The sera of 46 Italian patients with chronic hepatitis delta virus (HDV) infection were analyzed for HDV RNA by polymerase chain reaction (PCR) amplification. Genetic analysis of sequences amplified from two regions of the HDV genome indicated that all HDV RNA-positive patients (98%) were infected with HDV genotype I. In Italy, infection with this genotype appeared to be associated with a bread spectrum of chronic disease. No subtypes of HDV genotype I were identified, nor were genetic variations clearly associated with different disease patterns; however, clustering of some sequences suggested correlations with geography and transmission route. Italian HDV genotype I sequences were more diverse than those from east Asia and North America, suggesting that HDV genotype I was likely introduced to Italy earlier and/or from multiple sources as compared to those areas. All sequences analyzed were predicted to fold into the unbranched rod structure typical of HDV RNA. Within this structure, three conserved features were identified, including sequences around the RNA editing site and the polyadenylation signal site. We conclude that in Italy, where HDV infection has been endemic, the overwhelmingly predominant genotype of HDV is genotype I.
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