The potency of live rubella virus vaccine is usually determined by the microtitration method using in vitro cytopathic effect (CPE) with
rabbit kidney epithelial (RK-13) cell culture. However, it is difficult to identify the rubella viral CPE through microscopic examination.
Therefore, developing a validated and accurate method for potency determination is important for the laboratories of the government and
vaccine manufacturers to ensure the effectiveness of rubella vaccination. In this study, we evaluated different culture conditions of RK-13
cells for the potency test of live rubella virus vaccine. We found that the RK-13 cells with the initial plating number of 13,000 per well of
96-well cell culture plate, supplied with 2% fetal bovine serum (FBS) could form and maintain a normal monolayer for 14 days when incubated
at 33°C. In addition, our results showed that the rubella viral CPEs are developed faster and simpler under 2% of serum concentration
and at 33°C. The results of validation analysis finally confirmed that the culture condition with plating number of 13,000 cells/well,
2% of serum concentration, and 33°C incubating temperature achieve the most accurate and precise results for the CPE potency test of live
rubella virus vaccine.