Successive subculture and genetic stability of hepatitis A virus vaccine strain H2 / 中华实验和临床病毒学杂志

ABSTRACT

Objective@#To investigate the genetic stability of virus seed H2M20K7 (K7) of live attenuated Hepatitis A virus H2 strain (HAV, H2 strain) for production of hepatitis A (Live) vaccine, lyophilized after continuous passages.@*Methods@#The virus seed K7 of H2 strain was proliferated and passaged in KMB17 cells in cell factories. Viruses of different passages were harvested after continuous passages. Virus RNA was extracted and the complete genomes of different virus passages (K7, K10, K11, K13, K15, K18) were sequenced by using next-generation deep sequencing. The mutation rates of different passages were compared. The infectivity titers of different virus passages of H2 strain were tested by ELISA.@*Results@#The mutation rates of complete genomes of different passages were low after continuous passages of master virus seed. The structure of gene was stable and non-synonymous mutation rate was lower than 0.57%. The mutation rate of 5 ’non-coding regions was lower than 0.1%. There was no significant mutation in VP1/2 A and 2C virulence site. The infectious titers of H2 strains of different passages were within 7.76-8.50 lgCCID50/ml. No statistically significant difference was found in this study.@*Conclusions@#The gene structure of the master virus seed, working seed and different passages of H2M20K7 after subculture was stable and the mutation rate was low. No significant mutation was found in 5’non-coding regions, and the critical virulence sites such as VP1/2 A, 2B and 2C showed attenuated characteristics with low mutation rate. Virulence of the virus did not changed. The H2 strain maintained stable viral infectivity and genetic stability and comply with the requirements as virus seed for vaccine manufacturing.