title: Molecular and functional analysis of occult hepatitis B virus isolates from patients with hepatocellular carcinoma.
abstract: Occult HBV infection is characterized by the persistence of HBV DNA in the liver of individuals negative for HBV surface antigen (HBsAg). Occult HBV may exist in the hepatocytes as a free genome, although the factors responsible for the very low viral replication and gene expression usually observed in this peculiar kind of infection are mostly unknown. Aims of this study were to investigate whether the viral genomic variability might account for the HBsAg negativity and the inhibition of the viral replication in occult HBV carriers, and to verify in vitro the replication capability of occult HBV strains. We studied liver viral isolates from 17 HBV patients, 13 with occult infection and 4 HBsAg-positive. Full-length HBV genomes from each case were amplified and directly sequenced. Additionally, full-length HBV DNA from eight occult-HBV and two HBsAg-positive cases were cloned and sequenced. Finally, three entire, linear HBV genomes from occult cases were transiently transfected in HuH7 cells. Direct sequencing showed the absence of mutations capable of interfering with viral replication and gene expression in the major viral population of each case. Cloning experiments showed highly divergent HBV strains both in HBsAg-positive and HBsAg-negative individual cases (range of divergence 1.4%-7.1%). All of the 3 transfected full-length HBV isolates showed normal patterns of replication in vitro.
  
  
  CONCLUSIONS
  Multiple viral variants accumulate in the liver of occult HBV-infected patients. Occult HBV strains are replication-competent in vitro, suggesting that host, rather than viral factors are responsible for cryptic HBV infection.
authors.affiliation: Unit of Clinical and Molecular Hepatology, Department of Internal Medicine, University of Messina, Messina, Italy. tpollicino@unime.it
authors.forename: Teresa
authors.initials: T
authors.lastname: Pollicino
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Raffa
authors.forename: Lucy
authors.initials: L
authors.lastname: Costantino
authors.forename: Antonella
authors.initials: A
authors.lastname: Lisa
authors.forename: Cesare
authors.initials: C
authors.lastname: Campello
authors.forename: Giovanni
authors.initials: G
authors.lastname: Squadrito
authors.forename: Massimo
authors.initials: M
authors.lastname: Levrero
authors.forename: Giovanni
authors.initials: G
authors.lastname: Raimondo
mesh_terms: D000368:Aged; D006528:Carcinoma, Hepatocellular / Q000821:virology*; D004252:DNA Mutational Analysis; D004279:DNA, Viral / Q000235:genetics; D005260:Female; D015967:Gene Expression Regulation, Viral; D015684:Gene Products, pol / Q000235:genetics; D005814:Genes, Viral / Q000235:genetics; D014644:Genetic Variation; D016679:Genome, Viral / Q000235:genetics; D006515:Hepatitis B virus / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology*; D006801:Humans; D008113:Liver Neoplasms / Q000821:virology*; D008297:Male; D008875:Middle Aged; D010802:Phylogeny; D014758:Viral Core Proteins / Q000235:genetics; D014779:Virus Replication / Q000502:physiology
chemical_list: D004279:DNA, Viral; D015684:Gene Products, pol; D014758:Viral Core Proteins