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Comparison of ZMAC and MARC-145 Cell Lines for Improving Porcine Reproductive and Respiratory Syndrome Virus
Wannarat Yim-Im1, Haiyan Huang1, Jie Park1
1Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames, Iowa, USA.
Abstract:
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 (C ) 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.
Insights
The ZMAC cell line shows improved porcine reproductive and respiratory syndrome virus (PRRSV) isolation from clinical samples compared to MARC-145 cells. ZMAC cells offer better PRRSV isolation rates, particularly from lung and serum samples, aiding diagnostics and vaccine development.
Area of Science:
- Veterinary Virology
- Cell Biology
- Animal Health
Background:
- Porcine reproductive and respiratory syndrome virus (PRRSV) isolation is crucial for diagnostics, research, and vaccine production.
- The MARC-145 cell line is standard for PRRSV isolation but has low success rates.
- The ZMAC cell line, derived from porcine alveolar macrophages, is a potential alternative for PRRSV isolation.
Purpose of the Study:
- To compare the efficiency of ZMAC and MARC-145 cell lines for PRRSV virus isolation (VI) from diverse clinical samples.
- To evaluate the impact of sample type and PRRSV genetic lineage on VI success rates in ZMAC versus MARC-145 cells.
- To provide guidelines for optimizing PRRSV isolation from clinical specimens.
Main Methods:
- PRRSV VI was performed on 375 clinical samples (lung, serum, oral fluid, processing fluid) using both ZMAC and MARC-145 cell lines.
- Virus isolation success rates were compared between the two cell lines across different sample types.
- PRRSV isolates were characterized based on genetic lineage and their ability to grow in the alternative cell line.
Main Results:
- PRRSV VI success rates were low in oral and processing fluids for both cell lines.
- ZMAC cells demonstrated significantly higher PRRSV VI success rates than MARC-145 cells for lung and serum samples.
- Lower Ct values (<30) in samples correlated with improved VI success; ZMAC showed better isolation for PRRSV-2 lineages 1 and 8.
Conclusions:
- ZMAC cells provide superior PRRSV isolation efficiency from lung and serum samples compared to MARC-145 cells.
- While ZMAC cells isolate a broader range of PRRSV field strains, not all isolates grow in MARC-145 cells.
- These findings offer critical insights for enhancing PRRSV isolation strategies in veterinary diagnostics and vaccine development.
