Molecular epidemiology and phylogenetic analysis of Hepatitis B virus in a group of migrants in Italy

Abstract

Background: Hepatitis B virus infection (HBV) is widespread and it is considered a major health problem worldwide. The global distribution of HBV varies significantly between countries and between regions of the world. Among the many factors contributing to the changing epidemiology of viral hepatitis, the movement of people within and between countries is a potentially important one. In Italy, the number of migrant individuals has been increasing during the past 25 years. HBV genotype D has been found throughout the world, although its highest prevalence is in the Mediterranean area, the Middle East and southern Asia. We describe the molecular epidemiology of HBV in a chronically infected population of migrants (living in Italy), by using the phylogenetic analysis.

Methods: HBV-DNA was amplified and sequenced from 43 HBV chronically infected patients. Phylogenetic and evolutionary analysis were performed using both maximum Likelihood and Bayesian methods.

Results and conclusion: Of the 43 HBV S gene isolates from migrants, 25 (58.1 %) were classified as D genotype. Maximum Likelihood analysis showed an intermixing between Moldavian and foreigners sequences mostly respect to Italian ones. Italian sequences clustered mostly together in a main clade separately from all others. The estimation of the time of the tree's root gave a mean value of 17 years ago, suggesting the origin of the tree back to 1992 year. The skyline plot showed that the number of infections softly increased until the early 2005s, after which reached a plateau. Comparing phylogenetic data to the migrants date of arrival in Italy, it should be possible that migrants arrived in Italy yet infected from their country of origin. In conclusion, this is the first paper where phylogenetic analysis and genetic evolution has been used to characterize HBV sub genotypes D1 circulation in a selected and homogenous group of migrants coming from a restricted area of Balkans and to approximately define the period of infection besides the migration date.

Fig. 1

Bayesian phylogenetic tree of 17 Moldavian HBV S gene sequences. The time of the most recent common ancestor, with the credibility interval based on 95 % highest posterior density interval (95 % HPD), was reported in years. Scale years is reported at the bottom of the figure

Fig. 2

Bayesian skyline plot (BSP) of the 17 HIV Moldavian HBV S gene sequences. The effective number of infections is reported on the Y-axis. Time is reported on the X-axis. The colored area corresponds to the credibility interval based on 95 % highest posterior density interval (HPD)