Characterization of Occult Hepatitis B Infection Among Injecting Drug Users in Tehran, Iran

Background: hepatitis b virus (hbv) infection is a major health problem worldwide. objectives: the aim of this study was to investigate the frequency of occult hepatitis b infection (obi) and its associated risk factors, together with the molecular characterization of the virus in injecting drug users of tehran. patients and methods: the study consisted of 229 injecting drug users. serum samples were collected and tested for the presence of hepatitis b core antibody (hbcab) and hepatitis b surface antigen (hbsag) by an enzyme-linked immunosorbent assay (elisa). hbv b virus dna was extracted from the serum samples, and a fragment of the s gene was amplified using the nested polymerase chain reaction. the genotype, sub genotypes, subtype, and s gene mutation of hbv were determined by direct sequencing. a phylogenetic tree was constructed using the neighbor-joining method. results: sixty-four (28%) participants were hbcab positive, 59 cases were hbcab positive and hbsag negative, and 5 cases were hbsag positive. hepatitis b dna was found in three hbsag-positive cases. thirteen of 59 (22%) individuals were hepatitis b dna positive. the phylogenetic tree of hepatitis b dna showed the existence of genotype d. the only significant correlation was between sharing a syringe and obi. conclusions: in comparison with the rate of hbcab positivity reported in other iranian studies, the rate was higher in the present study. there were a few variations, genotypes, and subtypes among the infected injecting drug users. further investigations are needed to unravel the molecular characterization of obi.