Phylogenetic Study Of Hepatitis B Virus

Hepatitis B is one of the most serious diseases threatening human health. HBV (Hepatitis B virus, HBV) infection is the main reason to cause acute and chronic hepatitis, cirrhosis and liver cancer. There are10genotypes and48subtypes of HBV. Significant diversity of Hepatitis B virus gives HBV research and clinical treatment huge challenge. This thesis combines decision tree in data mining with the traditional phylogenetic analysis method to classify HBV genotypes and subtypes.Researches on the phyletic evolution of hepatitis B virus help to understand the evolution of the pathogenesis of it and to provide reference for clinical treatment in China. The research contents of this thesis are as follows:Edit clinical HBV data and the reference HBV sequences to get standardized genome and X/PreC gene datasets, which is to be processed in later experiment. Then we build a subtype decision tree by mining critical information sites in HBV dataset to classify HBV subtypes.On the basis of the multiple sequence alignment, we build a phylogenetic tree based on X/PreC gene in genotype A-I to study the evolutionary relationships between genotype B and other genotypes; build a phylogenetic tree based on genome of ten subtypes of HBV/B to research evolutionary relationship between B1-B10. Verify the presence of new subtype B10in the Hani minority of Xishuangbanna by phylogenetic analysis.Integrate the classification result in decision tree built of discrete information sites and the phylogenetic trees based on sequence similarity, to analysis the consistency of experiment. And genotyping HBV clinical dataset, we found a recombinant of genotype B and C in the new subtype. It is the first time to discover a B/C recombinant structure in Hani of Xishuangbanna.In addition, the thesis also discussed the original sequence of hepatitis B virus and the classification reasonableness of the virus. The experimental results develop HBV evolutionary theory, and have a certain value to HBV research in minority ethnics of Yunnan Province.