Amino acid (AA) changes in specific hepatitis B core antigen (HBcAg) regions were assessed in patients infected with chronic hepatitis B (CHB) after a 12-month untreated period and after receiving antiviral therapy (interferon, lamivudine or adefovir dipivoxil), and in inactive hepatitis B surface antigen-positive carriers.
Methods
Samples corresponding to different time points in 76 CHB cases (64 on-treatment) and 4 inactive carriers were included. The main precore mutation, T-helper immunodominant epitope at AA 50–69 (Th50–69), minor T-helper epitope (Th28–47), B-cell immunodominant epitope (B74–84) and a conserved region of HBcAg at AA 1–11 (AA1–11) were directly sequenced. For comparisons, the average number of AA changes in each region was standardized to 12 months (Av12).
Results
AA changes clustered mainly in immunodominant regions (69%). The highest percentage of cases (%n) with changes and highest Av12 changes were detected after interferon treatment (%n=73%, Av12=3.1 in Th50–69 and %n=86%, Av12=2.7 in B74–84). At baseline, immunodominant regions had higher Av12 changes in hepatitis B e antigen-negative patients and those with main precore mutations. Changes in the Th28–47 region were more frequent after nucleoside/nucleotide analogue treatment (40%) than before treatment (9%). Codons 74 and 77 were the most polymorphic, and the double change E64D-N67T was significantly observed. Codon 84 substitutions were mainly associated with interferon treatment (P=0.05).
Conclusions
Natural and treatment-induced substitutions in HBV core protein, occurring especially with interferon treatment, were characterized. Some immune-stimulating activity related to the minor Th28–47 epitope might be associated with nucleoside/nucleotide analogues; this activity was also seen in inactive carriers.
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