The hepatitis B virus (HBV) is a global public health problem with more than 240 million people chronicallyinfected worldwide, who are at risk for end-stage liverdisease and hepatocellular carcinoma. There are anestimated 600000 deaths annually from complications ofHBV-related liver disease. Antiviral therapy with nucleos/tide analogs (NA) targeting the HBV polymerase (P) caninhibit disease progression by long-term suppression ofHBV replication. However, treatment may fail with firstgeneration NA therapy due to the emergence of drugresistantmutants, as well as incomplete medicationadherence. The HBV replicates via an error-prone reversetranscriptase leading to quasispecies. Due to overlappingopen reading frames mutations within the HBV P cancause concomitant changes in the HBV surface gene (S )and vice versa. HBV quasispecies diversity is associatedwith response to antiviral therapy, disease severity andlong-term clinical outcomes. Specific mutants havebeen associated with antiviral drug resistance, immuneescape, liver fibrosis development and tumorgenesis.An understanding of HBV variants and their clinicalrelevance may be important for monitoring chronichepatitis B disease progression and treatment response.In this review, we will discuss HBV molecular virology,mechanism of variant development, and their potentialclinical impact.
The hepatitis B virus (HBV) is a global public health problem with more than 240 million people chronicallyinfected worldwide, who are at risk for end-stage liverdisease and hepatocellular carcinoma. There are anestimated 600000 deaths annually from complications ofHBV-related liver disease. Antiviral therapy with nucleos/tide analogs (NA) targeting the HBV polymerase (P) caninhibit disease progression by long-term suppression ofHBV replication. However, treatment may fail with firstgeneration NA therapy due to the emergence of drugresistantmutants, as well as incomplete medicationadherence. The HBV replicates via an error-prone reversetranscriptase leading to quasispecies. Due to overlappingopen reading frames mutations within the HBV P cancause concomitant changes in the HBV surface gene (S )and vice versa. HBV quasispecies diversity is associatedwith response to antiviral therapy, disease severity andlong-term clinical outcomes. Specific mutants havebeen associated with antiviral drug resistance, immuneescape, liver fibrosis development and tumorgenesis.An understanding of HBV variants and their clinicalrelevance may be important for monitoring chronichepatitis B disease progression and treatment response.In this review, we will discuss HBV molecular virology,mechanism of variant development, and their potentialclinical impact.