Objective: To explore the variations of gene C in hepatitis B viruses between hepatitis B patients and healthy carriers, and provide experimental evidences for analysis of virus gene mutations acting on the virus material science and response of the body to the virus.
Methods: The virus DNA load in hepatitis B patients and healthy blood donors was investigated by real-time polymerase chain reaction (PCR). Gene sequence analysis was taken to detect gene polymorphism, and all the success samples were compaired with standard strain by DNAstar.
Results: (1)G Compared with standard strain, C region in all samples had mutations, there were 31 mutations in at least 2 samples (3 mutations in gene PreC and 28 mutations in gene C), including 9 missense mutations, 1 chain termination mutation and 21 synonymous mutation. Mutations nt 1827 c-->a and nt 2221 c-->t existed in all the samples, and most samples had 6 synonymous mutations. Four hepatitis B patients had mutation nt1896 g-->a, and another 4 patients had 2 mutations, namely, S87G and I97F (or 197L) in HBcAg CTL recognition episome. (2) The success ratio of amplification and sequencing of HBV DNA was closely associated with its copy numbers. In the present study, copy numbers of HBV DNA which were successfully amplified and sequenced were almost more than 40 193/ml.
Conclusions: HBV genome were easily affected by nucleotide mutations, 2 residues had mutations in gene of C region, which is firstly reported, suggesting these mutations may be geographical restricted. Mutations in gene of C region may either change the structure and function of HBeAg and HBcAg, which may further induce the escape of immune clearance for HBV or influence the detection of HBsAg or HBeAg, which may creat new problems for the prevention, diagnosis and treatment of hepatitis B.