Gene Variations In The Basic Core Promotor And The PreC/C Region Of Hepatitis B Virus

HBV is a multiple imitative virus. The important nucleotides changed in some regions would change the biologic characters of the virus. In this study, we studied the mutants of preC/C gene and the base core promo tor (BCP) in hepatitis B e antigen (HBeAg) positive and negative patients with chronic hepatitis B, and aimed to find out the relationship between hot spots in different regions and the disease progress.The HBV DNA of BCP and PreC/C ware amplified by PCR from serum samples of patients with chronic hepatitis B, products were cloned into T vector. Three clones of each sample were chosen to directly sequence and compared with adr subtype from Genbank.Of BCP variants, the double mutations of T1762/A1764 were found in 19 of 42 patients with chronic hepatitis, and the prevalence was significantly lower in HBeAg positive patients (7/20) than in HBeAg negative patients (12/22) (p<0.05). Another double variants were T1673/G1799 that were found in 22 of 42 patients. It was a novel double variant and might be not correlated with HBeAg status.Precore variant, A1896, was detected in 18 individuals, 6 of them were positive for HBeAg and 12 were negative (P<0.05).Core variations, AA5, AA38, AA60, AA87, AA97, AA135 were the hot spots that were clustered in the middle of the gene that harbor several major B-and T-cell epitopes. They could alter the immune recognition sites and effect the response of the CTL, helper T-cell and B-cell, then might help the virus to escape the immune attack.There were another mutants in preC/C region such as inserts, deletions, etc. nineteen patients inserting or deleting a single codon made the ORF shifting, and some formed no stop codon resulting in a large protein. Three patients contained in-frame and/or out-frame core internal deletions, whichalways coexisted with the wild type virus and could interfere the wild type virus to produce the normal core protein as DIP. The mutations in the BCP and the preC/C region were varied and combined, implying that these mutations may be related to the immune clearance and persistent infection of hepatitis B virus.We associated the hot spots in the BCP and preC/C regions with the different phase of chronic hepatitis.Of the BCP double mutations, 5 patients (25%) in the mild hepatitis group, 4 patients (20%) in the moderate hepatitis group and 11 patents (55%) in the severe hepatitis group occurred the T1762/A1764 mutants. There were no significant correlations between the disease severity and the T1762/A1764 double mutations. So were the T1673/G1799 double mutations.A1896 mutation in the preC region can occur in different hepatitis state. The rate of the spot in mild hepatitis group was 22.2%, in moderate hepatitis group was 33.3% and in the severe hepatitis group was 44.4%. A1896 mutation occurred in the severe hepatitis group was distinctly higher than the other groups.Among the hot spots in the core region, each patient was differed on the amounts of the mutations. The results showed that there were 23 amino acids substituted in mild hepatitis group, 33 in moderate hepatitis group and 40 in severe hepatitis group. Following the disease progression, core mutations were increasing. We suggested the mutations were accumulated with infection progressing.In brief, the mutation in the preC/C and BCP gene was multiple and complex and associated with chronic hepatitis progression and immune clearance.