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Generation of defective interfering particles by two vaccine strains of measles virus
T Whistler1, W J Bellini, P A Rota
1Division of Viral and Rickettsial Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.
Abstract:
A systematic study was made to measure the generation of defective interfering particles upon up to 13 serial passages of two measles vaccine strains, Edmonston and Edmonston-Zagreb, through either simian (Vero) or human (WI-38) cell lines. Results for the Vero cell passage were nearly identical for both viruses. Infectivity titers dropped by nearly 8 logs to undetectable levels at passage 4 and cycled between maximum and minimum levels every 4 passages. Samples with the lowest infectivity titers produced the greatest reduction in titer of standard virus and contained an approximately 900-nucleotide subgenomic RNA for the Edmonston strain and two subgenomic RNAs of 4300 and 3000 nucleotides for the Edmonston-Zagreb vaccine strain. A defective interfering RNA-specific reverse transcription-polymerase chain reaction (RT-PCR) detected subgenomic RNAs at all passage levels. In contrast, samples obtained after passage of these viruses in WI-38 did not reduce the yield of standard virus and did not contain subgenomic RNAs in both Northern blot and RT-PCR assays. These results clearly show that cell type rather than virus strain affects defective interfering particle generation for measles virus.
Insights
Measles vaccine strains generate defective interfering particles in simian Vero cells but not human WI-38 cells. Cell type, not virus strain, dictates the generation of these viral variants.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Defective interfering particles (DIPs) are truncated viral genomes that require a helper virus for replication.
- DIPs can influence viral pathogenesis and vaccine efficacy.
- Understanding factors influencing DIP generation is crucial for vaccine development.
Purpose of the Study:
- To investigate the generation of defective interfering particles (DIPs) from measles vaccine strains.
- To determine the influence of cell type and virus strain on DIP generation.
- To characterize the subgenomic RNAs associated with DIPs.
Main Methods:
- Serial cell culture passage of measles vaccine strains (Edmonston and Edmonston-Zagreb) in Vero and WI-38 cells.
- Measurement of viral infectivity titers.
- Detection and characterization of subgenomic RNAs using Northern blot and RT-PCR.
Main Results:
- Measles viruses serially passaged in Vero cells produced DIPs, characterized by reduced infectivity and the presence of subgenomic RNAs.
- DIP generation in Vero cells showed cyclical patterns of infectivity and subgenomic RNA production.
- Measles viruses passaged in WI-38 cells did not produce detectable DIPs or subgenomic RNAs.
- Subgenomic RNA sizes varied between measles vaccine strains (Edmonston and Edmonston-Zagreb).
Conclusions:
- Cell type is a critical determinant in the generation of measles virus defective interfering particles.
- Simian Vero cells support DIP generation, while human WI-38 cells do not.
- These findings have implications for measles vaccine production and stability.