Hepatitis B virus precore mutants in serum and liver of Southern African Blacks with hepatocellular carcinoma.
OBJECTIVE
The aim of this study was to sequence the precore region of HBV isolated from serum and tumorous and non-tumorous liver tissue from patients with hepatocellular carcinoma to identify mutations that might play a role in malignant transformation.


METHODS
HBV DNA was extracted from 62 sera, 14 tumorous and 12 non-tumorous liver tissue samples of patients with hepatocellular carcinoma, amplified by the polymerase chain reaction and sequenced directly.


RESULTS
Thirty-nine patients were HBeAg-negative and 23 HBeAg-positive. Missense mutations were present predominantly in HBeAg-negative sera. The most common missense mutation, a guanine to thymine transversion, occurred at nucleotide 1862 in the bulge of the encapsidation signal; it was more prevalent in HBeAg-negative (10/39) than in HBeAg-positive patients (1/23) (p = 0.03). Mutations known to prevent HBeAg synthesis were detected in seven sera; five with an 1896 stop-codon mutation, one with an 1817 nonsense mutation, and one with a frameshift mutation caused by an insertion between 1838 and 1839. Missense mutations and deletions were present more often in tumorous tissue derived from HBsAg-negative patients. In the tumours missense mutations occurred at position 1862 and 1899, and the deletions affected direct repeat 1 and/or the encapsidation signal and included the x gene stop-codon.


CONCLUSIONS
The 1862 mutation, and other missense mutations and deletions detected in the precore gene, may disrupt HBV DNA replication and/or signal peptide cleavage leading to HBeAg-negativity. Disruption of viral replication may promote integration of unencapsidated replicative intermediates and hence contribute to hepatocarcinogenesis.
Kramvis
A
A
Medical Research Council, Department of Medicine, University of the Witwatersrand, Johannesburg, South Africa.
Kew
M C
MC
Bukofzer
S
S
D000328:Adult; D000595:Amino Acid Sequence; D001483:Base Sequence; D044383:Black People; D006528:Carcinoma, Hepatocellular / Q000097:blood / Q000473:pathology / Q000821:virology*; D018388:Codon, Terminator; D004279:DNA, Viral / Q000032:analysis* / Q000097:blood; D006147:Guanine; D006513:Hepatitis B e Antigens / Q000097:blood / Q000737:chemistry / Q000235:genetics*; D006515:Hepatitis B virus / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D008099:Liver / Q000473:pathology / Q000821:virology*; D008113:Liver Neoplasms / Q000097:blood / Q000473:pathology / Q000821:virology*; D008969:Molecular Sequence Data; D009154:Mutation; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D016415:Sequence Alignment; D017384:Sequence Deletion; D013019:South Africa; D013941:Thymine
D018388:Codon, Terminator; D004279:DNA, Viral; D006513:Hepatitis B e Antigens; D006147:Guanine; D013941:Thymine