Characterization and phylogenetic analysis of Hepatitis B virus genotypes circulating in the Brazilian territory.
Hepatitis B is defined as inflammation of the liver caused by an infection by the Hepatitis B virus (HBV), a DNA virus of the Hepadnaviridae family. Hepatitis B is a major public health problem, with approximately 350 million carriers worldwide. HBV can be divided into eight major genotypes, called A to H, and defined by the divergence over 8% between them. The different genotypes have different geographical distribution. In order to determine the prevalence prevalence of HBsAg and anti-HBc. In Rio de Janeiro overall prevalence estimates were0.27% for HBsAg and 3.68% for anti-HBc. There was a significant decrease in the overall prevalence of HBsAg (from 0.36 to 0.14%) and anti-HBc (from 6.12 to 2.05%) in the periodencompassed between 1998-2005. These prevalence estimates were higher than those found in other countries. This study also evaluated the distribution of the different HBV genotypesin the Brazilian territory and its genetic variability based on the geographic structure of the viral population. Three hundred ninteen samples of HBsAg positive blood donors fromdifferent regions of Brazil were collected and three HBV genotypes were found: A (73%), D (23%) and F (4%). The most frequent viral subtypes were adw2 (75.5%), followed by ayw2 (18.01%), adw4 (3.83%), ayw1 (1.92%) and ayw3 (1.15%). All three HBV genotypes showed many variants, and great variation in the nucleotide sequence of the S gene. The nucleotide diversity (p) found for the genotypes A, D and F were statistic different. The analysis of the intragenotypic diversity (h), showed a balance between the genotypes. It was not possible to infer different populations based on analysis of median joining, however there was some tendency of samples to occupy specific regions within the network. AMOVA sugested that there was no structure between the different geographical regions studied, and that analyzed populations are not isolated. The adherence test was accepted in the mismacth distribution for the genotype A and D, indicating a past event of expansion in the population. Analysis of maximum likelihood revealed the presence in the Brazilian population of 3 HBV subgenotypes (FII, FIII and FIV) of 5 previously described for the genotype F corroborating the possibility of entry of the man in South America coming from Central America and migrated to the south for routes along the coast.
Advisor:Cibele Rodrigues Bonvicino
School:Faculdades Oswaldo Cruz
Source Type:Master's Thesis
Date of Publication:05/19/2008