In this study, we determined the prevalence of HBV subgenotypes in Maranhão state, located in northeastern Brazil, where the population is heterogeneous, with a high proportion of African descendants. HBV was detected in 119 of 133 (89.5%) chronic hepatitis B patients, including 103 (86.5%) who were HBeAg-negative. Using phylogenetic analysis of the S/Polymerase region of HBV DNA, subgenotype A1 was found to be the most prevalent (67%), followed by genotype D (28%; subgenotype D4 was detected in 24%, D3 in 3%, and D2 in 1%). Genotype F, clustering with subgenotype F2a, was found in six (5%) patients. The topology of the phylogenetic tree showed that HBV/A1 sequences did not cluster together, suggesting that more than one strain was introduced into Maranhão. On the other hand, HBV/D4 sequences formed a monophyletic cluster, suggesting a single entry of this strain in this population. This study showed that HBV/A1 was the only subgenotype of HBV/A present in the population from Maranhão and indicated that in this region HBV/A1 was not restricted to an Afro-descendant community where it was previously reported, but is widely distributed among general population of HBV chronic carriers. Unexpectedly, we found a high frequency of HBV subgenotype D4. Together with previously reported data on the distribution of HBV/D4 in the world, these findings suggest that this subgenotype was more prevalent in the African continent in the past and may have been introduced in Maranhão by means of the slave trade during the late XVIII century, when the largest number of African slaves arrived to this region.
Keywords: Brazil; Maranhão; Phylogenetics; Slave trade; Subgenotype A1; Subgenotype D4.
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