title: Molecular analysis of hepatitis B virus "a" determinant in asymptomatic and symptomatic Mexican carriers.
abstract: BACKGROUND
  Hepatitis B virus (HBV) is a small DNA-containing virus with 4 genes, C, S, X and P. The S gene codes for the surface antigen (HBsAg), which contains the "a" determinant, the main region for induction of a protective humoral immune response. To compare the genotype and sequence of the "a" determinant between strains isolated from asymptomatic and symptomatic Mexican HBV carriers.
  
  
  RESULTS
  21 asymptomatic (blood donors) and 12 symptomatic (with clinical signs and with >1 year lamivudine treatment) HBV carriers were studied; all patients were positive for the HBsAg in serum. Viral load, genotypes, and subtypes were determined in plasma. A fragment of the S gene including the "a" determinant was PCR amplified and sequenced to determine genotype, subtype and to identify mutations. Mean viral load was 0.7965 x 104 copies/ml in asymptomatic carriers and 2.73 x 106 copies/ml in symptomatic patients. Genotypes H, C, and F were identified in asymptomatic individuals; whereas H was dominant in symptomatic patients. A fragment of 279 bp containing the "a" determinant was amplified from all 33 carriers and sequences aligned with S gene sequences in the GenBank. Mutations identified were Y100N, T126I, Q129H and N146K in the asymptomatic group, and F93I and A128V in the symptomatic group.
  
  
  CONCLUSIONS
  Differences in genotype and in mutations in the "a" determinant were found between strains from asymptomatic and symptomatic HBV Mexican carriers.
authors.affiliation: Unidad de Investigación en Enfermedades Infecciosas, Unidad Médica de Alta Especialidad-Pediatría, Centro Médico Nacional-Siglo XXI, Instituto Mexicano del Seguro Social, México DF, México. mertachiquin@yahoo.com.mx <mertachiquin@yahoo.com.mx>
authors.forename: Martha-Eugenia
authors.initials: ME
authors.lastname: Ruiz-Tachiquín
authors.forename: Hilda-Alicia
authors.initials: HA
authors.lastname: Valdez-Salazar
authors.forename: Vicencio
authors.initials: V
authors.lastname: Juárez-Barreto
authors.forename: Margarita
authors.initials: M
authors.lastname: Dehesa-Violante
authors.forename: Javier
authors.initials: J
authors.lastname: Torres
authors.forename: Onofre
authors.initials: O
authors.lastname: Muñoz-Hernández
authors.forename: Ma-Teresa
authors.initials: MT
authors.lastname: Alvarez-Muñoz
mesh_terms: D000328:Adult; D001782:Blood Donors; D002353:Carrier State / Q000503:physiopathology / Q000821:virology*; D004279:DNA, Viral / Q000032:analysis / Q000302:isolation & purification; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D006514:Hepatitis B Surface Antigens / Q000737:chemistry / Q000235:genetics*; D006515:Hepatitis B virus / Q000145:classification* / Q000235:genetics* / Q000472:pathogenicity; D019694:Hepatitis B, Chronic / Q000503:physiopathology / Q000821:virology*; D006801:Humans; D008297:Male; D008800:Mexico; D008875:Middle Aged; D009154:Mutation; D016133:Polymerase Chain Reaction; D019562:Viral Load
chemical_list: D004279:DNA, Viral; D006514:Hepatitis B Surface Antigens