Molecular analysis of hepatitis B virus "a" determinant in asymptomatic and symptomatic Mexican carriers.
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.
Ruiz-Tachiquín
Martha-Eugenia
ME
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>
Valdez-Salazar
Hilda-Alicia
HA
Juárez-Barreto
Vicencio
V
Dehesa-Violante
Margarita
M
Torres
Javier
J
Muñoz-Hernández
Onofre
O
Alvarez-Muñoz
Ma-Teresa
MT
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
D004279:DNA, Viral; D006514:Hepatitis B Surface Antigens