Dynamics Of Seral HBV Quasispecies In A Patient With Acute Exacerbation Of Chronic Hepatitis B

The word 'quasispecies' is used to describe the genetic heterogeneity of a single virus species in virology. Viral quasispecies study has been a hot spot in virology in recent few years. It has been confirmed that quasispecies characteristic is the general biological characteristic that all RNA viruses possess. The study on hepatitis B virus (HBV) quasispecies has also been considered important gradually. It has been indicated that the significance of HBV quasispecies study is to understand the relationship between the cause of HBV quasispecies forming and host clinical manifestation. The quasispecies nature of HBV may be an important virological factor in chronicalization of hepatitis and failure of antiviral therapy. The study on the effect of immune pressure and antiviral reagents in the forming of HBV quasispecies, on the relationship between the forming of HBV quasispecies, persistence of HBV infection and the clinical outcome of chronic HBV infection may provide important clues for exploit new treatment method for HBV infection.It is generally accepted that virus factors and host factors are both important in the exacerbation and severity of chronic hepatitis B. Hepatocytes' damage is induced by host immune attack, in the course of which cytotoxic T lymphocyte (CTL) plays an important role. PreC/C gene product is the main target of host immune system. HBcAg, which is encoded by core opening reading frame (C-ORF) of HBV genome, is the target antigen of CTL. B cell epitopes and CD4+ T lymphocyte epitopes are also encoded by C-ORF. Therefore, variations of C-ORF are closely related to host immune response level. ntG1896A mutation, which causes forming of a stop codon, has been reported to be associated with severity of hepatitis B. Current researches focus mainly on the detection of single variant and mutations and the comparison of these mutations in different host background, so that to discover the possible relationship between HBV variation and clinical manifestation. However, the PCR-nucleotide sequence analysis method detects only the predominant sequence of the virus population. Minor quasispecies are missed and the dynamics of quasispecies during the clinical course of persistent infection and exacerbationhas not been well shown.In order to preliminarily discuss the relationship between the'quasispecies of HBV PreC/C gene plus core promoter (BCP) region and host clinical manifestation, a series of serum samples collected from different time points during the clinical course of a patient with chronic hepatitis B (CHB), who had suffered from acute exacerbation of hepatitis as well as severe hepatitis, are analyzed with the method of PCR-clone-conformation sensitive gel electrophoresis (CSGE)-nucleotide sequence analysis. PreC/C gene plus the BCP region was amplified and cloned by nested PCR and TA cloning. 33 clones from a single sample was measured by CSGE to determine the different clonetypes. Clones with different clonetypes were sequenced. Our research demonstrated the dynamic changes of quasispecies of HBV PreC/C gene plus basal core promoter region during the clinical course of a CHB patient with acute exacerbation of chronic hepatitis and severe hepatitis, and discussed the relationship between the quasispecies of HBV PreC/C gene plus basal core promoter region and host clinical manifestationResults: 5 serum samples collected from 5 different time points, which were ゝirst exacerbation of chronic hepatitis ?recovery from exacerbation of hepatitis (3) exacerbation of severe hepatitis (4)2 months after recovery from severe hepatitis (5)4 months after recovery from severe hepatitis, during the clinical course were analyzed by the method mentioned above. The main results were :1. There does exist quasispecies phenomenon in HBV PreC/C gene plus BCP region in CHB patients serum. The contribution of the quasispecies of this region changed during the clinical course of this CHB patient. The complexity and heterogeneity of quasispecies of this region were low at the time points of exacerbation...