Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, USA.
Transbound Emerg Dis. 2022 Sep;69(5):e3045-e3059. doi: 10.1111/tbed.14661. Epub 2022 Jul 26.
Isolation of porcine reproductive and respiratory syndrome virus (PRRSV) in cell culture is a primary means of obtaining virus isolates for autogenous vaccine production and other applications. However, it has not been well characterized whether cell culture isolate and the virus in clinical sample are equivalent. This study compared PRRSV ORF5 sequences from 1024 clinical samples (995 PRRSV-2, 26 PRRSV-1, and three PRRSV-1 and PRRSV-2 PCR-positive) and their isolates in MARC-145 and/or ZMAC cells. For three PRRSV-1 and PRRSV-2 PCR-positive clinical samples, both PRRSV-1 and PRRSV-2 were isolated in ZMAC cells, whereas either PRRSV-1 or PRRSV-2, but not both, was isolated in MARC-145 cells, with isolate sequences matching the respective viruses in clinical samples. Twenty-six PRRSV-1 and most of 995 PRRSV-2 PCR-positive clinical samples had matching viral ORF5 sequences with their cell culture isolates. However, 14 out of 995 PRRSV-2 cases (1.4%) had nonmatching viral sequences between clinical samples and MARC-145 isolates, although viral sequences from clinical samples and ZMAC isolates matched. This is concerning because, if the MARC-145 isolate is directly used for autogenous vaccine production without sequencing confirmation against the virus in the clinical sample, it is possible that the produced autogenous vaccine does not include the desired wild-type virus strain found on the farm and instead contains vaccine-like virus. Vaccine-specific PCR and next-generation sequencing performed on six selected cases indicated presence of ≥2 PRRSV-2 strains (mixed infection) in such clinical samples. In summary, PRRSV ORF5 sequences from clinical samples and cell culture isolates matched each other for majority of the cases. However, PRRSV sequences between clinical sample and MARC-145 cell culture isolate could occasionally be different when the clinical sample contains ≥2 PRRSV-2 strains. Characterizing PRRSV sequences from clinical samples and cell culture isolates should be conducted before using isolates for producing autogenous vaccines or other applications.
猪繁殖与呼吸综合征病毒（PRRSV）的细胞培养分离是获得用于同源疫苗生产和其他应用的病毒分离株的主要手段。然而，细胞培养分离株与临床样本中的病毒是否等效尚未得到充分表征。本研究比较了来自 1024 份临床样本（995 份 PRRSV-2、26 份 PRRSV-1 和 3 份 PRRSV-1 和 PRRSV-2 PCR 阳性）及其在 MARC-145 和/或 ZMAC 细胞中的分离株的 PRRSV ORF5 序列。对于 3 份 PRRSV-1 和 PRRSV-2 PCR 阳性的临床样本，PRRSV-1 和 PRRSV-2 均在 ZMAC 细胞中分离得到，而在 MARC-145 细胞中仅分离得到 PRRSV-1 或 PRRSV-2，而不是两者，分离株序列与临床样本中的相应病毒相匹配。26 份 PRRSV-1 和大多数 995 份 PRRSV-2 PCR 阳性的临床样本与细胞培养分离株具有匹配的病毒 ORF5 序列。然而，在 995 份 PRRSV-2 病例中有 14 例（1.4%）在临床样本与 MARC-145 分离株之间存在不匹配的病毒序列，尽管临床样本和 ZMAC 分离株的病毒序列相匹配。这令人担忧，因为如果在没有对临床样本中的病毒进行测序确认的情况下，直接使用 MARC-145 分离株用于同源疫苗生产，那么生产的同源疫苗可能不包含农场中存在的所需野生型病毒株，而是包含类似疫苗的病毒。对 6 个选定病例进行的 PRRSV 特异性 PCR 和下一代测序表明，在这些临床样本中存在≥2 种 PRRSV-2 株（混合感染）。总之，大多数情况下，临床样本和细胞培养分离株的 PRRSV ORF5 序列相互匹配。然而，当临床样本中含有≥2 种 PRRSV-2 株时，临床样本与 MARC-145 细胞培养分离株之间的 PRRSV 序列偶尔会有所不同。在使用分离株生产同源疫苗或其他应用之前，应对临床样本和细胞培养分离株的 PRRSV 序列进行特征分析。
