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Comparative morphogenesis of three PRRS virus strains
J M Pol1, F Wagenaar, J E Reus
1Institute for Animal Science and Health, Lelystad, The Netherlands.
Abstract:
The morphogenesis of a Dutch PRRS field strain virus (Lelystad virus) was studied and compared to that of a U.S. field strain VR2332 and its attenuated vaccine strain JJ1882. Porcine lung alveolar macrophages (PLAM) and CL2621 cells were infected with high doses of virus (MOI = 10). At 4, 6, 9, 12, 18, 24, and 48 h post infection (hpi) cells were fixed for electronmicroscopy or for detection of viral antigens by immunoperoxidase staining. From 6 hpi on, viral antigens were detected in the cytoplasm and from 9 hpi on completely assembled virus particles could be detected in infected cells. The three strains were similar in assembly of new virus particles, envelopment at the smooth endoplasmic reticulum, and egress from infected cells. However, distinct differences were seen in replication time of the three strains in various cell types. The Lelystad virus replicated very fast and efficiently in PLAM while VR2332 and JJ1882 replicated preferably in CL2621 cells. JJ1882 replicated faster in CL2621 cells than VR2332 did, probably because of increased adaptation to the cell-line. Although the U.S. and European strains differ at the level of the genome, morphogenesis is not visibly altered. There is however a distinct difference in preferred cell type between the European strain and the two U.S. strains.
Insights
European and U.S. Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) strains show similar morphogenesis but differ in preferred cell types. Lelystad virus prefers porcine lung alveolar macrophages, while U.S. strains prefer CL2621 cells.
Area of Science:
- Virology
- Cell Biology
- Animal Health
Background:
- Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) causes significant economic losses in the swine industry.
- Understanding PRRSV strain variations is crucial for effective disease control and vaccine development.
- Morphogenesis and cellular tropism of different PRRSV strains are not fully elucidated.
Purpose of the Study:
- To compare the morphogenesis of a Dutch PRRSV field strain (Lelystad virus) with a U.S. field strain (VR2332) and its attenuated vaccine strain (JJ1882).
- To investigate the replication kinetics and preferred cell types of these PRRSV strains.
Main Methods:
- Infection of porcine lung alveolar macrophages (PLAM) and CL2621 cells with high virus doses (MOI = 10).
- Analysis of viral morphogenesis and antigen detection using electron microscopy and immunoperoxidase staining at various time points post-infection (4-48 hpi).
- Comparative analysis of replication rates and cellular tropism between the three PRRSV strains.
Main Results:
- All three PRRSV strains exhibited similar virus particle assembly, envelopment at the smooth endoplasmic reticulum, and egress.
- Viral antigens were detected from 6 hpi, and assembled virus particles from 9 hpi in infected cells.
- Lelystad virus replicated efficiently in PLAM, whereas VR2332 and JJ1882 showed preference for CL2621 cells. JJ1882 replicated faster in CL2621 cells than VR2332.
Conclusions:
- Despite genomic differences, the morphogenesis of European and U.S. PRRSV strains is visually similar.
- A distinct difference in preferred host cell type exists between the European Lelystad virus and the U.S. strains (VR2332 and JJ1882).
- These findings highlight the importance of cellular tropism in PRRSV strain characterization and potential implications for disease spread and control strategies.