Molecular analysis of hepatitis B virus "a" determinant in asymptomatic and symptomatic Mexican carriers
Martha-Eugenia Ruiz-Tachiquín1, Hilda-Alicia Valdez-Salazar1, Vicencio Juárez-Barreto2, Margarita Dehesa-Violante3, Javier Torres1, Onofre Muñoz-Hernández1 and Ma-Teresa Alvarez-Muñoz1
1Unidad de Investigación en Enfermedades Infecciosas, Unidad Médica de Alta Especialidad (UMAE)-Pediatría, Centro Médico Nacional-Siglo XXI, Instituto Mexicano del Seguro Social, México DF, México
2Laboratorio de Análisis Clínicos, Unidad Médica de Alta Especialidad (UMAE)-Pediatría, Centro Médico Nacional-Siglo XXI, Instituto Mexicano del Seguro Social, México DF, México
3Clínica de Hepatitis, Departamento de Gastroenterología, Unidad Médica de Alta Especialidad (UMAE)-Hospital General. Centro Médico Nacional-Siglo XXI, Instituto Mexicano del Seguro Social, México DF, México
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.
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 × 104 copies/ml in asymptomatic carriers and 2.73 × 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.
Differences in genotype and in mutations in the "a" determinant were found between strains from asymptomatic and symptomatic HBV Mexican carriers.
Virology Journal 2007, 4:6. This is an Open Access article distributed under the terms of the Creative Commons Attribution License.