Objective To establish a method for determining the virus titer of the Culex flavivirus (CxFV) strain (SDDM06-11) isolated in China. Methods C6/36 cells were cultured in a 6-well cell culture plate and were then inoculated with CxFV. Methylcellulose was added to the cells and cultured for 4 days. Crystal violet was used for staining, and the number of plaques was determined to calculate the plaque forming unit of the virus. Results Observation of plaques using methylcellulose and crystal violet showed that CxFV (SDDM06-11) strain formed clear round plaques with the size of a needle tip after infecting C6/36 cells, and the virus titer of SDDM06-11 strain was successfully determined as 106.85 pfu/ml. Conclusion The methylcellulose-crystal violet plaque forming assay can be used to determine the titer of CxFV.
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