An Extremely Aberrant Subtype of Hepatitis B Virus Genotype D in Iran

Background and Aims: Hepatitis B virus (HBV) infection is a global health problem, with more than 350 million people chronically infected worldwide. Previous studies revealed that ayw2 is the predominant subtype in Iran. There are also some reports other HBV subtypes including ayw1, ayw3 and ayw4 which are widespread subtypes of genotype D. In this study, we reported on an exceptional and extremely rare subtype of HBV genotype D in an Iranian patient chronically infected with HBV who was also co-infected with hepatitis delta virus (HDV). 

Methods: The HBV and HDV genotypes and sub-genotypes were determined by polymerase chain reaction (PCR) followed by direct sequencing and phylogenetic analysis. The HBV subtype was determined from the amino acid sequence of the region of viral genome encoding the hepatitis B surface antigen (HBsAg).

Results: Phylogenetic analysis based on the HBV S gene revealed that the patient was infected with HBV genotype D and sub-genotype D1. Further amino acid mapping on the amino acid of the HBV S gene sequence showed that the our patient who was chronically infected with HBV was infected by an unusual subtype "ayr" of the virus which is not typical for the genotype D of HBV. HDV phylogenetic analysis also revealed that the patient was co-infected with HDV clade1.

Conclusions: The results indicated the presence of the uncommon subtype "ayr" of HBV genotype D in Iran. This may show that the virus is going further evolution by changing its genome, though the importance of this atypical subtype in genotype D of HBV is still not clear and needs longitudinal studies.