'Defective' mutations of hepatitis D viruses in chronic hepatitis D patients

摘要

AIM: To verify whether 'defective' mutations existed in hepatitis D virus (HDV).METHODS: Hepatitis delta antigen (HDAg)-codingsequences were amplified using Pfu DNA polymerases with proof-reading activities from sera of five patients with chronic hepatitis D. Multiple colonies were sequenced for each patient. Pfu analyzed a total of 270 HDV clones.Three representative defective HDV clones were constructed in expression plasmids and transfected into a human hepatoma cell line. Cellular proteins were extracted and analyzed by Western blot.RESULTS: Four of five cases (80%) showed defective HDV genomes in their sera. The percentage of defective genomes was 3.7% (10/270). The majority (90%) of the defective mutations were insertions or deletions that resulted in frameshift and abnormal stop translation of the HDAg. The predicted mutated HDAg ranged from 45amino acids to ＞214 amino acids in length. Various domains of HDAg associated with viral replication or packaging were affected in different HDV isolates. Western blot analysis showed defected HDAg in predicted positions.CONCLUSION: 'Defective' viruses do exist in chronic HDV infected patients, but represented as minor strains. The clinical significance of the 'defected' HDV needs further study to evaluate.