Gastroenterology

Gastroenterology

Volume 125, Issue 5, November 2003, Pages 1370-1378
Gastroenterology

Clinical-liver, pancreas, and biliary tract
Sequence variation upstream of precore translation initiation codon reduces hepatitis B virus e antigen production

Presented in part at the annual meeting of the Molecular Biology of Hepatitis B Virus, September-October, 2002, Pacific Grove, California, and at the 53rd annual meeting of the American Association for the Study of Liver Diseases, November, 2002, Boston, Massachusetts.
https://doi.org/10.1016/j.gastro.2003.07.016Get rights and content

Abstract

Background & Aims:

Most South African hepatitis B virus strains harbor point mutations immediately upstream of the precore AUG codon. The aim of this study was to determine their effect on hepatitis B e antigen expression.

Methods:

The hepatitis B virus DNA sequence around the precore region was determined from sera of 45 black South Africans. The South African mutations were introduced into hepatitis B virus dimers of the same genotype, and hepatitis B e antigen was quantified from culture medium of transfected HepG2 or Huh7 cells.

Results:

The South African sequence changes were easily detectable in the acute, hepatitis B e antigen-positive phase of infection, suggesting that they were stable traits and were not selected by immune pressure. Triple mutations at the −5, −3, and −2 positions of the AUG codon severely impaired hepatitis B e antigen expression (P < 0.001). The frequent double mutation at the −5 and −2 positions moderately reduced hepatitis B e antigen levels (P < 0.001) to an extent comparable to that of the common core promoter mutations (1762T1764A). The presence of both South African and core promoter mutations diminished hepatitis B e antigen expression in an additive manner. It is interesting to note that the triple South African mutations enabled core protein translation from precore messenger RNA, which could rescue the replication defect of a hepatitis B virus genome with an ablated core gene.

Conclusions:

We have identified a novel class of hepatitis B e antigen variants with reduced hepatitis B e antigen translation by a ribosomal leaky scanning mechanism. Reduction in hepatitis B e antigen expression may contribute to accelerated seroconversion from hepatitis B e antigen to its antibody in black South Africans infected with hepatitis B virus very early in life.

Section snippets

Subjects

Blood was obtained, with informed consent, from 45 black Africans. Eighteen were hepatitis B surface antigen (HBsAg)-positive asymptomatic carriers with normal serum alanine aminotransferase (ALT) levels. The HBeAg status of these patients is summarized in Table 1. Five patients had acute hepatitis. The ALT levels in these patients ranged from 799 to 4747 IU/L. One patient with fulminant hepatitis was a woman aged 32 years with an ALT level of 979 IU/L. In addition, 21 children were studied.

The SA mutations are present throughout the course of infection

Many individuals described in a previous study had seroconverted to anti-HBe and contained core promoter mutations, and a subset had developed hepatocellular carcinoma.8 Thus, whether the sequence changes at 1809–1812 were stable traits or whether they represented adaptive change under the immune pressure of anti-HBe, similar to that observed with core promoter and precore mutations, could not be established. For this reason, we sequenced HBV isolates from 6 patients with acute hepatitis (1

Discussion

The sequence around the precore initiation codon is conserved in all the 8 known genotypes as 5′-AGCACCAUGC-3′ (nucleotides 1808–1817).28 This sequence conforms to the optimal context for translational initiation, the so-called Kozak sequence (5′-GCCA/GCCAUGG-3′).15, 24 In contrast, many SA HBV strains, which belong to a subgroup of genotype A,8, 18, 19, 20 harbor point mutations at 1809–1812.8 Such HBV variants have also been found occasionally in other parts of the world.29, 30, 31 The most

Acknowledgements

The authors thank Professor R. Bhimma of the Department of Paediatrics & Child Health, Nelson R. Mandela School of Medicine, University of Natal, Durban, South Africa, for providing the serum samples from children for analysis.

References (41)

  • B Larouze et al.

    Host responses to hepatitis-B infection in patients with primary hepatic carcinoma and their familiesA case/control study in Senegal, West Africa

    Lancet

    (1976)
  • J Kao et al.

    Hepatitis B genotypes correlate with clinical outcomes in patients with chronic hepatitis B

    Gastroenterology

    (2000)
  • E Orito et al.

    Geographic distribution of hepatitis B virus (HBV) genotype in patients with chronic HBV infection in Japan

    Hepatology

    (2001)
  • C Wai et al.

    HBV genotype B is associated with better response to interferon therapy in HBeAg(+) chronic hepatitis than genotype C

    Hepatology

    (2002)
  • H Sumi et al.

    Influence of hepatitis B virus genotypes on the progression of chronic type B liver disease

    Hepatology

    (2003)
  • C Chu et al.

    Hepatitis B virus genotype B is associated with earlier HBeAg seroconversion compared with hepatitis B virus genotype C

    Gastroenterology

    (2002)
  • F Hollinger et al.

    Hepatitis B virus

  • L Magnius et al.

    New specificities in Australia antigen positive sera distinct from the Le Bouvier determinants

    J Immunol

    (1972)
  • D Milich et al.

    Is a function of the secreted hepatitis B e antigen to induce immunologic tolerance in utero?

    Proc Natl Acad Sci U S A

    (1990)
  • D Milich et al.

    The secreted hepatitis B precore antigen can modulate the immune response to the nucleocapsida mechanism for persistence

    J Immunol

    (1998)
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    Supported by a grant from the Brain Korea 21 Project for Medical Science (to S.H.A.); Lifespan Research Funds; grants CA35711, AA20169, p20RR15578, R13 AI5224101, AI54535, and DK62857 from the National Institutes of Health; and Ernst-Jung-Stiftung, Hamburg, Germany. J.L. is a Liver Scholar from the American Liver Foundation.

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