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Detection and growth kinetics of SV40 preparations with different enhancer element copy number
P D Minor1, G Dunn, P A Pipkin
1NIBSC, Blanche Lane, South Mimms, Potters Bar, EN6 3QG, Herts, UK. p.minor@nibsc.ac.uk
Abstract:
It has been reported that the rate of growth of SV40 in certain cell culture systems is affected by the number of copies of the enhancer element, and that this might in turn affect the ability of manufacturers of polio vaccines to detect SV40 contamination in tests for adventitious agents. Eleven strains of SV40 of which three were primary isolates, three were control strains used in different laboratories and five were well characterised were examined for their enhancer copy number. It was found that the three primary isolates contained a single copy while three preparations used as controls in different laboratories were mixtures of single and multiple copy strains. The remaining five strains consisted of one known double enhancer and four known single enhancer strains. All eleven strains were titrated in BSC-1 cells. There was no correlation between the number of copies of the enhancer element and the rate of growth or the final titre reached, although there was variation between the strains.
Insights
The number of Simian virus 40 (SV40) enhancer copies did not correlate with viral growth rates or final titers in cell cultures. This finding impacts the detection of SV40 contamination in polio vaccines.
Area of Science:
- Virology
- Cell Biology
- Vaccine Manufacturing
Background:
- SV40 (Simian virus 40) enhancer copy number may influence viral growth rates.
- This could affect the detection of SV40 contamination in adventitious agent testing for polio vaccines.
Purpose of the Study:
- To investigate the relationship between SV40 enhancer copy number and viral growth characteristics.
- To assess the implications for SV40 contamination detection in vaccine production.
Main Methods:
- Examined eleven SV40 strains for enhancer copy number (primary isolates, control strains, characterized strains).
- Titrated all eleven strains in BSC-1 cells to determine growth rates and final titers.
Main Results:
- Three primary isolates had single enhancer copies.
- Three control strains were mixtures of single and multiple copy strains.
- Five characterized strains included one double and four single enhancer strains.
- No correlation was found between enhancer copy number and viral growth rate or final titer.
- Variations in growth and titer were observed among different SV40 strains.
Conclusions:
- SV40 enhancer copy number does not appear to be a determinant of viral growth rate or achievable titer in BSC-1 cells.
- The presence of mixed enhancer copy numbers in control strains highlights potential variability in SV40 stock characterization.
- Further investigation is needed to understand factors influencing SV40 growth and detection in vaccine safety testing.