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The purpose of this study was to understand the stability and possibility of back mutation of Japanese encephalitis (JE) attenuated vaccine virus strain SA_(14)-14-2 HK_8 on molecular level. The E genes of the SA_(14)-14-2 HK_8 vaccine virus and its PHK cells passaged virus (SA_(14)-14-2 HK_(17)), its mouse brain passaged virus (SA_(14)-14-2 SM_1) were sequenced and compared with the E gene of parental SA_(14) virus. The total RNA was extracted from infected Vero cells and amplified by RT-PCR. The RT-PCR products were purified and cloned into T-vector. Positive clones were screened, identified and sequenced. There were twelve nucleotides and eight amino acids substitutions between SA_(14) parent virus and SA_(14)-14-2 PHK_8 vaccine virus. The SA_(14)-14-2 PHK_(17 )virus showed two additional mutations (E-331 and E-398) which were not back mutations. Although five additional mutations were found in SA_(14)-14-2 SM_1 virus, only one (E-107) was back mutation. Genetic characteristics of the attenuated vaccine virus SA_(14)-14-2 were stable when it was passaged 17 times on PHK cells or one time in mouse brains.
The purpose of this study was to understand the stability and possibility of back mutation of Japanese encephalitis (JE) attenuated vaccine virus strain SA_ (14) -14-2 HK_8 on molecular level. The E genes of the SA_ (14) -14- 2 HK_8 vaccine virus and its PHK cells passaged virus (SA_ (14) -14-2 HK_ (17)), its mouse brain passaged virus (SA_ (14) -14-2 SM_1) were sequenced and compared with the E gene of The total RNA was extracted from infected Vero cells and amplified by RT-PCR. The RT-PCR products were purified and cloned into T-vector. Positive clones were screened, identified and sequenced. (14) -14-2 PHK_ (17) virus showed two additional mutations (E-331 and E- 398) which were not back mutations. Although five additional mutations were found in SA_ (14) -14-2 SM_1 virus, only one (E-107) was back mutation. Genetic characteristics of t he attenuated vaccine virus SA_ (14) -14-2 were stable when it was passaged 17 times on PHK cells or one time in mouse brains.