title: Evidence for reduced selection pressure on the hepatitis B virus core gene in hepatitis B e antigen-negative chronic hepatitis B.
abstract: The mechanisms underlying the high levels of hepatitis B virus (HBV) replication that cause hepatitis B e antigen (HBeAg)-negative chronic hepatitis B (e-CHB) are unknown. Impaired anti-HBV immunity, which may be measurable as a relaxation of selection pressure on the virus, is possible. A group of Tongans (n = 345) with a chronic HBV infection, including seven with e-CHB, were genotyped at HLA class I. The repertoire of HBV core-gene codons under positive selection pressure was defined by phylogenetic analysis (by using the paml program) of 708 cloned sequences extracted from the 67 of these 345 subjects with the same repertoire of HLA class I alleles as the seven e-CHB individuals and matched controls (see below). The frequency of non-synonymous mutations at these codons was measured in longitudinal data from 15 subjects. Finally, the number of non-synonymous mutations at these codons was compared in seven groups comprised of one subject with e-CHB and 1-3 HLA class I-matched controls with an inactive, HBeAg-negative chronic HBV infection (e-InD). Nineteen codons in the core gene were under positive selection pressure. There was a high frequency of new non-synonymous mutations at these codons (P<0.0001) in longitudinal data. The mean number of these 19 codons with non-synonymous mutations was lower (P = 0.02) in HBV from subjects with e-CHB (4.4±0.5 codons per subject) versus those with e-InD (6.4±0.4 codons per subject). There is a subtle relaxation in selection pressure on the HBV core gene in e-CHB. This may be due to impaired antiviral immunity, and could contribute to the high levels of viral replication that cause liver inflammation in this disease.
authors.affiliation: Bioinformatics Institute, University of Auckland, Private Bag 92-019, Auckland, New Zealand.
authors.forename: Brook G
authors.initials: BG
authors.lastname: Warner
authors.affiliation: Bioinformatics Institute, University of Auckland, Private Bag 92-019, Auckland, New Zealand.
authors.forename: Peter
authors.initials: P
authors.lastname: Tsai
authors.affiliation: Biology Department, 3103 French Science Center, Duke University, 125 Science Drive, Durham, NC 27708, USA.|Bioinformatics Institute, University of Auckland, Private Bag 92-019, Auckland, New Zealand.
authors.forename: Allen G
authors.initials: AG
authors.lastname: Rodrigo
authors.affiliation: The School of Population Health, University of Auckland, Private Bag 92-019, Auckland, New Zealand.
authors.forename: Malakai
authors.initials: M
authors.lastname: 'Ofanoa
authors.affiliation: The New Zealand Liver Transplant Unit, Auckland City Hospital, Private Bag 92-024, Auckland, New Zealand.
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Gane
authors.affiliation: The New Zealand Liver Transplant Unit, Auckland City Hospital, Private Bag 92-024, Auckland, New Zealand.
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Munn
authors.affiliation: The New Zealand Liver Transplant Unit, Auckland City Hospital, Private Bag 92-024, Auckland, New Zealand.
authors.forename: William G H
authors.initials: WGH
authors.lastname: Abbott
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D005260:Female; D006512:Hepatitis B Core Antigens / Q000235:genetics* / Q000378:metabolism; D006513:Hepatitis B e Antigens / Q000235:genetics* / Q000378:metabolism; D006515:Hepatitis B virus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology; D019694:Hepatitis B, Chronic / Q000821:virology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D012641:Selection, Genetic
chemical_list: D006512:Hepatitis B Core Antigens; D006513:Hepatitis B e Antigens