率明显高于 MARC-145 细胞。阈值循环（Ct）值<30 的肺和血清样本具有更高的 VI 成功率。ZMAC 细胞中分离到的基因谱系 1 和 8 的 PRRSV-2 比 MARC-145 细胞中更成功，而基因谱系 5 的 PRRSV-2 在两种细胞系中的分离成功率相似。对于在 ZMAC 和 MARC-145 细胞中均有阳性 VI 的样本，23 个 PRRSV-2 分离株中有 14 个在两种细胞系中的滴度相似。在 ZMAC 细胞中获得的 51 个（53.7%）PRRSV-2 或 PRRSV-1 分离株在 MARC-145 细胞中生长，而在 MARC-145 细胞中获得的所有 46 个（100%）分离株在 ZMAC 细胞中生长。总之，ZMAC 细胞允许更好地分离广泛的 PRRSV 田间株，但并非所有在 ZMAC 细胞中获得的 PRRSV 分离株都能在 MARC-145 细胞中生长。本报告为提高从临床样本中分离 PRRSV 以进行进一步鉴定和/或生产同源疫苗提供了重要指导。
