title: Genotyping of Tunisian hepatitis B virus isolates based on the sequencing of preS2 and S regions.
abstract: The S nucleotide sequences of five hepatitis B virus strains isolated from plasma samples of Tunisian patients with chronic hepatitis B were determined; the preS2 region of three of them were sequenced. According to the comparative analysis of S peptide sequences with the reported sequences in the database bank, the five hepatitis B strains were shown to be related to the D genotypic group, subtype ayw. The nature of residues at positions 125 and 127 allowed us to distinguish between each subtype of the D group and to class all five Tunisian sequences in the 'ayw2' subtype. Moreover, two of them (1366 and 523) contained a substitution of the invariant Cys69 by Arg and Cys221 by Phe, respectively. Potential structural modifications due to the Cys-Arg change are discussed.
authors.affiliation: Centre de Biotechnologie de Sfax, BP'K', 3038, Sfax, Tunisia.
authors.forename: I
authors.initials: I
authors.lastname: Borchani-Chabchoub
authors.forename: A
authors.initials: A
authors.lastname: Gargouri
authors.forename: R
authors.initials: R
authors.lastname: Mokdad-Gargouri
mesh_terms: D000595:Amino Acid Sequence; D004279:DNA, Viral / Q000097:blood; D005838:Genotype; D006514:Hepatitis B Surface Antigens / Q000737:chemistry / Q000235:genetics*; D006515:Hepatitis B virus / Q000145:classification* / Q000235:genetics*; D019694:Hepatitis B, Chronic / Q000821:virology*; D006801:Humans; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction / Q000379:methods; D011498:Protein Precursors / Q000737:chemistry / Q000235:genetics*; D017422:Sequence Analysis, DNA; D014416:Tunisia; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics*
chemical_list: D004279:DNA, Viral; D006514:Hepatitis B Surface Antigens; D011498:Protein Precursors; C118669:S envelope protein, hepatitis B virus; D014759:Viral Envelope Proteins; C050807:presurface protein 2, hepatitis B surface antigen