Evolutionary Rate of E2 Genes of Classical Swine Fever Virus in China

Classical swine fever (CSF) is caused by classical swine fever virus (CSFV), a member of the genus Pestivirus of the family Flaviviridae, and engender important economic ramifications. Our previous study reported that both CSFV Group 1 and Group 2 were both contributed to the epidemic of CSF in mainland China, and showed the trend of switch from Group 1 to Group 2. In order to investigate the relationship between epidemiological trend and evolutionary rate of two Groups, the E2 glycoprotein gene (located in 25082697) of 68 CSFVs isolated from mainland China during 1982-2009 were aligned, and Bayesian Markov Chain Monte Carlo (MCMC) analysis was performed. The results indicated that the mean evolutionary rate of Group 2 (3.6861x10(-3) substitutions per site per year (subs/site/year)) evolved much faster than Group 1 (4.9852x10(-4) subs/site/year). We presumed that the differences in evolutionary rates of two groups likely implied that Group 2 possessed higher mutation rate and experienced higher selection pressure, however the real mechanism for the diversity in the evolutionary rate requires further investigation.